Merge branch 'eugenp:master' into master

apache-poi/pom.xml

@@ -32,9 +32,27 @@
         </dependency>
     </dependencies>
 
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-resources-plugin</artifactId>
+                <version>${maven.resources.plugin.version}</version>
+                <configuration>
+                    <encoding>UTF-8</encoding>
+                    <nonFilteredFileExtensions>
+                        <nonFilteredFileExtension>xlsx</nonFilteredFileExtension>
+                        <nonFilteredFileExtension>xls</nonFilteredFileExtension>
+                    </nonFilteredFileExtensions>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
     <properties>
         <poi.version>5.2.0</poi.version>
         <jexcel.version>1.0.6</jexcel.version>
+        <maven.resources.plugin.version>3.2.0</maven.resources.plugin.version>
     </properties>
 
 </project>

apache-poi/src/test/java/com/baeldung/poi/excel/cellstyle/CellBorderHandlerUnitTest.java

@@ -12,7 +12,7 @@ import java.nio.file.Paths;
 import static org.junit.Assert.assertEquals;
 
 public class CellBorderHandlerUnitTest {
-    private static final String FILE_NAME = "cellstyle/CellStyleHandlerTest.xlsx";
+    private static final String FILE_NAME = "cellstyle/CellStyleBorderHandlerTest.xlsx";
     private static final int SHEET_INDEX = 0;
 
     private static CellBordersHandler cellBordersHandler;

core-java-modules/core-java-8-2/src/main/java/com/baeldung/game/RockPaperScissorsGame.java

@@ -0,0 +1,66 @@
+package com.baeldung.game;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Random;
+import java.util.Scanner;
+
+class RockPaperScissorsGame {
+
+    private static Map<Integer, String> movesMap = new HashMap<Integer, String>() {{
+        put(0, "rock");
+        put(1, "paper");
+        put(2, "scissors");
+    }};
+
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+        int wins = 0;
+        int losses = 0;
+
+        System.out.println("Welcome to Rock-Paper-Scissors! Please enter \"rock\", \"paper\", \"scissors\", or \"quit\" to exit.");
+
+        while (true) {
+            System.out.println("-------------------------");
+            System.out.print("Enter your move: ");
+            String playerMove = scanner.nextLine();
+
+            if (playerMove.equals("quit")) {
+                System.out.println("You won " + wins + " times and lost " + losses + " times.");
+                System.out.println("Thanks for playing! See you again.");
+                break;
+            }
+
+            if (!movesMap.containsValue(playerMove)) {
+                System.out.println("Your move isn't valid!");
+                continue;
+            }
+
+            String computerMove = getComputerMove();
+
+            if (playerMove.equals(computerMove)) {
+                System.out.println("It's a tie!");
+            } else if (isPlayerWin(playerMove, computerMove)) {
+                System.out.println("You won!");
+                wins++;
+            } else {
+                System.out.println("You lost!");
+                losses++;
+            }
+        }
+    }
+
+    private static boolean isPlayerWin(String playerMove, String computerMove) {
+        return playerMove.equals("rock") && computerMove.equals("scissors")
+                || (playerMove.equals("scissors") && computerMove.equals("paper"))
+                || (playerMove.equals("paper") && computerMove.equals("rock"));
+    }
+
+    private static String getComputerMove() {
+        Random random = new Random();
+        int randomNumber = random.nextInt(3);
+        String computerMove = movesMap.get(randomNumber);
+        System.out.println("Computer move: " + computerMove);
+        return computerMove;
+    }
+}

core-java-modules/core-java-8-2/src/main/java/com/baeldung/uuid/UuidHelper.java

@@ -0,0 +1,33 @@
+package com.baeldung.uuid;
+
+import java.nio.ByteBuffer;
+import java.util.Arrays;
+import java.util.UUID;
+
+public class UuidHelper {
+
+    public static byte[] convertUUIDToBytes(UUID uuid) {
+        ByteBuffer bb = ByteBuffer.wrap(new byte[16]);
+        bb.putLong(uuid.getMostSignificantBits());
+        bb.putLong(uuid.getLeastSignificantBits());
+        return bb.array();
+    }
+
+    public static UUID convertBytesToUUID(byte[] bytes) {
+        ByteBuffer byteBuffer = ByteBuffer.wrap(bytes);
+        long high = byteBuffer.getLong();
+        long low = byteBuffer.getLong();
+        return new UUID(high, low);
+    }
+
+    public static void main(String[] args) {
+        UUID uuid = UUID.randomUUID();
+        System.out.println("Original UUID: " + uuid);
+
+        byte[] bytes = convertUUIDToBytes(uuid);
+        System.out.println("Converted byte array: " + Arrays.toString(bytes));
+
+        UUID uuidNew = convertBytesToUUID(bytes);
+        System.out.println("Converted UUID: " + uuidNew);
+    }
+}

core-java-modules/core-java-collections-4/src/main/java/com/baeldung/maps/initialize/EmptyMapInitializer.java

@@ -0,0 +1,56 @@
+package com.baeldung.maps.initialize;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Maps;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import java.util.NavigableMap;
+import java.util.SortedMap;
+import java.util.TreeMap;
+
+public class EmptyMapInitializer {
+
+  public static Map<String, String> articleMap;
+  static {
+    articleMap = new HashMap<>();
+  }
+
+  public static Map<String, String> createEmptyMap() {
+    return Collections.emptyMap();
+  }
+
+  public void createMapUsingConstructors() {
+    Map hashMap = new HashMap();
+    Map linkedHashMap = new LinkedHashMap();
+    Map treeMap = new TreeMap();
+  }
+
+  public Map<String, String> createEmptyMapUsingMapsObject() {
+    Map<String, String> emptyMap = Maps.newHashMap();
+    return emptyMap;
+  }
+
+  public Map createGenericEmptyMapUsingMapsObject() {
+    Map genericEmptyMap = Maps.<String, Integer>newHashMap();
+    return genericEmptyMap;
+  }
+
+  public static Map<String, String> createMapUsingGuava() {
+    Map<String, String> emptyMapUsingGuava =
+        Maps.newHashMap(ImmutableMap.of());
+    return emptyMapUsingGuava;
+  }
+
+  public SortedMap<String, String> createEmptySortedMap() {
+    SortedMap<String, String> sortedMap = Collections.emptySortedMap();
+    return sortedMap;
+  }
+
+  public NavigableMap<String, String> createEmptyNavigableMap() {
+    NavigableMap<String, String> navigableMap = Collections.emptyNavigableMap();
+    return navigableMap;
+  }
+
+}

core-java-modules/core-java-collections-4/src/test/java/com/baeldung/maps/initialize/EmptyMapInitializerUnitTest.java

@@ -0,0 +1,31 @@
+package com.baeldung.maps.initialize;
+
+import java.util.Map;
+import org.junit.Test;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class EmptyMapInitializerUnitTest {
+
+  @Test(expected=UnsupportedOperationException.class)
+  public void givenEmptyMap_whenAddingEntries_throwsException() {
+    Map<String, String> map = EmptyMapInitializer.createEmptyMap();
+    map.put("key", "value");
+  }
+
+  @Test
+  public void givenEmptyMap_whenChecked_returnsTrue() {
+    assertTrue(EmptyMapInitializer.articleMap.isEmpty());
+  }
+
+  @Test
+  public void givenEmptyMap_whenCreatedUsingGuava_returnsEmptyOrNot() {
+    Map<String, String> emptyMapUsingGuava =
+        EmptyMapInitializer.createMapUsingGuava();
+    assertTrue(emptyMapUsingGuava.isEmpty());
+    emptyMapUsingGuava.put("key", "value");
+    assertFalse(emptyMapUsingGuava.isEmpty());
+  }
+
+}

core-java-modules/core-java-collections-maps-4/src/main/java/com/baeldung/mapandhashmap/Main.java

@@ -0,0 +1,25 @@
+package com.baeldung.mapandhashmap;
+
+import com.baeldung.mapandhashmap.printer.HashMapPrinter;
+import com.baeldung.mapandhashmap.printer.MapPrinter;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.TreeMap;
+
+public class Main {
+    public static void main(String[] args) {
+        Map<String, String> map = new HashMap<>();
+        HashMap<String, String> hashMap = new HashMap<>();
+        TreeMap<String, String> treeMap = new TreeMap<>();
+
+        HashMapPrinter hashMapPrinter = new HashMapPrinter();
+        hashMapPrinter.printMap(hashMap);
+//        hashMapPrinter.printMap(treeMap); Compile time error
+//        hashMapPrinter.printMap(map); Compile time error
+
+        MapPrinter mapPrinter = new MapPrinter();
+        mapPrinter.printMap(hashMap);
+        mapPrinter.printMap(treeMap);
+        mapPrinter.printMap(map);
+    }
+}

core-java-modules/core-java-collections-maps-4/src/main/java/com/baeldung/mapandhashmap/printer/HashMapPrinter.java

@@ -0,0 +1,13 @@
+package com.baeldung.mapandhashmap.printer;
+
+import java.util.HashMap;
+import java.util.Map.Entry;
+
+public class HashMapPrinter {
+
+    public void printMap(final HashMap<?, ?> map) {
+        for (final Entry<?, ?> entry : map.entrySet()) {
+            System.out.println(entry.getKey() + " " + entry.getValue());
+        }
+    }
+}

core-java-modules/core-java-collections-maps-4/src/main/java/com/baeldung/mapandhashmap/printer/MapPrinter.java

@@ -0,0 +1,13 @@
+package com.baeldung.mapandhashmap.printer;
+
+import java.util.Map;
+import java.util.Map.Entry;
+
+public class MapPrinter {
+
+    public void printMap(final Map<?, ?> map) {
+        for (final Entry<?, ?> entry : map.entrySet()) {
+            System.out.println(entry.getKey() + " " + entry.getValue());
+        }
+    }
+}

core-java-modules/core-java-collections-maps-4/src/main/java/com/baeldung/mapandhashmap/printer/MapReporter.java

@@ -0,0 +1,19 @@
+package com.baeldung.mapandhashmap.printer;
+
+import java.util.Map;
+import java.util.Map.Entry;
+
+public class MapReporter {
+
+    private final Map<?, ?> map;
+
+    public MapReporter(final Map<?, ?> map) {
+        this.map = map;
+    }
+
+    public void printMap() {
+        for (final Entry<?, ?> entry : this.map.entrySet()) {
+            System.out.println(entry.getKey() + " " + entry.getValue());
+        }
+    }
+}

core-java-modules/core-java-collections-maps-4/src/test/java/com/baeldung/mapandhashmap/printer/HashMapPrinterUnitTest.java

@@ -0,0 +1,56 @@
+package com.baeldung.mapandhashmap.printer;
+
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+class HashMapPrinterUnitTest {
+
+    private final HashMapPrinter mapPrinter = new HashMapPrinter();
+    private final ByteArrayOutputStream outputStreamCaptor = new ByteArrayOutputStream();
+
+    @BeforeEach
+    public void setUp() {
+        System.setOut(new PrintStream(outputStreamCaptor));
+    }
+
+    @Test
+    @DisplayName("Test hash map printer with HashMap")
+    void testPrintHashMap() {
+        // given
+        String key = "HashMap";
+        String value = "Main default implementation for the Map interface";
+        String expected = key + " " + value;
+        HashMap<String, String> map = new HashMap<>();
+        map.put(key, value);
+        // when
+        mapPrinter.printMap(map);
+        // then
+        String actual = outputStreamCaptor.toString().trim();
+        assertThat(actual).isEqualTo(expected);
+
+    }
+
+    @Test
+    @DisplayName("Test hash map printer with LinkedHash")
+    void testPrintLinkedHashMap() {
+        // given
+        String key = "LinkedHashMap";
+        String value = "Use this implementation if you need keep the order of elements";
+        String expected = key + " " + value;
+        LinkedHashMap<String, String> map = new LinkedHashMap<>();
+        map.put(key, value);
+        // when
+        mapPrinter.printMap(map);
+        // then
+        String actual = outputStreamCaptor.toString().trim();
+        assertThat(actual).isEqualTo(expected);
+
+    }
+}

core-java-modules/core-java-collections-maps-4/src/test/java/com/baeldung/mapandhashmap/printer/MapPrinterUnitTest.java

