Merge branch 'master' of https://github.com/eugenp/tutorials

README.md

@@ -1,12 +1,16 @@
 
-The "REST with Spring" Classes
+The Courses
 ==============================
 
-Here's the Master Class of REST With Spring (along with the newly announced Boot 2 material): <br/>
-**[>> THE REST WITH SPRING - MASTER CLASS](http://www.baeldung.com/rest-with-spring-course?utm_source=github&utm_medium=social&utm_content=tutorials&utm_campaign=rws#master-class)**
 
-And here's the Master Class of Learn Spring Security: <br/>
+Here's the new "Learn Spring" course: <br/>
-**[>> LEARN SPRING SECURITY - MASTER CLASS](http://www.baeldung.com/learn-spring-security-course?utm_source=github&utm_medium=social&utm_content=tutorials&utm_campaign=lss#master-class)**
+**[>> LEARN SPRING - THE MASTER CLASS](https://www.baeldung.com/learn-spring-course?utm_source=github&utm_medium=social&utm_content=tutorials&utm_campaign=ls#master-class)**
+
+Here's the Master Class of "REST With Spring" (along with the new announced Boot 2 material): <br/>
+**[>> THE REST WITH SPRING - MASTER CLASS](https://www.baeldung.com/rest-with-spring-course?utm_source=github&utm_medium=social&utm_content=tutorials&utm_campaign=rws#master-class)**
+
+And here's the Master Class of "Learn Spring Security": <br/>
+**[>> LEARN SPRING SECURITY - MASTER CLASS](https://www.baeldung.com/learn-spring-security-course?utm_source=github&utm_medium=social&utm_content=tutorials&utm_campaign=lss#master-class)**
 
 
 
@@ -15,7 +19,7 @@ Java and Spring Tutorials
 
 This project is **a collection of small and focused tutorials** - each covering a single and well defined area of development in the Java ecosystem. 
 A strong focus of these is, of course, the Spring Framework - Spring, Spring Boot and Spring Security. 
-In additional to Spring, the following technologies are in focus: `core Java`, `Jackson`, `HttpClient`, `Guava`. 
+In additional to Spring, the modules here are covering a number of aspects in Java. 
 
 
 Building the project
@@ -32,8 +36,15 @@ Running a Spring Boot module
 ====================
 To run a Spring Boot module run the command: `mvn spring-boot:run` in the module directory
 
-###Running Tests
 
+Working with the IDE
+====================
+This repo contains a large number of modules. 
+When you're working with an individual module, there's no need to import all of them (or build all of them) - you can simply import that particular module in either Eclipse or IntelliJ. 
+
+
+Running Tests
+=============
 The command `mvn clean install` will run the unit tests in a module.
 To run the integration tests, use the command `mvn clean install -Pintegration-lite-first`
 

core-java-modules/core-java-12/README.md

@@ -1,3 +1,4 @@
-## Relevant articles:
+## Relevant Articles:
+
 
 - [String API Updates in Java 12](https://www.baeldung.com/java12-string-api)

core-java-modules/core-java-arrays-2/.gitignore

@@ -0,0 +1,25 @@
+*.class
+
+0.*
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+.resourceCache
+
+# Packaged files #
+*.jar
+*.war
+*.ear
+
+# Files generated by integration tests
+backup-pom.xml
+/bin/
+/temp
+
+#IntelliJ specific
+.idea/
+*.iml

core-java-modules/core-java-arrays-2/pom.xml

@@ -0,0 +1,50 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung</groupId>
+    <artifactId>core-java-arrays-2</artifactId>
+    <version>0.1.0-SNAPSHOT</version>
+    <name>core-java-arrays-2</name>
+    <packaging>jar</packaging>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>parent-java</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+        <relativePath>../../parent-java</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+        <!-- test scoped -->
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <finalName>core-java-arrays-2</finalName>
+        <resources>
+            <resource>
+                <directory>src/main/resources</directory>
+                <filtering>true</filtering>
+            </resource>
+        </resources>
+    </build>
+
+    <properties>
+
+        <!-- util -->
+        <commons-lang3.version>3.9</commons-lang3.version>
+        <!-- testing -->
+        <assertj-core.version>3.10.0</assertj-core.version>
+    </properties>
+
+</project>

core-java-modules/core-java-arrays-2/src/test/java/com/baeldung/array/looping/LoopDiagonallyUnitTest.java

@@ -4,7 +4,7 @@ import org.junit.Test;
 
 import static org.junit.Assert.assertEquals;
 
-public class LoopDiagonallyTest {
+public class LoopDiagonallyUnitTest {
 
     @Test
     public void twoArrayIsLoopedDiagonallyAsExpected() {

core-java-modules/core-java-exceptions/README.md

@@ -1,3 +1,3 @@
-## Relevant articles:
+## Relevant Articles:
 
 - [Will an Error Be Caught by Catch Block in Java?](https://www.baeldung.com/java-error-catch)

core-java-modules/core-java-io/src/main/java/com/baeldung/files/Main.java

@@ -0,0 +1,24 @@
+package com.baeldung.files;
+
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingApacheCommonsIO;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingBufferedReader;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingGoogleGuava;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingLineNumberReader;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingNIOFileChannel;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingNIOFiles;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingScanner;
+
+public class Main {
+
+    private static final String INPUT_FILE_NAME = "src/main/resources/input.txt";
+
+    public static void main(String... args) throws Exception {
+        System.out.printf("Total Number of Lines Using BufferedReader: %s%n", getTotalNumberOfLinesUsingBufferedReader(INPUT_FILE_NAME));
+        System.out.printf("Total Number of Lines Using LineNumberReader: %s%n", getTotalNumberOfLinesUsingLineNumberReader(INPUT_FILE_NAME));
+        System.out.printf("Total Number of Lines Using Scanner: %s%n", getTotalNumberOfLinesUsingScanner(INPUT_FILE_NAME));
+        System.out.printf("Total Number of Lines Using NIO Files: %s%n", getTotalNumberOfLinesUsingNIOFiles(INPUT_FILE_NAME));
+        System.out.printf("Total Number of Lines Using NIO FileChannel: %s%n", getTotalNumberOfLinesUsingNIOFileChannel(INPUT_FILE_NAME));
+        System.out.printf("Total Number of Lines Using Apache Commons IO: %s%n", getTotalNumberOfLinesUsingApacheCommonsIO(INPUT_FILE_NAME));
+        System.out.printf("Total Number of Lines Using NIO Google Guava: %s%n", getTotalNumberOfLinesUsingGoogleGuava(INPUT_FILE_NAME));
+    }
+}

core-java-modules/core-java-io/src/main/java/com/baeldung/files/NumberOfLineFinder.java

@@ -0,0 +1,112 @@
+package com.baeldung.files;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileReader;
+import java.io.IOException;
+import java.io.LineNumberReader;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+import java.nio.channels.FileChannel.MapMode;
+import java.nio.charset.Charset;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import java.nio.file.StandardOpenOption;
+import java.util.List;
+import java.util.Scanner;
+import java.util.stream.Stream;
+
+import org.apache.commons.io.FileUtils;
+import org.apache.commons.io.LineIterator;
+
+public class NumberOfLineFinder {
+
+    public static int getTotalNumberOfLinesUsingBufferedReader(String fileName) {
+        int lines = 0;
+        try (BufferedReader reader = new BufferedReader(new FileReader(fileName))) {
+            while (reader.readLine() != null) {
+                lines++;
+            }
+        } catch (IOException ioe) {
+            ioe.printStackTrace();
+        }
+        return lines;
+    }
+
+    public static int getTotalNumberOfLinesUsingLineNumberReader(String fileName) {
+        int lines = 0;
+        try (LineNumberReader reader = new LineNumberReader(new FileReader(fileName))) {
+            reader.skip(Integer.MAX_VALUE);
+            lines = reader.getLineNumber() + 1;
+        } catch (IOException ioe) {
+            ioe.printStackTrace();
+        }
+        return lines;
+    }
+
+    public static int getTotalNumberOfLinesUsingScanner(String fileName) {
+        int lines = 0;
+        try (Scanner scanner = new Scanner(new FileReader(fileName))) {
+            while (scanner.hasNextLine()) {
+                scanner.nextLine();
+                lines++;
+            }
+        } catch (IOException ioe) {
+            ioe.printStackTrace();
+        }
+        return lines;
+    }
+
+    public static int getTotalNumberOfLinesUsingNIOFiles(String fileName) {
+        int lines = 0;
+        try (Stream<String> fileStream = Files.lines(Paths.get(fileName))) {
+            lines = (int) fileStream.count();
+        } catch (IOException ioe) {
+            ioe.printStackTrace();
+        }
+        return lines;
+    }
+
+    public static int getTotalNumberOfLinesUsingNIOFileChannel(String fileName) {
+        int lines = 1;
+        try (FileChannel channel = FileChannel.open(Paths.get(fileName), StandardOpenOption.READ)) {
+            ByteBuffer byteBuffer = channel.map(MapMode.READ_ONLY, 0, channel.size());
+            while (byteBuffer.hasRemaining()) {
+                byte currentChar = byteBuffer.get();
+                if (currentChar == '\n') {
+                    lines++;
+                }
+            }
+        } catch (IOException ioe) {
+            ioe.printStackTrace();
+        }
+        return lines;
+    }
+
+    public static int getTotalNumberOfLinesUsingApacheCommonsIO(String fileName) {
+        int lines = 0;
+        try {
+            LineIterator lineIterator = FileUtils.lineIterator(new File(fileName));
+            while (lineIterator.hasNext()) {
+                lineIterator.nextLine();
+                lines++;
+            }
+        } catch (IOException ioe) {
+            ioe.printStackTrace();
+        }
+        return lines;
+    }
+
+    public static int getTotalNumberOfLinesUsingGoogleGuava(String fileName) {
+        int lines = 0;
+        try {
+            List<String> lineItems = com.google.common.io.Files.readLines(Paths.get(fileName)
+                .toFile(), Charset.defaultCharset());
+            lines = lineItems.size();
+        } catch (IOException ioe) {
+            ioe.printStackTrace();
+        }
+        return lines;
+    }
+
+}

core-java-modules/core-java-io/src/test/java/com/baeldung/file/NumberOfLineFinderUnitTest.java

@@ -0,0 +1,60 @@
+package com.baeldung.file;
+
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingApacheCommonsIO;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingBufferedReader;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingGoogleGuava;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingLineNumberReader;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingNIOFileChannel;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingNIOFiles;
+import static com.baeldung.files.NumberOfLineFinder.getTotalNumberOfLinesUsingScanner;
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class NumberOfLineFinderUnitTest {
+    private static final String INPUT_FILE_NAME = "src/main/resources/input.txt";
+    private static final int ACTUAL_LINE_COUNT = 45;
+
+    @Test
+    public void whenUsingBufferedReader_thenReturnTotalNumberOfLines() {
+        int lines = getTotalNumberOfLinesUsingBufferedReader(INPUT_FILE_NAME);
+        assertEquals(ACTUAL_LINE_COUNT, lines);
+    }
+
+    @Test
+    public void whenUsingLineNumberReader_thenReturnTotalNumberOfLines() {
+        int lines = getTotalNumberOfLinesUsingLineNumberReader(INPUT_FILE_NAME);
+        assertEquals(ACTUAL_LINE_COUNT, lines);
+    }
+
+    @Test
+    public void whenUsingScanner_thenReturnTotalNumberOfLines() {
+        int lines = getTotalNumberOfLinesUsingScanner(INPUT_FILE_NAME);
+        assertEquals(ACTUAL_LINE_COUNT, lines);
+    }
+
+    @Test
+    public void whenUsingNIOFiles_thenReturnTotalNumberOfLines() {
+        int lines = getTotalNumberOfLinesUsingNIOFiles(INPUT_FILE_NAME);
+        assertEquals(ACTUAL_LINE_COUNT, lines);
+    }
+
+    @Test
+    public void whenUsingNIOFileChannel_thenReturnTotalNumberOfLines() {
+        int lines = getTotalNumberOfLinesUsingNIOFileChannel(INPUT_FILE_NAME);
+        assertEquals(ACTUAL_LINE_COUNT, lines);
+    }
+
+    @Test
+    public void whenUsingApacheCommonsIO_thenReturnTotalNumberOfLines() {
+        int lines = getTotalNumberOfLinesUsingApacheCommonsIO(INPUT_FILE_NAME);
+        assertEquals(ACTUAL_LINE_COUNT, lines);
+    }
+
+    @Test
+    public void whenUsingGoogleGuava_thenReturnTotalNumberOfLines() {
+        int lines = getTotalNumberOfLinesUsingGoogleGuava(INPUT_FILE_NAME);
+        assertEquals(ACTUAL_LINE_COUNT, lines);
+    }
+
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/relationships/aggregation/Car.java

@@ -0,0 +1,9 @@
+package com.baeldung.relationships.aggregation;
+
+import java.util.List;
+
+public class Car {
+
+    private List<Wheel> wheels;
+    
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/relationships/aggregation/CarWithStaticInnerWheel.java

@@ -0,0 +1,13 @@
+package com.baeldung.relationships.aggregation;
+
+import java.util.List;
+
+public class CarWithStaticInnerWheel {
+
+    private List<Wheel> wheels;
+
+    public static class Wheel {
+
+    }
+
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/relationships/aggregation/Wheel.java

@@ -0,0 +1,7 @@
+package com.baeldung.relationships.aggregation;
+
+public class Wheel {
+
+    private Car car;
+    
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/relationships/association/Child.java

@@ -0,0 +1,7 @@
+package com.baeldung.relationships.association;
+
+public class Child {
+
+    private Mother mother;
+
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/relationships/association/Mother.java

@@ -0,0 +1,9 @@
+package com.baeldung.relationships.association;
+
+import java.util.List;
+
+public class Mother {
+
+    private List<Child> children;
+
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/relationships/composition/Building.java

@@ -0,0 +1,18 @@
+package com.baeldung.relationships.composition;
+
+import java.util.List;
+
+public class Building {
+
+    private String address;
+    private List<Room> rooms;
+    
+    public class Room {
+        
+        public String getBuildingAddress() {
+            return Building.this.address;
+        }
+        
+    }
+    
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/relationships/composition/BuildingWithDefinitionRoomInMethod.java

@@ -0,0 +1,28 @@
+package com.baeldung.relationships.composition;
+
+public class BuildingWithDefinitionRoomInMethod {
+
+    public Room createAnonymousRoom() {
+        return new Room() {
+            @Override
+            public void doInRoom() {}
+        };
+    }
+
+    public Room createInlineRoom() {
+        class InlineRoom implements Room {
+            @Override
+            public void doInRoom() {}
+        }
+        return new InlineRoom();
+    }
+    
+    public Room createLambdaRoom() {
+        return () -> {};
+    }
+
+    public interface Room {
+        void doInRoom();
+    }
+
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/relationships/university/Department.java

@@ -0,0 +1,9 @@
+package com.baeldung.relationships.university;
+
+import java.util.List;
+
+public class Department {
+
+    private List<Professor> professors;
+
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/relationships/university/Professor.java

