Merge branch 'eugenp:master' into master

algorithms-searching/src/main/java/com/baeldung/algorithms/dfs/BinaryTree.java

@@ -1,7 +1,5 @@
 package com.baeldung.algorithms.dfs;
 
-import java.util.LinkedList;
-import java.util.Queue;
 import java.util.Stack;
 
 public class BinaryTree {
@@ -124,52 +122,26 @@ public class BinaryTree {
         }
     }
 
-    public void traverseLevelOrder() {
-        if (root == null) {
-            return;
-        }
-
-        Queue<Node> nodes = new LinkedList<>();
-        nodes.add(root);
-
-        while (!nodes.isEmpty()) {
-
-            Node node = nodes.remove();
-
-            System.out.print(" " + node.value);
-
-            if (node.left != null) {
-                nodes.add(node.left);
-            }
-
-            if (node.left != null) {
-                nodes.add(node.right);
-            }
-        }
-    }
-
 
     public void traverseInOrderWithoutRecursion() {
-        Stack<Node> stack = new Stack<Node>();
+        Stack<Node> stack = new Stack<>();
         Node current = root;
-        stack.push(root);
+
-        while(! stack.isEmpty()) {
+        while (current != null || !stack.isEmpty()) {
-            while(current.left != null) {
+            while (current != null) {
+                stack.push(current);
                 current = current.left;
-                stack.push(current);                
-            }
-            current = stack.pop();
-            visit(current.value);
-            if(current.right != null) {
-                current = current.right;                
-                stack.push(current);
             }
+
+            Node top = stack.pop();
+            visit(top.value);
+            current = top.right;
         }
     }
 
     public void traversePreOrderWithoutRecursion() {
-        Stack<Node> stack = new Stack<Node>();
+        Stack<Node> stack = new Stack<>();
-        Node current = root;
+        Node current;
         stack.push(root);
         while(! stack.isEmpty()) {
             current = stack.pop();
@@ -184,9 +156,9 @@ public class BinaryTree {
     }
 
     public void traversePostOrderWithoutRecursion() {
-        Stack<Node> stack = new Stack<Node>();
+        Stack<Node> stack = new Stack<>();
         Node prev = root;
-        Node current = root;
+        Node current;
         stack.push(root);
 
         while (!stack.isEmpty()) {
@@ -213,7 +185,7 @@ public class BinaryTree {
         System.out.print(" " + value);
     }
 
-    class Node {
+    static class Node {
         int value;
         Node left;
         Node right;

algorithms-searching/src/test/java/com/baeldung/algorithms/dfs/BinaryTreeUnitTest.java

@@ -1,11 +1,11 @@
 package com.baeldung.algorithms.dfs;
 
+import org.junit.Test;
+
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
-import org.junit.Test;
-
 public class BinaryTreeUnitTest {
 
     @Test
@@ -13,7 +13,7 @@ public class BinaryTreeUnitTest {
 
         BinaryTree bt = createBinaryTree();
 
-        assertTrue(!bt.isEmpty());
+        assertFalse(bt.isEmpty());
     }
 
     @Test
@@ -111,14 +111,6 @@ public class BinaryTreeUnitTest {
         bt.traversePostOrderWithoutRecursion();
     }
 
-    @Test
-    public void givenABinaryTree_WhenTraversingLevelOrder_ThenPrintValues() {
-
-        BinaryTree bt = createBinaryTree();
-
-        bt.traverseLevelOrder();
-    }
-
     private BinaryTree createBinaryTree() {
         BinaryTree bt = new BinaryTree();
 

core-java-modules/core-java-8-2/README.md

@@ -8,4 +8,5 @@ This module contains articles about Java 8 core features
 - [Java 8 Stream skip() vs limit()](https://www.baeldung.com/java-stream-skip-vs-limit)
 - [Guide to Java BiFunction Interface](https://www.baeldung.com/java-bifunction-interface)
 - [Interface With Default Methods vs Abstract Class](https://www.baeldung.com/java-interface-default-method-vs-abstract-class)
+- [Convert Between Byte Array and UUID in Java](https://www.baeldung.com/java-byte-array-to-uuid)
 - [[<-- Prev]](/core-java-modules/core-java-8)

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

@@ -1,17 +1,24 @@
 package com.baeldung.game;
 
-import java.util.HashMap;
+import java.util.*;
-import java.util.Map;
-import java.util.Random;
-import java.util.Scanner;
 
 class RockPaperScissorsGame {
 
-    private static Map<Integer, String> movesMap = new HashMap<Integer, String>() {{
+    enum Move {
-        put(0, "rock");
+        ROCK("rock"),
-        put(1, "paper");
+        PAPER("paper"),
-        put(2, "scissors");
+        SCISSORS("scissors");
-    }};
+
+        private String value;
+
+        Move(String value) {
+            this.value = value;
+        }
+
+        public String getValue() {
+            return value;
+        }
+    }
 
     public static void main(String[] args) {
         Scanner scanner = new Scanner(System.in);
@@ -31,7 +38,7 @@ class RockPaperScissorsGame {
                 break;
             }
 
-            if (!movesMap.containsValue(playerMove)) {
+            if (Arrays.stream(Move.values()).noneMatch(x -> x.getValue().equals(playerMove))) {
                 System.out.println("Your move isn't valid!");
                 continue;
             }
@@ -51,15 +58,15 @@ class RockPaperScissorsGame {
     }
 
     private static boolean isPlayerWin(String playerMove, String computerMove) {
-        return playerMove.equals("rock") && computerMove.equals("scissors")
+        return playerMove.equals(Move.ROCK.value) && computerMove.equals(Move.SCISSORS.value)
-                || (playerMove.equals("scissors") && computerMove.equals("paper"))
+                || (playerMove.equals(Move.SCISSORS.value) && computerMove.equals(Move.PAPER.value))
-                || (playerMove.equals("paper") && computerMove.equals("rock"));
+                || (playerMove.equals(Move.PAPER.value) && computerMove.equals(Move.ROCK.value));
     }
 
     private static String getComputerMove() {
         Random random = new Random();
         int randomNumber = random.nextInt(3);
-        String computerMove = movesMap.get(randomNumber);
+        String computerMove = Move.values()[randomNumber].getValue();
         System.out.println("Computer move: " + computerMove);
         return computerMove;
     }

core-java-modules/core-java-collections-4/README.md

@@ -7,3 +7,4 @@
 - [ArrayList vs. LinkedList vs. HashMap in Java](https://www.baeldung.com/java-arraylist-vs-linkedlist-vs-hashmap)
 - [Java Deque vs. Stack](https://www.baeldung.com/java-deque-vs-stack)
 - [Collection.toArray(new T[0]) or .toArray(new T[size])](https://www.baeldung.com/java-collection-toarray-methods)
+- [Create an Empty Map in Java](https://www.baeldung.com/java-create-empty-map)

core-java-modules/core-java-collections-maps-4/pom.xml

@@ -15,6 +15,16 @@
     </parent>
 
     <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-collections4</artifactId>
+            <version>${commons-collections4.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+        </dependency>
         <dependency>
             <groupId>junit</groupId>
             <artifactId>junit</artifactId>
@@ -37,12 +47,23 @@
                 </plugin>
             </plugins>
         </pluginManagement>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>${maven-compiler-plugin.version}</version>
+                <configuration>
+                    <source>${maven.compiler.source}</source>
+                    <target>${maven.compiler.target}</target>
+                </configuration>
+            </plugin>
+        </plugins>
     </build>
 
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.source>1.9</maven.compiler.source>
-        <maven.compiler.target>1.8</maven.compiler.target>
+        <maven.compiler.target>1.9</maven.compiler.target>
     </properties>
 
 </project>

core-java-modules/core-java-collections-maps-4/src/main/java/com/baeldung/entries/SimpleCustomKeyValue.java

@@ -0,0 +1,53 @@
+package com.baeldung.entries;
+
+import java.util.Map;
+import java.util.Objects;
+import java.util.StringJoiner;
+
+public class SimpleCustomKeyValue<K, V> implements Map.Entry<K, V> {
+
+    private final K key;
+    private V value;
+
+    public SimpleCustomKeyValue(K key, V value) {
+        this.key = key;
+        this.value = value;
+    }
+
+    @Override
+    public K getKey() {
+        return key;
+    }
+
+    @Override
+    public V getValue() {
+        return value;
+    }
+
+    @Override
+    public V setValue(V value) {
+        return this.value = value;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        SimpleCustomKeyValue<?, ?> that = (SimpleCustomKeyValue<?, ?>) o;
+        return Objects.equals(key, that.key) && Objects.equals(value, that.value);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(key, value);
+    }
+
+    @Override
+    public String toString() {
+        return new StringJoiner(", ", SimpleCustomKeyValue.class.getSimpleName() + "[", "]").add("key=" + key).add("value=" + value).toString();
+    }
+}

core-java-modules/core-java-collections-maps-4/src/test/java/com/baeldung/entries/EntriesExampleUnitTest.java

@@ -0,0 +1,113 @@
+package com.baeldung.entries;
+
+import com.google.common.collect.Maps;
+import org.apache.commons.collections4.KeyValue;
+import org.apache.commons.collections4.keyvalue.DefaultMapEntry;
+import org.apache.commons.collections4.keyvalue.UnmodifiableMapEntry;
+import org.junit.jupiter.api.Test;
+
+import java.util.AbstractMap;
+import java.util.Map;
+import java.util.stream.Stream;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.tuple;
+
+public class EntriesExampleUnitTest {
+
+    @Test
+    public void givenEntries_whenVerifying_thenShouldContainKeyValues() {
+        AbstractMap.SimpleEntry<String, String> firstEntry = new AbstractMap.SimpleEntry<>("key1", "value1");
+        AbstractMap.SimpleEntry<String, String> secondEntry = new AbstractMap.SimpleEntry<>("key2", "value2");
+        AbstractMap.SimpleEntry<String, String> thirdEntry = new AbstractMap.SimpleEntry<>(firstEntry);
+        thirdEntry.setValue("a different value");
+
+        assertThat(Stream.of(firstEntry, secondEntry, thirdEntry))
+          .extracting("key", "value")
+          .containsExactly(
+            tuple("key1", "value1"),
+            tuple("key2", "value2"),
+            tuple("key1", "a different value"));
+    }
+
+    @Test
+    public void givenImmutableEntries_whenVerifying_thenShouldContainKeyValues() {
+        AbstractMap.SimpleImmutableEntry<String, String> firstEntry = new AbstractMap.SimpleImmutableEntry<>("key1", "value1");
+        AbstractMap.SimpleImmutableEntry<String, String> secondEntry = new AbstractMap.SimpleImmutableEntry<>("key2", "value2");
+        AbstractMap.SimpleImmutableEntry<String, String> thirdEntry = new AbstractMap.SimpleImmutableEntry<>(firstEntry);
+
+        assertThat(Stream.of(firstEntry, secondEntry, thirdEntry))
+          .extracting("key", "value")
+          .containsExactly(
+            tuple("key1", "value1"),
+            tuple("key2", "value2"),
+            tuple("key1", "value1"));
+    }
+
+    @Test
+    public void givenImmutableEntryUsingJava9_whenVerifying_thenShouldContainKeyValues() {
+        Map.Entry<String, String> entry = Map.entry("key", "value");
+
+        assertThat(entry.getKey())
+          .isEqualTo("key");
+        assertThat(entry.getValue())
+          .isEqualTo("value");
+    }
+
+
+    @Test
+    public void givenEntriesWithApacheCommons_whenVerifying_thenShouldContainKeyValues() {
+        Map.Entry<String, String> firstEntry = new DefaultMapEntry<>("key1", "value1");
+        KeyValue<String, String> secondEntry = new DefaultMapEntry<>("key2", "value2");
+
+        KeyValue<String, String> thirdEntry = new DefaultMapEntry<>(firstEntry);
+        KeyValue<String, String> fourthEntry = new DefaultMapEntry<>(secondEntry);
+
+        firstEntry.setValue("a different value");
+
+        assertThat(firstEntry)
+          .extracting("key", "value")
+          .containsExactly("key1", "a different value");
+
+        assertThat(Stream.of(secondEntry, thirdEntry, fourthEntry))
+          .extracting("key", "value")
+          .containsExactly(
+            tuple("key2", "value2"),
+            tuple("key1", "value1"),
+            tuple("key2", "value2"));
+    }
+
+    @Test
+    public void givenImmutableEntriesWithApacheCommons_whenVerifying_thenShouldContainKeyValues() {
+        Map.Entry<String, String> firstEntry = new UnmodifiableMapEntry<>("key1", "value1");
+        KeyValue<String, String> secondEntry = new UnmodifiableMapEntry<>("key2", "value2");
+
+        KeyValue<String, String> thirdEntry = new UnmodifiableMapEntry<>(firstEntry);
+        KeyValue<String, String> fourthEntry = new UnmodifiableMapEntry<>(secondEntry);
+
+        assertThat(firstEntry)
+          .extracting("key", "value")
+          .containsExactly("key1", "value1");
+
+        assertThat(Stream.of(secondEntry, thirdEntry, fourthEntry))
+          .extracting("key", "value")
+          .containsExactly(
+            tuple("key2", "value2"),
+            tuple("key1", "value1"),
+            tuple("key2", "value2"));
+    }
+
+
+    @Test
+    public void givenImmutableEntriesWithGuava_whenVerifying_thenShouldContainKeyValues() {
+        Map.Entry<String, String> firstEntry = Maps.immutableEntry("key1", "value1");
+        Map.Entry<String, String> secondEntry = Maps.immutableEntry("key2", "value2");
+
+        assertThat(Stream.of(firstEntry, secondEntry))
+          .extracting("key", "value")
+          .containsExactly(
+            tuple("key1", "value1"),
+            tuple("key2", "value2"));
+    }
+
+}

core-java-modules/core-java-collections-maps-4/src/test/java/com/baeldung/entries/SimpleCustomKeyValueUnitTest.java