@@ -0,0 +1,71 @@
+package com.baeldung.mapandhashmap.printer;
+
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.TreeMap;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+class MapPrinterUnitTest {
+
+    private final MapPrinter mapPrinter = new MapPrinter();
+    private final ByteArrayOutputStream outputStreamCaptor = new ByteArrayOutputStream();
+
+    @BeforeEach
+    public void setUp() {
+        System.setOut(new PrintStream(outputStreamCaptor));
+    }
+
+    @Test
+    @DisplayName("Test printer with TreeMap")
+    void testPrintTreeMap() {
+        // given
+        String key = "TreeMap";
+        String value = "Used when sorting is needed";
+        String expected = key + " " + value;
+        TreeMap<String, String> map = new TreeMap<>();
+        map.put(key, value);
+        // when
+        mapPrinter.printMap(map);
+        // then
+        String actual = outputStreamCaptor.toString().trim();
+        assertThat(actual).isEqualTo(expected);
+    }
+
+    @Test
+    @DisplayName("Test printer with HashMap")
+    void testPrintHashMap() {
+        // given
+        String key = "HashMap";
+        String value = "Main default implementation for the Map interface";
+        String expected = key + " " + value;
+        HashMap<String, String> map = new HashMap<>();
+        map.put(key, value);
+        // when
+        mapPrinter.printMap(map);
+        // then
+        String actual = outputStreamCaptor.toString().trim();
+        assertThat(actual).isEqualTo(expected);
+    }
+
+    @Test
+    @DisplayName("Test printer with LinkedHash")
+    void testPrintLinkedHashMap() {
+        // given
+        String key = "LinkedHashMap";
+        String value = "Use this implementation if you need keep the order of elements";
+        String expected = key + " " + value;
+        LinkedHashMap<String, String> map = new LinkedHashMap<>();
+        map.put(key, value);
+        // when
+        mapPrinter.printMap(map);
+        // then
+        String actual = outputStreamCaptor.toString().trim();
+        assertThat(actual).isEqualTo(expected);
+    }
+}

core-java-modules/core-java-collections-maps-4/src/test/java/com/baeldung/mapandhashmap/printer/MapReporterUnitTest.java

@@ -0,0 +1,74 @@
+package com.baeldung.mapandhashmap.printer;
+
+import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.TreeMap;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+class MapReporterUnitTest {
+
+    private final ByteArrayOutputStream outputStreamCaptor = new ByteArrayOutputStream();
+
+    @BeforeEach
+    public void setUp() {
+        System.setOut(new PrintStream(outputStreamCaptor));
+    }
+
+    @Test
+    @DisplayName("Test reporter with TreeMap")
+    void testPrintTreeMap() {
+        // given
+        String key = "TreeMap";
+        String value = "Used when sorting is needed";
+        String expected = key + " " + value;
+        TreeMap<String, String> map = new TreeMap<>();
+        map.put(key, value);
+        // when
+        MapReporter mapReporter = new MapReporter(map);
+        mapReporter.printMap();
+        // then
+        String actual = outputStreamCaptor.toString().trim();
+        assertThat(actual).isEqualTo(expected);
+    }
+
+    @Test
+    @DisplayName("Test reporter with HashMap")
+    void testPrintHashMap() {
+        // given
+        String key = "HashMap";
+        String value = "Main default implementation for the Map interface";
+        String expected = key + " " + value;
+        HashMap<String, String> map = new HashMap<>();
+        map.put(key, value);
+        // when
+        MapReporter mapReporter = new MapReporter(map);
+        mapReporter.printMap();
+        // then
+        String actual = outputStreamCaptor.toString().trim();
+        assertThat(actual).isEqualTo(expected);
+    }
+
+    @Test
+    @DisplayName("Test reporter with LinkedHash")
+    void testPrintLinkedHashMap() {
+        // given
+        String key = "LinkedHashMap";
+        String value = "Use this implementation if you need keep the order of elements";
+        String expected = key + " " + value;
+        LinkedHashMap<String, String> map = new LinkedHashMap<>();
+        map.put(key, value);
+        // when
+        MapReporter mapReporter = new MapReporter(map);
+        mapReporter.printMap();
+        // then
+        String actual = outputStreamCaptor.toString().trim();
+        assertThat(actual).isEqualTo(expected);
+    }
+
+}

core-java-modules/core-java-concurrency-advanced-3/src/main/java/com/baeldung/atomicstampedreference/StampedAccount.java

@@ -1,25 +1,22 @@
 package com.baeldung.atomicstampedreference;
 
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicStampedReference;
 
 public class StampedAccount {
 
-    private AtomicInteger stamp = new AtomicInteger(0);
-    private AtomicStampedReference<Integer> account = new AtomicStampedReference<>(0, 0);
-
-    public int getBalance() {
-        return account.getReference();
-    }
-
-    public int getStamp() {
-        return account.getStamp();
-    }
+    private final AtomicInteger stamp = new AtomicInteger(0);
+    private final AtomicStampedReference<Integer> account = new AtomicStampedReference<>(0, 0);
 
     public boolean deposit(int funds) {
         int[] stamps = new int[1];
         int current = this.account.get(stamps);
         int newStamp = this.stamp.incrementAndGet();
+
+        // Thread is paused here to allow other threads to update the stamp and amount (for testing only)
+        sleep();
+
         return this.account.compareAndSet(current, current + funds, stamps[0], newStamp);
     }
 
@@ -29,4 +26,19 @@ public class StampedAccount {
         int newStamp = this.stamp.incrementAndGet();
         return this.account.compareAndSet(current, current - funds, stamps[0], newStamp);
     }
+
+    public int getBalance() {
+        return account.getReference();
+    }
+
+    public int getStamp() {
+        return account.getStamp();
+    }
+
+    private static void sleep() {
+        try {
+            TimeUnit.SECONDS.sleep(1);
+        } catch (InterruptedException ignored) {
+        }
+    }
 }

core-java-modules/core-java-concurrency-advanced-3/src/test/java/com/baeldung/atomicstampedreference/ThreadStampedAccountUnitTest.java

@@ -1,21 +1,38 @@
 package com.baeldung.atomicstampedreference;
 
-import org.junit.Assert;
 import org.junit.Test;
 
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
 public class ThreadStampedAccountUnitTest {
 
     @Test
     public void givenMultiThread_whenStampedAccount_thenSetBalance() throws InterruptedException {
         StampedAccount account = new StampedAccount();
+
         Thread t = new Thread(() -> {
-            while (!account.withdrawal(100))
+            while (!account.deposit(100)) {
                 Thread.yield();
+            }
         });
         t.start();
-        Assert.assertTrue(account.deposit(100));
-        t.join(1_000);
-        Assert.assertFalse(t.isAlive());
-        Assert.assertSame(0, account.getBalance());
+
+        Thread t2 = new Thread(() -> {
+            while (!account.withdrawal(100)) {
+                Thread.yield();
+            }
+        });
+        t2.start();
+
+        t.join(10_000);
+        t2.join(10_000);
+
+        assertFalse(t.isAlive());
+        assertFalse(t2.isAlive());
+
+        assertEquals(0, account.getBalance());
+        assertTrue(account.getStamp() > 0);
     }
 }

core-java-modules/core-java-concurrency-advanced/src/main/java/com/baeldung/concurrent/phaser/LongRunningAction.java

@@ -16,12 +16,17 @@ class LongRunningAction implements Runnable {
     public void run() {
         System.out.println("This is phase " + ph.getPhase());
         System.out.println("Thread " + threadName + " before long running action");
-        ph.arriveAndAwaitAdvance();
+        
         try {
-            Thread.sleep(20);
+            Thread.sleep(2000);
         } catch (InterruptedException e) {
             e.printStackTrace();
         }
+        
+        System.out.println("Thread " + threadName + " action completed and waiting for others");
+        ph.arriveAndAwaitAdvance();
+        System.out.println("Thread " + threadName + " proceeding in phase " + ph.getPhase());
+        
         ph.arriveAndDeregister();
     }
 }

core-java-modules/core-java-concurrency-advanced/src/test/java/com/baeldung/concurrent/phaser/PhaserUnitTest.java

@@ -26,13 +26,20 @@ public class PhaserUnitTest {
         executorService.submit(new LongRunningAction("thread-3", ph));
 
         //then
+        System.out.println("Thread " + Thread.currentThread().getName() + " waiting for others");
         ph.arriveAndAwaitAdvance();
+        System.out.println("Thread " + Thread.currentThread().getName() + " proceeding in phase " + ph.getPhase());
+        
         assertEquals(1, ph.getPhase());
 
         //and
         executorService.submit(new LongRunningAction("thread-4", ph));
         executorService.submit(new LongRunningAction("thread-5", ph));
+        
+        System.out.println("Thread " + Thread.currentThread().getName() + " waiting for others");
         ph.arriveAndAwaitAdvance();
+        System.out.println("Thread " + Thread.currentThread().getName() + " proceeding in phase " + ph.getPhase());
+        
         assertEquals(2, ph.getPhase());
 
 

core-java-modules/core-java-exceptions-4/src/main/java/com/baeldung/exception/missingreturnstatement/MissingReturnStatement.java

@@ -0,0 +1,41 @@
+package com.baeldung.exception.missingreturnstatement;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+public class MissingReturnStatement {
+    public static void main(String[] args) {
+        int a = -12;
+        int result = pow(a);
+        System.out.println(result);
+        Map<String, Integer> dictionary = createDictionary();
+        dictionary.forEach((s, integer) -> System.out.println(s + " " + integer));
+    }
+
+    public static int pow(int number) {
+        int pow = number * number;
+        return pow;
+    }
+
+    public static String checkNumber(int number) {
+        if (number == 0) {
+            return "It's equals to zero";
+        }
+
+        for (int i = 0; i < number; i++) {
+            if (i > 100) {
+                return "It's a big number";
+            }
+        }
+        return "It's a negative number";
+    }
+
+    public static Map<String, Integer> createDictionary() {
+        List<String> words = Arrays.asList("Hello", "World");
+        return words.stream()
+            .collect(Collectors.toMap(s -> s, s -> 1));
+    }
+
+}

core-java-modules/core-java-exceptions-4/src/test/java/com/baeldung/exception/missingreturnstatement/MissingReturnStatementUnitTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.exception.missingreturnstatement;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.Map;
+
+import org.junit.Test;
+
+public class MissingReturnStatementUnitTest {
+
+    @Test
+    public void givenANumber_thenReturnItsPow() {
+        int number = 10;
+        int pow = MissingReturnStatement.pow(number);
+        assertEquals(100, pow);
+    }
+
+    @Test
+    public void givenABigNumber_thenReturnItsType() {
+        int number = 200;
+        String type = MissingReturnStatement.checkNumber(number);
+        assertEquals("It's a big number", type);
+    }
+
+    @Test
+    public void givenANegativeNumber_thenReturnItsType() {
+        int number = -10;
+        String type = MissingReturnStatement.checkNumber(number);
+        assertEquals("It's a negative number", type);
+    }
+
+    @Test
+    public void getStringDictionary_thenPrintValues() {
+        Map<String, Integer> dictionary = MissingReturnStatement.createDictionary();
+        assertEquals(2, dictionary.size());
+        dictionary.forEach((s, integer) -> System.out.println(s + " - " + integer));
+    }
+}

core-java-modules/core-java-jar/pom.xml

@@ -259,110 +259,7 @@
                 </plugins>
             </build>
         </profile>
-        <!-- java instrumentation profiles to build jars -->
-        <profile>
-            <id>buildAgentLoader</id>
-            <build>
-                <plugins>
-                    <plugin>
-                        <groupId>org.apache.maven.plugins</groupId>
-                        <artifactId>maven-jar-plugin</artifactId>
-                        <executions>
-                            <execution>
-                                <phase>package</phase>
-                                <goals>
-                                    <goal>jar</goal>
-                                </goals>
-                                <configuration>
-                                    <classifier>agentLoader</classifier>
-                                    <classesDirectory>target/classes</classesDirectory>
-                                    <archive>
-                                        <manifest>
-                                            <addClasspath>true</addClasspath>
-                                        </manifest>
-                                        <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF</manifestFile>
-                                    </archive>
-
-                                    <includes>
-                                        <include>com/baeldung/instrumentation/application/AgentLoader.class</include>
-                                        <include>com/baeldung/instrumentation/application/Launcher.class</include>
-                                    </includes>
-                                </configuration>
-                            </execution>
-                        </executions>
-                    </plugin>
-                </plugins>
-            </build>
-        </profile>
-        <profile>
-            <id>buildApplication</id>
-            <build>
-                <plugins>
-                    <plugin>
-                        <groupId>org.apache.maven.plugins</groupId>
-                        <artifactId>maven-jar-plugin</artifactId>
-                        <executions>
-                            <execution>
-                                <phase>package</phase>
-                                <goals>
-                                    <goal>jar</goal>
-                                </goals>
-                                <configuration>
-                                    <classifier>application</classifier>
-                                    <classesDirectory>target/classes</classesDirectory>
-                                    <archive>
-                                        <manifest>
-                                            <addClasspath>true</addClasspath>
-                                        </manifest>
-                                        <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF</manifestFile>
-                                    </archive>
-
-                                    <includes>
-                                        <include>com/baeldung/instrumentation/application/MyAtm.class</include>
-                                        <include>com/baeldung/instrumentation/application/MyAtmApplication.class</include>
-                                        <include>com/baeldung/instrumentation/application/Launcher.class</include>
-                                    </includes>
-                                </configuration>
-                            </execution>
-                        </executions>
-                    </plugin>
-                </plugins>
-            </build>
-        </profile>
-        <profile>
-            <id>buildAgent</id>
-            <build>
-                <plugins>
-                    <plugin>
-                        <groupId>org.apache.maven.plugins</groupId>
-                        <artifactId>maven-jar-plugin</artifactId>
-                        <executions>
-                            <execution>
-                                <phase>package</phase>
-                                <goals>
-                                    <goal>jar</goal>
-                                </goals>
-                                <configuration>
-                                    <classifier>agent</classifier>
-                                    <classesDirectory>target/classes</classesDirectory>
-                                    <archive>
-                                        <manifest>
-                                            <addClasspath>true</addClasspath>
-                                        </manifest>
-                                        <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF</manifestFile>
-                                    </archive>
-
-                                    <includes>
-                                        <include>com/baeldung/instrumentation/agent/AtmTransformer.class</include>
-                                        <include>com/baeldung/instrumentation/agent/MyInstrumentationAgent.class</include>
-                                    </includes>
-                                </configuration>
-                            </execution>
-                        </executions>
-                    </plugin>
-                </plugins>
-            </build>
-        </profile>
+       
     </profiles>
 
