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

core-java-modules/core-java-14/src/test/java/com/baeldung/java14/character/IsLetterOrAlphabetUnitTest.java

@@ -0,0 +1,30 @@
+package com.baeldung.java14.character;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.assertFalse;
+
+public class IsLetterOrAlphabetUnitTest {
+
+    @Test
+    public void givenACharacter_whenLetter_thenAssertIsLetterTrue() {
+        assertTrue(Character.isLetter(65));
+    }
+
+    @Test
+    public void givenACharacter_whenLetter_thenAssertIsAlphabeticTrue() {
+        assertTrue(Character.isAlphabetic(65));
+    }
+
+    @Test
+    public void givenACharacter_whenAlphabeticAndNotLetter_thenAssertIsLetterFalse() {
+        assertFalse(Character.isLetter(837));
+    }
+
+    @Test
+    public void givenACharacter_whenAlphabeticAndNotLetter_thenAssertIsAlphabeticTrue() {
+        assertTrue(Character.isAlphabetic(837));
+    }
+
+}

core-java-modules/core-java-arrays-guides/src/main/java/com/baeldung/genericarrays/MyStack.java

@@ -0,0 +1,30 @@
+package com.baeldung.genericarrays;
+
+import java.lang.reflect.Array;
+
+public class MyStack<E> {
+    private E[] elements;
+    private int size = 0;
+
+    public MyStack(Class<E> clazz, int capacity) {
+        elements = (E[]) Array.newInstance(clazz, capacity);
+    }
+
+    public void push(E item) {
+        if (size == elements.length) {
+            throw new RuntimeException();
+        }
+        elements[size++] = item;
+    }
+
+    public E pop() {
+        if (size == 0) {
+            throw new RuntimeException();
+        }
+        return elements[--size];
+    }
+
+    public E[] getAllElements() {
+        return elements;
+    }
+}

core-java-modules/core-java-arrays-guides/src/test/java/com/baeldung/genericarrays/ListToArrayUnitTest.java

@@ -0,0 +1,24 @@
+package com.baeldung.genericarrays;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class ListToArrayUnitTest {
+
+    @Test
+    public void givenListOfItems_whenToArray_thenReturnArrayOfItems() {
+        List<String> items = new LinkedList<>();
+        items.add("first item");
+        items.add("second item");
+
+        String[] itemsAsArray = items.toArray(new String[0]);
+
+        assertEquals("first item", itemsAsArray[0]);
+        assertEquals("second item", itemsAsArray[1]);
+    }
+}

core-java-modules/core-java-arrays-guides/src/test/java/com/baeldung/genericarrays/MyStackUnitTest.java

@@ -0,0 +1,44 @@
+package com.baeldung.genericarrays;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class MyStackUnitTest {
+
+    @Test
+    public void givenStackWithTwoItems_whenPop_thenReturnLastAdded() {
+        MyStack<String> myStack = new MyStack<>(String.class, 2);
+        myStack.push("hello");
+        myStack.push("example");
+
+        assertEquals("example", myStack.pop());
+    }
+
+    @Test (expected = RuntimeException.class)
+    public void givenStackWithFixedCapacity_whenExceedCapacity_thenThrowException() {
+        MyStack<Integer> myStack = new MyStack<>(Integer.class, 2);
+        myStack.push(100);
+        myStack.push(200);
+        myStack.push(300);
+    }
+
+    @Test(expected = RuntimeException.class)
+    public void givenStack_whenPopOnEmptyStack_thenThrowException() {
+        MyStack<Integer> myStack = new MyStack<>(Integer.class, 1);
+        myStack.push(100);
+        myStack.pop();
+        myStack.pop();
+    }
+
+    @Test
+    public void givenStackWithItems_whenGetAllElements_thenSizeShouldEqualTotal() {
+        MyStack<String> myStack = new MyStack<>(String.class, 2);
+        myStack.push("hello");
+        myStack.push("example");
+
+        String[] items = myStack.getAllElements();
+
+        assertEquals(2, items.length);
+    }
+}