@@ -0,0 +1,10 @@
+package com.baeldung.relationships.university;
+
+import java.util.List;
+
+public class Professor {
+
+    private List<Department> department;
+    private List<Professor> friends;
+    
+}

core-java-modules/core-java-lang-oop-2/src/main/java/com/baeldung/relationships/university/University.java

@@ -0,0 +1,9 @@
+package com.baeldung.relationships.university;
+
+import java.util.List;
+
+public class University {
+
+    private List<Department> department;
+    
+}

core-java-modules/core-java-security/src/main/java/com/baeldung/sasl/ClientCallbackHandler.java

@@ -0,0 +1,29 @@
+package com.baeldung.sasl;
+
+import java.io.IOException;
+
+import javax.security.auth.callback.Callback;
+import javax.security.auth.callback.CallbackHandler;
+import javax.security.auth.callback.NameCallback;
+import javax.security.auth.callback.PasswordCallback;
+import javax.security.auth.callback.UnsupportedCallbackException;
+import javax.security.sasl.RealmCallback;
+
+public class ClientCallbackHandler implements CallbackHandler {
+
+    @Override
+    public void handle(Callback[] cbs) throws IOException, UnsupportedCallbackException {
+        for (Callback cb : cbs) {
+            if (cb instanceof NameCallback) {
+                NameCallback nc = (NameCallback) cb;
+                nc.setName("username");
+            } else if (cb instanceof PasswordCallback) {
+                PasswordCallback pc = (PasswordCallback) cb;
+                pc.setPassword("password".toCharArray());
+            } else if (cb instanceof RealmCallback) {
+                RealmCallback rc = (RealmCallback) cb;
+                rc.setText("myServer");
+            }
+        }
+    }
+}

core-java-modules/core-java-security/src/main/java/com/baeldung/sasl/ServerCallbackHandler.java

@@ -0,0 +1,34 @@
+package com.baeldung.sasl;
+
+import java.io.IOException;
+
+import javax.security.auth.callback.Callback;
+import javax.security.auth.callback.CallbackHandler;
+import javax.security.auth.callback.NameCallback;
+import javax.security.auth.callback.PasswordCallback;
+import javax.security.auth.callback.UnsupportedCallbackException;
+import javax.security.sasl.AuthorizeCallback;
+import javax.security.sasl.RealmCallback;
+
+public class ServerCallbackHandler implements CallbackHandler {
+
+    @Override
+    public void handle(Callback[] cbs) throws IOException, UnsupportedCallbackException {
+        for (Callback cb : cbs) {
+            if (cb instanceof AuthorizeCallback) {
+                AuthorizeCallback ac = (AuthorizeCallback) cb;
+                ac.setAuthorized(true);
+            } else if (cb instanceof NameCallback) {
+                NameCallback nc = (NameCallback) cb;
+                nc.setName("username");
+
+            } else if (cb instanceof PasswordCallback) {
+                PasswordCallback pc = (PasswordCallback) cb;
+                pc.setPassword("password".toCharArray());
+            } else if (cb instanceof RealmCallback) {
+                RealmCallback rc = (RealmCallback) cb;
+                rc.setText("myServer");
+            }
+        }
+    }
+}

core-java-modules/core-java-security/src/test/java/com/baeldung/sasl/SaslUnitTest.java

@@ -0,0 +1,76 @@
+package com.baeldung.sasl;
+
+import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.nio.charset.StandardCharsets;
+import java.util.HashMap;
+import java.util.Map;
+
+import javax.security.sasl.Sasl;
+import javax.security.sasl.SaslClient;
+import javax.security.sasl.SaslException;
+import javax.security.sasl.SaslServer;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+public class SaslUnitTest {
+
+    private static final String MECHANISM = "DIGEST-MD5";
+    private static final String SERVER_NAME = "myServer";
+    private static final String PROTOCOL = "myProtocol";
+    private static final String AUTHORIZATION_ID = null;
+    private static final String QOP_LEVEL = "auth-conf";
+
+    private SaslServer saslServer;
+    private SaslClient saslClient;
+
+    @Before
+    public void setUp() throws SaslException {
+
+        ServerCallbackHandler serverHandler = new ServerCallbackHandler();
+        ClientCallbackHandler clientHandler = new ClientCallbackHandler();
+
+        Map<String, String> props = new HashMap<>();
+        props.put(Sasl.QOP, QOP_LEVEL);
+
+        saslServer = Sasl.createSaslServer(MECHANISM, PROTOCOL, SERVER_NAME, props, serverHandler);
+        saslClient = Sasl.createSaslClient(new String[] { MECHANISM }, AUTHORIZATION_ID, PROTOCOL, SERVER_NAME, props, clientHandler);
+
+    }
+
+    @Test
+    public void givenHandlers_whenStarted_thenAutenticationWorks() throws SaslException {
+
+        byte[] challenge;
+        byte[] response;
+
+        challenge = saslServer.evaluateResponse(new byte[0]);
+        response = saslClient.evaluateChallenge(challenge);
+
+        challenge = saslServer.evaluateResponse(response);
+        response = saslClient.evaluateChallenge(challenge);
+
+        assertTrue(saslServer.isComplete());
+        assertTrue(saslClient.isComplete());
+
+        String qop = (String) saslClient.getNegotiatedProperty(Sasl.QOP);
+        assertEquals("auth-conf", qop);
+
+        byte[] outgoing = "Baeldung".getBytes();
+        byte[] secureOutgoing = saslClient.wrap(outgoing, 0, outgoing.length);
+
+        byte[] secureIncoming = secureOutgoing;
+        byte[] incoming = saslServer.unwrap(secureIncoming, 0, secureIncoming.length);
+        assertEquals("Baeldung", new String(incoming, StandardCharsets.UTF_8));
+    }
+
+    @After
+    public void tearDown() throws SaslException {
+        saslClient.dispose();
+        saslServer.dispose();
+    }
+
+}

core-java-modules/multimodulemavenproject/README.md

@@ -0,0 +1,3 @@
+## Relevant Articles
+
+- [Multi-Module Maven Application with Java Modules](https://www.baeldung.com/maven-multi-module-project-java-jpms)

data-structures/src/main/java/com/baeldung/graph/Graph.java

@@ -0,0 +1,72 @@
+package com.baeldung.graph;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Stack;
+
+public class Graph {
+
+    private Map<Integer, List<Integer>> adjVertices;
+
+    public Graph() {
+        this.adjVertices = new HashMap<Integer, List<Integer>>();
+    }
+
+    public void addVertex(int vertex) {
+        adjVertices.putIfAbsent(vertex, new ArrayList<>());
+    }
+
+    public void addEdge(int src, int dest) {
+        adjVertices.get(src).add(dest);
+    }
+
+    public void dfsWithoutRecursion(int start) {
+        Stack<Integer> stack = new Stack<Integer>();
+        boolean[] isVisited = new boolean[adjVertices.size()];
+        stack.push(start);
+        while (!stack.isEmpty()) {
+            int current = stack.pop();
+            isVisited[current] = true;
+            System.out.print(" " + current);
+            for (int dest : adjVertices.get(current)) {
+                if (!isVisited[dest])
+                    stack.push(dest);
+            }
+        }
+    }
+
+    public void dfs(int start) {
+        boolean[] isVisited = new boolean[adjVertices.size()];
+        dfsRecursive(start, isVisited);
+    }
+
+    private void dfsRecursive(int current, boolean[] isVisited) {
+        isVisited[current] = true;
+        System.out.print(" " + current);
+        for (int dest : adjVertices.get(current)) {
+            if (!isVisited[dest])
+                dfsRecursive(dest, isVisited);
+        }
+    }
+
+    public void topologicalSort(int start) {
+        Stack<Integer> result = new Stack<Integer>();
+        boolean[] isVisited = new boolean[adjVertices.size()];
+        topologicalSortRecursive(start, isVisited, result);
+        while (!result.isEmpty()) {
+            System.out.print(" " + result.pop());
+        }
+    }
+
+    private void topologicalSortRecursive(int current, boolean[] isVisited, Stack<Integer> result) {
+        isVisited[current] = true;
+        for (int dest : adjVertices.get(current)) {
+            if (!isVisited[dest])
+                topologicalSortRecursive(dest, isVisited, result);
+        }
+        result.push(current);
+    }
+
+}

data-structures/src/main/java/com/baeldung/tree/BinaryTree.java

@@ -2,6 +2,7 @@ package com.baeldung.tree;
 
 import java.util.LinkedList;
 import java.util.Queue;
+import java.util.Stack;
 
 public class BinaryTree {
 
@@ -147,6 +148,68 @@ public class BinaryTree {
         }
     }
 
+    
+    public void traverseInOrderWithoutRecursion() {
+        Stack<Node> stack = new Stack<Node>();
+        Node current = root;
+        stack.push(root);
+        while(! stack.isEmpty()) {
+            while(current.left != null) {
+                current = current.left;                
+                stack.push(current);                
+            }
+            current = stack.pop();
+            System.out.print(" " + current.value);
+            if(current.right != null) {
+                current = current.right;                
+                stack.push(current);
+            }
+        }
+    }
+    
+    public void traversePreOrderWithoutRecursion() {
+        Stack<Node> stack = new Stack<Node>();
+        Node current = root;
+        stack.push(root);
+        while(! stack.isEmpty()) {
+            current = stack.pop();
+            System.out.print(" " + current.value);
+            
+            if(current.right != null)
+                stack.push(current.right);
+                
+            if(current.left != null)
+                stack.push(current.left);
+        }        
+    }
+    
+    public void traversePostOrderWithoutRecursion() {
+        Stack<Node> stack = new Stack<Node>();
+        Node prev = root;
+        Node current = root;
+        stack.push(root);
+
+        while (!stack.isEmpty()) {
+            current = stack.peek();
+            boolean hasChild = (current.left != null || current.right != null);
+            boolean isPrevLastChild = (prev == current.right || (prev == current.left && current.right == null));
+
+            if (!hasChild || isPrevLastChild) {
+                current = stack.pop();
+                System.out.print(" " + current.value);
+                prev = current;
+            } else {
+                if (current.right != null) {
+                    stack.push(current.right);
+                }
+                if (current.left != null) {
+                    stack.push(current.left);
+                }
+            }
+        }   
+    }    
+    
+    
     class Node {
         int value;
         Node left;

data-structures/src/test/java/com/baeldung/graph/GraphUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.graph;
+
+import org.junit.Test;
+
+public class GraphUnitTest {
+
+    @Test
+    public void givenDirectedGraph_whenDFS_thenPrintAllValues() {
+        Graph graph = createDirectedGraph();
+        graph.dfs(0);
+        System.out.println();
+        graph.dfsWithoutRecursion(0);
+    }
+
+    @Test
+    public void givenDirectedGraph_whenGetTopologicalSort_thenPrintValuesSorted() {
+        Graph graph = createDirectedGraph();
+        graph.topologicalSort(0);
+    }
+
+    private Graph createDirectedGraph() {
+        Graph graph = new Graph();
+        graph.addVertex(0);
+        graph.addVertex(1);
+        graph.addVertex(2);
+        graph.addVertex(3);
+        graph.addVertex(4);
+        graph.addVertex(5);
+        graph.addEdge(0, 1);
+        graph.addEdge(0, 2);
+        graph.addEdge(1, 3);
+        graph.addEdge(2, 3);
+        graph.addEdge(3, 4);
+        graph.addEdge(4, 5);
+        return graph;
+    }
+}

data-structures/src/test/java/com/baeldung/tree/BinaryTreeUnitTest.java

@@ -87,6 +87,8 @@ public class BinaryTreeUnitTest {
         BinaryTree bt = createBinaryTree();
 
         bt.traverseInOrder(bt.root);
+        System.out.println();
+        bt.traverseInOrderWithoutRecursion();
     }
 
     @Test
@@ -95,6 +97,8 @@ public class BinaryTreeUnitTest {
         BinaryTree bt = createBinaryTree();
 
         bt.traversePreOrder(bt.root);
+        System.out.println();
+        bt.traversePreOrderWithoutRecursion();
     }
 
     @Test
@@ -103,6 +107,8 @@ public class BinaryTreeUnitTest {
         BinaryTree bt = createBinaryTree();
 
         bt.traversePostOrder(bt.root);
+        System.out.println();
+        bt.traversePostOrderWithoutRecursion();
     }
 
     @Test

java-numbers-2/src/main/java/com/baeldung/binarynumbers/BinaryNumbers.java

@@ -0,0 +1,148 @@
+package com.baeldung.binarynumbers;
+
+public class BinaryNumbers {
+
+    /**
+     * This method takes a decimal number and convert it into a binary number.
+     * example:- input:10, output:1010
+     *
+     * @param decimalNumber
+     * @return binary number
+     */
+    public Integer convertDecimalToBinary(Integer decimalNumber) {
+
+        if (decimalNumber == 0) {
+            return decimalNumber;
+        }
+
+        StringBuilder binaryNumber = new StringBuilder();
+
+        while (decimalNumber > 0) {
+
+            int remainder = decimalNumber % 2;
+            int result = decimalNumber / 2;
+
+            binaryNumber.append(remainder);
+            decimalNumber = result;
+        }
+
+        binaryNumber = binaryNumber.reverse();
+
+        return Integer.valueOf(binaryNumber.toString());
+    }
+
+    /**
+     * This method takes a binary number and convert it into a decimal number.
+     * example:- input:101, output:5
+     *
+     * @param binary number
+     * @return decimal Number
+     */
+    public Integer convertBinaryToDecimal(Integer binaryNumber) {
+
+        Integer result = 0;
+        Integer base = 1;
+
+        while (binaryNumber > 0) {
+
+            int lastDigit = binaryNumber % 10;
+            binaryNumber = binaryNumber / 10;
+
+            result += lastDigit * base;
+
+            base = base * 2;
+        }
+        return result;
+    }
+
+    /**
+     * This method accepts two binary numbers and returns sum of input numbers.
+     * Example:- firstNum: 101, secondNum: 100, output: 1001
+     *
+     * @param firstNum
+     * @param secondNum
+     * @return addition of input numbers
+     */
+    public Integer addBinaryNumber(Integer firstNum, Integer secondNum) {
+
+        StringBuilder output = new StringBuilder();
+
+        int carry = 0;
+        int temp;
+
+        while (firstNum != 0 || secondNum != 0) {
+
+            temp = (firstNum % 10 + secondNum % 10 + carry) % 2;
+            output.append(temp);
+
+            carry = (firstNum % 10 + secondNum % 10 + carry) / 2;
+
+            firstNum = firstNum / 10;
+            secondNum = secondNum / 10;
+        }
+
+        if (carry != 0) {
+            output.append(carry);
+        }
+
+        return Integer.valueOf(output.reverse()
+            .toString());
+    }
+
+    /**
+    * This method takes two binary number as input and subtract second number from the first number.
+    * example:- firstNum: 1000, secondNum: 11, output: 101
+    * @param firstNum
+    * @param secondNum
+    * @return Result of subtraction of secondNum from first
+    */
+    public Integer substractBinaryNumber(Integer firstNum, Integer secondNum) {
+
+        int onesComplement = Integer.valueOf(getOnesComplement(secondNum));
+
+        StringBuilder output = new StringBuilder();
+
+        int carry = 0;
+        int temp;
+
+        while (firstNum != 0 || onesComplement != 0) {
+
+            temp = (firstNum % 10 + onesComplement % 10 + carry) % 2;
+            output.append(temp);
+
+            carry = (firstNum % 10 + onesComplement % 10 + carry) / 2;
+
+            firstNum = firstNum / 10;
+            onesComplement = onesComplement / 10;
+        }
+
+        String additionOfFirstNumAndOnesComplement = output.reverse()
+            .toString();
+
+        if (carry == 1) {
+            return addBinaryNumber(Integer.valueOf(additionOfFirstNumAndOnesComplement), carry);
+        } else {
+            return getOnesComplement(Integer.valueOf(additionOfFirstNumAndOnesComplement));
+        }
+
+    }
+
+    public Integer getOnesComplement(Integer num) {
+
+        StringBuilder onesComplement = new StringBuilder();
+
+        while (num > 0) {
+            int lastDigit = num % 10;
+            if (lastDigit == 0) {
+                onesComplement.append(1);
+            } else {
+                onesComplement.append(0);
+            }
+            num = num / 10;
+        }
+
+        return Integer.valueOf(onesComplement.reverse()
+            .toString());
+    }
+
+}

java-numbers-2/src/test/java/com/baeldung/binarynumbers/BinaryNumbersUnitTest.java