     <properties>

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

@@ -15,3 +15,13 @@ This module contains articles about working with the Java Virtual Machine (JVM).
 - [What Causes java.lang.OutOfMemoryError: unable to create new native thread](https://www.baeldung.com/java-outofmemoryerror-unable-to-create-new-native-thread)
 - [View Bytecode of a Class File in Java](https://www.baeldung.com/java-class-view-bytecode)
 - More articles: [[next -->]](/core-java-modules/core-java-jvm-2)
+
+
+To run the code for the Instrumentation: https://www.baeldung.com/java-instrumentation article:
+1- build the module
+2- run the module 3 times to build the 3 jars:
+    mvn install -PbuildAgentLoader
+    mvn install -PbuildApplication
+    mvn install -PbuildAgent
+3- update the commands in the article with the exact names of the jars generated in the target folder
+4- update the path in the AgentLoader class with the path of the agent on your system 

core-java-modules/core-java-jvm/pom.xml

@@ -57,6 +57,11 @@
             <artifactId>jol-core</artifactId>
             <version>${jol-core.version}</version>
         </dependency>
+        <dependency> <!-- needed to bridge to slf4j for projects that use the log4j APIs directly -->
+            <groupId>org.slf4j</groupId>
+            <artifactId>log4j-over-slf4j</artifactId>
+            <version>${org.slf4j.version}</version>
+        </dependency>
     </dependencies>
 
     <properties>
@@ -66,5 +71,114 @@
         <asm.version>8.0.1</asm.version>
         <bcel.version>6.5.0</bcel.version>
     </properties>
+    <profiles>
+        <!-- java instrumentation profiles to build jars -->
+        <profile>
+            <id>buildAgentLoader</id>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-jar-plugin</artifactId>
+                        <executions>
+                            <execution>
+                                <phase>package</phase>
+                                <goals>
+                                    <goal>jar</goal>
+                                </goals>
+                                <configuration>
+                                    <classifier>agentLoader</classifier>
+                                    <classesDirectory>target/classes</classesDirectory>
+                                    <archive>
+                                        <manifest>
+                                            <addClasspath>true</addClasspath>
+                                            <mainClass>com.baeldung.instrumentation.application.Launcher</mainClass>
+                                        </manifest>
+                                        <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF</manifestFile>
+                                    </archive>
+
+                                    <includes>
+                                        <include>com/baeldung/instrumentation/application/AgentLoader.class</include>
+                                        <include>com/baeldung/instrumentation/application/Launcher.class</include>
+                                    </includes>
+                                </configuration>
+                            </execution>
+                        </executions>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
+        <profile>
+            <id>buildApplication</id>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-jar-plugin</artifactId>
+                        <executions>
+                            <execution>
+                                <phase>package</phase>
+                                <goals>
+                                    <goal>jar</goal>
+                                </goals>
+                                <configuration>
+                                    <classifier>application</classifier>
+                                    <classesDirectory>target/classes</classesDirectory>
+                                    <archive>
+                                        <manifest>
+                                            <addClasspath>true</addClasspath>
+                                            <mainClass>com.baeldung.instrumentation.application.Launcher</mainClass>
+                                        </manifest>
+                                        <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF</manifestFile>
+                                    </archive>
+
+                                    <includes>
+                                        <include>com/baeldung/instrumentation/application/MyAtm.class</include>
+                                        <include>com/baeldung/instrumentation/application/MyAtmApplication.class</include>
+                                        <include>com/baeldung/instrumentation/application/Launcher.class</include>
+                                    </includes>
+                                </configuration>
+                            </execution>
+                        </executions>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
+        <profile>
+            <id>buildAgent</id>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-jar-plugin</artifactId>
+                        <executions>
+                            <execution>
+                                <phase>package</phase>
+                                <goals>
+                                    <goal>jar</goal>
+                                </goals>
+                                <configuration>
+                                    <classifier>agent</classifier>
+                                    <classesDirectory>target/classes</classesDirectory>
+                                    <archive>
+                                        <manifest>
+                                            <addClasspath>true</addClasspath>
+                                            <mainClass>com.baeldung.instrumentation.application.Launcher</mainClass>
+                                        </manifest>
+                                        <manifestFile>${project.build.outputDirectory}/META-INF/MANIFEST.MF</manifestFile>
+                                    </archive>
+
+                                    <includes>
+                                        <include>com/baeldung/instrumentation/agent/AtmTransformer.class</include>
+                                        <include>com/baeldung/instrumentation/agent/MyInstrumentationAgent.class</include>
+                                    </includes>
+                                </configuration>
+                            </execution>
+                        </executions>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>
+    </profiles>
 
 </project>

core-java-modules/core-java-jvm/src/main/resources/META-INF/MANIFEST.MF

@@ -0,0 +1,5 @@
+Agent-Class: com.baeldung.instrumentation.agent.MyInstrumentationAgent
+Can-Redefine-Classes: true
+Can-Retransform-Classes: true
+Premain-Class: com.baeldung.instrumentation.agent.MyInstrumentationAgent
+Main-Class: com.baeldung.instrumentation.application.Launcher

core-java-modules/core-java-security-3/src/test/java/com/baeldung/truststore/TrustStoreUnitTest.java

@@ -0,0 +1,29 @@
+package com.baeldung.truststore;
+
+import org.junit.Test;
+import org.junit.jupiter.api.Assertions;
+
+import java.io.IOException;
+import java.security.InvalidAlgorithmParameterException;
+import java.security.KeyStore;
+import java.security.KeyStoreException;
+import java.security.NoSuchAlgorithmException;
+import java.security.cert.CertificateException;
+import java.security.cert.PKIXParameters;
+
+public class TrustStoreUnitTest {
+
+    @Test
+    public void whenOpeningTrustStore_thenExceptionIsThrown() throws Exception {
+        KeyStore keyStore = getKeyStore();
+        InvalidAlgorithmParameterException invalidAlgorithmParameterException =
+          Assertions.assertThrows(InvalidAlgorithmParameterException.class, () -> new PKIXParameters(keyStore));
+        Assertions.assertEquals("the trustAnchors parameter must be non-empty", invalidAlgorithmParameterException.getMessage());
+    }
+
+    private KeyStore getKeyStore() throws CertificateException, NoSuchAlgorithmException, IOException, KeyStoreException {
+        KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType());
+        ks.load(null, "changeIt".toCharArray());
+        return ks;
+    }
+}

docker/docker-include-outside-build-context/projects/config/Dockerfile

@@ -0,0 +1,2 @@
+FROM nginx:latest
+COPY nginx.conf /etc/nginx/nginx.conf

docker/docker-include-outside-build-context/projects/config/nginx.conf

@@ -0,0 +1,8 @@
+events {}  
+  
+http {  
+ server {  
+    listen 80;
+    index index.html;
+  }  
+}

docker/docker-include-outside-build-context/projects/sample-site/docker/Dockerfile

@@ -0,0 +1,3 @@
+FROM nginx:latest
+COPY sample-site/html/* /etc/nginx/html/
+COPY config/nginx.conf /etc/nginx/nginx.conf

docker/docker-include-outside-build-context/projects/sample-site/docker/Dockerfile-from-base

@@ -0,0 +1,2 @@
+FROM sample-site-base:latest
+COPY html/* /etc/nginx/html/

docker/docker-include-outside-build-context/projects/sample-site/docker/Dockerfile-script

@@ -0,0 +1,3 @@
+FROM nginx:latest
+COPY html/* /etc/nginx/html/
+COPY config/nginx.conf /etc/nginx/nginx.conf

docker/docker-include-outside-build-context/projects/sample-site/docker/build-docker.sh

@@ -0,0 +1,6 @@
+mkdir tmp-context
+cp -R ../html tmp-context/
+cp -R ../../config tmp-context/
+cp Dockerfile-script tmp-context/Dockerfile
+docker build -t sample-site:latest tmp-context
+rm -rf tmp-context

docker/docker-include-outside-build-context/projects/sample-site/html/index.html

@@ -0,0 +1,10 @@
+<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <title>Sample Site</title>
+</head>
+<body>
+  <h2>Welcome to the first page of the site</h2>
+</body>
+</html>

gradle/gradle-source-vs-target-compatibility/build.gradle

@@ -0,0 +1,12 @@
+plugins {
+    id 'java'
+}
+
+description = 'gradle-source-vs-target-compatibility'
+
+group 'com.baeldung'
+
+java {
+    sourceCompatibility = "1.6"
+    targetCompatibility = "1.8"
+}

gradle/gradle-source-vs-target-compatibility/src/main/java/com/baeldung/helloworld/HelloWorldApp.java

@@ -0,0 +1,9 @@
+package com.baeldung.helloworld;
+
+public class HelloWorldApp {
+
+    public static void main(String[] args) {
+        System.out.println("Hello World!");
+    }
+
+}

gradle/settings.gradle

@@ -6,5 +6,6 @@ include 'greeter'
 include 'gradletaskdemo'
 include 'junit5'
 include 'gradle-employee-app'
+include 'gradle-source-vs-target-compatibility'
 
 println 'This will be executed during the initialization phase.'

java-collections-maps-3/src/main/java/com/baeldung/map/invert/InvertHashMapExample.java

@@ -0,0 +1,59 @@
+package com.baeldung.map.invert;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.stream.Collectors;
+
+public class InvertHashMapExample {
+
+    public static void main(String[] args) {
+
+        Map<String, Integer> map = new HashMap<>();
+        map.put("first", 1);
+        map.put("second", 2);
+        System.out.println(map);
+
+        invertMapUsingForLoop(map);
+        invertMapUsingStreams(map);
+        invertMapUsingMapper(map);
+
+        map.put("two", 2);
+        invertMapUsingGroupingBy(map);
+    }
+
+    public static <V, K> Map<V, K> invertMapUsingForLoop(Map<K, V> map) {
+        Map<V, K> inversedMap = new HashMap<V, K>();
+        for (Entry<K, V> entry : map.entrySet()) {
+            inversedMap.put(entry.getValue(), entry.getKey());
+        }
+        System.out.println(inversedMap);
+        return inversedMap;
+    }
+
+    public static <V, K> Map<V, K> invertMapUsingStreams(Map<K, V> map) {
+        Map<V, K> inversedMap = map.entrySet()
+            .stream()
+            .collect(Collectors.toMap(Entry::getValue, Entry::getKey));
+        System.out.println(inversedMap);
+        return inversedMap;
+    }
+
+    public static <K, V> Map<V, K> invertMapUsingMapper(Map<K, V> sourceMap) {
+        Map<V, K> inversedMap = sourceMap.entrySet()
+            .stream()
+            .collect(Collectors.toMap(Entry::getValue, Entry::getKey, (oldValue, newValue) -> oldValue));
+        System.out.println(inversedMap);
+        return inversedMap;
+    }
+
+    public static <V, K> Map<V, List<K>> invertMapUsingGroupingBy(Map<K, V> map) {
+        Map<V, List<K>> inversedMap = map.entrySet()
+            .stream()
+            .collect(Collectors.groupingBy(Map.Entry::getValue, Collectors.mapping(Map.Entry::getKey, Collectors.toList())));
+        System.out.println(inversedMap);
+        return inversedMap;
+    }
+
+}

java-collections-maps-3/src/test/java/com/baeldung/map/invert/InvertHashMapUnitTest.java