@@ -0,0 +1,31 @@
+package com.baeldung.entries;
+
+import com.google.common.collect.ImmutableMap;
+import org.junit.jupiter.api.Test;
+
+import java.util.Map;
+import java.util.stream.Stream;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.tuple;
+
+class SimpleCustomKeyValueUnitTest {
+
+
+    @Test
+    public void givenModifiableEntries_whenVerifying_thenShouldContainKeyValues() {
+        Map.Entry<String, String> firstEntry = new SimpleCustomKeyValue<>("key1", "value1");
+
+        Map.Entry<String, String> secondEntry = new SimpleCustomKeyValue<>("key2", "value2");
+        secondEntry.setValue("different value");
+
+        Map<String, String> map = Map.ofEntries(firstEntry, secondEntry);
+
+        assertThat(map)
+          .isEqualTo(ImmutableMap.<String,String>builder()
+            .put("key1", "value1")
+            .put("key2", "different value")
+            .build());
+    }
+
+}

core-java-modules/core-java-exceptions-4/src/main/java/com/baeldung/exception/variablemightnothavebeeninitialized/VariableMightNotHaveBeenInitialized.java

@@ -0,0 +1,45 @@
+package com.baeldung.exception.variablemightnothavebeeninitialized;
+
+public class VariableMightNotHaveBeenInitialized {
+
+    private static int instanceVariableCount;
+
+    /**
+     * Method would not compile if lines 14 and 18 are uncommented.
+     */
+    public static void countEven() {
+        //uninstantiated
+        int count;
+        int[] arr = new int[]{23, 56, 89, 12, 23};
+        for (int i = 0; i < arr.length; i++) {
+            if ((arr[i] % 2) == 0) {
+                // count++;
+            }
+
+        }
+        // System.out.println("Total Even Numbers : " + count);
+    }
+
+    public static int countEvenUsingInstanceVariable(int[] arr) {
+
+        for (int i = 0; i < arr.length; i++) {
+            if ((arr[i] % 2) == 0) {
+                instanceVariableCount++;
+            }
+
+        }
+        return instanceVariableCount;
+    }
+
+    public static int countEvenUsingIfElse(int[] arr, int args) {
+        int count;
+        count = args > 0 ? args : 0;
+        for (int i = 0; i < arr.length; i++) {
+            if ((arr[i] % 2) == 0) {
+                count++;
+            }
+
+        }
+        return count;
+    }
+}

core-java-modules/core-java-exceptions-4/src/test/java/com/baeldung/exception/variablemightnothavebeeninitialized/VariableMightNotHaveBeenInitializedUnitTest.java

@@ -0,0 +1,24 @@
+package com.baeldung.exception.variablemightnothavebeeninitialized;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class VariableMightNotHaveBeenInitializedUnitTest {
+
+    @Test
+    public void usingInstanceVariable_returnCount() {
+        int[] arr = new int[]{1, 2, 3, 4, 5, 6};
+        int value = VariableMightNotHaveBeenInitialized.countEvenUsingInstanceVariable(arr);
+
+        assertEquals(3, value);
+    }
+
+    @Test
+    public void usingArgumentsAndIfElse_returnCount() {
+        int[] arr = new int[]{1, 2, 3, 4, 5, 6};
+        int value = VariableMightNotHaveBeenInitialized.countEvenUsingIfElse(arr, 2);
+
+        assertEquals(5, value);
+    }
+}

core-java-modules/core-java-nio-2/src/test/java/com/baeldung/bytebuffer/ByteBufferUnitTest.java

@@ -0,0 +1,339 @@
+package com.baeldung.bytebuffer;
+
+import org.junit.Test;
+
+import java.lang.reflect.Field;
+import java.nio.*;
+import java.nio.charset.StandardCharsets;
+
+import static org.junit.Assert.*;
+
+public class ByteBufferUnitTest {
+    @Test
+    public void givenBufferCreation_whenUsingAllocate_thenSuccess() {
+        ByteBuffer buffer = ByteBuffer.allocate(10);
+        assertNotNull(buffer);
+    }
+
+    @Test
+    public void givenBufferCreation_whenUsingAllocateDirect_thenSuccess() {
+        ByteBuffer buffer = ByteBuffer.allocateDirect(10);
+        assertNotNull(buffer);
+    }
+
+    @Test
+    public void givenBufferCreation_whenUsingWrap_thenSuccess() {
+        byte[] bytes = new byte[10];
+        ByteBuffer buffer = ByteBuffer.wrap(bytes);
+        assertNotNull(buffer);
+    }
+
+    @Test
+    public void givenBufferIndex_whenUsingAllocate_thenInitialIndices() {
+        // create instance using allocate
+        ByteBuffer buffer = ByteBuffer.allocate(10);
+
+        // get index
+        int position = buffer.position();
+        int limit = buffer.limit();
+        int capacity = buffer.capacity();
+
+        // assert
+        assertEquals(0, position);
+        assertEquals(10, limit);
+        assertEquals(10, capacity);
+    }
+
+    @Test
+    public void givenBufferIndex_whenChangingPositionAndLimit_thenSuccess() {
+        // create instance
+        ByteBuffer buffer = ByteBuffer.allocate(10);
+
+        // change index
+        buffer.position(2);
+        buffer.limit(5);
+
+        // assert
+        assertIndex(buffer, -1, 2, 5, 10);
+    }
+
+    @Test
+    public void givenBufferIndex_whenUsingWrap_thenInitialIndices() {
+        // create instance
+        byte[] bytes = new byte[10];
+        ByteBuffer buffer = ByteBuffer.wrap(bytes);
+
+        // assert
+        assertIndex(buffer, -1, 0, 10, 10);
+    }
+
+    @Test
+    public void givenBufferIndex_whenUsingWrapWithOffsetAndLength_thenInitialIndices() {
+        // create instance
+        byte[] bytes = new byte[10];
+        ByteBuffer buffer = ByteBuffer.wrap(bytes, 2, 6);
+
+        // assert
+        assertIndex(buffer, -1, 2, 8, 10);
+    }
+
+    @Test
+    public void givenBufferIndex_whenUsingMarkAndReset_thenOK() {
+        ByteBuffer buffer = ByteBuffer.allocate(10);
+        assertIndex(buffer, -1, 0, 10, 10);
+
+        buffer.position(2);
+        assertIndex(buffer, -1, 2, 10, 10);
+
+        buffer.mark();
+        assertIndex(buffer, 2, 2, 10, 10);
+
+        buffer.position(5);
+        assertIndex(buffer, 2, 5, 10, 10);
+
+        buffer.reset();
+        assertIndex(buffer, 2, 2, 10, 10);
+    }
+
+    @Test
+    public void givenBufferIndex_whenUsingClear_thenOK() {
+        // create instance
+        ByteBuffer buffer = ByteBuffer.allocate(10);
+        assertIndex(buffer, -1, 0, 10, 10);
+
+        // change index
+        buffer.position(2);
+        buffer.mark();
+        buffer.position(5);
+        buffer.limit(8);
+        assertIndex(buffer, 2, 5, 8, 10);
+
+        // clear
+        buffer.clear();
+        assertIndex(buffer, -1, 0, 10, 10);
+    }
+
+    @Test
+    public void givenBufferIndex_whenUsingFlip_thenOK() {
+        // create instance
+        ByteBuffer buffer = ByteBuffer.allocate(10);
+        assertIndex(buffer, -1, 0, 10, 10);
+
+        // change index
+        buffer.position(2);
+        buffer.mark();
+        buffer.position(5);
+        buffer.limit(8);
+        assertIndex(buffer, 2, 5, 8, 10);
+
+        // flip
+        buffer.flip();
+        assertIndex(buffer, -1, 0, 5, 10);
+    }
+
+    @Test
+    public void givenBufferIndex_whenUsingRewind_thenOK() {
+        // create instance
+        ByteBuffer buffer = ByteBuffer.allocate(10);
+        assertIndex(buffer, -1, 0, 10, 10);
+
+        // change index
+        buffer.position(2);
+        buffer.mark();
+        buffer.position(5);
+        buffer.limit(8);
+        assertIndex(buffer, 2, 5, 8, 10);
+
+        // rewind
+        buffer.rewind();
+        assertIndex(buffer, -1, 0, 8, 10);
+    }
+
+    @Test
+    public void givenBufferIndex_whenUsingCompact_thenOK() {
+        // create instance
+        ByteBuffer buffer = ByteBuffer.allocate(10);
+        assertIndex(buffer, -1, 0, 10, 10);
+
+        // change index
+        buffer.position(2);
+        buffer.mark();
+        buffer.position(5);
+        buffer.limit(8);
+        assertIndex(buffer, 2, 5, 8, 10);
+
+        // compact
+        buffer.compact();
+        assertIndex(buffer, -1, 3, 10, 10);
+    }
+
+    @Test
+    public void givenBufferIndex_whenUsingRemain_thenOK() {
+        // create instance
+        ByteBuffer buffer = ByteBuffer.allocate(10);
+
+        // change index
+        buffer.position(2);
+        buffer.limit(8);
+
+        // remain
+        boolean flag = buffer.hasRemaining();
+        int remaining = buffer.remaining();
+
+        // assert
+        assertTrue(flag);
+        assertEquals(6, remaining);
+    }
+
+    @Test(expected = BufferUnderflowException.class)
+    public void givenNotEnoughRemaining_WhenCallingGetInt_thenBufferUnderflowException() {
+        ByteBuffer buffer = ByteBuffer.allocate(2);
+        buffer.getInt();
+    }
+
+    @Test(expected = BufferOverflowException.class)
+    public void givenNotEnoughRemaining_WhenCallingPutInt_thenBufferOverflowException() {
+        ByteBuffer buffer = ByteBuffer.allocate(2);
+        buffer.putInt(10);
+    }
+
+    @Test
+    public void givenBufferView_whenUsingDuplicate_thenOK() {
+        // create instance
+        ByteBuffer buffer = ByteBuffer.allocate(10);
+        assertIndex(buffer, -1, 0, 10, 10);
+
+        // change index
+        buffer.position(2);
+        buffer.mark();
+        buffer.position(5);
+        buffer.limit(8);
+        assertIndex(buffer, 2, 5, 8, 10);
+
+        // view
+        ByteBuffer view = buffer.duplicate();
+        assertIndex(view, 2, 5, 8, 10);
+    }
+
+    @Test
+    public void givenBufferView_whenUsingSlice_thenOK() {
+        // create instance
+        ByteBuffer buffer = ByteBuffer.allocate(10);
+        assertIndex(buffer, -1, 0, 10, 10);
+
+        // change index
+        buffer.position(2);
+        buffer.mark();
+        buffer.position(5);
+        buffer.limit(8);
+        assertIndex(buffer, 2, 5, 8, 10);
+
+        // view
+        ByteBuffer view = buffer.slice();
+        assertIndex(view, -1, 0, 3, 3);
+    }
+
+    @Test
+    public void givenBufferView_whenUsingAsReaOnlyBuffer_thenOK() {
+        // create instance
+        ByteBuffer buffer = ByteBuffer.allocate(10);
+        assertIndex(buffer, -1, 0, 10, 10);
+
+        // change index
+        buffer.position(2);
+        buffer.mark();
+        buffer.position(5);
+        buffer.limit(8);
+        assertIndex(buffer, 2, 5, 8, 10);
+
+        // view
+        ByteBuffer view = buffer.asReadOnlyBuffer();
+        assertIndex(view, 2, 5, 8, 10);
+    }
+
+    @Test
+    public void givenBufferView_whenUsingAsIntBuffer_thenOK() {
+        // create instance
+        byte[] bytes = new byte[]{
+                (byte) 0xCA, (byte) 0xFE, (byte) 0xBA, (byte) 0xBE, // CAFEBABE ---> cafebabe
+                (byte) 0xF0, (byte) 0x07, (byte) 0xBA, (byte) 0x11, // F007BA11 ---> football
+                (byte) 0x0F, (byte) 0xF1, (byte) 0xCE               // 0FF1CE   ---> office
+        };
+        ByteBuffer buffer = ByteBuffer.wrap(bytes);
+        assertIndex(buffer, -1, 0, 11, 11);
+
+        // view
+        IntBuffer intBuffer = buffer.asIntBuffer();
+        int capacity = intBuffer.capacity();
+        assertEquals(2, capacity);
+        assertIndex(intBuffer, -1, 0, 2, 2);
+    }
+
+    @Test
+    public void givenByteOrder_whenUsingBigEndian_thenOK() {
+        // create instance
+        byte[] bytes = new byte[]{(byte) 0xCA, (byte) 0xFE, (byte) 0xBA, (byte) 0xBE};
+        ByteBuffer buffer = ByteBuffer.wrap(bytes);
+
+        // change byte order
+        buffer.order(ByteOrder.BIG_ENDIAN);
+        int val = buffer.getInt();
+
+        // assert
+        assertEquals(0xCAFEBABE, val);
+    }
+
+    @Test
+    public void givenByteOrder_whenUsingLittleEndian_thenOK() {
+        // create instance
+        byte[] bytes = new byte[]{(byte) 0xCA, (byte) 0xFE, (byte) 0xBA, (byte) 0xBE};
+        ByteBuffer buffer = ByteBuffer.wrap(bytes);
+
+        // change byte order
+        buffer.order(ByteOrder.LITTLE_ENDIAN);
+        int val = buffer.getInt();
+
+        // assert
+        assertEquals(0xBEBAFECA, val);
+    }
+
+    @Test
+    public void givenComparing_whenUsingEqualsAndCompareTo_thenOK() {
+        // create instance
+        byte[] bytes1 = "World".getBytes(StandardCharsets.UTF_8);
+        byte[] bytes2 = "HelloWorld".getBytes(StandardCharsets.UTF_8);
+        ByteBuffer buffer1 = ByteBuffer.wrap(bytes1);
+        ByteBuffer buffer2 = ByteBuffer.wrap(bytes2);
+
+        // change index
+        buffer2.position(5);
+
+        // equals and compareTo
+        boolean equal = buffer1.equals(buffer2);
+        int result = buffer1.compareTo(buffer2);
+
+        // assert
+        assertTrue(equal);
+        assertEquals(0, result);
+    }
+
+    private void assertIndex(Buffer buffer, int mark, int position, int limit, int capacity) {
+        assertEquals(mark, getMark(buffer));
+        assertEquals(position, buffer.position());
+        assertEquals(limit, buffer.limit());
+        assertEquals(capacity, buffer.capacity());
+    }
+
+    private int getMark(Buffer buffer) {
+        try {
+            Class<?> clazz = Buffer.class;
+            Field f = clazz.getDeclaredField("mark");
+            f.setAccessible(true);
+            Object result = f.get(buffer);
+            return (int) result;
+        } catch (NoSuchFieldException | IllegalAccessException e) {
+            e.printStackTrace();
+        }
+        return -1;
+    }
+}