core-java-modules/core-java-lang-oop-types/pom.xml

@@ -12,12 +12,20 @@
     <artifactId>core-java-lang-oop-types</artifactId>
     <name>core-java-lang-oop-types</name>
     <packaging>jar</packaging>
-    
+
     <dependencies>
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
             <version>${commons-lang3.version}</version>
         </dependency>
+        <dependency>
+            <groupId>commons-codec</groupId>
+            <artifactId>commons-codec</artifactId>
+            <version>${commons-codec.version}</version>
+        </dependency>
     </dependencies>
+    <properties>
+        <commons-codec.version>1.15</commons-codec.version>
+    </properties>
 </project>

core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/Application.java

@@ -0,0 +1,35 @@
+package com.baeldung.enums.extendenum;
+
+import org.apache.commons.lang3.StringUtils;
+
+import java.util.Arrays;
+import java.util.EnumMap;
+import java.util.Map;
+
+public class Application {
+    private static final Map<ImmutableOperation, Operator> OPERATION_MAP;
+
+    static {
+        OPERATION_MAP = new EnumMap<>(ImmutableOperation.class);
+        OPERATION_MAP.put(ImmutableOperation.TO_LOWER, String::toLowerCase);
+        OPERATION_MAP.put(ImmutableOperation.INVERT_CASE, StringUtils::swapCase);
+        OPERATION_MAP.put(ImmutableOperation.REMOVE_WHITESPACES, input -> input.replaceAll("\\s", ""));
+
+        if (Arrays.stream(ImmutableOperation.values()).anyMatch(it -> !OPERATION_MAP.containsKey(it))) {
+            throw new IllegalStateException("Unmapped enum constant found!");
+        }
+    }
+
+    public String applyImmutableOperation(ImmutableOperation operation, String input) {
+        return OPERATION_MAP.get(operation).apply(input);
+    }
+
+    public String getDescription(StringOperation stringOperation) {
+        return stringOperation.getDescription();
+    }
+
+    public String applyOperation(StringOperation operation, String input) {
+        return operation.apply(input);
+    }
+
+}

core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/ApplicationWithEx.java

@@ -0,0 +1,26 @@
+package com.baeldung.enums.extendenum;
+
+import org.apache.commons.lang3.StringUtils;
+
+import java.util.Arrays;
+import java.util.EnumMap;
+import java.util.Map;
+
+public class ApplicationWithEx {
+    private static final Map<ImmutableOperation, Operator> OPERATION_MAP;
+
+    static {
+        OPERATION_MAP = new EnumMap<>(ImmutableOperation.class);
+        OPERATION_MAP.put(ImmutableOperation.TO_LOWER, String::toLowerCase);
+        OPERATION_MAP.put(ImmutableOperation.INVERT_CASE, StringUtils::swapCase);
+        // ImmutableOperation.REMOVE_WHITESPACES is not mapped
+
+        if (Arrays.stream(ImmutableOperation.values()).anyMatch(it -> !OPERATION_MAP.containsKey(it))) {
+            throw new IllegalStateException("Unmapped enum constant found!");
+        }
+    }
+
+    public String applyImmutableOperation(ImmutableOperation operation, String input) {
+        return OPERATION_MAP.get(operation).apply(input);
+    }
+}

core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/BasicStringOperation.java

@@ -0,0 +1,33 @@
+package com.baeldung.enums.extendenum;
+
+public enum BasicStringOperation implements StringOperation {
+    TRIM("Removing leading and trailing spaces.") {
+        @Override
+        public String apply(String input) {
+            return input.trim();
+        }
+    },
+    TO_UPPER("Changing all characters into upper case.") {
+        @Override
+        public String apply(String input) {
+            return input.toUpperCase();
+        }
+    },
+    REVERSE("Reversing the given string.") {
+        @Override
+        public String apply(String input) {
+            return new StringBuilder(input).reverse().toString();
+        }
+    };
+
+    private String description;
+
+    public String getDescription() {
+        return description;
+    }
+
+    BasicStringOperation(String description) {
+        this.description = description;
+    }
+}
+

core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/ExtendedStringOperation.java