@@ -0,0 +1,72 @@
+package com.baeldung.map.invert;
+
+import static org.junit.Assert.assertNotEquals;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+public class InvertHashMapUnitTest {
+
+    Map<String, Integer> sourceMap;
+
+    @BeforeEach
+    void setup() {
+        sourceMap = new HashMap<>();
+        sourceMap.put("Sunday", 0);
+        sourceMap.put("Monday", 1);
+        sourceMap.put("Tuesday", 2);
+        sourceMap.put("Wednesday", 3);
+        sourceMap.put("Thursday", 4);
+        sourceMap.put("Friday", 5);
+        sourceMap.put("Saturday", 6);
+    }
+
+    @Test
+    void givenSourceMap_whenUsingForLoop_returnsInvertedMap() {
+        Map<Integer, String> inversedMap = InvertHashMapExample.invertMapUsingForLoop(sourceMap);
+        
+        assertNotNull(inversedMap);
+        assertEquals(sourceMap.size(), inversedMap.size());
+        assertEquals("Monday", inversedMap.get(1));
+    }
+
+    @Test
+    void givenSourceMap_whenUsingStreams_returnsInvertedMap() {
+        Map<Integer, String> inversedMap = InvertHashMapExample.invertMapUsingStreams(sourceMap);
+        
+        assertNotNull(inversedMap);
+        assertEquals(sourceMap.size(), inversedMap.size());
+        assertEquals("Monday", inversedMap.get(1));
+    }
+
+    @Test
+    void givenSourceMap_whenUsingMapper_returnsInvertedMap() {
+        Map<Integer, String> inversedMap = InvertHashMapExample.invertMapUsingMapper(sourceMap);
+        
+        assertNotNull(inversedMap);
+        assertEquals(sourceMap.size(), inversedMap.size());
+        assertEquals("Monday", inversedMap.get(1));
+    }
+
+    @Test
+    void givenSourceMapWithDuplicateValues_whenUsingGroupBy_returnsInvertedMap() {
+        sourceMap.put("MONDAY", 1);
+        Map<Integer, List<String>> inversedMap = InvertHashMapExample.invertMapUsingGroupingBy(sourceMap);
+        
+        assertNotNull(inversedMap);
+        assertNotEquals(sourceMap.size(), inversedMap.size()); // duplicate keys are merged now
+        assertEquals(2, inversedMap.get(1).size());
+        assertTrue(inversedMap.get(1).contains("Monday"));
+        assertTrue(inversedMap.get(1).contains("MONDAY"));
+    }
+
+}

java-native/src/main/cpp/com_baeldung_jni_RegisterNativesHelloWorldJNI.cpp

@@ -0,0 +1,21 @@
+#include "com_baeldung_jni_RegisterNativesHelloWorldJNI.h"
+#include <iostream>
+
+
+JNIEXPORT jstring JNICALL hello (JNIEnv* env, jobject thisObject) {
+    std::string hello = "Hello from registered native C++ !!";
+    std::cout << hello << std::endl;
+    return env->NewStringUTF(hello.c_str());
+}
+
+static JNINativeMethod methods[] = {
+  {"sayHello", "()Ljava/lang/String;", (void*) &hello },
+};
+
+
+JNIEXPORT void JNICALL Java_com_baeldung_jni_RegisterNativesHelloWorldJNI_register (JNIEnv* env, jobject thsObject) {
+    jclass clazz = env->FindClass("com/baeldung/jni/RegisterNativesHelloWorldJNI");
+
+    (env)->RegisterNatives(clazz, methods, sizeof(methods)/sizeof(methods[0]));
+}
+

java-native/src/main/cpp/com_baeldung_jni_RegisterNativesHelloWorldJNI.h

@@ -0,0 +1,29 @@
+/* DO NOT EDIT THIS FILE - it is machine generated */
+#include <jni.h>
+/* Header for class com_baeldung_jni_RegisterNativesHelloWorldJNI */
+
+#ifndef _Included_com_baeldung_jni_RegisterNativesHelloWorldJNI
+#define _Included_com_baeldung_jni_RegisterNativesHelloWorldJNI
+#ifdef __cplusplus
+extern "C" {
+#endif
+/*
+ * Class:     com_baeldung_jni_RegisterNativesHelloWorldJNI
+ * Method:    sayHello
+ * Signature: ()Ljava/lang/String;
+ */
+JNIEXPORT jstring JNICALL Java_com_baeldung_jni_RegisterNativesHelloWorldJNI_sayHello
+  (JNIEnv *, jobject);
+
+/*
+ * Class:     com_baeldung_jni_RegisterNativesHelloWorldJNI
+ * Method:    register
+ * Signature: ()V
+ */
+JNIEXPORT void JNICALL Java_com_baeldung_jni_RegisterNativesHelloWorldJNI_register
+  (JNIEnv *, jobject);
+
+#ifdef __cplusplus
+}
+#endif
+#endif

java-native/src/main/cpp/generateNativeLibMac.sh

@@ -3,4 +3,5 @@
 g++ -c -fPIC -I${JAVA_HOME}/include -I${JAVA_HOME}/include/darwin com_baeldung_jni_HelloWorldJNI.cpp -o com_baeldung_jni_HelloWorldJNI.o
 g++ -c -fPIC -I${JAVA_HOME}/include -I${JAVA_HOME}/include/darwin com_baeldung_jni_ExampleParametersJNI.cpp -o com_baeldung_jni_ExampleParametersJNI.o
 g++ -c -fPIC -I${JAVA_HOME}/include -I${JAVA_HOME}/include/darwin com_baeldung_jni_ExampleObjectsJNI.cpp -o com_baeldung_jni_ExampleObjectsJNI.o
-g++ -dynamiclib -o ../../../native/macos/libnative.dylib com_baeldung_jni_HelloWorldJNI.o com_baeldung_jni_ExampleParametersJNI.o com_baeldung_jni_ExampleObjectsJNI.o -lc
+g++ -c -fPIC -I${JAVA_HOME}/include -I${JAVA_HOME}/include/darwin com_baeldung_jni_RegisterNativesHelloWorldJNI.cpp -o com_baeldung_jni_RegisterNativesHelloWorldJNI.o
+g++ -dynamiclib -o ../../../native/macos/libnative.dylib com_baeldung_jni_HelloWorldJNI.o com_baeldung_jni_ExampleParametersJNI.o com_baeldung_jni_ExampleObjectsJNI.o com_baeldung_jni_RegisterNativesHelloWorldJNI.o -lc

java-native/src/main/java/com/baeldung/jni/RegisterNativesHelloWorldJNI.java

@@ -0,0 +1,18 @@
+package com.baeldung.jni;
+
+public class RegisterNativesHelloWorldJNI {
+
+    static {
+        System.loadLibrary("native");
+    }
+
+    public static void main(String[] args) {
+        RegisterNativesHelloWorldJNI helloWorldJNI = new RegisterNativesHelloWorldJNI();
+        helloWorldJNI.register();
+        helloWorldJNI.sayHello();
+    }
+
+    public native String sayHello();
+
+    public native void register();
+}

java-native/src/test/java/com/baeldung/jni/registernatives/JNIRegisterNativesManualTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.jni.registernatives;
+
+import com.baeldung.jni.RegisterNativesHelloWorldJNI;
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+
+public class JNIRegisterNativesManualTest {
+    @Before
+    public void setup() {
+        System.loadLibrary("native");
+    }
+
+    @Test
+    public void whenRegisteredNativeHelloWorld_thenOutputIsAsExpected() {
+        RegisterNativesHelloWorldJNI helloWorld = new RegisterNativesHelloWorldJNI();
+        helloWorld.register();
+
+        String helloFromNative = helloWorld.sayHello();
+
+        assertNotNull(helloFromNative);
+        assertTrue(helloFromNative.equals("Hello from registered native C++ !!"));
+    }
+}

parent-spring-5/pom.xml

@@ -24,7 +24,7 @@
     </dependencies>
 
     <properties>
-        <spring.version>5.3.13</spring.version>
+        <spring.version>5.3.16</spring.version>
         <spring-security.version>5.6.0</spring-security.version>
         <spring-boot-starter-test.version>1.5.10.RELEASE</spring-boot-starter-test.version>
     </properties>

persistence-modules/hibernate-queries/src/main/java/com/baeldung/hibernate/scalarmethod/HibernateScalarExample.java

@@ -0,0 +1,47 @@
+package com.baeldung.hibernate.scalarmethod;
+
+import java.util.List;
+
+import org.hibernate.Session;
+import org.hibernate.type.StandardBasicTypes;
+
+public class HibernateScalarExample {
+
+    private Session session;
+
+    public HibernateScalarExample(Session session) {
+        this.session = session;
+    }
+
+    public List<Object[]> fetchColumnWithNativeQuery() {
+        return session.createNativeQuery("SELECT * FROM Student student")
+          .list();
+    }
+
+    public List<Object[]> fetchColumnWithScalar() {
+        return session.createNativeQuery("SELECT * FROM Student student")
+          .addScalar("studentId", StandardBasicTypes.LONG)
+          .addScalar("name", StandardBasicTypes.STRING)
+          .addScalar("age", StandardBasicTypes.INTEGER)
+          .list();
+    }
+
+    public List<String> fetchLimitedColumnWithScalar() {
+        return session.createNativeQuery("SELECT * FROM Student student")
+          .addScalar("name", StandardBasicTypes.STRING)
+          .list();
+    }
+
+    public List<Object[]> fetchColumnWithOverloadedScalar() {
+        return session.createNativeQuery("SELECT * FROM Student student")
+          .addScalar("name", StandardBasicTypes.STRING)
+          .addScalar("age")
+          .list();
+    }
+
+    public Integer fetchAvgAgeWithScalar() {
+        return (Integer) session.createNativeQuery("SELECT AVG(age) as avgAge FROM Student student")
+          .addScalar("avgAge")
+          .uniqueResult();
+    }
+}

persistence-modules/hibernate-queries/src/test/java/com/baeldung/hibernate/scalarmethod/HibernateScalarExampleUnitTest.java

@@ -0,0 +1,83 @@
+package com.baeldung.hibernate.scalarmethod;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.Random;
+
+import org.hibernate.Session;
+import org.hibernate.Transaction;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import com.baeldung.hibernate.HibernateUtil;
+import com.baeldung.hibernate.pojo.Student;
+
+public class HibernateScalarExampleUnitTest {
+
+    private static Session session;
+    private static Transaction transaction;
+    private static final int DATA_SIZE = 50000;
+    private static HibernateScalarExample scalarExample;
+
+    @BeforeClass
+    public static void setUp() throws IOException {
+        session = HibernateUtil.getSessionFactory().openSession();
+        transaction = session.beginTransaction();
+        scalarExample = new HibernateScalarExample(session);
+        session.createNativeQuery("delete from Student").executeUpdate();
+        for (int i = 0; i < DATA_SIZE; i++) {
+            Student student = new Student("John-" + i, generateRandomAge(5, 24));
+            session.persist(student);
+        }
+        transaction.commit();
+        transaction = session.beginTransaction();
+    }
+
+    @AfterClass
+    public static void tearDown() {
+        transaction.rollback();
+        session.close();
+    }
+
+    @Test
+    public void givenNativeQuery_whenNoScalarUsed_ThenFetchAll() {
+        List<Object[]> list = scalarExample.fetchColumnWithNativeQuery();
+        assertEquals(DATA_SIZE, list.size());
+    }
+
+    @Test
+    public void givenNativeQuery_whenScalarUsed_ThenFetchAll() {
+        List<Object[]> list = scalarExample.fetchColumnWithScalar();
+        assertEquals(DATA_SIZE, list.size());
+    }
+
+    @Test
+    public void givenNativeQuery_whenScalarUsed_ThenFetchLimitedColumns() {
+        List<String> list = scalarExample.fetchLimitedColumnWithScalar();
+        for (String colValue : list) {
+            assertTrue(colValue.startsWith("John"));
+        }
+    }
+
+    @Test
+    public void givenNativeQuery_whenScalarUsedForSingleResult_ThenSingleValueReturned() {
+        List<Object[]> list = scalarExample.fetchColumnWithOverloadedScalar();
+        for (Object[] colArray : list) {
+            assertEquals(2, colArray.length);
+        }
+    }
+
+    @Test
+    public void whenScalarUsedForAvgAge_ThenSingleValueReturned() {
+        Integer avgAge = scalarExample.fetchAvgAgeWithScalar();
+        assertEquals(true, (avgAge >= 5 && avgAge <= 24));
+    }
+
+    private static int generateRandomAge(int min, int max) {
+        return new Random().nextInt(max - min + 1) + min;
+    }
+}

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

@@ -1,3 +1,4 @@
 ### Relevant Articles:
 