@@ -0,0 +1,73 @@
+package com.baeldung.binarynumbers;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+public class BinaryNumbersUnitTest {
+
+    private BinaryNumbers binaryNumbers = new BinaryNumbers();
+
+    @Test
+    public void given_decimalNumber_then_returnBinaryNumber() {
+        assertEquals(Integer.valueOf(1000), binaryNumbers.convertDecimalToBinary(8));
+        assertEquals(Integer.valueOf(10100), binaryNumbers.convertDecimalToBinary(20));
+    }
+
+    @Test
+    public void given_decimalNumber_then_convertToBinaryNumber() {
+        assertEquals("1000", Integer.toBinaryString(8));
+        assertEquals("10100", Integer.toBinaryString(20));
+    }
+
+    @Test
+    public void given_binaryNumber_then_ConvertToDecimalNumber() {
+        assertEquals(8, Integer.parseInt("1000", 2));
+        assertEquals(20, Integer.parseInt("10100", 2));
+    }
+
+    @Test
+    public void given_binaryNumber_then_returnDecimalNumber() {
+        assertEquals(Integer.valueOf(8), binaryNumbers.convertBinaryToDecimal(1000));
+        assertEquals(Integer.valueOf(20), binaryNumbers.convertBinaryToDecimal(10100));
+    }
+
+    @Test
+    public void given_twoBinaryNumber_then_returnAddition() {
+        // adding 4 and 10
+        assertEquals(Integer.valueOf(1110), binaryNumbers.addBinaryNumber(100, 1010));
+
+        // adding 26 and 14
+        assertEquals(Integer.valueOf(101000), binaryNumbers.addBinaryNumber(11010, 1110));
+    }
+
+    @Test
+    public void given_twoBinaryNumber_then_returnSubtraction() {
+        // subtracting 16 from 25
+        assertEquals(Integer.valueOf(1001), binaryNumbers.substractBinaryNumber(11001, 10000));
+
+        // subtracting 29 from 16, the output here is negative
+        assertEquals(Integer.valueOf(1101), binaryNumbers.substractBinaryNumber(10000, 11101));
+    }
+
+    @Test
+    public void given_binaryLiteral_thenReturnDecimalValue() {
+
+        byte five = 0b101;
+        assertEquals((byte) 5, five);
+
+        short three = 0b11;
+        assertEquals((short) 3, three);
+
+        int nine = 0B1001;
+        assertEquals(9, nine);
+
+        long twentyNine = 0B11101;
+        assertEquals(29, twentyNine);
+
+        int minusThirtySeven = -0B100101;
+        assertEquals(-37, minusThirtySeven);
+
+    }
+
+}

java-strings-2/src/test/java/com/baeldung/string/changecase/ToLowerCaseUnitTest.java

@@ -0,0 +1,29 @@
+package com.baeldung.string.changecase;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.Locale;
+
+import org.junit.Test;
+
+public class ToLowerCaseUnitTest {
+
+    private static final Locale TURKISH = new Locale("tr");
+    private String name = "John Doe";
+    private String foreignUppercase = "\u0049";
+
+    @Test
+    public void givenMixedCaseString_WhenToLowerCase_ThenResultIsLowerCase() {
+        assertEquals("john doe", name.toLowerCase());
+    }
+
+    @Test
+    public void givenForeignString_WhenToLowerCaseWithoutLocale_ThenResultIsLowerCase() {
+        assertEquals("\u0069", foreignUppercase.toLowerCase());
+    }
+
+    @Test
+    public void givenForeignString_WhenToLowerCaseWithLocale_ThenResultIsLowerCase() {
+        assertEquals("\u0131", foreignUppercase.toLowerCase(TURKISH));
+    }
+}

java-strings-2/src/test/java/com/baeldung/string/changecase/ToUpperCaseUnitTest.java

@@ -0,0 +1,29 @@
+package com.baeldung.string.changecase;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.Locale;
+
+import org.junit.Test;
+
+public class ToUpperCaseUnitTest {
+
+    private static final Locale TURKISH = new Locale("tr");
+    private String name = "John Doe";
+    private String foreignLowercase = "\u0069";
+
+    @Test
+    public void givenMixedCaseString_WhenToUpperCase_ThenResultIsUpperCase() {
+        assertEquals("JOHN DOE", name.toUpperCase());
+    }
+
+    @Test
+    public void givenForeignString_WhenToUpperCaseWithoutLocale_ThenResultIsUpperCase() {
+        assertEquals("\u0049", foreignLowercase.toUpperCase());
+    }
+
+    @Test
+    public void givenForeignString_WhenToUpperCaseWithLocale_ThenResultIsUpperCase() {
+        assertEquals("\u0130", foreignLowercase.toUpperCase(TURKISH));
+    }
+}

java-strings-2/src/test/java/com/baeldung/string/todouble/StringToDoubleConversionUnitTest.java

@@ -0,0 +1,56 @@
+package com.baeldung.string.todouble;
+
+import static org.junit.Assert.assertEquals;
+
+import java.text.DecimalFormat;
+import java.text.ParseException;
+
+import org.junit.Test;
+
+public class StringToDoubleConversionUnitTest {
+
+    @Test
+    public void givenValidString_WhenParseDouble_ThenResultIsPrimitiveDouble() {
+        assertEquals(1.23, Double.parseDouble("1.23"), 0.000001);
+    }
+    
+    @Test(expected = NullPointerException.class)
+    public void givenNullString_WhenParseDouble_ThenNullPointerExceptionIsThrown() {
+        Double.parseDouble(null);
+    }
+    
+    @Test(expected = NumberFormatException.class)
+    public void givenInalidString_WhenParseDouble_ThenNumberFormatExceptionIsThrown() {
+        Double.parseDouble("&");
+    }
+    
+    @Test
+    public void givenValidString_WhenValueOf_ThenResultIsPrimitiveDouble() {
+        assertEquals(1.23, Double.valueOf("1.23"), 0.000001);
+    }
+    
+    @Test(expected = NullPointerException.class)
+    public void givenNullString_WhenValueOf_ThenNullPointerExceptionIsThrown() {
+        Double.valueOf(null);
+    }
+    
+    @Test(expected = NumberFormatException.class)
+    public void givenInalidString_WhenValueOf_ThenNumberFormatExceptionIsThrown() {
+        Double.valueOf("&");
+    }
+    
+    @Test
+    public void givenValidString_WhenDecimalFormat_ThenResultIsValidDouble() throws ParseException {
+        assertEquals(1.23, new DecimalFormat("#").parse("1.23").doubleValue(), 0.000001);
+    }
+    
+    @Test(expected = NullPointerException.class)
+    public void givenNullString_WhenDecimalFormat_ThenNullPointerExceptionIsThrown() throws ParseException {
+        new DecimalFormat("#").parse(null);
+    }
+    
+    @Test(expected = ParseException.class)
+    public void givenInvalidString_WhenDecimalFormat_ThenParseExceptionIsThrown() throws ParseException {
+        new DecimalFormat("#").parse("&");
+    }
+}

javaxval/src/main/java/org/baeldung/javabeanconstraints/bigdecimal/Invoice.java

@@ -0,0 +1,19 @@
+package org.baeldung.javabeanconstraints.bigdecimal;
+
+import java.math.BigDecimal;
+
+import javax.validation.constraints.DecimalMin;
+import javax.validation.constraints.Digits;
+
+public class Invoice {
+	
+	@DecimalMin(value = "0.0", inclusive = false)
+	@Digits(integer=3, fraction=2)
+    private BigDecimal price;
+    private String description;
+    
+	public Invoice(BigDecimal price, String description) {
+		this.price = price;
+		this.description = description;
+	}
+}

javaxval/src/test/java/org/baeldung/javabeanconstraints/bigdecimal/InvoiceUnitTest.java

@@ -0,0 +1,62 @@
+package org.baeldung.javabeanconstraints.bigdecimal;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.math.BigDecimal;
+import java.util.Set;
+
+import javax.validation.ConstraintViolation;
+import javax.validation.Validation;
+import javax.validation.Validator;
+
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class InvoiceUnitTest {
+	
+	private static Validator validator;
+
+    @BeforeClass
+    public static void setupValidatorInstance() {
+        validator = Validation.buildDefaultValidatorFactory().getValidator();
+    }
+    
+    @Test
+    public void whenPriceIntegerDigitLessThanThreeWithDecimalValue_thenShouldGiveConstraintViolations() {
+    	Invoice invoice = new Invoice(new BigDecimal(10.21), "Book purchased");
+        Set<ConstraintViolation<Invoice>> violations = validator.validate(invoice);
+        assertThat(violations.size()).isEqualTo(1);
+        violations.forEach(action-> assertThat(action.getMessage()).isEqualTo("numeric value out of bounds (<3 digits>.<2 digits> expected)"));
+    }
+    
+    @Test
+    public void whenPriceIntegerDigitLessThanThreeWithIntegerValue_thenShouldNotGiveConstraintViolations() {
+    	Invoice invoice = new Invoice(new BigDecimal(10), "Book purchased");
+        Set<ConstraintViolation<Invoice>> violations = validator.validate(invoice);
+        assertThat(violations.size()).isEqualTo(0);
+    }
+    
+    @Test
+    public void whenPriceIntegerDigitGreaterThanThree_thenShouldGiveConstraintViolations() {
+    	Invoice invoice = new Invoice(new BigDecimal(1021.21), "Book purchased");
+        Set<ConstraintViolation<Invoice>> violations = validator.validate(invoice);
+        assertThat(violations.size()).isEqualTo(1);
+        violations.forEach(action-> assertThat(action.getMessage()).isEqualTo("numeric value out of bounds (<3 digits>.<2 digits> expected)"));
+    }
+    
+    @Test
+    public void whenPriceIsZero_thenShouldGiveConstraintViolations() {
+    	Invoice invoice = new Invoice(new BigDecimal(000.00), "Book purchased");
+        Set<ConstraintViolation<Invoice>> violations = validator.validate(invoice);
+        assertThat(violations.size()).isEqualTo(1);
+        violations.forEach(action-> assertThat(action.getMessage()).isEqualTo("must be greater than 0.0"));
+    }
+    
+    @Test
+    public void whenPriceIsGreaterThanZero_thenShouldNotGiveConstraintViolations() {
+    	Invoice invoice = new Invoice(new BigDecimal(100.50), "Book purchased");
+        Set<ConstraintViolation<Invoice>> violations = validator.validate(invoice);
+        assertThat(violations.size()).isEqualTo(0);
+    }
+
+}

jhipster/jhipster-microservice/README.md

@@ -0,0 +1,3 @@
+## Relevant Articles
+
+- [JHipster with a Microservice Architecture](https://www.baeldung.com/jhipster-microservices)

jhipster/jhipster-monolithic/README.md

@@ -1,4 +1,6 @@
-### Relevant articles
+## Relevant Articles
+
+- [Intro to JHipster](https://www.baeldung.com/jhipster)
 
 
 # baeldung

jhipster/jhipster-uaa/README.md

@@ -0,0 +1,3 @@
+## Relevant Articles
+
+- [Building a Basic UAA-Secured JHipster Microservice](https://www.baeldung.com/jhipster-uaa-secured-micro-service)

oauth2-framework-impl/oauth2-authorization-server/src/main/java/com/baeldung/oauth2/authorization/server/api/AuthorizationEndpoint.java

@@ -121,8 +121,8 @@ public class AuthorizationEndpoint {
         String redirectUri = originalParams.getFirst("resolved_redirect_uri");
         StringBuilder sb = new StringBuilder(redirectUri);
 
-        String approbationStatus = params.getFirst("approbation_status");
+        String approvalStatus = params.getFirst("approval_status");
-        if ("NO".equals(approbationStatus)) {
+        if ("NO".equals(approvalStatus)) {
             URI location = UriBuilder.fromUri(sb.toString())
                     .queryParam("error", "User doesn't approved the request.")
                     .queryParam("error_description", "User doesn't approved the request.")

oauth2-framework-impl/oauth2-authorization-server/src/main/java/com/baeldung/oauth2/authorization/server/api/TokenEndpoint.java

@@ -15,15 +15,14 @@ import javax.ws.rs.core.HttpHeaders;
 import javax.ws.rs.core.MediaType;
 import javax.ws.rs.core.MultivaluedMap;
 import javax.ws.rs.core.Response;
+import java.util.Arrays;
 import java.util.Base64;
-import java.util.Collections;
 import java.util.List;
-import java.util.Objects;
 
 @Path("token")
 public class TokenEndpoint {
 
-    List<String> supportedGrantTypes = Collections.singletonList("authorization_code");
+    List<String> supportedGrantTypes = Arrays.asList("authorization_code", "refresh_token");
 
     @Inject
     private AppDataRepository appDataRepository;
@@ -39,36 +38,36 @@ public class TokenEndpoint {
 
         //Check grant_type params
         String grantType = params.getFirst("grant_type");
-        Objects.requireNonNull(grantType, "grant_type params is required");
+        if (grantType == null || grantType.isEmpty())
-        if (!supportedGrantTypes.contains(grantType)) {
+            return responseError("Invalid_request", "grant_type is required", Response.Status.BAD_REQUEST);
-            JsonObject error = Json.createObjectBuilder()
-                    .add("error", "unsupported_grant_type")
-                    .add("error_description", "grant type should be one of :" + supportedGrantTypes)
-                    .build();
-            return Response.status(Response.Status.BAD_REQUEST)
-                    .entity(error).build();
 
+        if (!supportedGrantTypes.contains(grantType)) {
+            return responseError("unsupported_grant_type", "grant_type should be one of :" + supportedGrantTypes, Response.Status.BAD_REQUEST);
         }
 