core-java-modules/core-java-security-3/README.md

@@ -10,4 +10,5 @@ This module contains articles about core Java Security
 - [HMAC in Java](https://www.baeldung.com/java-hmac)
 - [Generating a Secure AES Key in Java](https://www.baeldung.com/java-secure-aes-key)
 - [Computing an X509 Certificate’s Thumbprint in Java](https://www.baeldung.com/java-x509-certificate-thumbprint)
+- [Error: “trustAnchors parameter must be non-empty”](https://www.baeldung.com/java-trustanchors-parameter-must-be-non-empty)
 - More articles: [[<-- prev]](/core-java-modules/core-java-security-2)

core-java-modules/pom.xml

@@ -38,7 +38,6 @@
         <module>core-java-collections-maps</module>
         <module>core-java-collections-maps-2</module>
         <module>core-java-collections-maps-3</module>
-        <module>core-java-collections-maps-4</module>
         <module>core-java-concurrency-2</module>
         <module>core-java-concurrency-advanced</module>
         <module>core-java-concurrency-advanced-2</module>

docker/README.md

@@ -6,3 +6,4 @@
 - [How To Configure Java Heap Size Inside a Docker Container](https://www.baeldung.com/ops/docker-jvm-heap-size)
 - [Dockerfile Strategies for Git](https://www.baeldung.com/ops/dockerfile-git-strategies)
 - [How to Get Docker-Compose to Always Use the Latest Image](https://www.baeldung.com/ops/docker-compose-latest-image)
+- [How to Include Files Outside of Docker’s Build Context](https://www.baeldung.com/ops/docker-include-files-outside-build-context)

docker/docker-caching/multi-module-caching/Dockerfile

@@ -0,0 +1,21 @@
+FROM maven:alpine as build
+ENV HOME=/usr/app
+RUN mkdir -p $HOME
+WORKDIR $HOME
+
+ADD pom.xml $HOME
+ADD core/pom.xml $HOME/core/pom.xml
+ADD runner/pom.xml $HOME/runner/pom.xml
+
+RUN mvn -pl core verify --fail-never
+ADD core $HOME/core
+RUN mvn -pl core install
+RUN mvn -pl runner verify --fail-never
+ADD runner $HOME/runner
+RUN mvn -pl core,runner package
+
+FROM openjdk:8-jdk-alpine
+
+COPY --from=build /usr/app/runner/target/runner-0.0.1-SNAPSHOT-jar-with-dependencies.jar /app/runner.jar
+
+ENTRYPOINT java -jar /app/runner.jar

docker/docker-caching/multi-module-caching/Dockerfile-Buildkit

@@ -0,0 +1,13 @@
+FROM maven:alpine as build
+ENV HOME=/usr/app
+RUN mkdir -p $HOME
+WORKDIR $HOME
+
+ADD . $HOME
+RUN --mount=type=cache,target=/root/.m2 mvn -f $HOME/pom.xml clean package
+
+FROM openjdk:8-jdk-alpine
+
+COPY --from=build /usr/app/runner/target/runner-0.0.1-SNAPSHOT-jar-with-dependencies.jar /app/runner.jar
+
+ENTRYPOINT java -jar /app/runner.jar

docker/docker-caching/multi-module-caching/core/pom.xml

@@ -0,0 +1,25 @@
+<?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>core</artifactId>
+
+    <parent>
+        <artifactId>multi-module-caching</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>0.0.1-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
+    </properties>
+</project>

docker/docker-caching/multi-module-caching/core/src/main/java/com/baeldung/maven_caching/CoreClass.java

@@ -0,0 +1,14 @@
+package com.baeldung.maven_caching;
+
+import com.google.common.io.Files;
+
+public class CoreClass {
+
+    public String method() {
+        return "Hello from core module!!";
+    }
+
+    public String dependencyMethod() {
+        return Files.simplifyPath("/home/app/test");
+    }
+}

docker/docker-caching/multi-module-caching/pom.xml

@@ -0,0 +1,29 @@
+<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <groupId>com.baeldung</groupId>
+    <artifactId>multi-module-caching</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <description>Multi-module Maven caching example</description>
+    <packaging>pom</packaging>
+
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>com.google.guava</groupId>
+                <artifactId>guava</artifactId>
+                <version>31.0.1-jre</version>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
+    <properties>
+        <java.version>1.8</java.version>
+    </properties>
+
+    <modules>
+        <module>runner</module>
+        <module>core</module>
+    </modules>
+</project>

docker/docker-caching/multi-module-caching/runner/pom.xml

@@ -0,0 +1,56 @@
+<?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>runner</artifactId>
+
+    <parent>
+        <artifactId>multi-module-caching</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>0.0.1-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.baeldung</groupId>
+            <artifactId>core</artifactId>
+            <version>0.0.1-SNAPSHOT</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-assembly-plugin</artifactId>
+                <version>3.3.0</version>
+                <configuration>
+                    <descriptorRefs>
+                        <descriptorRef>jar-with-dependencies</descriptorRef>
+                    </descriptorRefs>
+                    <archive>
+                        <manifest>
+                            <addClasspath>true</addClasspath>
+                            <mainClass>com.baeldung.maven_caching.MavenCachingApplication</mainClass>
+                        </manifest>
+                    </archive>
+                </configuration>
+                <executions>
+                    <execution>
+                        <id>assemble-all</id>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>single</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
+    </properties>
+</project>

docker/docker-caching/multi-module-caching/runner/src/main/java/com/baeldung/maven_caching/MavenCachingApplication.java

@@ -0,0 +1,11 @@
+package com.baeldung.maven_caching;
+
+public class MavenCachingApplication {
+
+    public static void main(String[] args) {
+        CoreClass cc = new CoreClass();
+        System.out.println(cc.method());
+        System.out.println(cc.dependencyMethod());
+    }
+
+}

docker/docker-caching/single-module-caching/Dockerfile

@@ -0,0 +1,15 @@
+FROM maven:alpine as build
+ENV HOME=/usr/app
+RUN mkdir -p $HOME
+WORKDIR $HOME
+ADD pom.xml $HOME
+RUN mvn verify --fail-never
+
+ADD . $HOME
+RUN mvn package
+
+FROM openjdk:8-jdk-alpine 
+
+COPY --from=build /usr/app/target/single-module-caching-1.0-SNAPSHOT-jar-with-dependencies.jar /app/runner.jar
+
+ENTRYPOINT java -jar /app/runner.jar

docker/docker-caching/single-module-caching/Dockerfile-Buildkit

@@ -0,0 +1,13 @@
+FROM maven:alpine as build
+ENV HOME=/usr/app
+RUN mkdir -p $HOME
+WORKDIR $HOME
+ADD . $HOME
+
+RUN --mount=type=cache,target=/root/.m2 mvn -f $HOME/pom.xml clean package
+
+FROM openjdk:8-jdk-alpine
+
+COPY --from=build /usr/app/target/single-module-caching-1.0-SNAPSHOT-jar-with-dependencies.jar /app/runner.jar
+
+ENTRYPOINT java -jar /app/runner.jar

docker/docker-caching/single-module-caching/pom.xml

@@ -0,0 +1,53 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>com.baeldung</groupId>
+    <artifactId>single-module-caching</artifactId>
+    <version>1.0-SNAPSHOT</version>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>31.0.1-jre</version>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-assembly-plugin</artifactId>
+                <version>3.3.0</version>
+                <configuration>
+                    <descriptorRefs>
+                        <descriptorRef>jar-with-dependencies</descriptorRef>
+                    </descriptorRefs>
+                    <archive>
+                        <manifest>
+                            <addClasspath>true</addClasspath>
+                            <mainClass>com.baeldung.maven_caching.MavenCachingMain</mainClass>
+                        </manifest>
+                    </archive>
+                </configuration>
+                <executions>
+                    <execution>
+                        <id>assemble-all</id>
+                        <phase>package</phase>
+                        <goals>
+                            <goal>single</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
+    <properties>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
+    </properties>
+</project>

docker/docker-caching/single-module-caching/src/main/java/com/baeldung/maven_caching/MavenCachingMain.java