+- [Configure and Use Multiple DataSources in Spring Boot](https://www.baeldung.com/spring-boot-configure-multiple-datasources)
 - [Introduction to Spring Data JDBC](https://www.baeldung.com/spring-data-jdbc-intro)

spring-boot-modules/pom.xml

@@ -51,6 +51,7 @@
         <!-- <module>spring-boot-keycloak</module> --> <!-- Fixing under JAVA-8271 -->
         <module>spring-boot-libraries</module>
         <module>spring-boot-libraries-2</module>
+        <module>spring-boot-libraries-comparison</module>
         <module>spring-boot-logging-log4j2</module>
         <module>spring-boot-multiple-datasources</module>
         <module>spring-boot-mvc</module>

spring-boot-modules/spring-boot-data-2/README.md

@@ -1,5 +1,6 @@
 ### Relevant Articles:
 
+- [HttpMessageNotWritableException: No Converter for [class …] With Preset Content-Type](https://www.baeldung.com/spring-no-converter-with-preset)
 - [Spring Boot: Customize the Jackson ObjectMapper](https://www.baeldung.com/spring-boot-customize-jackson-objectmapper)
 - [“HttpMessageNotWritableException: No converter found for return value of type”](https://www.baeldung.com/spring-no-converter-found)
 - [Creating a Read-Only Repository with Spring Data](https://www.baeldung.com/spring-data-read-only-repository)

spring-boot-modules/spring-boot-libraries-comparison/README.md

@@ -0,0 +1,7 @@
+## Spring Boot Libraries
+
+This module contains articles about various Spring Boot libraries Comparison
+
+### Relevant Articles:
+
+- [GraphQL vs REST](https://www.baeldung.com/graphql-vs-rest/)

spring-boot-modules/spring-boot-libraries-comparison/pom.xml

@@ -0,0 +1,46 @@
+<?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-libraries-comparison</artifactId>
+
+    <parent>
+        <groupId>com.baeldung.spring-boot-modules</groupId>
+        <artifactId>spring-boot-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.data</groupId>
+            <artifactId>spring-data-jpa</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.graphql-java</groupId>
+            <artifactId>graphql-spring-boot-starter</artifactId>
+            <version>${graphql-spring-boot-starter.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.graphql-java</groupId>
+            <artifactId>graphql-java-tools</artifactId>
+            <version>${graphql-java-tools.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.graphql-java</groupId>
+            <artifactId>graphiql-spring-boot-starter</artifactId>
+            <version>${graphql-spring-boot-starter.version}</version>
+        </dependency>
+    </dependencies>
+
+
+    <properties>
+        <graphql-spring-boot-starter.version>5.0.2</graphql-spring-boot-starter.version>
+        <graphql-java-tools.version>5.2.4</graphql-java-tools.version>
+    </properties>
+
+</project>

spring-boot-modules/spring-boot-libraries-comparison/src/main/java/com/baeldung/graphqlvsrest/GraphqlVsRestApplication.java

@@ -0,0 +1,19 @@
+package com.baeldung.graphqlvsrest;
+
+import com.baeldung.graphqlvsrest.configuration.GraphqlConfiguration;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration;
+import org.springframework.context.annotation.Import;
+
+@SpringBootApplication
+@Import(GraphqlConfiguration.class)
+@EnableAutoConfiguration(exclude = {SecurityAutoConfiguration.class})
+public class GraphqlVsRestApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(GraphqlVsRestApplication.class, args);
+    }
+
+}

spring-boot-modules/spring-boot-libraries-comparison/src/main/java/com/baeldung/graphqlvsrest/configuration/GraphqlConfiguration.java

@@ -0,0 +1,35 @@
+package com.baeldung.graphqlvsrest.configuration;
+
+import com.baeldung.graphqlvsrest.repository.OrderRepository;
+import com.baeldung.graphqlvsrest.resolver.Mutation;
+import com.baeldung.graphqlvsrest.resolver.ProductResolver;
+import com.baeldung.graphqlvsrest.resolver.Query;
+import com.baeldung.graphqlvsrest.repository.ProductRepository;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+public class GraphqlConfiguration {
+
+    @Autowired
+    ProductRepository productRepository;
+
+    @Autowired
+    OrderRepository orderRepository;
+
+    @Bean
+    public Query query() {
+        return new Query(productRepository);
+    }
+
+    @Bean
+    public ProductResolver productResolver(){
+        return new ProductResolver(orderRepository);
+    }
+
+    @Bean
+    public Mutation mutation() {
+        return new Mutation(productRepository);
+    }
+}

spring-boot-modules/spring-boot-libraries-comparison/src/main/java/com/baeldung/graphqlvsrest/controller/OrderController.java

@@ -0,0 +1,25 @@
+package com.baeldung.graphqlvsrest.controller;
+
+import com.baeldung.graphqlvsrest.entity.Order;
+import com.baeldung.graphqlvsrest.entity.Product;
+import com.baeldung.graphqlvsrest.model.ProductModel;
+import com.baeldung.graphqlvsrest.repository.OrderRepository;
+import com.baeldung.graphqlvsrest.repository.ProductRepository;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.data.domain.Pageable;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.List;
+
+@RestController
+@RequestMapping("order")
+public class OrderController {
+
+    @Autowired
+    OrderRepository orderRepository;
+
+    @GetMapping()
+    public List<Order> getOrders(@RequestParam("product-id") Integer productId){
+        return orderRepository.getOrdersByProduct(productId);
+    }
+}

spring-boot-modules/spring-boot-libraries-comparison/src/main/java/com/baeldung/graphqlvsrest/controller/ProductController.java

@@ -0,0 +1,38 @@
+package com.baeldung.graphqlvsrest.controller;
+
+import com.baeldung.graphqlvsrest.entity.Product;
+import com.baeldung.graphqlvsrest.model.ProductModel;
+import com.baeldung.graphqlvsrest.repository.ProductRepository;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.data.domain.Pageable;
+import org.springframework.web.bind.annotation.*;
+
+import java.util.List;
+
+@RestController
+@RequestMapping("product")
+public class ProductController {
+
+    @Autowired
+    ProductRepository productRepository;
+
+    @GetMapping
+    public List<Product> getProducts(Pageable pageable){
+        return productRepository.getProducts(pageable.getPageSize(), pageable.getPageNumber());
+    }
+
+    @GetMapping("/{product-id}")
+    public Product getProducts(@PathVariable("product-id") Integer productId){
+        return productRepository.getProduct(productId);
+    }
+
+    @PostMapping
+    public Product save(@RequestBody ProductModel productModel){
+        return productRepository.save(productModel);
+    }
+
+    @PutMapping("/{product-id}")
+    public Product update(@PathVariable("product-id") Integer productId, @RequestBody ProductModel productModel){
+        return productRepository.update(productId, productModel);
+    }
+}

spring-boot-modules/spring-boot-libraries-comparison/src/main/java/com/baeldung/graphqlvsrest/entity/Order.java

@@ -0,0 +1,58 @@
+package com.baeldung.graphqlvsrest.entity;
+
+public class Order {
+    private Integer id;
+    private Integer product_id;
+    private String customer_uuid;
+    private String status;
+    private String address;
+    private String creation_date;
+
+    public Integer getId() {
+        return id;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
+    public Integer getProduct_id() {
+        return product_id;
+    }
+
+    public void setProduct_id(Integer product_id) {
+        this.product_id = product_id;
+    }
+
+    public String getStatus() {
+        return status;
+    }
+
+    public void setStatus(String status) {
+        this.status = status;
+    }
+
+    public String getCustomer_uuid() {
+        return customer_uuid;
+    }
+
+    public void setCustomer_uuid(String customer_uuid) {
+        this.customer_uuid = customer_uuid;
+    }
+
+    public String getAddress() {
+        return address;
+    }
+
+    public void setAddress(String address) {
+        this.address = address;
+    }
+
+    public String getCreation_date() {
+        return creation_date;
+    }
+
+    public void setCreation_date(String creation_date) {
+        this.creation_date = creation_date;
+    }
+}

spring-boot-modules/spring-boot-libraries-comparison/src/main/java/com/baeldung/graphqlvsrest/entity/Product.java

@@ -0,0 +1,115 @@
+package com.baeldung.graphqlvsrest.entity;
+
+import com.baeldung.graphqlvsrest.model.ProductModel;
+
+import java.util.List;
+
+public class Product {
+    private Integer id;
+    private String name;
+    private String description;
+    private String status;
+    private String currency;
+    private Double price;
+    private List<String> image_url;
+    private List<String> video_url;
+    private Integer stock;
+    private Float average_rating;
+
+    public Product(Integer id, ProductModel productModel) {
+        this.id = id;
+        this.name = productModel.getName();
+        this.description = productModel.getDescription();
+        this.currency = productModel.getCurrency();
+        this.price = productModel.getPrice();
+        this.stock = productModel.getStock();
+        this.image_url = productModel.getImage_url();
+        this.video_url = productModel.getVideo_url();
+        this.average_rating = 0F;
+        this.status = productModel.getStatus();
+    }
+
+    public Product(){
+
+    }
+
+    public Integer getId() {
+        return id;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getDescription() {
+        return description;
+    }
+
+    public void setDescription(String description) {
+        this.description = description;
+    }
+
+    public String getStatus() {
+        return status;
+    }
+
+    public void setStatus(String status) {
+        this.status = status;
+    }
+
+    public String getCurrency() {
+        return currency;
+    }
+
+    public void setCurrency(String currency) {
+        this.currency = currency;
+    }
+
+    public Double getPrice() {
+        return price;
+    }
+
+    public void setPrice(Double price) {
+        this.price = price;
+    }
+
+    public List<String> getImage_url() {
+        return image_url;
+    }
+
+    public void setImage_url(List<String> image_url) {
+        this.image_url = image_url;
+    }
+
+    public List<String> getVideo_url() {
+        return video_url;
+    }
+
+    public void setVideo_url(List<String> video_url) {
+        this.video_url = video_url;
+    }
+
+    public Integer getStock() {
+        return stock;
+    }
+
+    public void setStock(Integer stock) {
+        this.stock = stock;
+    }
+
+    public Float getAverage_rating() {
+        return average_rating;
+    }
+
+    public void setAverage_rating(Float average_rating) {
+        this.average_rating = average_rating;
+    }
+}

spring-boot-modules/spring-boot-libraries-comparison/src/main/java/com/baeldung/graphqlvsrest/model/ProductModel.java

@@ -0,0 +1,92 @@
+package com.baeldung.graphqlvsrest.model;
+
+import java.util.List;
+
+public class ProductModel {
+    private String name;
+    private String description;
+    private String status;
+    private String currency;
+    private Double price;
+    private List<String> image_url;
+    private List<String> video_url;
+    private Integer stock;
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getDescription() {
+        return description;
+    }
+
+    public void setDescription(String description) {
+        this.description = description;
+    }
+
+    public String getStatus() {
+        return status;
+    }
+
+    public void setStatus(String status) {
+        this.status = status;
+    }
+
+    public String getCurrency() {
+        return currency;
+    }
+
+    public void setCurrency(String currency) {
+        this.currency = currency;
+    }
+
+    public Double getPrice() {
+        return price;
+    }
+
+    public void setPrice(Double price) {
+        this.price = price;
+    }
+
+    public List<String> getImage_url() {
+        return image_url;
+    }
+
+    public void setImage_url(List<String> image_url) {
+        this.image_url = image_url;
+    }
+
+    public List<String> getVideo_url() {
+        return video_url;
+    }
+
+    public void setVideo_url(List<String> video_url) {
+        this.video_url = video_url;
+    }
+
+    public Integer getStock() {
+        return stock;
+    }
+
+    public void setStock(Integer stock) {
+        this.stock = stock;
+    }
+
+    @Override
+    public String toString() {
+        return "ProductModel{" +
+                "name='" + name + '\'' +
+                ", description='" + description + '\'' +
+                ", status='" + status + '\'' +
+                ", currency='" + currency + '\'' +
+                ", price=" + price +
+                ", image_url=" + image_url +
+                ", video_url=" + video_url +
+                ", stock=" + stock +
+                '}';
+    }
+}

spring-boot-modules/spring-boot-libraries-comparison/src/main/java/com/baeldung/graphqlvsrest/repository/OrderRepository.java

@@ -0,0 +1,11 @@
+package com.baeldung.graphqlvsrest.repository;
+
+import com.baeldung.graphqlvsrest.entity.Order;
+import com.baeldung.graphqlvsrest.entity.Product;
+import com.baeldung.graphqlvsrest.model.ProductModel;
+
+import java.util.List;
+
+public interface OrderRepository {
+    List<Order> getOrdersByProduct(Integer productId);
+}

spring-boot-modules/spring-boot-libraries-comparison/src/main/java/com/baeldung/graphqlvsrest/repository/ProductRepository.java