         //Client Authentication
         String[] clientCredentials = extract(authHeader);
+        if (clientCredentials.length != 2) {
+            return responseError("Invalid_request", "Bad Credentials client_id/client_secret", Response.Status.BAD_REQUEST);
+        }
         String clientId = clientCredentials[0];
-        String clientSecret = clientCredentials[1];
         Client client = appDataRepository.getClient(clientId);
-        if (client == null || clientSecret == null || !clientSecret.equals(client.getClientSecret())) {
+        if (client == null) {
-            JsonObject error = Json.createObjectBuilder()
+            return responseError("Invalid_request", "Invalid client_id", Response.Status.BAD_REQUEST);
-                    .add("error", "invalid_client")
+        }
-                    .build();
+        String clientSecret = clientCredentials[1];
-            return Response.status(Response.Status.UNAUTHORIZED)
+        if (!clientSecret.equals(client.getClientSecret())) {
-                    .entity(error).build();
+            return responseError("Invalid_request", "Invalid client_secret", Response.Status.UNAUTHORIZED);
         }
 
         AuthorizationGrantTypeHandler authorizationGrantTypeHandler = authorizationGrantTypeHandlers.select(NamedLiteral.of(grantType)).get();
         JsonObject tokenResponse = null;
         try {
             tokenResponse = authorizationGrantTypeHandler.createAccessToken(clientId, params);
+        } catch (WebApplicationException e) {
+            return e.getResponse();
         } catch (Exception e) {
-            e.printStackTrace();
+            return responseError("Invalid_request", "Can't get token", Response.Status.INTERNAL_SERVER_ERROR);
         }
 
         return Response.ok(tokenResponse)
@@ -81,6 +80,15 @@ public class TokenEndpoint {
         if (authHeader != null && authHeader.startsWith("Basic ")) {
             return new String(Base64.getDecoder().decode(authHeader.substring(6))).split(":");
         }
-        return null;
+        return new String[]{};
+    }
+
+    private Response responseError(String error, String errorDescription, Response.Status status) {
+        JsonObject errorResponse = Json.createObjectBuilder()
+                .add("error", error)
+                .add("error_description", errorDescription)
+                .build();
+        return Response.status(status)
+                .entity(errorResponse).build();
     }
 }

oauth2-framework-impl/oauth2-authorization-server/src/main/java/com/baeldung/oauth2/authorization/server/handler/AbstractGrantTypeHandler.java

@@ -0,0 +1,87 @@
+package com.baeldung.oauth2.authorization.server.handler;
+
+import com.baeldung.oauth2.authorization.server.PEMKeyUtils;
+import com.nimbusds.jose.*;
+import com.nimbusds.jose.crypto.RSASSASigner;
+import com.nimbusds.jose.crypto.RSASSAVerifier;
+import com.nimbusds.jose.jwk.JWK;
+import com.nimbusds.jose.jwk.RSAKey;
+import com.nimbusds.jwt.JWTClaimsSet;
+import com.nimbusds.jwt.SignedJWT;
+import org.eclipse.microprofile.config.Config;
+
+import javax.inject.Inject;
+import java.time.Instant;
+import java.time.temporal.ChronoUnit;
+import java.util.Arrays;
+import java.util.Date;
+import java.util.UUID;
+
+public abstract class AbstractGrantTypeHandler implements AuthorizationGrantTypeHandler {
+
+    //Always RSA 256, but could be parametrized
+    protected JWSHeader jwsHeader = new JWSHeader.Builder(JWSAlgorithm.RS256).type(JOSEObjectType.JWT).build();
+
+    @Inject
+    protected Config config;
+
+    //30 min
+    protected Long expiresInMin = 30L;
+
+    protected JWSVerifier getJWSVerifier() throws Exception {
+        String verificationkey = config.getValue("verificationkey", String.class);
+        String pemEncodedRSAPublicKey = PEMKeyUtils.readKeyAsString(verificationkey);
+        RSAKey rsaPublicKey = (RSAKey) JWK.parseFromPEMEncodedObjects(pemEncodedRSAPublicKey);
+        return new RSASSAVerifier(rsaPublicKey);
+    }
+
+    protected JWSSigner getJwsSigner() throws Exception {
+        String signingkey = config.getValue("signingkey", String.class);
+        String pemEncodedRSAPrivateKey = PEMKeyUtils.readKeyAsString(signingkey);
+        RSAKey rsaKey = (RSAKey) JWK.parseFromPEMEncodedObjects(pemEncodedRSAPrivateKey);
+        return new RSASSASigner(rsaKey.toRSAPrivateKey());
+    }
+
+    protected String getAccessToken(String clientId, String subject, String approvedScope) throws Exception {
+        //4. Signing
+        JWSSigner jwsSigner = getJwsSigner();
+
+        Instant now = Instant.now();
+        //Long expiresInMin = 30L;
+        Date expirationTime = Date.from(now.plus(expiresInMin, ChronoUnit.MINUTES));
+
+        //3. JWT Payload or claims
+        JWTClaimsSet jwtClaims = new JWTClaimsSet.Builder()
+                .issuer("http://localhost:9080")
+                .subject(subject)
+                .claim("upn", subject)
+                .claim("client_id", clientId)
+                .audience("http://localhost:9280")
+                .claim("scope", approvedScope)
+                .claim("groups", Arrays.asList(approvedScope.split(" ")))
+                .expirationTime(expirationTime) // expires in 30 minutes
+                .notBeforeTime(Date.from(now))
+                .issueTime(Date.from(now))
+                .jwtID(UUID.randomUUID().toString())
+                .build();
+        SignedJWT signedJWT = new SignedJWT(jwsHeader, jwtClaims);
+        signedJWT.sign(jwsSigner);
+        return signedJWT.serialize();
+    }
+
+    protected String getRefreshToken(String clientId, String subject, String approvedScope) throws Exception {
+        JWSSigner jwsSigner = getJwsSigner();
+        Instant now = Instant.now();
+        //6.Build refresh token
+        JWTClaimsSet refreshTokenClaims = new JWTClaimsSet.Builder()
+                .subject(subject)
+                .claim("client_id", clientId)
+                .claim("scope", approvedScope)
+                //refresh token for 1 day.
+                .expirationTime(Date.from(now.plus(1, ChronoUnit.DAYS)))
+                .build();
+        SignedJWT signedRefreshToken = new SignedJWT(jwsHeader, refreshTokenClaims);
+        signedRefreshToken.sign(jwsSigner);
+        return signedRefreshToken.serialize();
+    }
+}

oauth2-framework-impl/oauth2-authorization-server/src/main/java/com/baeldung/oauth2/authorization/server/handler/AuthorizationCodeGrantTypeHandler.java

@@ -1,18 +1,7 @@
 package com.baeldung.oauth2.authorization.server.handler;
 
-import com.baeldung.oauth2.authorization.server.PEMKeyUtils;
 import com.baeldung.oauth2.authorization.server.model.AuthorizationCode;
-import com.nimbusds.jose.JOSEObjectType;
-import com.nimbusds.jose.JWSAlgorithm;
-import com.nimbusds.jose.JWSHeader;
-import com.nimbusds.jose.crypto.RSASSASigner;
-import com.nimbusds.jose.jwk.JWK;
-import com.nimbusds.jose.jwk.RSAKey;
-import com.nimbusds.jwt.JWTClaimsSet;
-import com.nimbusds.jwt.SignedJWT;
-import org.eclipse.microprofile.config.Config;
 
-import javax.inject.Inject;
 import javax.inject.Named;
 import javax.json.Json;
 import javax.json.JsonObject;
@@ -20,22 +9,14 @@ import javax.persistence.EntityManager;
 import javax.persistence.PersistenceContext;
 import javax.ws.rs.WebApplicationException;
 import javax.ws.rs.core.MultivaluedMap;
-import java.time.Instant;
 import java.time.LocalDateTime;
-import java.time.temporal.ChronoUnit;
-import java.util.Arrays;
-import java.util.Date;
-import java.util.UUID;
 
 @Named("authorization_code")
-public class AuthorizationCodeGrantTypeHandler implements AuthorizationGrantTypeHandler {
+public class AuthorizationCodeGrantTypeHandler extends AbstractGrantTypeHandler {
 
     @PersistenceContext
     private EntityManager entityManager;
 
-    @Inject
-    private Config config;
-
     @Override
     public JsonObject createAccessToken(String clientId, MultivaluedMap<String, String> params) throws Exception {
         //1. code is required
@@ -58,42 +39,16 @@ public class AuthorizationCodeGrantTypeHandler implements AuthorizationGrantType
             throw new WebApplicationException("invalid_grant");
         }
 
-        //JWT Header
-        JWSHeader jwsHeader = new JWSHeader.Builder(JWSAlgorithm.RS256).type(JOSEObjectType.JWT).build();
-
-        Instant now = Instant.now();
-        Long expiresInMin = 30L;
-        Date expiresIn = Date.from(now.plus(expiresInMin, ChronoUnit.MINUTES));
-
         //3. JWT Payload or claims
-        JWTClaimsSet jwtClaims = new JWTClaimsSet.Builder()
+        String accessToken = getAccessToken(clientId, authorizationCode.getUserId(), authorizationCode.getApprovedScopes());
-                .issuer("http://localhost:9080")
+        String refreshToken = getRefreshToken(clientId, authorizationCode.getUserId(), authorizationCode.getApprovedScopes());
-                .subject(authorizationCode.getUserId())
-                .claim("upn", authorizationCode.getUserId())
-                .audience("http://localhost:9280")
-                .claim("scope", authorizationCode.getApprovedScopes())
-                .claim("groups", Arrays.asList(authorizationCode.getApprovedScopes().split(" ")))
-                .expirationTime(expiresIn) // expires in 30 minutes
-                .notBeforeTime(Date.from(now))
-                .issueTime(Date.from(now))
-                .jwtID(UUID.randomUUID().toString())
-                .build();
-        SignedJWT signedJWT = new SignedJWT(jwsHeader, jwtClaims);
-
-        //4. Signing
-        String signingkey = config.getValue("signingkey", String.class);
-        String pemEncodedRSAPrivateKey = PEMKeyUtils.readKeyAsString(signingkey);
-        RSAKey rsaKey = (RSAKey) JWK.parseFromPEMEncodedObjects(pemEncodedRSAPrivateKey);
-        signedJWT.sign(new RSASSASigner(rsaKey.toRSAPrivateKey()));
-
-        //5. Finally the JWT access token
-        String accessToken = signedJWT.serialize();
 
         return Json.createObjectBuilder()
                 .add("token_type", "Bearer")
                 .add("access_token", accessToken)
                 .add("expires_in", expiresInMin * 60)
                 .add("scope", authorizationCode.getApprovedScopes())
+                .add("refresh_token", refreshToken)
                 .build();
     }
 }

oauth2-framework-impl/oauth2-authorization-server/src/main/java/com/baeldung/oauth2/authorization/server/handler/RefreshTokenGrantTypeHandler.java

@@ -0,0 +1,72 @@
+package com.baeldung.oauth2.authorization.server.handler;
+
+import com.nimbusds.jose.JWSVerifier;
+import com.nimbusds.jwt.SignedJWT;
+
+import javax.inject.Named;
+import javax.json.Json;
+import javax.json.JsonObject;
+import javax.ws.rs.WebApplicationException;
+import javax.ws.rs.core.MultivaluedMap;
+import javax.ws.rs.core.Response;
+import java.util.Arrays;
+import java.util.Date;
+import java.util.HashSet;
+import java.util.Set;
+
+@Named("refresh_token")
+public class RefreshTokenGrantTypeHandler extends AbstractGrantTypeHandler {
+
+    @Override
+    public JsonObject createAccessToken(String clientId, MultivaluedMap<String, String> params) throws Exception {
+        String refreshToken = params.getFirst("refresh_token");
+        if (refreshToken == null || "".equals(refreshToken)) {
+            throw new WebApplicationException("invalid_grant");
+        }
+
+        //Decode refresh token
+        SignedJWT signedRefreshToken = SignedJWT.parse(refreshToken);
+        JWSVerifier verifier = getJWSVerifier();
+
+        if (!signedRefreshToken.verify(verifier)) {
+            throw new WebApplicationException("Invalid refresh token.");
+        }
+        if (!(new Date().before(signedRefreshToken.getJWTClaimsSet().getExpirationTime()))) {
+            throw new WebApplicationException("Refresh token expired.");
+        }
+        String refreshTokenClientId = signedRefreshToken.getJWTClaimsSet().getStringClaim("client_id");
+        if (!clientId.equals(refreshTokenClientId)) {
+            throw new WebApplicationException("Invalid client_id.");
+        }
+
+        //At this point, the refresh token is valid and not yet expired
+        //So create a new access token from it.
+        String subject = signedRefreshToken.getJWTClaimsSet().getSubject();
+        String approvedScopes = signedRefreshToken.getJWTClaimsSet().getStringClaim("scope");
+
+        String requestedScopes = params.getFirst("scope");
+        if (requestedScopes != null && !requestedScopes.isEmpty()) {
+            Set<String> rScopes = new HashSet(Arrays.asList(requestedScopes.split(" ")));
+            Set<String> aScopes = new HashSet(Arrays.asList(approvedScopes.split(" ")));
+            if (!aScopes.containsAll(rScopes)) {
+                JsonObject error = Json.createObjectBuilder()
+                        .add("error", "Invalid_request")
+                        .add("error_description", "Requested scopes should be a subset of the original scopes.")
+                        .build();
+                Response response = Response.status(Response.Status.BAD_REQUEST).entity(error).build();
+                throw new WebApplicationException(response);
+            }
+        } else {
+            requestedScopes = approvedScopes;
+        }
+
+        String accessToken = getAccessToken(clientId, subject, requestedScopes);
+        return Json.createObjectBuilder()
+                .add("token_type", "Bearer")
+                .add("access_token", accessToken)
+                .add("expires_in", expiresInMin * 60)
+                .add("scope", requestedScopes)
+                .add("refresh_token", refreshToken)
+                .build();
+    }
+}

oauth2-framework-impl/oauth2-authorization-server/src/main/webapp/authorize.jsp

@@ -41,8 +41,8 @@
 
             <tr>
                 <td colspan="2">
-                    <input type="submit" name="approbation_status" value="YES"/>
+                    <input type="submit" name="approval_status" value="YES"/>
-                    <input type="submit" name="approbation_status" value="NO"/>
+                    <input type="submit" name="approval_status" value="NO"/>
                 </td>
             </tr>
         </table>

oauth2-framework-impl/oauth2-client/src/main/java/com/baeldung/oauth2/client/AbstractServlet.java

@@ -0,0 +1,23 @@
+package com.baeldung.oauth2.client;
+
+import javax.servlet.RequestDispatcher;
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.io.IOException;
+import java.util.Base64;
+
+public abstract class AbstractServlet extends HttpServlet {
+
+    protected void dispatch(String location, HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+        RequestDispatcher requestDispatcher = request.getRequestDispatcher(location);
+        requestDispatcher.forward(request, response);
+    }
+
+    protected String getAuthorizationHeaderValue(String clientId, String clientSecret) {
+        String token = clientId + ":" + clientSecret;
+        String encodedString = Base64.getEncoder().encodeToString(token.getBytes());
+        return "Basic " + encodedString;
+    }
+}

oauth2-framework-impl/oauth2-client/src/main/java/com/baeldung/oauth2/client/CallbackServlet.java