@@ -0,0 +1,11 @@
+package com.baeldung.maven_caching;
+
+import com.google.common.io.Files;
+
+public class MavenCachingMain {
+
+    public static void main(String[] args) {
+        System.out.println("Hello from maven_caching app!!!");
+        System.out.println(Files.simplifyPath("/home/app/test"));
+    }
+}

docker/pom.xml

@@ -26,6 +26,8 @@
         <module>docker-internal-dto</module>
         <module>docker-spring-boot</module>
         <module>docker-sample-app</module>
+        <module>docker-caching/single-module-caching</module>
+        <module>docker-caching/multi-module-caching</module>
     </modules>
 
 </project>

gradle/gradle-source-vs-target-compatibility/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [Gradle: sourceCompatiblity vs targetCompatibility](https://www.baeldung.com/gradle-sourcecompatiblity-vs-targetcompatibility)

java-collections-maps-3/README.md

@@ -7,3 +7,4 @@
 - [Update the Value Associated With a Key in a HashMap](https://www.baeldung.com/java-hashmap-update-value-by-key)
 - [Java Map – keySet() vs. entrySet() vs. values() Methods](https://www.baeldung.com/java-map-entries-methods)
 - [Java IdentityHashMap Class and Its Use Cases](https://www.baeldung.com/java-identityhashmap)
+- [How to Invert a Map in Java](https://www.baeldung.com/java-invert-map)

java-native/README.md

@@ -7,3 +7,4 @@ This module contains articles about the Java Native Interface (JNI).
 - [Guide to JNI (Java Native Interface)](https://www.baeldung.com/jni)
 - [Using JNA to Access Native Dynamic Libraries](https://www.baeldung.com/java-jna-dynamic-libraries)
 - [Check if a Java Program Is Running in 64-Bit or 32-Bit JVM](https://www.baeldung.com/java-detect-jvm-64-or-32-bit)
+- [How to use JNI’s RegisterNatives() method?](https://www.baeldung.com/jni-registernatives)

jta/pom.xml

@@ -16,6 +16,18 @@
         <relativePath>../parent-boot-2</relativePath>
     </parent>
     
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>org.apache.logging.log4j</groupId>
+                <artifactId>log4j-bom</artifactId>
+                <version>${log4j2.version}</version>
+                <scope>import</scope>
+                <type>pom</type>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
     <dependencies>
         <dependency>
             <groupId>org.springframework.boot</groupId>
@@ -37,6 +49,7 @@
 
     <properties>
         <spring-boot.version>2.4.7</spring-boot.version>
+        <log4j2.version>2.17.1</log4j2.version>
     </properties>
 
 </project>

maven-modules/maven-classifier/maven-classifier-example-consumer/pom.xml

@@ -0,0 +1,53 @@
+<?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">
+    <parent>
+        <artifactId>maven-classifier</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>0.0.1-SNAPSHOT</version>
+    </parent>
+
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>maven-classifier-example-consumer</artifactId>
+
+    <properties>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.baeldung</groupId>
+            <artifactId>maven-classifier-example-provider</artifactId>
+            <version>0.0.1-SNAPSHOT</version>
+        </dependency>
+        <dependency>
+            <groupId>com.baeldung</groupId>
+            <artifactId>maven-classifier-example-provider</artifactId>
+            <version>0.0.1-SNAPSHOT</version>
+            <classifier>arbitrary</classifier>
+        </dependency>
+        <!--        For example purpose not building as it requires both JDK 8 and 11 executables on the build machine -->
+        <!--        <dependency>-->
+        <!--            <groupId>com.baeldung</groupId>-->
+        <!--            <artifactId>maven-classifier-example-provider</artifactId>-->
+        <!--            <version>0.0.1-SNAPSHOT</version>-->
+        <!--            <classifier>jdk11</classifier>-->
+        <!--        </dependency>-->
+        <dependency>
+            <groupId>com.baeldung</groupId>
+            <artifactId>maven-classifier-example-provider</artifactId>
+            <version>0.0.1-SNAPSHOT</version>
+            <classifier>sources</classifier>
+        </dependency>
+        <dependency>
+            <groupId>com.baeldung</groupId>
+            <artifactId>maven-classifier-example-provider</artifactId>
+            <version>0.0.1-SNAPSHOT</version>
+            <classifier>tests</classifier>
+        </dependency>
+    </dependencies>
+
+</project>

maven-modules/maven-classifier/maven-classifier-example-consumer/src/main/java/com/baeldung/maven/classifier/consumer/FuelStation.java

@@ -0,0 +1,17 @@
+
+package com.baeldung.maven.classifier.consumer;
+
+import com.baeldung.maven.dependency.classifier.provider.model.Car;
+import com.baeldung.maven.dependency.classifier.provider.model.PowerSource;
+
+public class FuelStation {
+
+    public FuelStation.Zone refill(Car car) {
+        return PowerSource.BATTERY.equals(car.getPowerSource()) ? FuelStation.Zone.BATTERY : FuelStation.Zone.UNKNOWN;
+    }
+
+    public enum Zone {
+        BATTERY,
+        UNKNOWN
+    }
+}

maven-modules/maven-classifier/maven-classifier-example-consumer/src/test/java/com/baeldung/maven/classifier/consumer/FuelStationUnitTest.java

@@ -0,0 +1,21 @@
+package com.baeldung.maven.classifier.consumer;
+
+import com.baeldung.maven.classifier.consumer.FuelStation.Zone;
+import com.baeldung.maven.dependency.classifier.provider.model.Car;
+import com.baeldung.maven.dependency.classifier.provider.stub.CarStub;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class FuelStationUnitTest {
+
+    @Test
+    @DisplayName("Given fuel type battery When request for refill Then Return Battery Zone")
+    public void givenFuelTypeBattery_whenRequestToRefill_thenReturnBatteryZone() {
+        FuelStation fuelStation = new FuelStation();
+        Car electricCar = CarStub.ELECTRIC_CAR;
+
+        assertEquals(Zone.BATTERY, fuelStation.refill(electricCar));
+    }
+}

maven-modules/maven-classifier/maven-classifier-example-provider/pom.xml

@@ -0,0 +1,122 @@
+<?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>
+
+    <parent>
+        <artifactId>maven-classifier</artifactId>
+        <groupId>com.baeldung</groupId>
+        <version>0.0.1-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>maven-classifier-example-provider</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+
+    <properties>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
+        <!--        <jdk.11.executable.path></jdk.11.executable.path>-->
+    </properties>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.10.0</version>
+                <executions>
+                    <execution>
+                        <id>JDK 8</id>
+                        <phase>compile</phase>
+                        <goals>
+                            <goal>compile</goal>
+                        </goals>
+                        <configuration>
+                            <source>8</source>
+                            <target>8</target>
+                            <fork>true</fork>
+                        </configuration>
+                    </execution>
+                    <!--        For example purpose not building as it requires both JDK 8 and 11 executables on the build machine -->
+                    <!--                    <execution>-->
+                    <!--                        <id>JDK 11</id>-->
+                    <!--                        <phase>compile</phase>-->
+                    <!--                        <goals>-->
+                    <!--                            <goal>compile</goal>-->
+                    <!--                        </goals>-->
+                    <!--                        <configuration>-->
+                    <!--                            <fork>true</fork>-->
+                    <!--                            <outputDirectory>${project.build.outputDirectory}_jdk11</outputDirectory>-->
+                    <!--                            <executable>${jdk.11.executable.path}</executable>-->
+                    <!--                            <source>8</source>-->
+                    <!--                            <target>11</target>-->
+                    <!--                        </configuration>-->
+                    <!--                    </execution>-->
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-jar-plugin</artifactId>
+                <version>3.2.2</version>
+                <executions>
+                    <execution>
+                        <id>Arbitrary</id>
+                        <goals>
+                            <goal>jar</goal>
+                        </goals>
+                        <configuration>
+                            <classifier>arbitrary</classifier>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>Test Jar</id>
+                        <goals>
+                            <goal>test-jar</goal>
+                        </goals>
+                    </execution>
+                    <!--        For example purpose not building as it requires both JDK 8 and 11 executables on the build machine -->
+                    <!--                    <execution>-->
+                    <!--                        <id>default-package-jdk11</id>-->
+                    <!--                        <phase>package</phase>-->
+                    <!--                        <goals>-->
+                    <!--                            <goal>jar</goal>-->
+                    <!--                        </goals>-->
+                    <!--                        <configuration>-->
+                    <!--                            <classesDirectory>${project.build.outputDirectory}_jdk11</classesDirectory>-->
+                    <!--                            <classifier>jdk11</classifier>-->
+                    <!--                        </configuration>-->
+                    <!--                    </execution>-->
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-source-plugin</artifactId>
+                <version>3.2.1</version>
+                <executions>
+                    <execution>
+                        <id>attach-sources</id>
+                        <phase>verify</phase>
+                        <goals>
+                            <goal>jar-no-fork</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-javadoc-plugin</artifactId>
+                <version>3.3.2</version>
+                <executions>
+                    <execution>
+                        <id>attach-javadocs</id>
+                        <goals>
+                            <goal>jar</goal>
+                        </goals>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+</project>

maven-modules/maven-classifier/maven-classifier-example-provider/src/main/java/com/baeldung/maven/dependency/classifier/provider/factory/CarFactory.java

@@ -0,0 +1,14 @@
+package com.baeldung.maven.dependency.classifier.provider.factory;
+
+import com.baeldung.maven.dependency.classifier.provider.model.Car;
+import com.baeldung.maven.dependency.classifier.provider.model.Car.Type;
+
+public class CarFactory {
+
+    public static Car manufacture(Type carType) {
+        Car car = new Car();
+        car.setType(carType);
+
+        return car;
+    }
+}

maven-modules/maven-classifier/maven-classifier-example-provider/src/main/java/com/baeldung/maven/dependency/classifier/provider/model/Car.java

@@ -0,0 +1,26 @@
+package com.baeldung.maven.dependency.classifier.provider.model;
+
+public class Car {
+    private Type type;
+    private PowerSource fuelType;
+
+    public Type getType() {
+        return this.type;
+    }
+
+    public void setType(Type carType) {
+        this.type = carType;
+    }
+
+    public PowerSource getPowerSource() {
+        return this.fuelType;
+    }
+
+    public void setFuelType(PowerSource fuelType) {
+        this.fuelType = fuelType;
+    }
+
+    public enum Type {
+        ELECTRIC
+    }
+}

maven-modules/maven-classifier/maven-classifier-example-provider/src/main/java/com/baeldung/maven/dependency/classifier/provider/model/PowerSource.java

@@ -0,0 +1,5 @@
+package com.baeldung.maven.dependency.classifier.provider.model;
+
+public enum PowerSource {
+    BATTERY
+}

maven-modules/maven-classifier/maven-classifier-example-provider/src/test/java/com/baeldung/maven/dependency/classifier/provider/factory/CarFactoryUnitTest.java

@@ -0,0 +1,32 @@
+
+package com.baeldung.maven.dependency.classifier.provider.factory;
+
+import com.baeldung.maven.dependency.classifier.provider.model.Car;
+import com.baeldung.maven.dependency.classifier.provider.model.Car.Type;
+import com.baeldung.maven.dependency.classifier.provider.model.PowerSource;
+import com.baeldung.maven.dependency.classifier.provider.stub.CarStub;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+class CarFactoryUnitTest {
+
+    @Test
+    @DisplayName("Given Car type When CarFactory manufacture is called Then create a Car of the given type")
+    public void givenCarType_whenCarFactoryManufactureCalled_thenCreateCarOfGivenType() {
+        Car car = CarFactory.manufacture(Type.ELECTRIC);
+
+        assertNotNull(car, "CarFactory didn't manufacture a car. Car is null");
+        assertEquals(Type.ELECTRIC, car.getType());
+    }
+
+    @Test
+    @DisplayName("Given an electric car When asked for fuel type Then return Battery")
+    public void givenElectricCar_whenAskedForFuelType_thenReturnBattery() {
+        Car car = CarStub.ELECTRIC_CAR;
+
+        assertEquals(PowerSource.BATTERY, car.getPowerSource());
+    }
+}

maven-modules/maven-classifier/maven-classifier-example-provider/src/test/java/com/baeldung/maven/dependency/classifier/provider/stub/CarStub.java