@@ -0,0 +1,31 @@
+package com.baeldung.enums.extendenum;
+
+import org.apache.commons.codec.binary.Base64;
+import org.apache.commons.codec.digest.DigestUtils;
+
+public enum ExtendedStringOperation implements StringOperation {
+    MD5_ENCODE("Encoding the given string using the MD5 algorithm.") {
+        @Override
+        public String apply(String input) {
+            return DigestUtils.md5Hex(input);
+        }
+    },
+    BASE64_ENCODE("Encoding the given string using the BASE64 algorithm.") {
+        @Override
+        public String apply(String input) {
+            return new String(new Base64().encode(input.getBytes()));
+        }
+    };
+
+    private String description;
+
+    ExtendedStringOperation(String description) {
+        this.description = description;
+    }
+
+
+    @Override
+    public String getDescription() {
+        return description;
+    }
+}

core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/ImmutableOperation.java

@@ -0,0 +1,6 @@
+package com.baeldung.enums.extendenum;
+
+public enum ImmutableOperation {
+    REMOVE_WHITESPACES, TO_LOWER, INVERT_CASE
+}
+

core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/Operator.java

@@ -0,0 +1,5 @@
+package com.baeldung.enums.extendenum;
+
+public interface Operator {
+    String apply(String input);
+}

core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/enums/extendenum/StringOperation.java

@@ -0,0 +1,7 @@
+package com.baeldung.enums.extendenum;
+
+public interface StringOperation {
+    String getDescription();
+
+    String apply(String input);
+}

core-java-modules/core-java-lang-oop-types/src/test/java/com/baeldung/enums/extendenum/ExtendEnumUnitTest.java

@@ -0,0 +1,43 @@
+package com.baeldung.enums.extendenum;
+
+import org.junit.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class ExtendEnumUnitTest {
+    private Application app = new Application();
+
+    @Test
+    public void givenAStringAndOperation_whenApplyOperation_thenGetExpectedResult() {
+        String input = " hello";
+        String expectedToUpper = " HELLO";
+        String expectedReverse = "olleh ";
+        String expectedTrim = "hello";
+        String expectedBase64 = "IGhlbGxv";
+        String expectedMd5 = "292a5af68d31c10e31ad449bd8f51263";
+        assertEquals(expectedTrim, app.applyOperation(BasicStringOperation.TRIM, input));
+        assertEquals(expectedToUpper, app.applyOperation(BasicStringOperation.TO_UPPER, input));
+        assertEquals(expectedReverse, app.applyOperation(BasicStringOperation.REVERSE, input));
+        assertEquals(expectedBase64, app.applyOperation(ExtendedStringOperation.BASE64_ENCODE, input));
+        assertEquals(expectedMd5, app.applyOperation(ExtendedStringOperation.MD5_ENCODE, input));
+    }
+
+    @Test
+    public void givenAStringAndImmutableOperation_whenApplyOperation_thenGetExpectedResult() {
+        String input = " He ll O ";
+        String expectedToLower = " he ll o ";
+        String expectedRmWhitespace = "HellO";
+        String expectedInvertCase = " hE LL o ";
+        assertEquals(expectedToLower, app.applyImmutableOperation(ImmutableOperation.TO_LOWER, input));
+        assertEquals(expectedRmWhitespace, app.applyImmutableOperation(ImmutableOperation.REMOVE_WHITESPACES, input));
+        assertEquals(expectedInvertCase, app.applyImmutableOperation(ImmutableOperation.INVERT_CASE, input));
+    }
+
+    @Test
+    public void givenUnmappedImmutableOperationValue_whenAppStarts_thenGetException() {
+        Throwable throwable = assertThrows(ExceptionInInitializerError.class, () -> {
+            ApplicationWithEx appEx = new ApplicationWithEx();
+        });
+        assertTrue(throwable.getCause() instanceof IllegalStateException);
+    }
+}

discord4j/.gitignore

@@ -1,4 +1,3 @@
-README.md
 target/
 !.mvn/wrapper/maven-wrapper.jar
 !**/src/main/**/target/

discord4j/README.md

@@ -0,0 +1,7 @@
+## DISCORD4J
+
+This module contains articles about Discord4J
+
+### Relevant Articles: 
+
+- [Creating a Discord Bot with Discord4J + Spring Boot](https://www.baeldung.com/spring-discord4j-bot)

discord4j/pom.xml

@@ -23,6 +23,14 @@
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter</artifactId>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-webflux</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-actuator</artifactId>
+		</dependency>
 