@@ -4,10 +4,8 @@ import org.eclipse.microprofile.config.Config;
 
 import javax.inject.Inject;
 import javax.json.JsonObject;
-import javax.servlet.RequestDispatcher;
 import javax.servlet.ServletException;
 import javax.servlet.annotation.WebServlet;
-import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 import javax.ws.rs.client.Client;
@@ -18,10 +16,9 @@ import javax.ws.rs.core.Form;
 import javax.ws.rs.core.HttpHeaders;
 import javax.ws.rs.core.MediaType;
 import java.io.IOException;
-import java.util.Base64;
 
 @WebServlet(urlPatterns = "/callback")
-public class CallbackServlet extends HttpServlet {
+public class CallbackServlet extends AbstractServlet {
 
     @Inject
     private Config config;
@@ -29,6 +26,9 @@ public class CallbackServlet extends HttpServlet {
     @Override
     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 
+        String clientId = config.getValue("client.clientId", String.class);
+        String clientSecret = config.getValue("client.clientSecret", String.class);
+
         //Error:
         String error = request.getParameter("error");
         if (error != null) {
@@ -53,24 +53,15 @@ public class CallbackServlet extends HttpServlet {
         form.param("code", code);
         form.param("redirect_uri", config.getValue("client.redirectUri", String.class));
 
-        JsonObject tokenResponse = target.request(MediaType.APPLICATION_JSON_TYPE)
+        try {
-                .header(HttpHeaders.AUTHORIZATION, getAuthorizationHeaderValue())
+            JsonObject tokenResponse = target.request(MediaType.APPLICATION_JSON_TYPE)
-                .post(Entity.entity(form, MediaType.APPLICATION_FORM_URLENCODED_TYPE), JsonObject.class);
+                    .header(HttpHeaders.AUTHORIZATION, getAuthorizationHeaderValue(clientId, clientSecret))
-
+                    .post(Entity.entity(form, MediaType.APPLICATION_FORM_URLENCODED_TYPE), JsonObject.class);
-        request.getSession().setAttribute("tokenResponse", tokenResponse);
+            request.getSession().setAttribute("tokenResponse", tokenResponse);
+        } catch (Exception ex) {
+            System.out.println(ex.getMessage());
+            request.setAttribute("error", ex.getMessage());
+        }
         dispatch("/", request, response);
     }
-
-    private void dispatch(String location, HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
-        RequestDispatcher requestDispatcher = request.getRequestDispatcher(location);
-        requestDispatcher.forward(request, response);
-    }
-
-    private String getAuthorizationHeaderValue() {
-        String clientId = config.getValue("client.clientId", String.class);
-        String clientSecret = config.getValue("client.clientSecret", String.class);
-        String token = clientId + ":" + clientSecret;
-        String encodedString = Base64.getEncoder().encodeToString(token.getBytes());
-        return "Basic " + encodedString;
-    }
 }

oauth2-framework-impl/oauth2-client/src/main/java/com/baeldung/oauth2/client/RefreshTokenServlet.java

@@ -0,0 +1,57 @@
+package com.baeldung.oauth2.client;
+
+import org.eclipse.microprofile.config.Config;
+
+import javax.inject.Inject;
+import javax.json.JsonObject;
+import javax.servlet.ServletException;
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import javax.ws.rs.client.Client;
+import javax.ws.rs.client.ClientBuilder;
+import javax.ws.rs.client.Entity;
+import javax.ws.rs.client.WebTarget;
+import javax.ws.rs.core.Form;
+import javax.ws.rs.core.HttpHeaders;
+import javax.ws.rs.core.MediaType;
+import javax.ws.rs.core.Response;
+import java.io.IOException;
+
+@WebServlet(urlPatterns = "/refreshtoken")
+public class RefreshTokenServlet extends AbstractServlet {
+
+    @Inject
+    private Config config;
+
+    @Override
+    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+
+        String clientId = config.getValue("client.clientId", String.class);
+        String clientSecret = config.getValue("client.clientSecret", String.class);
+
+        JsonObject actualTokenResponse = (JsonObject) request.getSession().getAttribute("tokenResponse");
+        Client client = ClientBuilder.newClient();
+        WebTarget target = client.target(config.getValue("provider.tokenUri", String.class));
+
+        Form form = new Form();
+        form.param("grant_type", "refresh_token");
+        form.param("refresh_token", actualTokenResponse.getString("refresh_token"));
+
+        String scope = request.getParameter("scope");
+        if (scope != null && !scope.isEmpty()) {
+            form.param("scope", scope);
+        }
+
+        Response jaxrsResponse = target.request(MediaType.APPLICATION_JSON_TYPE)
+                .header(HttpHeaders.AUTHORIZATION, getAuthorizationHeaderValue(clientId, clientSecret))
+                .post(Entity.entity(form, MediaType.APPLICATION_FORM_URLENCODED_TYPE), Response.class);
+        JsonObject tokenResponse = jaxrsResponse.readEntity(JsonObject.class);
+        if (jaxrsResponse.getStatus() == 200) {
+            request.getSession().setAttribute("tokenResponse", tokenResponse);
+        } else {
+            request.setAttribute("error", tokenResponse.getString("error_description", "error!"));
+        }
+        dispatch("/", request, response);
+    }
+}

oauth2-framework-impl/oauth2-client/src/main/webapp/index.jsp

@@ -10,6 +10,7 @@
         body {
             margin: 0px;
         }
+
         input[type=text], input[type=password] {
             width: 75%;
             padding: 4px 0px;
@@ -17,6 +18,7 @@
             border: 1px solid #502bcc;
             box-sizing: border-box;
         }
+
         .container-error {
             padding: 16px;
             border: 1px solid #cc102a;
@@ -25,6 +27,7 @@
             margin-left: 25px;
             margin-bottom: 25px;
         }
+
         .container {
             padding: 16px;
             border: 1px solid #130ecc;
@@ -81,8 +84,20 @@
         <li>access_token: ${tokenResponse.getString("access_token")}</li>
         <li>scope: ${tokenResponse.getString("scope")}</li>
         <li>Expires in (s): ${tokenResponse.getInt("expires_in")}</li>
+        <li>refresh_token: ${tokenResponse.getString("refresh_token")}</li>
     </ul>
 </div>
+
+<div class="container">
+    <span><h4>Refresh Token</h4></span>
+    <hr>
+    <ul>
+        <li><a href="refreshtoken">Refresh token (original scope)</a></li>
+        <li><a href="refreshtoken?scope=resource.read">Refresh token (scope: resource.read)</a></li>
+        <li><a href="refreshtoken?scope=resource.write">Refresh token (scope: resource.write)</a></li>
+    </ul>
+</div>
+
 <div class="container">
     <span><h4>OAuth2 Resource Server Call</h4></span>
     <hr>
@@ -90,7 +105,6 @@
         <li><a href="downstream?action=read">Read Protected Resource</a></li>
         <li><a href="downstream?action=write">Write Protected Resource</a></li>
     </ul>
-
 </div>
 
 </body>

parent-boot-performance/README.md

@@ -1 +0,0 @@
-This is a parent module for projects that want to take advantage of the latest Spring Boot improvements/features.

parent-boot-performance/pom.xml

@@ -1,92 +0,0 @@
-<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-    <modelVersion>4.0.0</modelVersion>
-    <artifactId>parent-boot-performance</artifactId>
-    <version>0.0.1-SNAPSHOT</version>
-    <name>parent-boot-performance</name>
-    <packaging>pom</packaging>
-    <description>Parent for all modules that want to take advantage of the latest Spring Boot improvements/features. Current version: 2.2</description>
-
-    <parent>
-        <groupId>com.baeldung</groupId>
-        <artifactId>parent-modules</artifactId>
-        <version>1.0.0-SNAPSHOT</version>
-    </parent>
-
-    <dependencyManagement>
-        <dependencies>
-            <dependency>
-                <groupId>org.springframework.boot</groupId>
-                <artifactId>spring-boot-dependencies</artifactId>
-                <version>${spring-boot.version}</version>
-                <type>pom</type>
-                <scope>import</scope>
-            </dependency>
-        </dependencies>
-    </dependencyManagement>
-	
-    <dependencies>
-        <dependency>
-            <groupId>io.rest-assured</groupId>
-            <artifactId>rest-assured</artifactId>
-            </dependency>
-        <dependency>
-            <groupId>org.springframework.boot</groupId>
-            <artifactId>spring-boot-starter-test</artifactId>
-            <scope>test</scope>
-        </dependency>
-    </dependencies>
-
-    <build>
-        <pluginManagement>
-            <plugins>
-                <plugin>
-                    <groupId>org.springframework.boot</groupId>
-                    <artifactId>spring-boot-maven-plugin</artifactId>
-                    <version>${spring-boot.version}</version>
-                    <configuration>
-                        <mainClass>${start-class}</mainClass>
-                        <!-- this is necessary as we're not using the Boot parent -->
-                    </configuration>
-                </plugin>
-            </plugins>
-        </pluginManagement>
-    </build>
-    
-    <repositories>
-        <repository>
-            <id>spring-milestones</id>
-            <name>Spring Milestones</name>
-            <url>https://repo.spring.io/milestone</url>
-        </repository>
-    </repositories>
-    
-    <profiles>
-        <profile>
-            <id>thin-jar</id>
-            <build>
-                <plugins>
-                    <plugin>
-                        <groupId>org.springframework.boot</groupId>
-                        <artifactId>spring-boot-maven-plugin</artifactId>
-                        <dependencies>
-                            <!-- The following enables the "thin jar" deployment option. -->
-                            <dependency>
-                                <groupId>org.springframework.boot.experimental</groupId>
-                                <artifactId>spring-boot-thin-layout</artifactId>
-                                <version>${thin.version}</version>
-                            </dependency>
-                        </dependencies>
-                    </plugin>
-                </plugins>
-            </build>
-        </profile>
-    </profiles>
-
-    <properties>
-        <rest-assured.version>3.1.0</rest-assured.version>
-        <!-- plugins -->
-        <thin.version>1.0.21.RELEASE</thin.version>
-        <spring-boot.version>2.2.0.M3</spring-boot.version>
-    </properties>
-</project>

parent-java/README.md

@@ -1 +1 @@
-## Relevant articles:
+## Relevant Articles:

parent-spring-4/README.md

@@ -1 +1 @@
-## Relevant articles:
+## Relevant Articles:

parent-spring-5/README.md

@@ -1 +1 @@
-## Relevant articles:
+## Relevant Articles:

patterns/backoff-jitter/README.md

@@ -0,0 +1,2 @@
+### Relevant Articles:
+- [Better Retries with Exponential Backoff and Jitter](https://baeldung.com/retries-with-exponential-backoff-and-jitter)

patterns/backoff-jitter/pom.xml

@@ -0,0 +1,54 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung</groupId>
+    <artifactId>backoff-jitter</artifactId>
+    <version>1.0.0-SNAPSHOT</version>
+    <packaging>pom</packaging>
+
+    <dependencies>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>${junit.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-core</artifactId>
+            <version>${mockito-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>io.github.resilience4j</groupId>
+            <artifactId>resilience4j-retry</artifactId>
+            <version>${resilience4j.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-api</artifactId>
+            <version>${slf4j.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-simple</artifactId>
+            <version>${slf4j.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
+        <junit.version>4.12</junit.version>
+        <mockito-core.version>2.27.0</mockito-core.version>
+        <slf4j.version>1.7.26</slf4j.version>
+        <resilience4j.version>0.16.0</resilience4j.version>
+    </properties>
+
+</project>

patterns/backoff-jitter/src/test/java/com/baeldung/backoff/jitter/BackoffWithJitterTest.java

@@ -0,0 +1,103 @@
+package com.baeldung.backoff.jitter;
+
+import io.github.resilience4j.retry.IntervalFunction;
+import io.github.resilience4j.retry.Retry;
+import io.github.resilience4j.retry.RetryConfig;
+import org.junit.Before;
+import org.junit.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.time.LocalDateTime;
+import java.util.List;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.function.Function;
+
+import static com.baeldung.backoff.jitter.BackoffWithJitterTest.RetryProperties.*;
+import static io.github.resilience4j.retry.IntervalFunction.ofExponentialBackoff;
+import static io.github.resilience4j.retry.IntervalFunction.ofExponentialRandomBackoff;
+import static java.util.Collections.nCopies;
+import static java.util.concurrent.Executors.newFixedThreadPool;
+import static org.mockito.ArgumentMatchers.anyString;
+import static org.mockito.Mockito.*;
+
+public class BackoffWithJitterTest {
+
+    static Logger log = LoggerFactory.getLogger(BackoffWithJitterTest.class);
+
+    interface PingPongService {
+
+        String call(String ping) throws PingPongServiceException;
+    }
+
+    class PingPongServiceException extends RuntimeException {
+
+        public PingPongServiceException(String reason) {
+            super(reason);
+        }
+    }
+
+    private PingPongService service;
+    private static final int NUM_CONCURRENT_CLIENTS = 8;
+
+    @Before
+    public void setUp() {
+        service = mock(PingPongService.class);
+    }
+
+    @Test
+    public void whenRetryExponentialBackoff_thenRetriedConfiguredNoOfTimes() {
+        IntervalFunction intervalFn = ofExponentialBackoff(INITIAL_INTERVAL, MULTIPLIER);
+        Function<String, String> pingPongFn = getRetryablePingPongFn(intervalFn);
+
+        when(service.call(anyString())).thenThrow(PingPongServiceException.class);
+        try {
+            pingPongFn.apply("Hello");
+        } catch (PingPongServiceException e) {
+            verify(service, times(MAX_RETRIES)).call(anyString());
+        }
+    }
+
+    @Test
+    public void whenRetryExponentialBackoffWithoutJitter_thenThunderingHerdProblemOccurs() throws InterruptedException {
+        IntervalFunction intervalFn = ofExponentialBackoff(INITIAL_INTERVAL, MULTIPLIER);
+        test(intervalFn);
+    }
+
+    @Test
+    public void whenRetryExponentialBackoffWithJitter_thenRetriesAreSpread() throws InterruptedException {
+        IntervalFunction intervalFn = ofExponentialRandomBackoff(INITIAL_INTERVAL, MULTIPLIER, RANDOMIZATION_FACTOR);
+        test(intervalFn);
+    }
+
+    private void test(IntervalFunction intervalFn) throws InterruptedException {
+        Function<String, String> pingPongFn = getRetryablePingPongFn(intervalFn);
+        ExecutorService executors = newFixedThreadPool(NUM_CONCURRENT_CLIENTS);
+        List<Callable<String>> tasks = nCopies(NUM_CONCURRENT_CLIENTS, () -> pingPongFn.apply("Hello"));
+
+        when(service.call(anyString())).thenThrow(PingPongServiceException.class);
+
+        executors.invokeAll(tasks);
+    }
+
+    private Function<String, String> getRetryablePingPongFn(IntervalFunction intervalFn) {
+        RetryConfig retryConfig = RetryConfig.custom()
+                .maxAttempts(MAX_RETRIES)
+                .intervalFunction(intervalFn)
+                .retryExceptions(PingPongServiceException.class)
+                .build();
+        Retry retry = Retry.of("pingpong", retryConfig);
+        return Retry.decorateFunction(retry, ping -> {
+            log.info("Invoked at {}", LocalDateTime.now());
+            return service.call(ping);
+        });
+    }
+
+    static class RetryProperties {
+        static final Long INITIAL_INTERVAL = 1000L;
+        static final Double MULTIPLIER = 2.0D;
+        static final Double RANDOMIZATION_FACTOR = 0.6D;
+        static final Integer MAX_RETRIES = 4;
+    }
+}

patterns/pom.xml

@@ -19,7 +19,8 @@
         <module>design-patterns</module>
         <module>design-patterns-2</module>
         <module>solid</module>
-        <module>dip</module>     
+        <module>dip</module>
+        <module>backoff-jitter</module>
     </modules>
 