@@ -0,0 +1,17 @@
+package com.baeldung.maven.dependency.classifier.provider.stub;
+
+import com.baeldung.maven.dependency.classifier.provider.model.Car;
+import com.baeldung.maven.dependency.classifier.provider.model.PowerSource;
+import com.baeldung.maven.dependency.classifier.provider.model.Car.Type;
+import org.mockito.Mockito;
+
+import static org.mockito.Mockito.when;
+
+public class CarStub {
+    public static Car ELECTRIC_CAR = Mockito.mock(Car.class);
+
+    static {
+        when(ELECTRIC_CAR.getType()).thenReturn(Type.ELECTRIC);
+        when(ELECTRIC_CAR.getPowerSource()).thenReturn(PowerSource.BATTERY);
+    }
+}

maven-modules/maven-classifier/pom.xml

@@ -0,0 +1,27 @@
+<?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>maven-classifier</artifactId>
+    <packaging>pom</packaging>
+    <version>0.0.1-SNAPSHOT</version>
+
+    <modules>
+        <module>maven-classifier-example-consumer</module>
+        <module>maven-classifier-example-provider</module>
+    </modules>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>maven-modules</artifactId>
+        <version>0.0.1-SNAPSHOT</version>
+    </parent>
+
+    <properties>
+        <maven.compiler.source>8</maven.compiler.source>
+        <maven.compiler.target>8</maven.compiler.target>
+    </properties>
+
+</project>

maven-modules/maven-generate-war/pom.xml

@@ -63,6 +63,7 @@
 
     <properties>
         <java.version>11</java.version>
+        <log4j2.version>2.17.1</log4j2.version>
     </properties>
 
 </project>

maven-modules/pom.xml

@@ -36,6 +36,7 @@
         <module>maven-surefire-plugin</module>
         <module>maven-parent-pom-resolution</module>
         <module>maven-simple</module>
+        <module>maven-classifier</module>
     </modules>
 
     <dependencyManagement>

patterns/enterprise-patterns/pom.xml

@@ -48,6 +48,13 @@
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
+            <dependency>
+                <groupId>org.apache.logging.log4j</groupId>
+                <artifactId>log4j-bom</artifactId>
+                <version>${log4j2.version}</version>
+                <scope>import</scope>
+                <type>pom</type>
+            </dependency>
         </dependencies>
     </dependencyManagement>
 
@@ -63,6 +70,7 @@
     <properties>
         <camel.version>3.7.4</camel.version>
         <spring-boot.version>2.2.2.RELEASE</spring-boot.version>
+         <log4j2.version>2.17.1</log4j2.version>
     </properties>
 
 </project>

persistence-modules/hibernate-mapping-2/.gitignore

@@ -0,0 +1,13 @@
+*.class
+
+#folders#
+/target
+/neoDb*
+/data
+/src/main/webapp/WEB-INF/classes
+*/META-INF/*
+
+# Packaged files #
+*.jar
+*.war
+*.ear

persistence-modules/hibernate-mapping-2/README.md

@@ -0,0 +1,7 @@
+## Hibernate Mapping
+
+This module contains articles about Hibernate Mappings.
+
+### Relevant articles
+
+- [Hibernate Many to Many Annotation Tutorial](https://www.baeldung.com/hibernate-many-to-many)

persistence-modules/hibernate-mapping-2/pom.xml

@@ -0,0 +1,86 @@
+<?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>hibernate-mapping-2y</artifactId>
+    <version>0.1-SNAPSHOT</version>
+    <name>hibernate-mapping-2</name>
+
+    <parent>
+        <groupId>com.baeldung</groupId>
+        <artifactId>persistence-modules</artifactId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+
+    <dependencies>
+        <!-- Spring -->
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-context</artifactId>
+            <version>${org.springframework.version}</version>
+        </dependency>
+        <!-- persistence -->
+        <dependency>
+            <groupId>org.springframework.data</groupId>
+            <artifactId>spring-data-jpa</artifactId>
+            <version>${org.springframework.data.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.hibernate</groupId>
+            <artifactId>hibernate-core</artifactId>
+            <version>${hibernate.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.apache.tomcat</groupId>
+            <artifactId>tomcat-dbcp</artifactId>
+            <version>${tomcat-dbcp.version}</version>
+        </dependency>
+        <!-- validation -->
+        <!-- utils -->
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+        </dependency>
+        <!-- test scoped -->
+        <dependency>
+            <groupId>org.springframework</groupId>
+            <artifactId>spring-test</artifactId>
+            <version>${org.springframework.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <version>${h2.version}</version>
+        </dependency>	  
+		<dependency>
+			 <groupId>com.sun.xml.bind</groupId>
+			 <artifactId>jaxb-core</artifactId>
+			 <version>${com.sun.xml.version}</version>
+		</dependency>
+		<dependency>
+			 <groupId>javax.xml.bind</groupId>
+			 <artifactId>jaxb-api</artifactId>
+			 <version>${javax.xml.bind.version}</version>
+		</dependency>
+		<dependency>
+			 <groupId>com.sun.xml.bind</groupId>
+			 <artifactId>jaxb-impl</artifactId>
+			 <version>${com.sun.xml.version}</version>
+		</dependency>
+    </dependencies>
+
+    <properties>
+        <!-- Spring -->
+        <org.springframework.version>5.0.2.RELEASE</org.springframework.version>
+        <org.springframework.data.version>1.10.6.RELEASE</org.springframework.data.version>
+        <!-- persistence -->
+        <hibernate.version>5.2.10.Final</hibernate.version>
+        <tomcat-dbcp.version>9.0.0.M26</tomcat-dbcp.version>
+        <com.sun.xml.version>2.3.0.1</com.sun.xml.version>
+        <javax.xml.bind.version>2.3.1</javax.xml.bind.version>
+    </properties>
+
+</project>

persistence-modules/hibernate-mapping-2/src/main/java/com/baeldung/manytomany/PersistenceConfig.java

@@ -1,7 +1,9 @@
-package com.baeldung.manytomany.spring;
+package com.baeldung.manytomany;
 
 import java.util.Properties;
+
 import javax.sql.DataSource;
+
 import org.apache.tomcat.dbcp.dbcp2.BasicDataSource;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.annotation.Bean;
@@ -20,7 +22,7 @@ import org.springframework.transaction.annotation.EnableTransactionManagement;
 @Configuration
 @EnableTransactionManagement
 @PropertySource({ "classpath:persistence-h2.properties" })
-@ComponentScan({ "com.baeldung.hibernate.manytomany" })
+@ComponentScan({ "com.baeldung.manytomany" })
 public class PersistenceConfig {
 
     @Autowired
@@ -30,7 +32,7 @@ public class PersistenceConfig {
     public LocalSessionFactoryBean sessionFactory() {
         final LocalSessionFactoryBean sessionFactory = new LocalSessionFactoryBean();
         sessionFactory.setDataSource(restDataSource());
-        sessionFactory.setPackagesToScan(new String[] { "com.baeldung.hibernate.manytomany" });
+        sessionFactory.setPackagesToScan(new String[] { "com.baeldung.manytomany" });
         sessionFactory.setHibernateProperties(hibernateProperties());
 
         return sessionFactory;

persistence-modules/hibernate-mapping-2/src/main/java/com/baeldung/manytomany/dao/IEmployeeDao.java

@@ -0,0 +1,8 @@
+package com.baeldung.manytomany.dao;
+
+import com.baeldung.manytomany.dao.common.IOperations;
+import com.baeldung.manytomany.model.Employee;
+
+public interface IEmployeeDao extends IOperations<Employee>{
+
+}

persistence-modules/hibernate-mapping-2/src/main/java/com/baeldung/manytomany/dao/IProjectDao.java

@@ -0,0 +1,8 @@
+package com.baeldung.manytomany.dao;
+
+import com.baeldung.manytomany.dao.common.IOperations;
+import com.baeldung.manytomany.model.Project;
+
+public interface IProjectDao extends IOperations<Project>{
+
+}

persistence-modules/hibernate-mapping-2/src/main/java/com/baeldung/manytomany/dao/common/AbstractDao.java

@@ -0,0 +1,14 @@
+package com.baeldung.manytomany.dao.common;
+
+import java.io.Serializable;
+
+import com.google.common.base.Preconditions;
+
+public abstract class AbstractDao<T extends Serializable> implements IOperations<T> {
+
+    protected Class<T> clazz;
+
+    protected final void setClazz(final Class<T> clazzToSet) {
+        clazz = Preconditions.checkNotNull(clazzToSet);
+    }
+}

persistence-modules/hibernate-mapping-2/src/main/java/com/baeldung/manytomany/dao/common/AbstractHibernateDao.java

@@ -0,0 +1,59 @@
+package com.baeldung.manytomany.dao.common;
+
+import java.io.Serializable;
+import java.util.List;
+
+import org.hibernate.Session;
+import org.hibernate.SessionFactory;
+import org.springframework.beans.factory.annotation.Autowired;
+
+import com.google.common.base.Preconditions;
+
+@SuppressWarnings("unchecked")
+public abstract class AbstractHibernateDao<T extends Serializable> extends AbstractDao<T> implements IOperations<T> {
+
+    @Autowired
+    protected SessionFactory sessionFactory;
+
+    // API
+
+    @Override
+    public T findOne(final long id) {
+        return (T) getCurrentSession().get(clazz, id);
+    }
+
+    @Override
+    public List<T> findAll() {
+        return getCurrentSession().createQuery("from " + clazz.getName()).getResultList();
+    }
+
+    @Override
+    public void create(final T entity) {
+        Preconditions.checkNotNull(entity);
+        getCurrentSession().saveOrUpdate(entity);
+    }
+
+    @Override
+    public T update(final T entity) {
+        Preconditions.checkNotNull(entity);
+        return (T) getCurrentSession().merge(entity);
+    }
+
+    @Override
+    public void delete(final T entity) {
+        Preconditions.checkNotNull(entity);
+        getCurrentSession().delete(entity);
+    }
+
+    @Override
+    public void deleteById(final long entityId) {
+        final T entity = findOne(entityId);
+        Preconditions.checkState(entity != null);
+        delete(entity);
+    }
+
+    protected Session getCurrentSession() {
+        return sessionFactory.getCurrentSession();
+    }
+
+}

persistence-modules/hibernate-mapping-2/src/main/java/com/baeldung/manytomany/dao/common/IOperations.java

@@ -0,0 +1,20 @@
+package com.baeldung.manytomany.dao.common;
+
+import java.io.Serializable;
+import java.util.List;
+
+public interface IOperations<T extends Serializable> {
+
+    T findOne(final long id);
+
+    List<T> findAll();
+
+    void create(final T entity);
+
+    T update(final T entity);
+
+    void delete(final T entity);
+
+    void deleteById(final long entityId);
+
+}

persistence-modules/hibernate-mapping-2/src/main/java/com/baeldung/manytomany/dao/impl/EmployeeDao.java

@@ -0,0 +1,17 @@
+package com.baeldung.manytomany.dao.impl;
+
+import org.springframework.stereotype.Repository;
+
+import com.baeldung.manytomany.dao.IEmployeeDao;
+import com.baeldung.manytomany.dao.common.AbstractHibernateDao;
+import com.baeldung.manytomany.model.Employee;
+
+@Repository
+public class EmployeeDao extends AbstractHibernateDao<Employee> implements IEmployeeDao {
+
+    public EmployeeDao() {
+        super();
+
+        setClazz(Employee.class);
+    }
+}

persistence-modules/hibernate-mapping-2/src/main/java/com/baeldung/manytomany/dao/impl/ProjectDao.java

@@ -0,0 +1,18 @@
+package com.baeldung.manytomany.dao.impl;
+
+import org.springframework.stereotype.Repository;
+
+import com.baeldung.manytomany.dao.IProjectDao;
+import com.baeldung.manytomany.dao.common.AbstractHibernateDao;
+import com.baeldung.manytomany.model.Project;
+
+
+@Repository
+public class ProjectDao extends AbstractHibernateDao<Project> implements IProjectDao {
+
+    public ProjectDao() {
+        super();
+
+        setClazz(Project.class);
+    }
+}

persistence-modules/hibernate-mapping-2/src/main/java/com/baeldung/manytomany/model/Employee.java