@@ -0,0 +1,14 @@
+package com.baeldung.graphqlvsrest.repository;
+
+import com.baeldung.graphqlvsrest.entity.Product;
+import com.baeldung.graphqlvsrest.model.ProductModel;
+
+import java.util.List;
+
+public interface ProductRepository {
+    List<Product> getProducts(Integer pageSize, Integer pageNumber);
+    Product getProduct(Integer id);
+    Product save(ProductModel productModel);
+    Product update(Integer productId, ProductModel productModel);
+
+}

spring-boot-modules/spring-boot-libraries-comparison/src/main/java/com/baeldung/graphqlvsrest/repository/impl/OrderRepositoryImpl.java

@@ -0,0 +1,36 @@
+package com.baeldung.graphqlvsrest.repository.impl;
+
+import com.baeldung.graphqlvsrest.entity.Order;
+import com.baeldung.graphqlvsrest.repository.OrderRepository;
+import org.springframework.stereotype.Repository;
+
+import java.util.ArrayList;
+import java.util.Date;
+import java.util.List;
+import java.util.UUID;
+import java.util.stream.Collectors;
+
+@Repository
+public class OrderRepositoryImpl implements OrderRepository {
+
+    private static List<Order> orderList = new ArrayList<>();
+
+    public OrderRepositoryImpl() {
+        for (int i = 1; i <= 100; i++){
+            Order order = new Order();
+            order.setId(i);
+            order.setProduct_id(i%10);
+            order.setAddress(UUID.randomUUID().toString());
+            order.setCustomer_uuid(UUID.randomUUID().toString());
+            order.setCreation_date(new Date(System.currentTimeMillis()).toString());
+            order.setStatus("Delivered");
+            orderList.add(order);
+        }
+    }
+
+
+    @Override
+    public List<Order> getOrdersByProduct(Integer productId) {
+        return orderList.stream().filter(order -> order.getProduct_id().equals(productId)).collect(Collectors.toList());
+    }
+}

spring-boot-modules/spring-boot-libraries-comparison/src/main/java/com/baeldung/graphqlvsrest/repository/impl/ProductRepositoryImpl.java

@@ -0,0 +1,74 @@
+package com.baeldung.graphqlvsrest.repository.impl;
+
+import com.baeldung.graphqlvsrest.entity.Product;
+import com.baeldung.graphqlvsrest.model.ProductModel;
+import com.baeldung.graphqlvsrest.repository.ProductRepository;
+import org.springframework.stereotype.Repository;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Collectors;
+
+@Repository
+public class ProductRepositoryImpl implements ProductRepository {
+
+    private static List<Product> productList = new ArrayList<>();
+
+    public ProductRepositoryImpl() {
+        for (int i = 1; i <= 10; i++){
+            Product product = new Product();
+            product.setId(i);
+            product.setName(String.format("Product %d", i));
+            product.setDescription(String.format("Product %d description", i));
+            product.setCurrency(String.format("Product %d currency", i));
+            product.setPrice(Double.valueOf(i^2));
+            product.setStock(10);
+            product.setAverage_rating(0F);
+            product.setImage_url(Arrays.asList(String.format("www.baeldung.com/imageurl/%d", i)));
+            product.setVideo_url(Arrays.asList(String.format("www.baeldung.com/videourl/%d", i)));
+            productList.add(product);
+        }
+    }
+
+    @Override
+    public List<Product> getProducts(Integer pageSize, Integer pageNumber) {
+        return productList.stream().skip(pageSize*pageNumber).limit(pageSize).collect(Collectors.toList());
+    }
+
+    @Override
+    public Product getProduct(Integer id) {
+        return productList.stream().filter(product -> product.getId().equals(id)).findFirst().orElse(null);
+    }
+
+    @Override
+    public Product save(ProductModel productModel) {
+        Product product = new Product(productList.size()+1, productModel);
+        productList.add(product);
+        return product;
+    }
+
+    @Override
+    public Product update(Integer productId, ProductModel productModel) {
+        Product product =  getProduct(productId);
+        if (product != null){
+            update(product, productModel);
+        }
+        return product;
+    }
+
+    private void update(Product product, ProductModel productModel){
+        if (productModel != null) {
+            System.out.println(productModel.toString());
+            Optional.ofNullable(productModel.getName()).ifPresent(product::setName);
+            Optional.ofNullable(productModel.getDescription()).ifPresent(product::setDescription);
+            Optional.ofNullable(productModel.getCurrency()).ifPresent(product::setCurrency);
+            Optional.ofNullable(productModel.getImage_url()).ifPresent(product::setImage_url);
+            Optional.ofNullable(productModel.getStock()).ifPresent(product::setStock);
+            Optional.ofNullable(productModel.getStatus()).ifPresent(product::setStatus);
+            Optional.ofNullable(productModel.getVideo_url()).ifPresent(product::setVideo_url);
+            Optional.ofNullable(productModel.getPrice()).ifPresent(product::setPrice);
+        }
+    }
+}

spring-boot-modules/spring-boot-libraries-comparison/src/main/java/com/baeldung/graphqlvsrest/resolver/Mutation.java

@@ -0,0 +1,22 @@
+package com.baeldung.graphqlvsrest.resolver;
+
+import com.baeldung.graphqlvsrest.entity.Product;
+import com.baeldung.graphqlvsrest.model.ProductModel;
+import com.baeldung.graphqlvsrest.repository.ProductRepository;
+import com.coxautodev.graphql.tools.GraphQLMutationResolver;
+
+public class Mutation implements GraphQLMutationResolver {
+
+    private ProductRepository productRepository;
+    public Mutation(ProductRepository productRepository){
+        this.productRepository = productRepository;
+    }
+
+    public Product saveProduct(ProductModel productModel) {
+        return productRepository.save(productModel);
+    }
+
+    public Product updateProduct(Integer productId, ProductModel productModel) {
+        return productRepository.update(productId, productModel);
+    }
+}

spring-boot-modules/spring-boot-libraries-comparison/src/main/java/com/baeldung/graphqlvsrest/resolver/ProductResolver.java

@@ -0,0 +1,18 @@
+package com.baeldung.graphqlvsrest.resolver;
+
+import com.baeldung.graphqlvsrest.entity.Order;
+import com.baeldung.graphqlvsrest.entity.Product;
+import com.baeldung.graphqlvsrest.repository.OrderRepository;
+import com.coxautodev.graphql.tools.GraphQLResolver;
+
+import java.util.List;
+
+public class ProductResolver implements GraphQLResolver<Product> {
+    private OrderRepository orderRepository;
+    public ProductResolver(OrderRepository orderRepository){
+        this.orderRepository = orderRepository;
+    }
+    public List<Order> getOrders(Product product){
+        return orderRepository.getOrdersByProduct(product.getId());
+    }
+}

spring-boot-modules/spring-boot-libraries-comparison/src/main/java/com/baeldung/graphqlvsrest/resolver/Query.java

@@ -0,0 +1,27 @@
+package com.baeldung.graphqlvsrest.resolver;
+
+import com.baeldung.graphqlvsrest.entity.Order;
+import com.baeldung.graphqlvsrest.entity.Product;
+import com.baeldung.graphqlvsrest.repository.OrderRepository;
+import com.baeldung.graphqlvsrest.repository.ProductRepository;
+import com.coxautodev.graphql.tools.GraphQLQueryResolver;
+
+import java.util.List;
+
+public class Query implements GraphQLQueryResolver {
+
+    private ProductRepository productRepository;
+    public Query(ProductRepository productRepository){
+        this.productRepository = productRepository;
+    }
+
+    public List<Product> getProducts(int pageSize, int pageNumber) {
+        return productRepository.getProducts(pageSize, pageNumber);
+    }
+
+    public Product getProduct(int id) {
+        return productRepository.getProduct(id);
+    }
+
+
+}

spring-boot-modules/spring-boot-libraries-comparison/src/main/resources/graphql/schema.graphqls

@@ -0,0 +1,57 @@
+type Product {
+    id: ID
+    name: String!
+    description: String
+    status: String
+    currency: String!
+    price: Float
+    image_url: [String]
+    video_url: [String]
+    stock: Int
+    average_rating: Float
+    orders:[Order]
+}
+
+type Order{
+    id:ID
+    product_id:Int
+    customer_uuid:String
+    address:String
+    status:String
+    creation_date:String
+}
+
+input ProductModel {
+    name: String!
+    description: String
+    status: String
+    currency: String!
+    price: Float
+    image_url: [String]
+    video_url: [String]
+    stock: Int
+}
+
+input ProductUpdateModel {
+    name: String
+    description: String
+    status: String
+    currency: String
+    price: Float
+    image_url: [String]
+    video_url: [String]
+    stock: Int
+}
+
+
+# The Root Query for the application
+type Query {
+    products(size: Int, page: Int): [Product]!
+    product(id: Int): Product!
+}
+
+# The Root Mutation for the application
+type Mutation {
+    saveProduct(product: ProductModel) : Product!
+    updateProduct(id: Int, product: ProductUpdateModel) : Product!
+}

spring-boot-modules/spring-boot-security/src/main/java/com/baeldung/antmatchers/AntMatchersExampleApplication.java

@@ -0,0 +1,13 @@
+package com.baeldung.antmatchers;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class AntMatchersExampleApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(AntMatchersExampleApplication.class, args);
+    }
+
+}

spring-boot-modules/spring-boot-security/src/main/java/com/baeldung/antmatchers/config/SecurityConfiguration.java

@@ -0,0 +1,39 @@
+package com.baeldung.antmatchers.config;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder;
+import org.springframework.security.config.annotation.web.builders.HttpSecurity;
+import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
+import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
+import org.springframework.security.crypto.password.PasswordEncoder;
+
+@Configuration
+public class SecurityConfiguration extends WebSecurityConfigurerAdapter {
+
+    @Override
+    public void configure(AuthenticationManagerBuilder auth) throws Exception {
+        auth.inMemoryAuthentication()
+                .withUser("admin").password(passwordEncoder().encode("password")).roles("USER", "ADMIN")
+                .and()
+                .withUser("user").password(passwordEncoder().encode("password")).roles("USER");
+    }
+
+    @Bean
+    public PasswordEncoder passwordEncoder() {
+        return new BCryptPasswordEncoder();
+    }
+
+    @Override
+    protected void configure(HttpSecurity http) throws Exception {
+        http
+                .authorizeRequests()
+                .antMatchers("/products/**").permitAll()
+                .and()
+                .authorizeRequests()
+                .antMatchers("/customers/**").hasRole("ADMIN")
+                .anyRequest().authenticated()
+                .and()
+                .httpBasic();
+    }
+}

spring-boot-modules/spring-boot-security/src/main/java/com/baeldung/antmatchers/controllers/CustomerController.java

@@ -0,0 +1,15 @@
+package com.baeldung.antmatchers.controllers;
+
+import com.baeldung.antmatchers.dtos.Customer;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class CustomerController {
+
+    @GetMapping("/customers/{id}")
+    public Customer getCustomerById(@PathVariable("id") String id) {
+        return new Customer("Customer 1", "Address 1", "Phone 1");
+    }
+}

spring-boot-modules/spring-boot-security/src/main/java/com/baeldung/antmatchers/controllers/ProductController.java

@@ -0,0 +1,21 @@
+package com.baeldung.antmatchers.controllers;
+
+import com.baeldung.antmatchers.dtos.Product;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+@RestController
+public class ProductController {
+
+    @GetMapping("/products")
+    public List<Product> getProducts() {
+        return new ArrayList<>(Arrays.asList(
+          new Product("Product 1", "Description 1", 1.0),
+          new Product("Product 2", "Description 2", 2.0)
+        ));
+    }
+}

spring-boot-modules/spring-boot-security/src/main/java/com/baeldung/antmatchers/dtos/Customer.java

@@ -0,0 +1,39 @@
+package com.baeldung.antmatchers.dtos;
+
+import java.io.Serializable;
+
+public class Customer implements Serializable {
+    private String name;
+    private String address;
+    private String phone;
+
+    public Customer(String name, String address, String phone) {
+        this.name = name;
+        this.address = address;
+        this.phone = phone;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getAddress() {
+        return address;
+    }
+
+    public void setAddress(String address) {
+        this.address = address;
+    }
+
+    public String getPhone() {
+        return phone;
+    }
+
+    public void setPhone(String phone) {
+        this.phone = phone;
+    }
+}

spring-boot-modules/spring-boot-security/src/main/java/com/baeldung/antmatchers/dtos/Product.java