     <dependencyManagement>

persistence-modules/java-jpa-2/README.md

@@ -0,0 +1 @@
+# Relevant Articles

persistence-modules/java-jpa-2/pom.xml

@@ -0,0 +1,115 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>java-jpa-2</artifactId>
+    <name>java-jpa-2</name>
+
+    <parent>
+        <artifactId>parent-modules</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>../../pom.xml</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.hibernate</groupId>
+            <artifactId>hibernate-core</artifactId>
+            <version>${hibernate.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.hibernate</groupId>
+            <artifactId>hibernate-jpamodelgen</artifactId>
+            <version>${hibernate.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <version>${h2.version}</version>
+        </dependency>
+
+        <!--Compile time JPA API-->
+        <dependency>
+            <groupId>javax.persistence</groupId>
+            <artifactId>javax.persistence-api</artifactId>
+            <version>${javax.persistence-api.version}</version>
+        </dependency>
+
+        <!--Runtime JPA implementation-->
+        <dependency>
+            <groupId>org.eclipse.persistence</groupId>
+            <artifactId>eclipselink</artifactId>
+            <version>${eclipselink.version}</version>
+            <scope>runtime</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.postgresql</groupId>
+            <artifactId>postgresql</artifactId>
+            <version>${postgres.version}</version>
+            <scope>runtime</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.5.1</version>
+                <configuration>
+                    <compilerArgument>-proc:none</compilerArgument>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.bsc.maven</groupId>
+                <artifactId>maven-processor-plugin</artifactId>
+                <version>3.3.3</version>
+                <executions>
+                    <execution>
+                        <id>process</id>
+                        <goals>
+                            <goal>process</goal>
+                        </goals>
+                        <phase>generate-sources</phase>
+                        <configuration>
+                            <outputDirectory>target/metamodel</outputDirectory>
+                            <processors>
+                                <processor>org.hibernate.jpamodelgen.JPAMetaModelEntityProcessor</processor>
+                            </processors>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>build-helper-maven-plugin</artifactId>
+                <version>3.0.0</version>
+                <executions>
+                    <execution>
+                        <id>add-source</id>
+                        <phase>generate-sources</phase>
+                        <goals>
+                            <goal>add-source</goal>
+                        </goals>
+                        <configuration>
+                            <sources>
+                                <source>target/metamodel</source>
+                            </sources>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <hibernate.version>5.4.0.Final</hibernate.version>
+        <eclipselink.version>2.7.4-RC1</eclipselink.version>
+        <postgres.version>42.2.5</postgres.version>
+        <javax.persistence-api.version>2.2</javax.persistence-api.version>
+    </properties>
+
+</project>

persistence-modules/java-jpa-2/src/main/java/com/baeldung/jpa/entity/Article.java

@@ -0,0 +1,12 @@
+package com.baeldung.jpa.entity;
+
+import javax.persistence.Entity;
+import javax.persistence.Table;
+
+@Entity(name = "MyArticle")
+@Table(name = Article.TABLE_NAME)
+public class Article {
+
+    public static final String TABLE_NAME = "ARTICLES";
+
+}

persistence-modules/java-sql2o/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [A Guide to Sql2o](http://www.baeldung.com/sql2o)

persistence-modules/java-sql2o/pom.xml

@@ -0,0 +1,54 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>java-sql2o</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <configuration>
+                    <source>8</source>
+                    <target>8</target>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+    <name>java-sql2o</name>
+
+    <parent>
+        <artifactId>persistence-modules</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>1.0.0-SNAPSHOT</version>
+        <relativePath>..</relativePath>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.sql2o</groupId>
+            <artifactId>sql2o</artifactId>
+            <version>${sql2o.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.hsqldb</groupId>
+            <artifactId>hsqldb</artifactId>
+            <version>${hsqldb.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>${junit.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <hsqldb.version>2.4.0</hsqldb.version>
+        <junit.version>4.12</junit.version>
+        <sql2o.version>1.6.0</sql2o.version>
+    </properties>
+
+</project>

persistence-modules/java-sql2o/src/test/java/com/baeldung/persistence/sql2o/Sql2oIntegrationTest.java

@@ -0,0 +1,340 @@
+package com.baeldung.persistence.sql2o;
+
+import org.junit.Test;
+import org.sql2o.Connection;
+import org.sql2o.Query;
+import org.sql2o.ResultSetIterable;
+import org.sql2o.Sql2o;
+import org.sql2o.data.Row;
+import org.sql2o.data.Table;
+
+import java.sql.SQLException;
+import java.text.SimpleDateFormat;
+import java.util.*;
+
+import static org.junit.Assert.*;
+
+public class Sql2oIntegrationTest {
+
+    @Test
+    public void whenSql2oCreated_thenSuccess() {
+        Sql2o sql2o = new Sql2o("jdbc:hsqldb:mem:testDB", "sa", "");
+        try(Connection connection = sql2o.open()) {
+            java.sql.Connection jdbcConnection = connection.getJdbcConnection();
+            assertFalse(jdbcConnection.isClosed());
+        } catch (SQLException e) {
+            fail(e.getMessage());
+        }
+    }
+
+    @Test
+    public void whenTableCreated_thenInsertIsPossible() {
+        Sql2o sql2o = new Sql2o("jdbc:hsqldb:mem:testDB", "sa", "");
+        try(Connection connection = sql2o.open()) {
+            connection.createQuery("create table PROJECT_1 (id integer identity, name varchar(50), url varchar(100))").executeUpdate();
+            assertEquals(0, connection.getResult());
+            connection.createQuery("INSERT INTO PROJECT_1 VALUES (1, 'tutorials', 'github.com/eugenp/tutorials')").executeUpdate();
+            assertEquals(1, connection.getResult());
+            connection.createQuery("drop table PROJECT_1").executeUpdate();
+        }
+    }
+
+    @Test
+    public void whenIdentityColumn_thenInsertReturnsNewId() {
+        Sql2o sql2o = new Sql2o("jdbc:hsqldb:mem:testDB", "sa", "");
+        try(Connection connection = sql2o.open()) {
+            connection.createQuery("create table PROJECT_2 (ID IDENTITY, NAME VARCHAR (50), URL VARCHAR (100))").executeUpdate();
+            Query query = connection.createQuery(
+                    "INSERT INTO PROJECT_2 (NAME, URL) VALUES ('tutorials', 'github.com/eugenp/tutorials')",
+                    true);
+            assertEquals(0, query.executeUpdate().getKey());
+            query = connection.createQuery("INSERT INTO PROJECT_2 (NAME, URL) VALUES ('REST with Spring', 'github.com/eugenp/REST-With-Spring')",
+                    true);
+            assertEquals(1, query.executeUpdate().getKeys()[0]);
+            connection.createQuery("drop table PROJECT_2").executeUpdate();
+        }
+    }
+
+    @Test
+    public void whenSelect_thenResultsAreObjects() {
+        Sql2o sql2o = new Sql2o("jdbc:hsqldb:mem:testDB", "sa", "");
+        try(Connection connection = sql2o.open()) {
+            connection.createQuery("create table PROJECT_3 (ID IDENTITY, NAME VARCHAR (50), URL VARCHAR (100))").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_3 (NAME, URL) VALUES ('tutorials', 'github.com/eugenp/tutorials')").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_3 (NAME, URL) VALUES ('REST with Spring', 'github.com/eugenp/REST-With-Spring')").executeUpdate();
+            Query query = connection.createQuery("select * from PROJECT_3 order by id");
+            List<Project> list = query.executeAndFetch(Project.class);
+
+            assertEquals("tutorials", list.get(0).getName());
+            assertEquals("REST with Spring", list.get(1).getName());
+
+            connection.createQuery("drop table PROJECT_3").executeUpdate();
+        }
+    }
+
+    @Test
+    public void whenSelectAlias_thenResultsAreObjects() {
+        Sql2o sql2o = new Sql2o("jdbc:hsqldb:mem:testDB", "sa", "");
+        try(Connection connection = sql2o.open()) {
+            connection.createQuery("create table PROJECT_4 (ID IDENTITY, NAME VARCHAR (50), URL VARCHAR (100), creation_date date)").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_4 (NAME, URL, creation_date) VALUES ('tutorials', 'github.com/eugenp/tutorials', '2019-01-01')").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_4 (NAME, URL, creation_date) VALUES ('REST with Spring', 'github.com/eugenp/REST-With-Spring', '2019-02-01')").executeUpdate();
+            Query query = connection.createQuery("select NAME, URL, creation_date as creationDate from PROJECT_4 order by id");
+            List<Project> list = query.executeAndFetch(Project.class);
+            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
+            assertEquals("2019-01-01", sdf.format(list.get(0).getCreationDate()));
+            assertEquals("2019-02-01", sdf.format(list.get(1).getCreationDate()));
+
+            connection.createQuery("drop table PROJECT_4").executeUpdate();
+        }
+    }
+
+    @Test
+    public void whenSelectMapping_thenResultsAreObjects() {
+        Sql2o sql2o = new Sql2o("jdbc:hsqldb:mem:testDB", "sa", "");
+        try(Connection connection = sql2o.open()) {
+            connection.createQuery("create table PROJECT_5 (ID IDENTITY, NAME VARCHAR (50), URL VARCHAR (100), creation_date date)").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_5 (NAME, URL, creation_date) VALUES ('tutorials', 'github.com/eugenp/tutorials', '2019-01-01')").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_5 (NAME, URL, creation_date) VALUES ('REST with Spring', 'github.com/eugenp/REST-With-Spring', '2019-02-01')").executeUpdate();
+            Query query = connection.createQuery("select * from PROJECT_5 order by id")
+                    .addColumnMapping("CrEaTiOn_date", "creationDate");
+            List<Project> list = query.executeAndFetch(Project.class);
+            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
+            assertEquals("2019-01-01", sdf.format(list.get(0).getCreationDate()));
+            assertEquals("2019-02-01", sdf.format(list.get(1).getCreationDate()));
+
+            connection.createQuery("drop table PROJECT_5").executeUpdate();
+        }
+    }
+
+    @Test
+    public void whenSelectCount_thenResultIsScalar() {
+        Sql2o sql2o = new Sql2o("jdbc:hsqldb:mem:testDB", "sa", "");
+        try(Connection connection = sql2o.open()) {
+            connection.createQuery("create table PROJECT_6 (ID IDENTITY, NAME VARCHAR (50), URL VARCHAR (100), creation_date date)").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_6 (NAME, URL, creation_date) VALUES ('tutorials', 'github.com/eugenp/tutorials', '2019-01-01')").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_6 (NAME, URL, creation_date) VALUES ('REST with Spring', 'github.com/eugenp/REST-With-Spring', '2019-02-01')").executeUpdate();
+            Query query = connection.createQuery("select count(*) from PROJECT_6");
+            assertEquals(2.0, query.executeScalar(Double.TYPE), 0.001);
+            connection.createQuery("drop table PROJECT_6").executeUpdate();
+        }
+    }
+
+    @Test
+    public void whenFetchTable_thenResultsAreMaps() {
+        Sql2o sql2o = new Sql2o("jdbc:hsqldb:mem:testDB", "sa", "");
+        try(Connection connection = sql2o.open()) {
+            connection.createQuery("create table PROJECT_5 (ID IDENTITY, NAME VARCHAR (50), URL VARCHAR (100), creation_date date)").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_5 (NAME, URL, creation_date) VALUES ('tutorials', 'github.com/eugenp/tutorials', '2019-01-01')").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_5 (NAME, URL, creation_date) VALUES ('REST with Spring', 'github.com/eugenp/REST-With-Spring', '2019-02-01')").executeUpdate();
+            Query query = connection.createQuery("select * from PROJECT_5 order by id");
+            Table table = query.executeAndFetchTable();
+            List<Map<String, Object>> list = table.asList();
+
+            assertEquals("tutorials", list.get(0).get("name"));
+            assertEquals("REST with Spring", list.get(1).get("name"));
+
+            connection.createQuery("drop table PROJECT_5").executeUpdate();
+        }
+    }
+
+    @Test
+    public void whenFetchTable_thenResultsAreRows() {
+        Sql2o sql2o = new Sql2o("jdbc:hsqldb:mem:testDB", "sa", "");
+        try(Connection connection = sql2o.open()) {
+            connection.createQuery("create table PROJECT_5 (ID IDENTITY, NAME VARCHAR (50), URL VARCHAR (100), creation_date date)").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_5 (NAME, URL, creation_date) VALUES ('tutorials', 'github.com/eugenp/tutorials', '2019-01-01')").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_5 (NAME, URL, creation_date) VALUES ('REST with Spring', 'github.com/eugenp/REST-With-Spring', '2019-02-01')").executeUpdate();
+            Query query = connection.createQuery("select * from PROJECT_5 order by id");
+            Table table = query.executeAndFetchTable();
+            List<Row> rows = table.rows();
+
+            assertEquals("tutorials", rows.get(0).getString("name"));
+            assertEquals("REST with Spring", rows.get(1).getString("name"));
+
+            connection.createQuery("drop table PROJECT_5").executeUpdate();
+        }
+    }
+
+    @Test
+    public void whenParameters_thenReplacement() {
+        Sql2o sql2o = new Sql2o("jdbc:hsqldb:mem:testDB", "sa", "");
+        try(Connection connection = sql2o.open()) {
+            connection.createQuery("create table PROJECT_10 (ID IDENTITY, NAME VARCHAR (50), URL VARCHAR (100))").executeUpdate();
+            Query query = connection.createQuery("INSERT INTO PROJECT_10 (NAME, URL) VALUES (:name, :url)")
+                    .addParameter("name", "REST with Spring")
+                    .addParameter("url", "github.com/eugenp/REST-With-Spring");
+            assertEquals(1, query.executeUpdate().getResult());
+
+            List<Project> list = connection.createQuery("SELECT * FROM PROJECT_10 WHERE NAME = 'REST with Spring'").executeAndFetch(Project.class);
+            assertEquals(1, list.size());
+
+            connection.createQuery("drop table PROJECT_10").executeUpdate();
+        }
+    }
+
+    @Test
+    public void whenPOJOParameters_thenReplacement() {
+        Sql2o sql2o = new Sql2o("jdbc:hsqldb:mem:testDB", "sa", "");
+        try(Connection connection = sql2o.open()) {
+            connection.createQuery("create table PROJECT_11 (ID IDENTITY, NAME VARCHAR (50), URL VARCHAR (100))").executeUpdate();
+
+            Project project = new Project();
+            project.setName("REST with Spring");
+            project.setUrl("github.com/eugenp/REST-With-Spring");
+            connection.createQuery("INSERT INTO PROJECT_11 (NAME, URL) VALUES (:name, :url)")
+                    .bind(project).executeUpdate();
+            assertEquals(1, connection.getResult());
+
+            List<Project> list = connection.createQuery("SELECT * FROM PROJECT_11 WHERE NAME = 'REST with Spring'").executeAndFetch(Project.class);
+            assertEquals(1, list.size());
+
+            connection.createQuery("drop table PROJECT_11").executeUpdate();
+        }
+    }
+
+    @Test
+    public void whenTransactionRollback_thenNoDataInserted() {
+        Sql2o sql2o = new Sql2o("jdbc:hsqldb:mem:testDB", "sa", "");
+        try(Connection connection = sql2o.beginTransaction()) {
+            connection.createQuery("create table PROJECT_12 (ID IDENTITY, NAME VARCHAR (50), URL VARCHAR (100))").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_12 (NAME, URL) VALUES ('tutorials', 'https://github.com/eugenp/tutorials')").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_12 (NAME, URL) VALUES ('REST with Spring', 'https://github.com/eugenp/REST-With-Spring')").executeUpdate();
+            connection.rollback();
+            List<Map<String, Object>> list = connection.createQuery("SELECT * FROM PROJECT_12").executeAndFetchTable().asList();
+            assertEquals(0, list.size());
+        }
+    }
+
+    @Test
+    public void whenTransactionEnds_thenSubsequentStatementsNotRolledBack() {
+        Sql2o sql2o = new Sql2o("jdbc:hsqldb:mem:testDB", "sa", "");
+        try(Connection connection = sql2o.beginTransaction()) {
+            connection.createQuery("create table PROJECT_13 (ID IDENTITY, NAME VARCHAR (50), URL VARCHAR (100))").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_13 (NAME, URL) VALUES ('tutorials', 'https://github.com/eugenp/tutorials')").executeUpdate();
+            List<Map<String, Object>> list = connection.createQuery("SELECT * FROM PROJECT_13").executeAndFetchTable().asList();
+            assertEquals(1, list.size());
+            connection.rollback();
+            list = connection.createQuery("SELECT * FROM PROJECT_13").executeAndFetchTable().asList();
+            assertEquals(0, list.size());
+            connection.createQuery("INSERT INTO PROJECT_13 (NAME, URL) VALUES ('REST with Spring', 'https://github.com/eugenp/REST-With-Spring')").executeUpdate();
+            list = connection.createQuery("SELECT * FROM PROJECT_13").executeAndFetchTable().asList();
+            assertEquals(1, list.size());
+            //No implicit rollback
+        }
+        try(Connection connection = sql2o.beginTransaction()) {
+            List<Map<String, Object>> list = connection.createQuery("SELECT * FROM PROJECT_13").executeAndFetchTable().asList();
+            assertEquals(1, list.size());
+        }
+    }
+
+    @Test
+    public void whenTransactionRollbackThenCommit_thenOnlyLastInserted() {
+        Sql2o sql2o = new Sql2o("jdbc:hsqldb:mem:testDB", "sa", "");
+        try(Connection connection = sql2o.beginTransaction()) {
+            connection.createQuery("create table PROJECT_14 (ID IDENTITY, NAME VARCHAR (50), URL VARCHAR (100))").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_14 (NAME, URL) VALUES ('tutorials', 'https://github.com/eugenp/tutorials')").executeUpdate();
+            List<Map<String, Object>> list = connection.createQuery("SELECT * FROM PROJECT_14").executeAndFetchTable().asList();
+            assertEquals(1, list.size());
+            connection.rollback(false);
+            list = connection.createQuery("SELECT * FROM PROJECT_14").executeAndFetchTable().asList();
+            assertEquals(0, list.size());
+            connection.createQuery("INSERT INTO PROJECT_14 (NAME, URL) VALUES ('REST with Spring', 'https://github.com/eugenp/REST-With-Spring')").executeUpdate();
+            list = connection.createQuery("SELECT * FROM PROJECT_14").executeAndFetchTable().asList();
+            assertEquals(1, list.size());
+            //Implicit rollback
+        }
+        try(Connection connection = sql2o.beginTransaction()) {
+            List<Map<String, Object>> list = connection.createQuery("SELECT * FROM PROJECT_14").executeAndFetchTable().asList();
+            assertEquals(0, list.size());
+            connection.createQuery("INSERT INTO PROJECT_14 (NAME, URL) VALUES ('tutorials', 'https://github.com/eugenp/tutorials')").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_14 (NAME, URL) VALUES ('REST with Spring', 'https://github.com/eugenp/REST-With-Spring')").executeUpdate();
+            connection.commit();
+            list = connection.createQuery("SELECT * FROM PROJECT_14").executeAndFetchTable().asList();
+            assertEquals(2, list.size());
+        }
+        try(Connection connection = sql2o.beginTransaction()) {
+            List<Map<String, Object>> list = connection.createQuery("SELECT * FROM PROJECT_14").executeAndFetchTable().asList();
+            assertEquals(2, list.size());
+        }
+    }
+
+    @Test
+    public void whenBatch_thenMultipleInserts() {
+        Sql2o sql2o = new Sql2o("jdbc:hsqldb:mem:testDB", "sa", "");
+        try(Connection connection = sql2o.beginTransaction()) {
+            connection.createQuery("create table PROJECT_15 (ID IDENTITY, NAME VARCHAR (50), URL VARCHAR (100))").executeUpdate();
+            Query query = connection.createQuery("INSERT INTO PROJECT_15 (NAME, URL) VALUES (:name, :url)");
+            for(int i = 0; i < 1000; i++) {
+                query.addParameter("name", "tutorials" + i);
+                query.addParameter("url", "https://github.com/eugenp/tutorials" + i);
+                query.addToBatch();
+            }
+            query.executeBatch();
+            connection.commit();
+        }
+        try(Connection connection = sql2o.beginTransaction()) {
+            assertEquals(1000L, connection.createQuery("SELECT count(*) FROM PROJECT_15").executeScalar());
+        }
+    }
+
+    @Test
+    public void whenLazyFetch_thenResultsAreObjects() {
+        Sql2o sql2o = new Sql2o("jdbc:hsqldb:mem:testDB", "sa", "");
+        try(Connection connection = sql2o.open()) {
+            connection.createQuery("create table PROJECT_16 (ID IDENTITY, NAME VARCHAR (50), URL VARCHAR (100))").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_16 (NAME, URL) VALUES ('tutorials', 'github.com/eugenp/tutorials')").executeUpdate();
+            connection.createQuery("INSERT INTO PROJECT_16 (NAME, URL) VALUES ('REST with Spring', 'github.com/eugenp/REST-With-Spring')").executeUpdate();
+            Query query = connection.createQuery("select * from PROJECT_16 order by id");
+            try(ResultSetIterable<Project> projects = query.executeAndFetchLazy(Project.class)) {
+                for(Project p : projects) {
+                    assertNotNull(p.getName());
+                    assertNotNull(p.getUrl());
+                    assertNull(p.getCreationDate());
+                }
+            }
+            connection.createQuery("drop table PROJECT_16").executeUpdate();
+        }
+    }
+
+    static class Project {
+        private long id;
+        private String name;
+        private String url;
+        private Date creationDate;
+
+        public long getId() {
+            return id;
+        }
+
+        public void setId(long id) {
+            this.id = id;
+        }
+
+        public String getName() {
+            return name;
+        }
+
+        public void setName(String name) {
+            this.name = name;
+        }
+
+        public String getUrl() {
+            return url;
+        }
+
+        public void setUrl(String url) {
+            this.url = url;
+        }
+
+        public Date getCreationDate() {
+            return creationDate;
+        }
+
+        public void setCreationDate(Date creationDate) {
+            this.creationDate = creationDate;
+        }
+    }
+
+
+}