@@ -1,4 +1,4 @@
-package com.baeldung.hibernate.manytomany.model;
+package com.baeldung.manytomany.model;
 
 import java.io.Serializable;
 import java.util.HashSet;

persistence-modules/hibernate-mapping-2/src/main/java/com/baeldung/manytomany/model/Project.java

@@ -1,8 +1,9 @@
-package com.baeldung.hibernate.manytomany.model;
+package com.baeldung.manytomany.model;
 
 import java.io.Serializable;
 import java.util.HashSet;
 import java.util.Set;
+
 import javax.persistence.Column;
 import javax.persistence.Entity;
 import javax.persistence.GeneratedValue;

persistence-modules/hibernate-mapping-2/src/main/java/com/baeldung/manytomany/util/HibernateUtil.java

@@ -1,14 +1,15 @@
-package com.baeldung.hibernate.manytomany.util;
+package com.baeldung.manytomany.util;
 
 import org.hibernate.SessionFactory;
 import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
 import org.hibernate.cfg.Configuration;
 import org.hibernate.service.ServiceRegistry;
-import com.baeldung.hibernate.manytomany.model.Employee;
-import com.baeldung.hibernate.manytomany.model.Project;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import com.baeldung.manytomany.model.Employee;
+import com.baeldung.manytomany.model.Project;
+
 public class HibernateUtil {
 
     private static final Logger LOGGER = LoggerFactory.getLogger(HibernateUtil.class);

persistence-modules/hibernate-mapping-2/src/main/resources/logback.xml

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<configuration>
+    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>web - %date [%thread] %-5level %logger{36} - %message%n
+            </pattern>
+        </encoder>
+    </appender>
+
+    <logger name="org.springframework" level="WARN" />
+    <logger name="org.springframework.transaction" level="WARN" />
+
+    <!-- in order to debug some marshalling issues, this needs to be TRACE -->
+    <logger name="org.springframework.web.servlet.mvc" level="WARN" />
+
+    <root level="INFO">
+        <appender-ref ref="STDOUT" />
+    </root>
+</configuration>

persistence-modules/hibernate-mapping-2/src/main/resources/persistence-h2.properties

@@ -0,0 +1,11 @@
+# jdbc.X
+jdbc.driverClassName=org.h2.Driver
+jdbc.url=jdbc:h2:mem:db;DB_CLOSE_DELAY=-1
+jdbc.eventGeneratedId=sa
+jdbc.user=sa
+jdbc.pass=
+
+# hibernate.X
+hibernate.dialect=org.hibernate.dialect.H2Dialect
+hibernate.show_sql=false
+hibernate.hbm2ddl.auto=create-drop

persistence-modules/hibernate-mapping-2/src/test/java/com/baeldung/SpringContextTest.java

@@ -0,0 +1,18 @@
+package com.baeldung;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.support.AnnotationConfigContextLoader;
+
+import com.baeldung.manytomany.PersistenceConfig;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(classes = { PersistenceConfig.class }, loader = AnnotationConfigContextLoader.class)
+public class SpringContextTest {
+
+    @Test
+    public void whenSpringContextIsBootstrapped_thenNoExceptions() {
+    }
+}

persistence-modules/hibernate-mapping-2/src/test/java/com/baeldung/hibernate/manytomany/HibernateManyToManyAnnotationJavaConfigMainIntegrationTest.java

@@ -2,6 +2,7 @@ package com.baeldung.hibernate.manytomany;
 
 import java.util.HashSet;
 import java.util.Set;
+
 import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 import org.junit.After;
@@ -12,9 +13,9 @@ import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.test.context.ContextConfiguration;
 import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
 import org.springframework.test.context.support.AnnotationConfigContextLoader;
-import com.baeldung.hibernate.manytomany.model.Employee;
+import com.baeldung.manytomany.PersistenceConfig;
-import com.baeldung.hibernate.manytomany.model.Project;
+import com.baeldung.manytomany.model.Employee;
-import com.baeldung.manytomany.spring.PersistenceConfig;
+import com.baeldung.manytomany.model.Project;
 
 @RunWith(SpringJUnit4ClassRunner.class)
 @ContextConfiguration(classes = { PersistenceConfig.class }, loader = AnnotationConfigContextLoader.class)

persistence-modules/hibernate-mapping-2/src/test/java/com/baeldung/hibernate/manytomany/HibernateManyToManyAnnotationMainIntegrationTest.java

@@ -1,10 +1,12 @@
 package com.baeldung.hibernate.manytomany;
 
-import static org.junit.Assert.assertNotNull;
 import static junit.framework.TestCase.assertEquals;
+import static org.junit.Assert.assertNotNull;
+
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
+
 import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 import org.junit.After;
@@ -13,9 +15,9 @@ import org.junit.Before;
 import org.junit.BeforeClass;
 import org.junit.Test;
 
-import com.baeldung.hibernate.manytomany.util.HibernateUtil;
+import com.baeldung.manytomany.model.Employee;
-import com.baeldung.hibernate.manytomany.model.Employee;
+import com.baeldung.manytomany.model.Project;
-import com.baeldung.hibernate.manytomany.model.Project;
+import com.baeldung.manytomany.util.HibernateUtil;
 
 /**
  * Configured in: manytomany.cfg.xml

persistence-modules/hibernate-queries/README.md

@@ -8,3 +8,4 @@ This module contains articles about use of Queries in Hibernate.
 - [Get All Data from a Table with Hibernate](https://www.baeldung.com/hibernate-select-all)
 - [Hibernate Named Query](https://www.baeldung.com/hibernate-named-query)
 - [Hibernate Query Plan Cache](https://www.baeldung.com/hibernate-query-plan-cache)
+- [Hibernate’s addScalar() Method](https://www.baeldung.com/hibernate-addscalar)

persistence-modules/java-mongodb/src/main/java/com/baeldung/mongo/update/MultipleFieldsExample.java

@@ -0,0 +1,44 @@
+package com.baeldung.mongo.update;
+
+import org.bson.Document;
+
+import com.mongodb.BasicDBObject;
+import com.mongodb.MongoClient;
+import com.mongodb.client.MongoCollection;
+import com.mongodb.client.MongoDatabase;
+import com.mongodb.client.result.UpdateResult;
+
+public class MultipleFieldsExample {
+
+	public static void main(String[] args) {
+
+	    //
+	    // Connect to cluster (default is localhost:27017)
+	    //
+
+		MongoClient mongoClient = new MongoClient("localhost", 27017);
+		MongoDatabase database = mongoClient.getDatabase("baeldung");
+		MongoCollection<Document> collection = database.getCollection("employee");
+
+		//
+		// Filter on the basis of employee_id
+		//
+
+		BasicDBObject searchQuery = new BasicDBObject("employee_id", 794875);
+
+		//
+		// Update the fields in Document
+		//
+
+		BasicDBObject updateFields = new BasicDBObject();
+		updateFields.append("department_id", 3);
+		updateFields.append("job", "Sales Manager");
+		BasicDBObject setQuery = new BasicDBObject();
+		setQuery.append("$set", updateFields);
+		UpdateResult updateResult = collection.updateMany(searchQuery, setQuery);
+
+		System.out.println("updateResult:- " + updateResult);
+		System.out.println("updateResult:- " + updateResult.getModifiedCount());
+
+	}
+}

persistence-modules/java-mongodb/src/main/java/com/baeldung/mongo/update/UpdateMultipleFields.java

@@ -0,0 +1,36 @@
+package com.baeldung.mongo.update;
+
+import org.bson.Document;
+
+import com.mongodb.MongoClient;
+import com.mongodb.client.MongoCollection;
+import com.mongodb.client.MongoDatabase;
+import com.mongodb.client.model.Filters;
+import com.mongodb.client.model.Updates;
+import com.mongodb.client.result.UpdateResult;
+
+public class UpdateMultipleFields {
+
+	public static void main(String[] args) {
+
+		//
+	    // Connect to cluster
+	    //
+
+		MongoClient mongoClient = new MongoClient("localhost", 27007);
+		MongoDatabase database = mongoClient.getDatabase("baeldung");
+		MongoCollection<Document> collection = database.getCollection("employee");
+
+		//
+		// Update query
+		//
+
+		UpdateResult updateResult = collection.updateMany(Filters.eq("employee_id", 794875),
+				Updates.combine(Updates.set("department_id", 4), Updates.set("job", "Sales Manager")));
+
+		System.out.println("updateResult:- " + updateResult);
+		System.out.println("updateResult:- " + updateResult.getModifiedCount());
+
+	}
+
+}

persistence-modules/java-mongodb/src/test/java/com/baeldung/update/UpdateMultipleFieldsLiveTest.java

@@ -0,0 +1,80 @@
+package com.baeldung.update;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertSame;
+
+import org.bson.Document;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.mongodb.BasicDBObject;
+import com.mongodb.MongoClient;
+import com.mongodb.client.MongoCollection;
+import com.mongodb.client.MongoDatabase;
+import com.mongodb.client.model.Filters;
+import com.mongodb.client.model.Updates;
+import com.mongodb.client.result.UpdateResult;
+
+public class UpdateMultipleFieldsLiveTest {
+
+    private MongoClient mongoClient;
+    private MongoDatabase db;
+    private MongoCollection<Document> collection;
+
+    @Before
+    public void setup() {
+        if (mongoClient == null) {
+            mongoClient = new MongoClient("localhost", 27017);
+            db = mongoClient.getDatabase("baeldung");
+            collection = db.getCollection("employee");
+
+            collection.insertOne(Document.parse(
+                    "{'employee_id':794875,'employee_name': 'David smith','job': 'Sales Representative','department_id': 2,'salary': 20000,'hire_date': NumberLong(\"1643969311817\")}"));
+        }
+    }
+
+    @Test
+    public void updateMultipleFieldsUsingDBObject() {
+
+        BasicDBObject searchQuery = new BasicDBObject("employee_id", 794875);
+        BasicDBObject updateFields = new BasicDBObject();
+        updateFields.append("department_id", 4);
+        updateFields.append("job", "Sales Manager");
+        BasicDBObject setQuery = new BasicDBObject();
+        setQuery.append("$set", updateFields);
+
+        collection.updateMany(searchQuery, setQuery);
+
+        Document nameDoc = collection.find(Filters.eq("employee_id", 794875)).first();
+        assertNotNull(nameDoc);
+        assertFalse(nameDoc.isEmpty());
+
+        String job = nameDoc.get("job", String.class);
+        assertNotNull(job);
+
+        Integer department_id = nameDoc.get("department_id", Integer.class);
+        assertNotNull(department_id);
+
+    }
+
+    @Test
+    public void updateMultipleFieldsUsingDocument() {
+
+        collection.updateMany(Filters.eq("employee_id", 794875),
+                Updates.combine(Updates.set("department_id", 4), Updates.set("job", "Sales Manager")));
+
+        Document nameDoc = collection.find(Filters.eq("employee_id", 794875)).first();
+        assertNotNull(nameDoc);
+        assertFalse(nameDoc.isEmpty());
+
+        String job = nameDoc.get("job", String.class);
+        assertNotNull(job);
+
+        Integer department_id = nameDoc.get("department_id", Integer.class);
+        assertNotNull(department_id);
+
+    }
+
+}

persistence-modules/spring-data-dynamodb/pom.xml

@@ -24,6 +24,13 @@
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
+            <dependency>
+                <groupId>org.apache.logging.log4j</groupId>
+                <artifactId>log4j-bom</artifactId>
+                <version>${log4j2.version}</version>
+                <scope>import</scope>
+                <type>pom</type>
+            </dependency>
         </dependencies>
     </dependencyManagement>
 
@@ -184,6 +191,7 @@
         <dynamodblocal.repository.url>https://s3-us-west-2.amazonaws.com/dynamodb-local/release</dynamodblocal.repository.url>
         <maven-dependency-plugin.version>3.1.1</maven-dependency-plugin.version>
         <spring-boot.version>2.4.7</spring-boot.version>
+        <log4j2.version>2.17.1</log4j2.version>
     </properties>
 
 </project>

persistence-modules/spring-hibernate-5/README.md

@@ -4,7 +4,6 @@ This module contains articles about Hibernate 5 with Spring.
 