 		<dependency>
 			<groupId>org.springframework.boot</groupId>

discord4j/src/main/java/com/baeldung/discordbot/BotConfiguration.java

@@ -36,8 +36,6 @@ public class BotConfiguration {
                   .onErrorResume(listener::handleError)
                   .subscribe();
             }
-
-            client.onDisconnect().block();
         }
         catch ( Exception exception ) {
             log.error( "Be sure to use a valid bot token!", exception );

docker/docker-internal-dto/pom.xml

@@ -0,0 +1,15 @@
+<?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>
+        <groupId>com.baeldung.docker</groupId>
+        <artifactId>docker</artifactId>
+        <version>0.0.1</version>
+    </parent>
+
+    <artifactId>docker-internal-dto</artifactId>
+    <name>docker-internal-dto</name>
+
+</project>

docker/docker-internal-dto/src/main/java/com/baeldung/docker/dto/VariableDto.java

@@ -0,0 +1,14 @@
+package com.baeldung.docker.dto;
+
+public class VariableDto {
+
+    private final String value;
+
+    public VariableDto(String value) {
+        this.value = value;
+    }
+
+    public String getValue() {
+        return value;
+    }
+}

docker/docker-spring-boot/pom.xml

@@ -1,21 +1,21 @@
 <?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">
+<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>
     <parent>
-        <groupId>org.springframework.boot</groupId>
-        <artifactId>spring-boot-starter-parent</artifactId>
-        <version>2.3.1.RELEASE</version>
-        <relativePath/> <!-- lookup parent from repository -->
+        <groupId>com.baeldung.docker</groupId>
+        <artifactId>docker</artifactId>
+        <version>0.0.1</version>
     </parent>
-    <groupId>com.baeldung.docker</groupId>
-    <artifactId>spring-boot-docker</artifactId>
-    <version>0.0.1-SNAPSHOT</version>
-    <name>spring-boot-docker</name>
+
+    <artifactId>docker-spring-boot</artifactId>
+
+    <name>docker-spring-boot</name>
     <description>Demo project showing Spring Boot and Docker</description>
 
     <properties>
-        <java.version>8</java.version>
+        <java.version>11</java.version>
     </properties>
 
     <dependencies>
@@ -24,6 +24,12 @@
             <artifactId>spring-boot-starter-web</artifactId>
         </dependency>
 
+        <dependency>
+            <groupId>com.baeldung.docker</groupId>
+            <artifactId>docker-internal-dto</artifactId>
+            <version>0.0.1</version>
+        </dependency>
+
         <dependency>
             <groupId>org.springframework.boot</groupId>
             <artifactId>spring-boot-starter-test</artifactId>
@@ -45,6 +51,7 @@
                 <configuration>
                     <layers>
                         <enabled>true</enabled>
+                        <configuration>${project.basedir}/src/layers.xml</configuration>
                     </layers>
                 </configuration>
             </plugin>

docker/docker-spring-boot/src/layers.xml

@@ -0,0 +1,27 @@
+<layers xmlns="http://www.springframework.org/schema/boot/layers"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="http://www.springframework.org/schema/boot/layers
+                     https://www.springframework.org/schema/boot/layers/layers-2.3.xsd">
+    <application>
+        <into layer="spring-boot-loader">
+            <include>org/springframework/boot/loader/**</include>
+        </into>
+        <into layer="application" />
+    </application>
+    <dependencies>
+        <into layer="snapshot-dependencies">
+            <include>*:*:*SNAPSHOT</include>
+        </into>
+        <into layer="internal-dependencies">
+            <include>com.baeldung.docker:*:*</include>
+        </into>
+        <into layer="dependencies" />
+    </dependencies>
+    <layerOrder>
+        <layer>dependencies</layer>
+        <layer>spring-boot-loader</layer>
+        <layer>internal-dependencies</layer>
+        <layer>snapshot-dependencies</layer>
+        <layer>application</layer>
+    </layerOrder>
+</layers>

docker/docker-spring-boot/src/main/docker/Dockerfile

@@ -9,7 +9,8 @@ RUN java -Djarmode=layertools -jar application.jar extract
 
 FROM adoptopenjdk:11-jre-hotspot
 COPY --from=builder dependencies/ ./
-COPY --from=builder snapshot-dependencies/ ./
 COPY --from=builder spring-boot-loader/ ./
+COPY --from=builder internal-dependencies/ ./
+COPY --from=builder snapshot-dependencies/ ./
 COPY --from=builder application/ ./
 ENTRYPOINT ["java", "org.springframework.boot.loader.JarLauncher"]

docker/docker-spring-boot/src/main/java/com/baeldung/docker/spring/DemoApplication.java