@@ -0,0 +1,39 @@
+package com.baeldung.antmatchers.dtos;
+
+import java.io.Serializable;
+
+public class Product implements Serializable {
+    private String name;
+    private String description;
+    private double price;
+
+    public Product(String name, String description, double price) {
+        this.name = name;
+        this.description = description;
+        this.price = price;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getDescription() {
+        return description;
+    }
+
+    public void setDescription(String description) {
+        this.description = description;
+    }
+
+    public double getPrice() {
+        return price;
+    }
+
+    public void setPrice(double price) {
+        this.price = price;
+    }
+}

spring-boot-modules/spring-boot-security/src/test/java/com/baeldung/antmatchers/controllers/CustomerControllerTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.antmatchers.controllers;
+
+import org.junit.jupiter.api.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.test.web.servlet.MockMvc;
+
+import static org.springframework.security.test.web.servlet.request.SecurityMockMvcRequestPostProcessors.user;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+@RunWith(SpringRunner.class)
+@WebMvcTest(value = CustomerController.class)
+class CustomerControllerIntegrationTest {
+
+    @Autowired
+    private MockMvc mockMvc;
+
+    @Test
+    void getCustomerByIdUnauthorized() throws Exception {
+        mockMvc.perform(get("/customers/1")).andExpect(status().isUnauthorized());
+    }
+
+    @Test
+    void getCustomerByIdForbidden() throws Exception {
+        mockMvc.perform(get("/customers/1").with(user("user").roles("USER")))
+          .andExpect(status().isForbidden());
+    }
+
+    @Test
+    void getCustomerByIdOk() throws Exception {
+        mockMvc.perform(get("/customers/1").with(user("admin").roles("ADMIN")))
+          .andExpect(status().isOk());
+    }
+
+}

spring-boot-modules/spring-boot-security/src/test/java/com/baeldung/antmatchers/controllers/ProductControllerTest.java

@@ -0,0 +1,25 @@
+package com.baeldung.antmatchers.controllers;
+
+import org.junit.jupiter.api.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
+import org.springframework.test.context.junit4.SpringRunner;
+import org.springframework.test.web.servlet.MockMvc;
+
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+@RunWith(SpringRunner.class)
+@WebMvcTest(value = ProductController.class)
+class ProductControllerIntegrationTest {
+
+    @Autowired
+    private MockMvc mockMvc;
+
+    @Test
+    void getProducts() throws Exception {
+        mockMvc.perform(get("/products"))
+          .andExpect(status().isOk());
+    }
+}

spring-boot-modules/spring-boot-swagger/generated/swagger-ui/swagger.json

@@ -1,57 +0,0 @@
-{
-  "swagger" : "2.0",
-  "info" : {
-    "description" : "This is a Baeldung Document Enum Sample Code",
-    "version" : "v1",
-    "title" : "Baeldung - Document Enum",
-    "contact" : {
-      "name" : "Parikshit Murria",
-      "email" : "pmurria@baeldung.com"
-    },
-    "license" : {
-      "name" : "Apache 2.0",
-      "url" : "https://www.apache.org/licenses/LICENSE-2.0.html"
-    }
-  },
-  "host" : "baeldung.com",
-  "basePath" : "/api",
-  "schemes" : [ "http", "https" ],
-  "paths" : {
-    "/hire" : {
-      "post" : {
-        "summary" : "This method is used to hire employee with a specific role",
-        "description" : "",
-        "operationId" : "hireEmployee",
-        "produces" : [ "application/json" ],
-        "parameters" : [ {
-          "in" : "body",
-          "name" : "body",
-          "description" : "role",
-          "required" : true,
-          "schema" : {
-            "$ref" : "#/definitions/Employee"
-          }
-        } ],
-        "responses" : {
-          "200" : {
-            "description" : "successful operation",
-            "schema" : {
-              "type" : "string"
-            }
-          }
-        }
-      }
-    }
-  },
-  "definitions" : {
-    "Employee" : {
-      "type" : "object",
-      "properties" : {
-        "role" : {
-          "type" : "string",
-          "enum" : [ "Engineer", "Clerk", "Driver", "Janitor" ]
-        }
-      }
-    }
-  }
-}

spring-boot-modules/spring-boot-swagger/pom.xml

@@ -63,7 +63,7 @@
                                     <name>Apache 2.0</name>
                                 </license>
                             </info>
-                            <swaggerDirectory>generated/swagger-ui</swaggerDirectory>
+                            <swaggerDirectory>${basedir}/target/swagger-ui</swaggerDirectory>
                         </apiSource>
                     </apiSources>
                 </configuration>

spring-cloud/spring-cloud-gateway/pom.xml

@@ -177,5 +177,21 @@
                 </plugins>
             </build>
         </profile>
+        
+        <profile>
+            <id>gateway-url-rewrite</id>
+            <build>
+                <plugins>
+                    <plugin>
+                        <groupId>org.springframework.boot</groupId>
+                        <artifactId>spring-boot-maven-plugin</artifactId>
+                        <configuration>
+                            <mainClass>com.baeldung.springcloudgateway.rewrite.URLRewriteGatewayApplication</mainClass>
+                            <jvmArguments>-Dspring.profiles.active=url-rewrite</jvmArguments>
+                        </configuration>
+                    </plugin>
+                </plugins>
+            </build>
+        </profile>        
     </profiles>
 </project>

spring-cloud/spring-cloud-gateway/src/main/java/com/baeldung/springcloudgateway/rewrite/URLRewriteGatewayApplication.java

@@ -0,0 +1,25 @@
+/**
+ * 
+ */
+package com.baeldung.springcloudgateway.rewrite;
+
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.builder.SpringApplicationBuilder;
+import org.springframework.cloud.gateway.filter.GatewayFilter;
+
+import reactor.core.publisher.Mono;
+
+/**
+ * @author Baeldung
+ *
+ */
+@SpringBootApplication
+public class URLRewriteGatewayApplication {
+    
+    public static void main(String[] args) {
+        new SpringApplicationBuilder(URLRewriteGatewayApplication.class)
+          .profiles("url-rewrite")
+          .run(args);
+    }
+    
+}

spring-cloud/spring-cloud-gateway/src/main/java/com/baeldung/springcloudgateway/rewrite/routes/DynamicRewriteRoute.java

@@ -0,0 +1,43 @@
+package com.baeldung.springcloudgateway.rewrite.routes;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.cloud.gateway.route.RouteLocator;
+import org.springframework.cloud.gateway.route.builder.RouteLocatorBuilder;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Profile;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR;
+import static org.springframework.cloud.gateway.support.ServerWebExchangeUtils.addOriginalRequestUrl;
+
+import java.util.Random;
+
+@Configuration
+@Profile("url-rewrite")
+public class DynamicRewriteRoute {
+    
+    @Value("${rewrite.backend.uri}")
+    private String backendUri;
+    private static Random rnd = new Random();
+    
+    @Bean
+    public RouteLocator dynamicZipCodeRoute(RouteLocatorBuilder builder) {
+        return builder.routes()
+          .route("dynamicRewrite", r ->
+             r.path("/v2/zip/**")
+              .filters(f -> f.filter((exchange, chain) -> {
+                  ServerHttpRequest req = exchange.getRequest();
+                  addOriginalRequestUrl(exchange, req.getURI());
+                  String path = req.getURI().getRawPath();
+                  String newPath = path.replaceAll(
+                    "/v2/zip/(?<zipcode>.*)", 
+                    "/api/zip/${zipcode}-" + String.format("%03d", rnd.nextInt(1000)));
+                  ServerHttpRequest request = req.mutate().path(newPath).build();
+                  exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, request.getURI());
+                  return chain.filter(exchange.mutate().request(request).build());
+              }))
+              .uri(backendUri))
+          .build();
+    }
+}

spring-cloud/spring-cloud-gateway/src/main/java/com/baeldung/springcloudgateway/webfilters/WebFilterGatewayApplication.java

@@ -8,7 +8,7 @@ public class WebFilterGatewayApplication {
 
     public static void main(String[] args) {
         new SpringApplicationBuilder(WebFilterGatewayApplication.class)
-          .profiles("webfilters")
+          .profiles("url-rewrite")
           .run(args);
     }
 

spring-cloud/spring-cloud-gateway/src/main/resources/application-nosecurity.yml

@@ -0,0 +1,8 @@
+# Enable this profile to disable security
+spring:
+  autoconfigure:
+    exclude:
+     - org.springframework.boot.autoconfigure.security.servlet.SecurityAutoConfiguration
+     - org.springframework.boot.actuate.autoconfigure.ManagementSecurityAutoConfiguration
+     - org.springframework.boot.autoconfigure.security.reactive.ReactiveSecurityAutoConfiguration
+     - org.springframework.boot.actuate.autoconfigure.security.reactive.ReactiveManagementWebSecurityAutoConfiguration

spring-cloud/spring-cloud-gateway/src/main/resources/application-url-rewrite.yml

@@ -0,0 +1,11 @@
+spring:
+  cloud:
+    gateway:
+      routes:
+      - id: rewrite_v1
+        uri: ${rewrite.backend.uri:http://example.com}
+        predicates:
+        - Path=/v1/customer/**
+        filters:
+        - RewritePath=/v1/customer/(?<segment>.*),/api/$\{segment}
+        

spring-cloud/spring-cloud-gateway/src/test/java/com/baeldung/springcloudgateway/rewrite/URLRewriteGatewayApplicationLiveTest.java

@@ -0,0 +1,109 @@
+package com.baeldung.springcloudgateway.rewrite;
+
+import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.io.OutputStream;
+import java.net.InetSocketAddress;
+
+import org.junit.AfterClass;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
+import org.springframework.boot.web.server.LocalServerPort;
+import org.springframework.test.context.ActiveProfiles;
+import org.springframework.test.context.DynamicPropertyRegistry;
+import org.springframework.test.context.DynamicPropertySource;
+import org.springframework.test.web.reactive.server.WebTestClient;
+
+import com.sun.net.httpserver.HttpServer;
+
+@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
+@ActiveProfiles({ "nosecurity", "url-rewrite" })
+class URLRewriteGatewayApplicationLiveTest {
+
+    // NOTE for Eclipse users: By default, Eclipse will complain about com.sun.** classes.
+    // To solve this issue, follow instructions available at the :
+    // https://stackoverflow.com/questions/13155734/eclipse-cant-recognize-com-sun-net-httpserver-httpserver-package
+    private static HttpServer mockServer;
+    private static Logger log = LoggerFactory.getLogger(URLRewriteGatewayApplicationLiveTest.class);
+
+    // Create a running HttpServer that echoes back the request URL.
+    private static HttpServer startTestServer() {
+
+        try {
+            log.info("[I26] Starting mock server");
+            mockServer = HttpServer.create();
+            mockServer.bind(new InetSocketAddress(0), 0);
+            mockServer.createContext("/api", (xchg) -> {
+                String uri = xchg.getRequestURI()
+                    .toString();
+                log.info("[I23] Backend called: uri={}", uri);
+                xchg.getResponseHeaders()
+                    .add("Content-Type", "text/plain");
+                xchg.sendResponseHeaders(200, 0);
+                OutputStream os = xchg.getResponseBody();
+                os.write(uri.getBytes());
+                os.flush();
+                os.close();
+            });
+
+            mockServer.start();
+            InetSocketAddress localAddr = mockServer.getAddress();
+            log.info("[I36] mock server started: local address={}", localAddr);
+            
+            return mockServer;
+        } catch (Exception ex) {
+            throw new RuntimeException(ex);
+        }
+
+    }
+
+    // TIP: https://www.baeldung.com/spring-dynamicpropertysource
+    @DynamicPropertySource
+    static void registerBackendServer(DynamicPropertyRegistry registry) {
+        registry.add("rewrite.backend.uri", () -> {
+            HttpServer s = startTestServer();
+            return "http://localhost:" + s.getAddress().getPort();
+        });
+    }
+
+    @AfterClass
+    public static void stopMockBackend() throws Exception {
+        log.info("[I40] Shutdown mock http server");
+        mockServer.stop(5);
+    }
+
+    @LocalServerPort
+    private int localPort;
+
+    @Test
+    void testWhenApiCall_thenRewriteSuccess(@Autowired WebTestClient webClient) {
+        webClient.get()
+          .uri("http://localhost:" + localPort + "/v1/customer/customer1")
+          .exchange()
+          .expectBody()
+          .consumeWith((result) -> {
+              String body = new String(result.getResponseBody());
+              log.info("[I99] body={}", body);
+              assertEquals("/api/customer1", body);
+          });
+    }
+
+    @Test
+    void testWhenDslCall_thenRewriteSuccess(@Autowired WebTestClient webClient) {
+        webClient.get()
+          .uri("http://localhost:" + localPort + "/v2/zip/123456")
+          .exchange()
+          .expectBody()
+          .consumeWith((result) -> {
+              String body = new String(result.getResponseBody());
+              log.info("[I99] body={}", body);
+              assertTrue(body.matches("/api/zip/123456-\\d{3}"));
+          });
+    }
+    
+}

spring-cloud/spring-cloud-openfeign/pom.xml

@@ -48,7 +48,15 @@
         <dependency>
             <groupId>io.github.openfeign.form</groupId>
             <artifactId>feign-form-spring</artifactId>
-            </dependency>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-security</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.springframework.security</groupId>
+            <artifactId>spring-security-oauth2-client</artifactId>
+        </dependency>
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-test</artifactId>

spring-cloud/spring-cloud-openfeign/src/main/java/com/baeldung/cloud/openfeign/client/PaymentClient.java