 ### Relevant articles
 
-- [Hibernate Many to Many Annotation Tutorial](https://www.baeldung.com/hibernate-many-to-many)
 - [Programmatic Transactions in the Spring TestContext Framework](https://www.baeldung.com/spring-test-programmatic-transactions)
 - [JPA Criteria Queries](https://www.baeldung.com/hibernate-criteria-queries)
 - [Introduction to Hibernate Search](https://www.baeldung.com/hibernate-search)

persistence-modules/spring-hibernate-5/pom.xml

@@ -108,6 +108,21 @@
             <artifactId>h2</artifactId>
             <version>${h2.version}</version>
         </dependency>	  
+		<dependency>
+			 <groupId>com.sun.xml.bind</groupId>
+			 <artifactId>jaxb-core</artifactId>
+			 <version>${com.sun.xml.version}</version>
+		</dependency>
+		<dependency>
+			 <groupId>javax.xml.bind</groupId>
+			 <artifactId>jaxb-api</artifactId>
+			 <version>${javax.xml.bind.version}</version>
+		</dependency>
+		<dependency>
+			 <groupId>com.sun.xml.bind</groupId>
+			 <artifactId>jaxb-impl</artifactId>
+			 <version>${com.sun.xml.version}</version>
+		</dependency>
     </dependencies>
 
     <properties>
@@ -122,6 +137,8 @@
         <tomcat-dbcp.version>9.0.0.M26</tomcat-dbcp.version>
         <jta.version>1.1</jta.version>
         <hsqldb.version>2.3.4</hsqldb.version>
+        <com.sun.xml.version>2.3.0.1</com.sun.xml.version>
+        <javax.xml.bind.version>2.3.1</javax.xml.bind.version>
     </properties>
 
 </project>

persistence-modules/spring-hibernate-5/src/main/java/com/baeldung/persistence/manytomany/dao/IEmployeeDao.java

@@ -1,8 +0,0 @@
-package com.baeldung.persistence.manytomany.dao;
-
-import com.baeldung.hibernate.manytomany.model.Employee;
-import com.baeldung.persistence.dao.common.IOperations;
-
-public interface IEmployeeDao extends IOperations<Employee>{
-
-}

persistence-modules/spring-hibernate-5/src/main/java/com/baeldung/persistence/manytomany/dao/IProjectDao.java

@@ -1,8 +0,0 @@
-package com.baeldung.persistence.manytomany.dao;
-
-import com.baeldung.hibernate.manytomany.model.Project;
-import com.baeldung.persistence.dao.common.IOperations;
-
-public interface IProjectDao extends IOperations<Project>{
-
-}

persistence-modules/spring-hibernate-5/src/main/java/com/baeldung/persistence/manytomany/dao/impl/EmployeeDao.java

@@ -1,16 +0,0 @@
-package com.baeldung.persistence.manytomany.dao.impl;
-
-import org.springframework.stereotype.Repository;
-import com.baeldung.hibernate.manytomany.model.Employee;
-import com.baeldung.persistence.dao.common.AbstractHibernateDao;
-import com.baeldung.persistence.manytomany.dao.IEmployeeDao;
-
-@Repository
-public class EmployeeDao extends AbstractHibernateDao<Employee> implements IEmployeeDao {
-
-    public EmployeeDao() {
-        super();
-
-        setClazz(Employee.class);
-    }
-}

persistence-modules/spring-hibernate-5/src/main/java/com/baeldung/persistence/manytomany/dao/impl/ProjectDao.java

@@ -1,17 +0,0 @@
-package com.baeldung.persistence.manytomany.dao.impl;
-
-import org.springframework.stereotype.Repository;
-import com.baeldung.hibernate.manytomany.model.Project;
-import com.baeldung.persistence.dao.common.AbstractHibernateDao;
-import com.baeldung.persistence.manytomany.dao.IProjectDao;
-
-
-@Repository
-public class ProjectDao extends AbstractHibernateDao<Project> implements IProjectDao {
-
-    public ProjectDao() {
-        super();
-
-        setClazz(Project.class);
-    }
-}

persistence-modules/spring-hibernate-5/src/main/resources/manytomany.cfg.xml

@@ -1,15 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE hibernate-configuration PUBLIC
-		"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
-		"http://hibernate.org/dtd/hibernate-configuration-3.0.dtd">
-<hibernate-configuration>
-    <session-factory>
-        <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
-        <property name="hibernate.connection.password">tutorialmy5ql</property>
-        <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/spring_hibernate_many_to_many</property>
-        <property name="hibernate.connection.username">tutorialuser</property>
-        <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
-        <property name="hibernate.current_session_context_class">thread</property>
-        <property name="hibernate.show_sql">false</property>
-    </session-factory>
-</hibernate-configuration>

persistence-modules/spring-hibernate-5/src/test/resources/criteria.cfg.xml

@@ -11,6 +11,7 @@
 		<property name="hibernate.connection.password"></property>
 		<property name="hibernate.dialect">org.hibernate.dialect.H2Dialect</property>
 	    <property name="hibernate.hbm2ddl.auto">create-drop</property>
+	    <property name="hibernate.hbm2ddl.import_files">import-db.sql</property>
 	    <property name="show_sql">false</property>        
 	    <mapping resource="com/baeldung/hibernate/criteria/model/Item.hbm.xml" />
 	</session-factory>

persistence-modules/spring-hibernate-5/src/test/resources/import-db.sql

@@ -1,3 +1,4 @@
+  
 insert into item (item_id, item_name, item_desc, item_price) values(1,'item One', 'test 1', 35.12);
 
 insert into item (item_id, item_name, item_desc, item_price) values(2,'Pogo stick', 'Pogo stick', 466.12);

pom.xml

@@ -400,7 +400,6 @@
                 <module>dagger</module>
                 <module>data-structures</module>
                 <module>ddd</module>
-                <!-- <module>ddd-modules</module>--> <!-- we haven't upgraded to Java 9 -->
                 <module>deeplearning4j</module>
                 <module>discord4j</module>
                 <module>disruptor</module>
@@ -432,7 +431,6 @@
                 <module>hazelcast</module>
                 <module>helidon</module>
                 <module>httpclient</module>
-                <!--<module>httpclient-2</module>--><!-- to be fixed in http://team.baeldung.com/browse/JAVA-2824 -->
                 <module>httpclient-simple</module>
                 <module>hystrix</module>
 
@@ -520,12 +518,12 @@
                 <module>micronaut</module>
                 <module>microprofile</module>
                 <module>msf4j</module>
-                <!-- <module>muleesb</module> --> <!-- Module broken, fixing in http://team.baeldung.com/browse/BAEL-20604 -->
+                <!-- <module>muleesb</module> --> <!-- Module broken, fixing in https://team.baeldung.com/browse/JAVA-10335 -->
                 <module>mustache</module>
                 <module>mybatis</module>
 
                 <module>netflix-modules</module>
-                <!-- <module>netty</module> --> <!-- we haven't upgraded to Java 13 -->
+                <module>netty</module>
                 <module>ninja</module>
                 <module>open-liberty</module>
 
@@ -886,7 +884,6 @@
                 <module>dagger</module>
                 <module>data-structures</module>
                 <module>ddd</module>
-                <!-- <module>ddd-modules</module>--> <!-- we haven't upgraded to Java 9 -->
                 <module>deeplearning4j</module>
                 <module>discord4j</module>
                 <module>disruptor</module>
@@ -917,7 +914,6 @@
                 <module>hazelcast</module>
                 <module>helidon</module>
                 <module>httpclient</module>
-                <!--<module>httpclient-2</module>--><!-- to be fixed in http://team.baeldung.com/browse/JAVA-2824 -->
                 <module>httpclient-simple</module>
                 <module>hystrix</module>
 
@@ -1005,12 +1001,12 @@
                 <module>micronaut</module>
                 <module>microprofile</module>
                 <module>msf4j</module>
-                <!-- <module>muleesb</module> --> <!-- Module broken, fixing in http://team.baeldung.com/browse/BAEL-20604 -->
+                <!-- <module>muleesb</module> --> <!-- Module broken, fixing in https://team.baeldung.com/browse/JAVA-10335 -->
                 <module>mustache</module>
                 <module>mybatis</module>
 
                 <module>netflix-modules</module>
-                <!-- <module>netty</module> --> <!-- we haven't upgraded to Java 13 -->
+                <module>netty</module>
                 <module>ninja</module>
                 <module>open-liberty</module>
 
@@ -1200,7 +1196,6 @@
                 <module>wildfly</module>
                 <module>xml</module>
                 <module>xstream</module>
-<!--                <module>libraries-concurrency</module>--> <!-- we haven't upgraded to Java 11 -->
             </modules>
 
         </profile>
@@ -1329,6 +1324,7 @@
                  <!-- <module>core-java-modules/core-java-14</module> --> <!-- uses preview features, to be decided how to handle -->
                  <!-- <module>core-java-modules/core-java-15</module> --> <!-- uses preview features, to be decided how to handle -->
                  <module>core-java-modules/core-java-collections-set</module>
+                 <module>core-java-modules/core-java-collections-maps-4</module>
                  <module>core-java-modules/core-java-date-operations-1</module>
                  <module>core-java-modules/core-java-datetime-conversion</module>
                  <module>core-java-modules/core-java-datetime-string</module>
@@ -1341,11 +1337,15 @@
                  <module>core-java-modules/core-java-time-measurements</module>
                  <module>core-java-modules/core-java-networking-3</module>
                  <module>core-java-modules/multimodulemavenproject</module>
+                 <module>ddd-modules</module>
+                 <module>httpclient-2</module>
+                 <module>libraries-concurrency</module>
                  <module>persistence-modules/sirix</module>
                  <module>persistence-modules/spring-data-cassandra-2</module>
                  <module>quarkus-vs-springboot</module>
                  <module>quarkus-jandex</module>
                  <module>spring-boot-modules/spring-boot-cassandre</module>
+                 <module>spring-boot-modules/spring-boot-camel</module>	 
                  <module>testing-modules/testing-assertions</module>
             </modules>
         </profile>
@@ -1386,6 +1386,7 @@
                 <!-- <module>core-java-modules/core-java-14</module> --> <!-- uses preview features, to be decided how to handle -->
                 <!-- <module>core-java-modules/core-java-15</module> --> <!-- uses preview features, to be decided how to handle -->
                 <module>core-java-modules/core-java-collections-set</module>
+                <module>core-java-modules/core-java-collections-maps-4</module>
                 <module>core-java-modules/core-java-date-operations-1</module>
                 <module>core-java-modules/core-java-datetime-conversion</module>
                 <module>core-java-modules/core-java-datetime-string</module>
@@ -1398,11 +1399,15 @@
                 <module>core-java-modules/core-java-networking-3</module>
                 <module>core-java-modules/multimodulemavenproject</module>
                 <module>core-java-modules/core-java-strings</module>
+                <module>ddd-modules</module>
+                <module>httpclient-2</module>
+                <module>libraries-concurrency</module>
                 <module>persistence-modules/sirix</module>
                 <module>persistence-modules/spring-data-cassandra-2</module>
                 <module>quarkus-vs-springboot</module>
                 <module>quarkus-jandex</module>
                 <module>spring-boot-modules/spring-boot-cassandre</module>
+                <module>spring-boot-modules/spring-boot-camel</module>
                 <module>testing-modules/testing-assertions</module>
             </modules>
         </profile>
@@ -1470,7 +1475,6 @@
         <custom-pmd.version>0.0.1</custom-pmd.version>
         <gitflow-incremental-builder.version>3.12.2</gitflow-incremental-builder.version>
         <maven-jxr-plugin.version>3.0.0</maven-jxr-plugin.version>
-        <!-- <maven-pmd-plugin.version>3.9.0</maven-pmd-plugin.version> -->
         <maven-pmd-plugin.version>3.13.0</maven-pmd-plugin.version>
         <lombok.version>1.18.20</lombok.version>
         <h2.version>1.4.200</h2.version>

quarkus-vs-springboot/spring-project/pom.xml

@@ -187,6 +187,7 @@
         <java.version>11</java.version>
         <repackage.classifier />
         <spring-native.version>0.11.0-RC1</spring-native.version>
+        <log4j2.version>2.17.1</log4j2.version>
     </properties>
 