@@ -1,4 +1,4 @@
-package com.baeldung.docker;
+package com.baeldung.docker.spring;
 
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;

docker/docker-spring-boot/src/main/java/com/baeldung/docker/spring/HelloController.java

@@ -1,4 +1,4 @@
-package com.baeldung.docker;
+package com.baeldung.docker.spring;
 
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.GetMapping;

docker/pom.xml

@@ -0,0 +1,30 @@
+<?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>
+
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.3.1.RELEASE</version>
+        <relativePath /> <!-- lookup parent from repository -->
+    </parent>
+
+    <groupId>com.baeldung.docker</groupId>
+    <artifactId>docker</artifactId>
+    <version>0.0.1</version>
+    <name>docker</name>
+    <description>Demo project showing Spring Boot and Docker</description>
+    <packaging>pom</packaging>
+
+    <properties>
+        <java.version>11</java.version>
+    </properties>
+
+    <modules>
+        <module>docker-internal-dto</module>
+        <module>docker-spring-boot</module>
+    </modules>
+
+</project>

persistence-modules/java-jpa-3/src/main/java/com/baeldung/jpa/index/Student.java

@@ -0,0 +1,70 @@
+package com.baeldung.jpa.index;
+
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.Id;
+import javax.persistence.Index;
+import javax.persistence.Table;
+import java.io.Serializable;
+import java.util.Objects;
+
+@Entity
+@Table(indexes = {
+  @Index(columnList = "firstName"),
+  @Index(name = "fn_index", columnList = "id"),
+  @Index(name = "multiIndex1", columnList = "firstName, lastName"),
+  @Index(name = "multiIndex2", columnList = "lastName, firstName"),
+  @Index(name = "multiSortIndex", columnList = "firstName, lastName DESC"),
+  @Index(name = "uniqueIndex", columnList = "firstName", unique = true),
+  @Index(name = "uniqueMultiIndex", columnList = "firstName, lastName", unique = true)
+})
+public class Student implements Serializable {
+    @Id
+    @GeneratedValue
+    private Long id;
+    private String firstName;
+    private String lastName;
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getFirstName() {
+        return firstName;
+    }
+
+    public void setFirstName(String firstName) {
+        this.firstName = firstName;
+    }
+
+    public String getLastName() {
+        return lastName;
+    }
+
+    public void setLastName(String lastName) {
+        this.lastName = lastName;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        Student student = (Student) o;
+        return Objects.equals(id, student.id) &&
+                Objects.equals(firstName, student.firstName) &&
+                Objects.equals(lastName, student.lastName);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(id, firstName, lastName);
+    }
+}

persistence-modules/java-jpa-3/src/main/resources/META-INF/persistence.xml

@@ -40,4 +40,19 @@
             <property name="hibernate.temp.use_jdbc_metadata_defaults" value="false"/>
         </properties>
     </persistence-unit>
+    <persistence-unit name="jpa-index">
+            <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
+            <class>com.baeldung.jpa.index.Student</class>
+            <exclude-unlisted-classes>true</exclude-unlisted-classes>
+            <properties>
+                <property name="javax.persistence.jdbc.driver" value="org.h2.Driver" />
+                <property name="javax.persistence.jdbc.url" value="jdbc:h2:mem:test" />
+                <property name="javax.persistence.jdbc.user" value="sa" />
+                <property name="javax.persistence.jdbc.password" value="" />
+            <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect" />
+            <property name="hibernate.hbm2ddl.auto" value="create-drop" />
+            <property name="show_sql" value="true" />
+            <property name="hibernate.temp.use_jdbc_metadata_defaults" value="false" />
+        </properties>
+    </persistence-unit>
 </persistence>

persistence-modules/java-jpa-3/src/main/resources/logback.xml

@@ -8,7 +8,7 @@
             </pattern>
         </encoder>
     </appender>
-
+    <logger name="org.hibernate.SQL" level="DEBUG" />
     <root level="INFO">
         <appender-ref ref="STDOUT" />
     </root>

persistence-modules/java-jpa-3/src/test/java/com/baeldung/jpa/index/IndexIntegrationTest.java