persistence-modules/jpa-hibernate-cascade-type/pom.xml

@@ -2,10 +2,6 @@
 <project xmlns="http://maven.apache.org/POM/4.0.0"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
-    <artifactId>jpa-hibernate-cascade-type</artifactId>
-    <modelVersion>4.0.0</modelVersion>
-    <version>1.0.0-SNAPSHOT</version>
-	
     <parent>
         <groupId>com.baeldung</groupId>
         <artifactId>parent-modules</artifactId>
@@ -13,6 +9,10 @@
         <relativePath>../../</relativePath>
     </parent>
 
+    <artifactId>jpa-hibernate-cascade-type</artifactId>
+    <modelVersion>4.0.0</modelVersion>
+    <version>1.0.0-SNAPSHOT</version>
+
     <dependencies>
         <dependency>
             <groupId>org.hibernate</groupId>

persistence-modules/pom.xml

@@ -29,7 +29,9 @@
         <module>java-cockroachdb</module>
         <module>java-jdbi</module>
         <module>java-jpa</module>
+        <module>java-jpa-2</module>
         <module>java-mongodb</module>
+        <module>java-sql2o</module>
         <module>jnosql</module>
         <module>liquibase</module>
         <module>orientdb</module>

persistence-modules/spring-data-jpa/README.md

@@ -10,7 +10,6 @@
 - [Spring Data Java 8 Support](http://www.baeldung.com/spring-data-java-8)
 - [A Simple Tagging Implementation with JPA](http://www.baeldung.com/jpa-tagging)
 - [Spring Data Composable Repositories](https://www.baeldung.com/spring-data-composable-repositories)
-- [Auditing with JPA, Hibernate, and Spring Data JPA](https://www.baeldung.com/database-auditing-jpa)
 - [Query Entities by Dates and Times with Spring Data JPA](https://www.baeldung.com/spring-data-jpa-query-by-date)
 - [DDD Aggregates and @DomainEvents](https://www.baeldung.com/spring-data-ddd)
 - [Spring Data – CrudRepository save() Method](https://www.baeldung.com/spring-data-crud-repository-save)

persistence-modules/spring-hibernate4/README.md

@@ -10,6 +10,7 @@
 - [Hibernate: save, persist, update, merge, saveOrUpdate](http://www.baeldung.com/hibernate-save-persist-update-merge-saveorupdate)
 - [Eager/Lazy Loading In Hibernate](http://www.baeldung.com/hibernate-lazy-eager-loading)
 - [The DAO with Spring and Hibernate](http://www.baeldung.com/persistence-layer-with-spring-and-hibernate)
+- [Auditing with JPA, Hibernate, and Spring Data JPA](https://www.baeldung.com/database-auditing-jpa)
 
 ### Quick Start
 

persistence-modules/spring-hibernate4/src/main/java/com/baeldung/spring/PersistenceConfig.java

@@ -47,7 +47,7 @@ import com.google.common.base.Preconditions;
 @EnableTransactionManagement
 @EnableJpaRepositories(basePackages = { "com.baeldung.persistence" }, transactionManagerRef = "jpaTransactionManager")
 @EnableJpaAuditing
-@PropertySource({ "classpath:persistence-mysql.properties" })
+@PropertySource({ "classpath:persistence-h2.properties" })
 @ComponentScan({ "com.baeldung.persistence" })
 public class PersistenceConfig {
 

persistence-modules/spring-hibernate4/src/test/java/com/baeldung/persistence/audit/EnversFooBarAuditIntegrationTest.java

@@ -2,6 +2,7 @@ package com.baeldung.persistence.audit;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
 
 import java.util.List;
 
@@ -17,6 +18,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Qualifier;
+import org.springframework.test.annotation.DirtiesContext;
 import org.springframework.test.context.ContextConfiguration;
 import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 import org.springframework.test.context.support.AnnotationConfigContextLoader;
@@ -29,6 +31,7 @@ import com.baeldung.spring.config.PersistenceTestConfig;
 
 @RunWith(SpringJUnit4ClassRunner.class)
 @ContextConfiguration(classes = { PersistenceTestConfig.class }, loader = AnnotationConfigContextLoader.class)
+@DirtiesContext(classMode = DirtiesContext.ClassMode.BEFORE_CLASS)
 public class EnversFooBarAuditIntegrationTest {
 
     private static Logger logger = LoggerFactory.getLogger(EnversFooBarAuditIntegrationTest.class);

pom.xml

@@ -10,10 +10,6 @@
 	<name>parent-modules</name>
 	<packaging>pom</packaging>
 
-	<modules>
-		<module>quarkus</module>
-	</modules>
-
 	<dependencies>
 		<!-- logging -->
 		<dependency>
@@ -392,6 +388,7 @@
                 <!--<module>core-java-modules/core-java-9</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
                 <!--<module>core-java-modules/core-java-os</module> --> <!-- We haven't upgraded to java 9.-->
                 <module>core-java-modules/core-java-arrays</module>
+                <module>core-java-modules/core-java-arrays-2</module>
                 <module>core-java-modules/core-java-collections</module>
                 <module>core-java-modules/core-java-collections-list</module>
                 <module>core-java-modules/core-java-collections-list-2</module>
@@ -482,7 +479,7 @@
                 <module>jee-7</module> -->
 				<module>jee-7-security</module>
 				<module>jersey</module>
-				<module>JGit</module>
+				<module>jgit</module>
 				<module>jgroups</module>
 				<module>jhipster-5</module>
 				<module>jib</module>
@@ -561,7 +558,7 @@
 				<module>tensorflow-java</module>
 				<module>spring-boot-flowable</module>
 				<module>spring-security-kerberos</module>
-
+				<module>oauth2-framework-impl</module>
 			</modules>
 
 		</profile>
@@ -743,7 +740,7 @@
 				<module>spring-security-mvc-ldap</module>
 				<module>spring-security-mvc-login</module>
 				<module>spring-security-mvc-persisted-remember-me</module>
-				<module>spring-security-mvc-session</module>
+				<module>spring-security-mvc</module>
 				<module>spring-security-mvc-socket</module>
 				<module>spring-security-openid</module>
 				<!--<module>spring-security-react</module> --> <!-- fails on Travis, fails intermittently on the new Jenkins (01.12.2018) BAEL-10834 -->
@@ -780,7 +777,7 @@
 				<module>testing-modules</module>
 
 				<module>twilio</module>
-				<module>Twitter4J</module>
+				<module>twitter4j</module>
 
 				<module>undertow</module>
 
@@ -919,7 +916,7 @@
 				<module>spring-security-mvc-digest-auth</module>
 				<module>spring-security-mvc-ldap</module>
 				<module>spring-security-mvc-persisted-remember-me</module>
-				<module>spring-security-mvc-session</module>
+				<module>spring-security-mvc</module>
 				<module>spring-security-mvc-socket</module>
 				<module>spring-security-rest</module>
 				<module>spring-security-sso</module>
@@ -1000,6 +997,7 @@
 				<module>persistence-modules/hibernate5</module>
 				<module>persistence-modules/hibernate-mapping</module>
 				<module>persistence-modules/java-jpa</module>
+				<module>persistence-modules/java-jpa-2</module>
 				<module>persistence-modules/java-mongodb</module>
 				<module>persistence-modules/jnosql</module>
 