 </project>

spring-5-autowiring-beans/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [Spring @Autowired Field Null – Common Causes and Solutions](https://www.baeldung.com/spring-autowired-field-null)

spring-5-data-reactive/pom.xml

@@ -14,6 +14,18 @@
         <relativePath>../parent-boot-2</relativePath>
     </parent>
     
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>org.apache.logging.log4j</groupId>
+                <artifactId>log4j-bom</artifactId>
+                <version>${log4j2.version}</version>
+                <scope>import</scope>
+                <type>pom</type>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
     <dependencies>
         <dependency>
             <groupId>io.projectreactor</groupId>
@@ -138,6 +150,7 @@
         <reactor-core.version>3.3.1.RELEASE</reactor-core.version>
         <!-- This spring-boot.version is set manually, For upgrading this please refer http://team.baeldung.com/browse/JAVA-2802 -->
         <spring-boot.version>2.2.6.RELEASE</spring-boot.version>
+        <log4j2.version>2.17.1</log4j2.version>
     </properties>
 
 </project>

spring-activiti/pom.xml

@@ -17,6 +17,18 @@
         <relativePath>../parent-boot-1</relativePath>
     </parent>
     
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>org.apache.logging.log4j</groupId>
+                <artifactId>log4j-bom</artifactId>
+                <version>${log4j2.version}</version>
+                <scope>import</scope>
+                <type>pom</type>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
     <dependencies>
         <dependency>
             <groupId>org.activiti</groupId>
@@ -59,6 +71,7 @@
 
     <properties>
         <activiti.version>6.0.0</activiti.version>
+        <log4j2.version>2.17.1</log4j2.version>
     </properties>
 
 </project>

spring-boot-modules/pom.xml

@@ -36,7 +36,6 @@
         <module>spring-boot-deployment</module>
         <module>spring-boot-di</module>
         <module>spring-boot-disable-logging</module>
-        <module>spring-boot-camel</module>
         <module>spring-boot-ci-cd</module>
         <!-- <module>spring-boot-cli</module> --> <!-- Not a maven project -->
         <module>spring-boot-custom-starter</module>

spring-boot-modules/spring-boot-2/pom.xml

@@ -62,7 +62,7 @@
     </build>
 
     <properties>
-        <log4j2.version>2.14.1</log4j2.version>
+        <log4j2.version>2.17.1</log4j2.version>
         <spring-core.version>5.3.15</spring-core.version>
         <maven.compiler.target>11</maven.compiler.target>
         <maven.compiler.source>11</maven.compiler.source>

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

@@ -16,22 +16,22 @@
 
     <dependencies>
         <dependency>
-            <groupId>org.apache.camel</groupId>
+            <groupId>org.apache.camel.springboot</groupId>
             <artifactId>camel-servlet-starter</artifactId>
             <version>${camel.version}</version>
         </dependency>
         <dependency>
-            <groupId>org.apache.camel</groupId>
+            <groupId>org.apache.camel.springboot</groupId>
             <artifactId>camel-jackson-starter</artifactId>
             <version>${camel.version}</version>
         </dependency>
         <dependency>
-            <groupId>org.apache.camel</groupId>
+            <groupId>org.apache.camel.springboot</groupId>
             <artifactId>camel-swagger-java-starter</artifactId>
             <version>${camel.version}</version>
         </dependency>
         <dependency>
-            <groupId>org.apache.camel</groupId>
+            <groupId>org.apache.camel.springboot</groupId>
             <artifactId>camel-spring-boot-starter</artifactId>
             <version>${camel.version}</version>
         </dependency>
@@ -64,7 +64,8 @@
     </build>
 
     <properties>
-        <camel.version>3.0.0-M4</camel.version>
+        <java.version>11</java.version>
+        <camel.version>3.15.0</camel.version>
     </properties>
 
 </project>

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

@@ -4,4 +4,4 @@ This module contains articles about various Spring Boot libraries Comparison
 
 ### Relevant Articles:
 
-- [GraphQL vs REST](https://www.baeldung.com/graphql-vs-rest/)
+- [GraphQL vs REST](https://www.baeldung.com/graphql-vs-rest)

spring-boot-modules/spring-boot-logging-log4j2/pom.xml

@@ -102,6 +102,7 @@
         <!-- used only in dependency management to force this version, not included as a direct dependency -->
         <junit.version>4.13.2</junit.version>
         <junit-jupiter.version>5.8.1</junit-jupiter.version>
+        <log4j2.version>2.17.1</log4j2.version>
     </properties>
 
 </project>

spring-boot-modules/spring-boot-mvc-birt/pom.xml

@@ -70,6 +70,7 @@
         <maven.compiler.target>1.8</maven.compiler.target>
         <eclipse.birt.runtime.version>4.8.0</eclipse.birt.runtime.version>
         <log4j.version>1.2.17</log4j.version>
+        <log4j2.version>2.17.1</log4j2.version>
     </properties>
 
 </project>

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

@@ -11,6 +11,18 @@
         <version>1.0.0-SNAPSHOT</version>
     </parent>
 
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>org.apache.logging.log4j</groupId>
+                <artifactId>log4j-bom</artifactId>
+                <version>${log4j2.version}</version>
+                <scope>import</scope>
+                <type>pom</type>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
     <dependencies>
         <dependency>
             <groupId>org.springframework.boot</groupId>
@@ -128,6 +140,7 @@
         <yarn.version>v1.12.1</yarn.version>
         <spring-boot.version>2.4.4</spring-boot.version>
         <javafaker.version>1.0.2</javafaker.version>
+        <log4j2.version>2.17.1</log4j2.version>
     </properties>
 
 </project>

spring-boot-modules/spring-boot-security/README.md

@@ -10,6 +10,7 @@ This module contains articles about Spring Boot Security
 - [Guide to @CurrentSecurityContext in Spring Security](https://www.baeldung.com/spring-currentsecuritycontext)
 - [Disable Security for a Profile in Spring Boot](https://www.baeldung.com/spring-security-disable-profile)
 - [Spring @EnableWebSecurity vs. @EnableGlobalMethodSecurity](https://www.baeldung.com/spring-enablewebsecurity-vs-enableglobalmethodsecurity)
+- [Spring Security – Configuring Different URLs](https://www.baeldung.com/spring-security-configuring-urls)
 
 
 ### Spring Boot Security Auto-Configuration

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

@@ -24,6 +24,13 @@
                 <type>pom</type>
                 <scope>import</scope>
             </dependency>
+            <dependency>
+                <groupId>org.apache.logging.log4j</groupId>
+                <artifactId>log4j-bom</artifactId>
+                <version>${log4j2.version}</version>
+                <scope>import</scope>
+                <type>pom</type>
+            </dependency>
         </dependencies>
     </dependencyManagement>
 
@@ -62,6 +69,7 @@
         <spring-boot.version>2.4.5</spring-boot.version>
         <springfox.version>3.0.0</springfox.version>
         <keycloak.version>15.0.2</keycloak.version>
+        <log4j2.version>2.17.1</log4j2.version>
     </properties>
 
 </project>

spring-boot-modules/spring-boot-swagger/README.md

@@ -5,3 +5,4 @@
 - [Generate PDF from Swagger API Documentation](https://www.baeldung.com/swagger-generate-pdf)
 - [Remove Basic Error Controller In SpringFox Swagger-UI](https://www.baeldung.com/spring-swagger-remove-error-controller)
 - [Setting Example and Description with Swagger](https://www.baeldung.com/swagger-set-example-description)
+- [Document Enum in Swagger](https://www.baeldung.com/swagger-enum)

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

@@ -14,6 +14,18 @@
         <version>1.0.0-SNAPSHOT</version>
     </parent>
 
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>org.apache.logging.log4j</groupId>
+                <artifactId>log4j-bom</artifactId>
+                <version>${log4j2.version}</version>
+                <scope>import</scope>
+                <type>pom</type>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
     <dependencies>
         <dependency>
             <groupId>org.springframework.boot</groupId>
@@ -131,6 +143,7 @@
         <gmavenplus-plugin.version>1.6</gmavenplus-plugin.version>
         <redis.version>0.7.2</redis.version>
         <spring-boot.version>2.5.0</spring-boot.version>
+        <log4j2.version>2.17.1</log4j2.version>
     </properties>
 
 </project>

spring-cloud/spring-cloud-contract/pom.xml

@@ -21,6 +21,13 @@
 
     <dependencyManagement>
         <dependencies>
+            <dependency>
+                <groupId>org.apache.logging.log4j</groupId>
+                <artifactId>log4j-bom</artifactId>
+                <version>${log4j2.version}</version>
+                <scope>import</scope>
+                <type>pom</type>
+            </dependency>
             <dependency>
                 <groupId>org.springframework.boot</groupId>
                 <artifactId>spring-boot-starter-web</artifactId>
@@ -55,6 +62,7 @@
     <properties>
         <spring-cloud.version>2.1.1.RELEASE</spring-cloud.version>
         <spring-boot.version>2.1.4.RELEASE</spring-boot.version>
+        <log4j2.version>2.17.1</log4j2.version>
     </properties>
 
 </project>

spring-cloud/spring-cloud-eureka-self-preservation/pom.xml

@@ -15,6 +15,18 @@
         <version>1.0.0-SNAPSHOT</version>
     </parent>
     
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>org.apache.logging.log4j</groupId>
+                <artifactId>log4j-bom</artifactId>
+                <version>${log4j2.version}</version>
+                <scope>import</scope>
+                <type>pom</type>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
     <modules>
         <module>spring-cloud-eureka-server</module>
         <module>spring-cloud-eureka-client</module>
@@ -32,6 +44,7 @@
     <properties>
         <spring-boot.version>2.1.3.RELEASE</spring-boot.version>
         <spring-cloud-dependencies.version>Greenwich.SR3</spring-cloud-dependencies.version>
+        <log4j2.version>2.17.1</log4j2.version>
     </properties>
 
 </project>

spring-cloud/spring-cloud-eureka/pom.xml

@@ -15,6 +15,18 @@
         <version>1.0.0-SNAPSHOT</version>
     </parent>
     
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>org.apache.logging.log4j</groupId>
+                <artifactId>log4j-bom</artifactId>
+                <version>${log4j2.version}</version>
+                <scope>import</scope>
+                <type>pom</type>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
     <modules>
         <module>spring-cloud-eureka-server</module>
         <module>spring-cloud-eureka-client</module>
@@ -34,6 +46,7 @@
     <properties>
         <spring-boot.version>2.1.2.RELEASE</spring-boot.version>
         <spring-cloud-dependencies.version>Greenwich.RELEASE</spring-cloud-dependencies.version>
+        <log4j2.version>2.17.1</log4j2.version>
     </properties>
 
 </project>

spring-cloud/spring-cloud-load-balancer/pom.xml

@@ -20,6 +20,18 @@
         <module>spring-cloud-loadbalancer-client</module>
     </modules>
     
+    <dependencyManagement>
+        <dependencies>
+            <dependency>
+                <groupId>org.apache.logging.log4j</groupId>
+                <artifactId>log4j-bom</artifactId>
+                <version>${log4j2.version}</version>
+                <scope>import</scope>
+                <type>pom</type>
+            </dependency>
+        </dependencies>
+    </dependencyManagement>
+
     <dependencies>
         <dependency>
             <groupId>org.springframework.boot</groupId>
@@ -32,6 +44,7 @@
     <properties>
         <spring-boot.version>2.6.1</spring-boot.version>
         <spring-cloud.version>2021.0.0</spring-cloud.version>
+         <log4j2.version>2.17.1</log4j2.version>
     </properties>
 
 </project>

spring-cloud/spring-cloud-openfeign/README.md

@@ -4,3 +4,4 @@
 - [Differences Between Netflix Feign and OpenFeign](https://www.baeldung.com/netflix-feign-vs-openfeign)
 - [File Upload With Open Feign](https://www.baeldung.com/java-feign-file-upload)
 - [Feign Logging Configuration](https://www.baeldung.com/java-feign-logging)
+- [Provide an OAuth2 Token to a Feign Client](https://www.baeldung.com/spring-cloud-feign-oauth-token)