@@ -0,0 +1,50 @@
+package com.baeldung.jpa.index;
+
+import org.hibernate.exception.ConstraintViolationException;
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.Persistence;
+import java.util.Optional;
+
+public class IndexIntegrationTest {
+    private static EntityManagerFactory factory;
+    private static EntityManager entityManager;
+
+    @BeforeClass
+    public static void setup() {
+        factory = Persistence.createEntityManagerFactory("jpa-index");
+        entityManager = factory.createEntityManager();
+    }
+
+    @Test
+    public void givenStudent_whenPersistStudentWithSameFirstName_thenConstraintViolationException() {
+        Student student = new Student();
+        student.setFirstName("FirstName");
+        student.setLastName("LastName");
+
+        Student student2 = new Student();
+        student2.setFirstName("FirstName");
+        student2.setLastName("LastName2");
+
+        entityManager.getTransaction().begin();
+        entityManager.persist(student);
+        entityManager.getTransaction().commit();
+
+        Assert.assertEquals(1L, (long) student.getId());
+
+        entityManager.getTransaction().begin();
+        try {
+            entityManager.persist(student2);
+            entityManager.getTransaction().commit();
+            Assert.fail("Should raise an exception - unique key violation");
+        } catch (Exception ex) {
+            Assert.assertTrue(Optional.of(ex).map(Throwable::getCause).map(Throwable::getCause).filter(x -> x instanceof ConstraintViolationException).isPresent());
+        } finally {
+            entityManager.getTransaction().rollback();
+        }
+    }
+}

persistence-modules/java-jpa/src/test/java/com/baeldung/jpa/enums/ArticleUnitTest.java

@@ -7,7 +7,9 @@ import javax.persistence.EntityManager;
 import javax.persistence.EntityManagerFactory;
 import javax.persistence.EntityTransaction;
 import javax.persistence.Persistence;
+import javax.persistence.TypedQuery;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
@@ -19,7 +21,7 @@ public class ArticleUnitTest {
 
     @BeforeClass
     public static void setup() {
-        Map properties = new HashMap();
+        Map<String, String> properties = new HashMap<>();
         properties.put("hibernate.show_sql", "true");
         properties.put("hibernate.format_sql", "true");
         emFactory = Persistence.createEntityManagerFactory("jpa-h2", properties);
@@ -115,4 +117,53 @@ public class ArticleUnitTest {
         assertEquals(Category.MUSIC, persistedArticle.getCategory());
     }
 
+    @Test
+    public void shouldFindArticleByCategory() {
+        // given
+        Article article = new Article();
+        article.setId(5);
+        article.setTitle("static");
+        article.setCategory(Category.SPORT);
+
+        EntityTransaction tx = em.getTransaction();
+        tx.begin();
+        em.persist(article);
+        tx.commit();
+
+        String jpql = "select a from Article a where a.category = com.baeldung.jpa.enums.Category.SPORT";
+
+        // when
+        List<Article> articles = em.createQuery(jpql, Article.class).getResultList();
+
+        // then
+        assertEquals(1, articles.size());
+        assertEquals(Category.SPORT, articles.get(0).getCategory());
+        assertEquals("static", articles.get(0).getTitle());
+    }
+
+    @Test
+    public void shouldFindArticleByCategoryParameter() {
+        // given
+        Article article = new Article();
+        article.setId(6);
+        article.setTitle("dynamic");
+        article.setCategory(Category.TECHNOLOGY);
+
+        EntityTransaction tx = em.getTransaction();
+        tx.begin();
+        em.persist(article);
+        tx.commit();
+
+        String jpql = "select a from Article a where a.category = :category";
+
+        // when
+        TypedQuery<Article> query = em.createQuery(jpql, Article.class);
+        query.setParameter("category", Category.TECHNOLOGY);
+        List<Article> articles = query.getResultList();
+
+        // then
+        assertEquals(1, articles.size());
+        assertEquals(Category.TECHNOLOGY, articles.get(0).getCategory());
+        assertEquals("dynamic", articles.get(0).getTitle());
+    }
 }