@@ -1088,6 +1086,7 @@
 				<!--<module>core-java-modules/core-java-9</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
 				<!--<module>core-java-modules/core-java-os</module> --> <!-- We haven't upgraded to java 9.-->
 				<module>core-java-modules/core-java-arrays</module>
+				<module>core-java-modules/core-java-arrays-2</module>
 				<module>core-java-modules/core-java-collections</module>
 				<module>core-java-modules/core-java-collections-list</module>
 				<module>core-java-modules/core-java-collections-list-2</module>
@@ -1174,7 +1173,7 @@
                 <module>jee-7</module> -->
 				<module>jee-7-security</module>
 				<module>jersey</module>
-				<module>JGit</module>
+				<module>jgit</module>
 				<module>jgroups</module>
 				<module>jhipster-5</module>
 				<module>jib</module>
@@ -1244,6 +1243,7 @@
 				<module>rsocket</module>
 				<module>rxjava</module>
 				<module>rxjava-2</module>
+				<module>oauth2-framework-impl</module>
 
 			</modules>
 
@@ -1411,7 +1411,7 @@
 				<module>spring-security-mvc-ldap</module>
 				<module>spring-security-mvc-login</module>
 				<module>spring-security-mvc-persisted-remember-me</module>
-				<module>spring-security-mvc-session</module>
+				<module>spring-security-mvc</module>
 				<module>spring-security-mvc-socket</module>
 				<module>spring-security-openid</module>
 				<!--<module>spring-security-react</module> --> <!-- fails on Travis, fails intermittently on the new Jenkins (01.12.2018) BAEL-10834 -->
@@ -1448,7 +1448,7 @@
 				<module>testing-modules</module>
 
 				<module>twilio</module>
-				<module>Twitter4J</module>
+				<module>twitter4j</module>
 
 				<module>undertow</module>
 
@@ -1508,6 +1508,7 @@
 
 				<module>persistence-modules/hibernate5</module>
 				<module>persistence-modules/java-jpa</module>
+				<module>persistence-modules/java-jpa-2</module>
 				<module>persistence-modules/java-mongodb</module>
 				<module>persistence-modules/jnosql</module>
 
@@ -1586,4 +1587,5 @@
 		<lombok.version>1.16.12</lombok.version>
 		<h2.version>1.4.197</h2.version>
 	</properties>
+
 </project>

quarkus/README.md

@@ -1,3 +1,3 @@
-## Relevant articles:
+## Relevant Articles:
 
 - [Guide to QuarkusIO](https://www.baeldung.com/quarkus-io)

resteasy/bin/README.md

@@ -1,6 +0,0 @@
-=========
-
-## A Guide to RESTEasy
-
-
-### Relevant Articles:

spring-5-mvc/README.md

@@ -1,4 +1,3 @@
 ### Relevant Articles:
 - [Spring Boot and Kotlin](http://www.baeldung.com/spring-boot-kotlin)
 - [Spring MVC Streaming and SSE Request Processing](https://www.baeldung.com/spring-mvc-sse-streams)
-- [Overview and Need for DelegatingFilterProxy in Spring](https://www.baeldung.com/spring-delegating-filter-proxy)

spring-5-mvc/pom.xml

@@ -23,10 +23,6 @@
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-data-jpa</artifactId>
         </dependency>
-        <dependency>
-            <groupId>org.springframework.boot</groupId>
-            <artifactId>spring-boot-starter-security</artifactId>
-        </dependency>
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-validation</artifactId>

spring-5-mvc/src/main/java/com/baeldung/Spring5Application.java

@@ -1,12 +1,8 @@
 package com.baeldung;
 
-import javax.servlet.Filter;
-
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration;
-import org.springframework.web.filter.DelegatingFilterProxy;
-import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;
 
 @SpringBootApplication( exclude = SecurityAutoConfiguration.class)
 public class Spring5Application {
@@ -14,32 +10,4 @@ public class Spring5Application {
     public static void main(String[] args) {
         SpringApplication.run(Spring5Application.class, args);
     }
-
-    public static class ApplicationInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
-
-        @Override
-        protected Class<?>[] getRootConfigClasses() {
-            return null;
-        }
-
-        @Override
-        protected Class<?>[] getServletConfigClasses() {
-            // TODO Auto-generated method stub
-            return null;
-        }
-
-        @Override
-        protected String[] getServletMappings() {
-            // TODO Auto-generated method stub
-            return null;
-        }
-
-        @Override
-        protected javax.servlet.Filter[] getServletFilters() {
-            DelegatingFilterProxy delegateFilterProxy = new DelegatingFilterProxy();
-            delegateFilterProxy.setTargetBeanName("loggingFilter");
-            return new Filter[] { delegateFilterProxy };
-        }
-    }
-
 }

spring-5-mvc/src/main/webapp/WEB-INF/web.xml

@@ -16,14 +16,5 @@
         <servlet-name>functional</servlet-name>
         <url-pattern>/</url-pattern>
     </servlet-mapping>
-	<filter>
-		<filter-name>loggingFilter</filter-name>
-		<filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
-	</filter>
-
-	<filter-mapping>
-		<filter-name>loggingFilter</filter-name>
-		<url-pattern>/*</url-pattern>
-	</filter-mapping>
 
 </web-app>

spring-5-reactive-client/README.md

@@ -4,3 +4,4 @@
 The "REST With Spring" Classes: http://bit.ly/restwithspring
 
 ### Relevant Articles
+

spring-boot-mvc-2/.gitignore

@@ -0,0 +1,25 @@
+/target/
+!.mvn/wrapper/maven-wrapper.jar
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+
+### NetBeans ###
+/nbproject/private/
+/build/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/

spring-boot-mvc-2/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [Functional Controllers in Spring MVC]()

spring-boot-mvc-2/pom.xml

@@ -0,0 +1,68 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <artifactId>spring-boot-mvc-2</artifactId>
+    <name>spring-boot-mvc-2</name>
+    <packaging>jar</packaging>
+    <description>Module For Spring Boot MVC Web Fn</description>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.2.0.BUILD-SNAPSHOT</version>
+        <relativePath /> <!-- lookup parent from repository -->
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+                <configuration>
+                    <mainClass>com.baeldung.springbootmvc.SpringBootMvcFnApplication</mainClass>
+                    <layout>JAR</layout>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+    <repositories>
+        <repository>
+            <id>spring-snapshots</id>
+            <name>Spring Snapshots</name>
+            <url>https://repo.spring.io/snapshot</url>
+            <snapshots>
+                <enabled>true</enabled>
+            </snapshots>
+        </repository>
+        <repository>
+            <id>spring-milestones</id>
+            <name>Spring Milestones</name>
+            <url>https://repo.spring.io/milestone</url>
+        </repository>
+    </repositories>
+    <pluginRepositories>
+        <pluginRepository>
+            <id>spring-snapshots</id>
+            <name>Spring Snapshots</name>
+            <url>https://repo.spring.io/snapshot</url>
+            <snapshots>
+                <enabled>true</enabled>
+            </snapshots>
+        </pluginRepository>
+        <pluginRepository>
+            <id>spring-milestones</id>
+            <name>Spring Milestones</name>
+            <url>https://repo.spring.io/milestone</url>
+        </pluginRepository>
+    </pluginRepositories>
+</project>

spring-boot-mvc-2/src/main/java/com/baeldung/springbootmvc/SpringBootMvcFnApplication.java

@@ -0,0 +1,74 @@
+package com.baeldung.springbootmvc;
+
+import static org.springframework.web.servlet.function.RouterFunctions.route;
+import static org.springframework.web.servlet.function.ServerResponse.notFound;
+import static org.springframework.web.servlet.function.ServerResponse.status;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.annotation.Bean;
+import org.springframework.http.HttpStatus;
+import org.springframework.web.servlet.function.RequestPredicates;
+import org.springframework.web.servlet.function.RouterFunction;
+import org.springframework.web.servlet.function.ServerResponse;
+
+import com.baeldung.springbootmvc.ctrl.ProductController;
+import com.baeldung.springbootmvc.svc.ProductService;
+
+@SpringBootApplication
+public class SpringBootMvcFnApplication {
+
+    private static final Logger LOG = LoggerFactory.getLogger(SpringBootMvcFnApplication.class);
+
+    public static void main(String[] args) {
+        SpringApplication.run(SpringBootMvcFnApplication.class, args);
+    }
+
+    @Bean
+    RouterFunction<ServerResponse> productListing(ProductController pc, ProductService ps) {
+        return pc.productListing(ps);
+    }
+
+    @Bean
+    RouterFunction<ServerResponse> allApplicationRoutes(ProductController pc, ProductService ps) {
+        return route().add(pc.remainingProductRoutes(ps))
+            .before(req -> {
+                LOG.info("Found a route which matches " + req.uri()
+                    .getPath());
+                return req;
+            })
+            .after((req, res) -> {
+                if (res.statusCode() == HttpStatus.OK) {
+                    LOG.info("Finished processing request " + req.uri()
+                        .getPath());
+                } else {
+                    LOG.info("There was an error while processing request" + req.uri());
+                }
+                return res;
+            })
+            .onError(Throwable.class, (e, res) -> {
+                LOG.error("Fatal exception has occurred", e);
+                return status(HttpStatus.INTERNAL_SERVER_ERROR).build();
+            })
+            .build()
+            .and(route(RequestPredicates.all(), req -> notFound().build()));
+    }
+
+    public static class Error {
+        private String errorMessage;
+
+        public Error(String message) {
+            this.errorMessage = message;
+        }
+
+        public String getErrorMessage() {
+            return errorMessage;
+        }
+
+        public void setErrorMessage(String errorMessage) {
+            this.errorMessage = errorMessage;
+        }
+    }
+}

spring-boot-mvc-2/src/main/java/com/baeldung/springbootmvc/ctrl/ProductController.java

@@ -0,0 +1,59 @@
+package com.baeldung.springbootmvc.ctrl;
+
+import static org.springframework.web.servlet.function.RouterFunctions.route;
+import static org.springframework.web.servlet.function.ServerResponse.ok;
+import static org.springframework.web.servlet.function.ServerResponse.status;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.http.HttpStatus;
+import org.springframework.stereotype.Component;
+import org.springframework.web.servlet.function.EntityResponse;
+import org.springframework.web.servlet.function.RequestPredicates;
+import org.springframework.web.servlet.function.RouterFunction;
+import org.springframework.web.servlet.function.ServerRequest;
+import org.springframework.web.servlet.function.ServerResponse;
+
+import com.baeldung.springbootmvc.SpringBootMvcFnApplication.Error;
+import com.baeldung.springbootmvc.model.Product;
+import com.baeldung.springbootmvc.svc.ProductService;
+
+@Component
+public class ProductController {
+
+    public RouterFunction<ServerResponse> productListing(ProductService ps) {
+        return route().GET("/product", req -> ok().body(ps.findAll()))
+            .build();
+    }
+
+    public RouterFunction<ServerResponse> productSearch(ProductService ps) {
+        return route().nest(RequestPredicates.path("/product"), builder -> {
+            builder.GET("/name/{name}", req -> ok().body(ps.findByName(req.pathVariable("name"))))
+                .GET("/id/{id}", req -> ok().body(ps.findById(Integer.parseInt(req.pathVariable("id")))));
+        })
+            .onError(ProductService.ItemNotFoundException.class, (e, req) -> EntityResponse.fromObject(new Error(e.getMessage()))
+                .status(HttpStatus.NOT_FOUND)
+                .build())
+            .build();
+    }
+
+    public RouterFunction<ServerResponse> adminFunctions(ProductService ps) {
+        return route().POST("/product", req -> ok().body(ps.save(req.body(Product.class))))
+            .filter((req, next) -> authenticate(req) ? next.handle(req) : status(HttpStatus.UNAUTHORIZED).build())
+            .onError(IllegalArgumentException.class, (e, req) -> EntityResponse.fromObject(new Error(e.getMessage()))
+                .status(HttpStatus.BAD_REQUEST)
+                .build())
+            .build();
+    }
+
+    public RouterFunction<ServerResponse> remainingProductRoutes(ProductService ps) {
+        return route().add(productSearch(ps))
+            .add(adminFunctions(ps))
+            .build();
+    }
+
+    private boolean authenticate(ServerRequest req) {
+        return Boolean.TRUE;
+    }
+
+}

spring-boot-mvc-2/src/main/java/com/baeldung/springbootmvc/model/Product.java

@@ -0,0 +1,72 @@
+package com.baeldung.springbootmvc.model;
+
+public class Product {
+    private String name;
+    private double price;
+    private int id;
+
+    public Product(String name, double price, int id) {
+        super();
+        this.name = name;
+        this.price = price;
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public double getPrice() {
+        return price;
+    }
+
+    public void setPrice(double price) {
+        this.price = price;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    @Override
+    public int hashCode() {
+        final int prime = 31;
+        int result = 1;
+        result = prime * result + id;
+        result = prime * result + ((name == null) ? 0 : name.hashCode());
+        long temp;
+        temp = Double.doubleToLongBits(price);
+        result = prime * result + (int) (temp ^ (temp >>> 32));
+        return result;
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (this == obj)
+            return true;
+        if (obj == null)
+            return false;
+        if (getClass() != obj.getClass())
+            return false;
+        Product other = (Product) obj;
+        if (id != other.id)
+            return false;
+        if (name == null) {
+            if (other.name != null)
+                return false;
+        } else if (!name.equals(other.name))
+            return false;
+        if (Double.doubleToLongBits(price) != Double.doubleToLongBits(other.price))
+            return false;
+        return true;
+    }
+
+}

spring-boot-mvc-2/src/main/java/com/baeldung/springbootmvc/svc/ProductService.java

@@ -0,0 +1,63 @@
+package com.baeldung.springbootmvc.svc;
+
+import java.util.HashSet;
+import java.util.Set;
+
+import org.springframework.stereotype.Service;
+import org.springframework.util.StringUtils;
+
+import com.baeldung.springbootmvc.model.Product;
+
+@Service
+public class ProductService {
+
+    private final Set<Product> products = new HashSet<>();
+
+    {
+        products.add(new Product("Book", 23.90, 1));
+        products.add(new Product("Pen", 44.34, 2));
+    }
+
+    public Product findById(int id) {
+        return products.stream()
+            .filter(obj -> obj.getId() == id)
+            .findFirst()
+            .orElseThrow(() -> new ItemNotFoundException("Product not found"));
+    }
+
+    public Product findByName(String name) {
+        return products.stream()
+            .filter(obj -> obj.getName()
+                .equalsIgnoreCase(name))
+            .findFirst()
+            .orElseThrow(() -> new ItemNotFoundException("Product not found"));
+    }
+
+    public Set<Product> findAll() {
+        return products;
+    }
+
+    public Product save(Product product) {
+        if (StringUtils.isEmpty(product.getName()) || product.getPrice() == 0.0) {
+            throw new IllegalArgumentException();
+        }
+        int newId = products.stream()
+            .mapToInt(Product::getId)
+            .max()
+            .getAsInt() + 1;
+        product.setId(newId);
+        products.add(product);
+        return product;
+    }
+
+    public static class ItemNotFoundException extends RuntimeException {
+        /**
+         * 
+         */
+        private static final long serialVersionUID = 1L;
+
+        public ItemNotFoundException(String msg) {
+            super(msg);
+        }
+    }
+}

spring-boot-mvc-2/src/main/resources/application.properties

@@ -0,0 +1 @@
+spring.main.allow-bean-definition-overriding=true