@@ -0,0 +1,16 @@
+package com.baeldung.cloud.openfeign.client;
+
+import com.baeldung.cloud.openfeign.model.Payment;
+import com.baeldung.cloud.openfeign.oauthfeign.OAuthFeignConfig;
+import org.springframework.cloud.openfeign.FeignClient;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RequestMethod;
+
+import java.util.List;
+
+@FeignClient(name = "payment-client", url = "http://localhost:8081/resource-server-jwt", configuration = OAuthFeignConfig.class)
+public interface PaymentClient {
+
+    @RequestMapping(value = "/payments", method = RequestMethod.GET)
+    List<Payment> getPayments();
+}

spring-cloud/spring-cloud-openfeign/src/main/java/com/baeldung/cloud/openfeign/controller/PaymentController.java

@@ -0,0 +1,24 @@
+package com.baeldung.cloud.openfeign.controller;
+
+import com.baeldung.cloud.openfeign.client.PaymentClient;
+import com.baeldung.cloud.openfeign.model.Payment;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.List;
+
+@RestController
+public class PaymentController {
+
+    private final PaymentClient paymentClient;
+
+    public PaymentController(PaymentClient paymentClient) {
+        this.paymentClient = paymentClient;
+    }
+
+    @GetMapping("/payments")
+    public List<Payment> getPayments() {
+        List<Payment> payments = paymentClient.getPayments();
+        return payments;
+    }
+}

spring-cloud/spring-cloud-openfeign/src/main/java/com/baeldung/cloud/openfeign/model/Payment.java

@@ -0,0 +1,23 @@
+package com.baeldung.cloud.openfeign.model;
+
+public class Payment {
+
+    private String id;
+    private double amount;
+
+    public String getId() {
+        return id;
+    }
+
+    public void setId(String id) {
+        this.id = id;
+    }
+
+    public double getAmount() {
+        return amount;
+    }
+
+    public void setAmount(double amount) {
+        this.amount = amount;
+    }
+}

spring-cloud/spring-cloud-openfeign/src/main/java/com/baeldung/cloud/openfeign/oauthfeign/OAuth2WebSecurityConfigurerAdapter.java

@@ -0,0 +1,19 @@
+package com.baeldung.cloud.openfeign.oauthfeign;
+
+import org.springframework.context.annotation.Configuration;
+import org.springframework.security.config.annotation.web.builders.HttpSecurity;
+import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
+
+@Configuration
+public class OAuth2WebSecurityConfigurerAdapter extends WebSecurityConfigurerAdapter {
+
+    @Override
+    protected void configure(HttpSecurity http) throws Exception {
+        http
+            .csrf()
+            .disable()
+            .oauth2Client();
+        http
+            .authorizeRequests().anyRequest().permitAll();
+    }
+}

spring-cloud/spring-cloud-openfeign/src/main/java/com/baeldung/cloud/openfeign/oauthfeign/OAuthClientCredentialsFeignManager.java

@@ -0,0 +1,85 @@
+package com.baeldung.cloud.openfeign.oauthfeign;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.security.core.Authentication;
+import org.springframework.security.core.GrantedAuthority;
+import org.springframework.security.oauth2.client.OAuth2AuthorizeRequest;
+import org.springframework.security.oauth2.client.OAuth2AuthorizedClient;
+import org.springframework.security.oauth2.client.OAuth2AuthorizedClientManager;
+import org.springframework.security.oauth2.client.registration.ClientRegistration;
+
+import java.util.Collection;
+import java.util.Collections;
+
+import static java.util.Objects.isNull;
+
+public class OAuthClientCredentialsFeignManager {
+
+    private static final Logger logger = LoggerFactory.getLogger(OAuthClientCredentialsFeignManager.class);
+
+    private final OAuth2AuthorizedClientManager manager;
+    private final Authentication principal;
+    private final ClientRegistration clientRegistration;
+
+    public OAuthClientCredentialsFeignManager(OAuth2AuthorizedClientManager manager, ClientRegistration clientRegistration) {
+        this.manager = manager;
+        this.clientRegistration = clientRegistration;
+        this.principal = createPrincipal();
+    }
+
+    private Authentication createPrincipal() {
+        return new Authentication() {
+            @Override
+            public Collection<? extends GrantedAuthority> getAuthorities() {
+                return Collections.emptySet();
+            }
+
+            @Override
+            public Object getCredentials() {
+                return null;
+            }
+
+            @Override
+            public Object getDetails() {
+                return null;
+            }
+
+            @Override
+            public Object getPrincipal() {
+                return this;
+            }
+
+            @Override
+            public boolean isAuthenticated() {
+                return false;
+            }
+
+            @Override
+            public void setAuthenticated(boolean isAuthenticated) throws IllegalArgumentException {
+            }
+
+            @Override
+            public String getName() {
+                return clientRegistration.getClientId();
+            }
+        };
+    }
+
+    public String getAccessToken() {
+        try {
+            OAuth2AuthorizeRequest oAuth2AuthorizeRequest = OAuth2AuthorizeRequest
+                .withClientRegistrationId(clientRegistration.getRegistrationId())
+                .principal(principal)
+                .build();
+            OAuth2AuthorizedClient client = manager.authorize(oAuth2AuthorizeRequest);
+            if (isNull(client)) {
+                throw new IllegalStateException("client credentials flow on " + clientRegistration.getRegistrationId() + " failed, client is null");
+            }
+            return client.getAccessToken().getTokenValue();
+        } catch (Exception exp) {
+            logger.error("client credentials error " + exp.getMessage());
+        }
+        return null;
+    }
+}

spring-cloud/spring-cloud-openfeign/src/main/java/com/baeldung/cloud/openfeign/oauthfeign/OAuthFeignConfig.java

@@ -0,0 +1,46 @@
+package com.baeldung.cloud.openfeign.oauthfeign;
+
+import feign.RequestInterceptor;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.security.oauth2.client.*;
+import org.springframework.security.oauth2.client.registration.ClientRegistration;
+import org.springframework.security.oauth2.client.registration.ClientRegistrationRepository;
+
+@Configuration
+public class OAuthFeignConfig {
+
+    public static final String CLIENT_REGISTRATION_ID = "keycloak";
+
+    private final OAuth2AuthorizedClientService oAuth2AuthorizedClientService;
+    private final ClientRegistrationRepository clientRegistrationRepository;
+
+    public OAuthFeignConfig(OAuth2AuthorizedClientService oAuth2AuthorizedClientService,
+            ClientRegistrationRepository clientRegistrationRepository) {
+        this.oAuth2AuthorizedClientService = oAuth2AuthorizedClientService;
+        this.clientRegistrationRepository = clientRegistrationRepository;
+    }
+
+    @Bean
+    public RequestInterceptor requestInterceptor() {
+        ClientRegistration clientRegistration = clientRegistrationRepository.findByRegistrationId(CLIENT_REGISTRATION_ID);
+        OAuthClientCredentialsFeignManager clientCredentialsFeignManager =
+            new OAuthClientCredentialsFeignManager(authorizedClientManager(), clientRegistration);
+        return requestTemplate -> {
+            requestTemplate.header("Authorization", "Bearer " + clientCredentialsFeignManager.getAccessToken());
+        };
+    }
+
+    @Bean
+    OAuth2AuthorizedClientManager authorizedClientManager() {
+        OAuth2AuthorizedClientProvider authorizedClientProvider = OAuth2AuthorizedClientProviderBuilder.builder()
+            .clientCredentials()
+            .build();
+
+        AuthorizedClientServiceOAuth2AuthorizedClientManager authorizedClientManager =
+            new AuthorizedClientServiceOAuth2AuthorizedClientManager(clientRegistrationRepository, oAuth2AuthorizedClientService);
+        authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider);
+        return authorizedClientManager;
+    }
+
+}

spring-cloud/spring-cloud-openfeign/src/main/resources/application.properties

@@ -1,3 +1,10 @@
+server.port=8085
+spring.main.allow-bean-definition-overriding=true
 spring.application.name= openfeign
 logging.level.com.baeldung.cloud.openfeign.client: DEBUG
 feign.hystrix.enabled=true
+
+spring.security.oauth2.client.registration.keycloak.authorization-grant-type=client_credentials
+spring.security.oauth2.client.registration.keycloak.client-id=payment-app
+spring.security.oauth2.client.registration.keycloak.client-secret=863e9de4-33d4-4471-b35e-f8d2434385bb
+spring.security.oauth2.client.provider.keycloak.token-uri=http://localhost:8083/auth/realms/master/protocol/openid-connect/token

spring-cloud/spring-cloud-openfeign/src/test/java/com/baeldung/cloud/openfeign/PaymentClientUnitTest.java

@@ -0,0 +1,30 @@
+package com.baeldung.cloud.openfeign;
+
+import com.baeldung.cloud.openfeign.client.PaymentClient;
+import com.baeldung.cloud.openfeign.model.Payment;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+
+import java.util.List;
+
+import static org.junit.Assert.assertFalse;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest
+public class PaymentClientUnitTest {
+
+    @Autowired
+    private PaymentClient paymentClient;
+
+    @Test
+    public void whenGetPayment_thenListPayments() {
+
+        List<Payment> payments = paymentClient.getPayments();
+
+        assertFalse(payments.isEmpty());
+    }
+
+}

spring-web-modules/spring-rest-testing/pom.xml

@@ -64,11 +64,6 @@
             <groupId>org.springframework.data</groupId>
             <artifactId>spring-data-commons</artifactId>
         </dependency>
-        <!-- deployment -->
-        <dependency>
-            <groupId>org.springframework.boot</groupId>
-            <artifactId>spring-boot-starter-tomcat</artifactId>
-        </dependency>
         <!-- web -->
         <dependency>
             <groupId>org.apache.httpcomponents</groupId>
@@ -154,17 +149,9 @@
             </plugin>
             <plugin>
                 <groupId>org.codehaus.cargo</groupId>
-                <artifactId>cargo-maven2-plugin</artifactId>
-                <version>${cargo-maven2-plugin.version}</version>
+                <artifactId>cargo-maven3-plugin</artifactId>
+                <version>${cargo-maven3-plugin.version}</version>
                 <configuration>
-                    <wait>true</wait>
-                    <container>
-                        <containerId>jetty8x</containerId>
-                        <type>embedded</type>
-                        <systemProperties>
-                            <!-- <provPersistenceTarget>cargo</provPersistenceTarget> -->
-                        </systemProperties>
-                    </container>
                     <configuration>
                         <properties>
                             <cargo.servlet.port>8082</cargo.servlet.port>
@@ -194,15 +181,32 @@
 
     <profiles>
         <profile>
-            <id>live</id>
+            <id>cargo-integration</id>
             <build>
                 <plugins>
+                    <plugin>
+                        <groupId>org.apache.maven.plugins</groupId>
+                        <artifactId>maven-surefire-plugin</artifactId>
+                        <executions>
+                            <execution>
+                                <phase>integration-test</phase>
+                                <goals>
+                                    <goal>test</goal>
+                                </goals>
+                                <configuration>
+                                    <excludes>
+                                        <exclude>none</exclude>
+                                    </excludes>
+                                    <includes>
+                                        <include>**/*LiveTest.java</include>
+                                    </includes>
+                                </configuration>
+                            </execution>
+                        </executions>
+                    </plugin>
                     <plugin>
                         <groupId>org.codehaus.cargo</groupId>
-                        <artifactId>cargo-maven2-plugin</artifactId>
-                        <configuration>
-                            <wait>false</wait>
-                        </configuration>
+                        <artifactId>cargo-maven3-plugin</artifactId>
                         <executions>
                             <execution>
                                 <id>start-server</id>
@@ -232,7 +236,7 @@
         <!-- util -->
         <javassist.version>3.25.0-GA</javassist.version>
         <!-- Maven plugins -->
-        <cargo-maven2-plugin.version>1.6.1</cargo-maven2-plugin.version>
+        <cargo-maven3-plugin.version>1.9.9</cargo-maven3-plugin.version>
         <apt-maven-plugin.version>1.1.3</apt-maven-plugin.version>
     </properties>
 

spring-web-modules/spring-rest-testing/src/test/java/com/baeldung/cargo/CargoPluginLiveTest.java

@@ -0,0 +1,13 @@
+package com.baeldung.cargo;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class CargoPluginLiveTest {
+
+    @Test
+    void givenCargoProfile_expectTestRuns() {
+        assertTrue(true);
+    }
+}