BAEL-6189 - Remove Entity with ManyToMany Relationship in JPA (#13634)

* BAEL-6189 - Remove Entity with ManyToMany Relationship in JPA

* Add property source

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

@@ -101,7 +101,7 @@
 
     <properties>
         <!-- Spring -->
-        <org.springframework.version>5.1.5.RELEASE</org.springframework.version>
+        <org.springframework.version>5.2.0.RELEASE</org.springframework.version>
         <spring-boot.version>2.2.6.RELEASE</spring-boot.version>
         <!-- persistence -->
         <tomcat-dbcp.version>9.0.0.M26</tomcat-dbcp.version>

persistence-modules/spring-jpa-2/src/main/java/com/baeldung/manytomanyremoval/Application.java

@@ -0,0 +1,12 @@
+package com.baeldung.manytomanyremoval;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class Application {
+
+    public static void main(String[] args) {
+        SpringApplication.run(Application.class, args);
+    }
+}

persistence-modules/spring-jpa-2/src/main/java/com/baeldung/manytomanyremoval/Author.java

@@ -0,0 +1,62 @@
+package com.baeldung.manytomanyremoval;
+
+import javax.persistence.*;
+import java.util.HashSet;
+import java.util.Set;
+
+@Entity
+@Table(name = "author")
+public class Author {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    @Column(name = "id")
+    private Long id;
+
+    @Column(name = "name")
+    private String name;
+
+    @ManyToMany(mappedBy = "authors")
+    private Set<Book> books = new HashSet<>();
+
+    // standard getters and setters
+
+    public Author() {
+    }
+
+    public Author(String name) {
+        this.name = name;
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public Set<Book> getBooks() {
+        return books;
+    }
+
+    public void setBooks(Set<Book> books) {
+        this.books = books;
+    }
+
+    @PreRemove
+    private void removeBookAssociations() {
+        for (Book book : this.books) {
+            book.getAuthors().remove(this);
+        }
+    }
+
+}

persistence-modules/spring-jpa-2/src/main/java/com/baeldung/manytomanyremoval/Book.java

@@ -0,0 +1,65 @@
+package com.baeldung.manytomanyremoval;
+
+
+import javax.persistence.*;
+import java.util.HashSet;
+import java.util.Set;
+
+@Entity
+@Table(name = "book")
+public class Book {
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    @Column(name = "id")
+    private Long id;
+
+    @Column(name = "title")
+    private String title;
+
+    @ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE})
+    @JoinTable(name = "book_author",
+            joinColumns = @JoinColumn(name = "book_id"),
+            inverseJoinColumns = @JoinColumn(name = "author_id")
+    )
+    private Set<Author> authors = new HashSet<>();
+
+    // standard getters and setters
+
+    public Book() {
+    }
+
+    public Book(String title) {
+        this.title = title;
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public Set<Author> getAuthors() {
+        return authors;
+    }
+
+    public void removeAuthor(Author author) {
+        this.authors.remove(author);
+        author.getBooks().remove(this);
+    }
+
+    public void addAuthor(Author author) {
+        authors.add(author);
+        author.getBooks().add(this);
+    }
+
+}

persistence-modules/spring-jpa-2/src/main/java/com/baeldung/manytomanyremoval/Category.java

@@ -0,0 +1,41 @@
+package com.baeldung.manytomanyremoval;
+
+import javax.persistence.*;
+
+@Entity
+@Table(name = "category")
+public class Category {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    @Column(name = "id")
+    private Long id;
+
+    @Column(name = "name")
+    private String name;
+
+    // getters and setters
+
+    public Category() {
+    }
+
+    public Category(String name) {
+        this.name = name;
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+}

persistence-modules/spring-jpa-2/src/main/java/com/baeldung/manytomanyremoval/Post.java

@@ -0,0 +1,59 @@
+package com.baeldung.manytomanyremoval;
+
+
+import javax.persistence.*;
+import java.util.HashSet;
+import java.util.Set;
+
+@Entity
+@Table(name = "post")
+public class Post {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    @Column(name = "id")
+    private Long id;
+
+    @Column(name = "title")
+    private String title;
+
+    @ManyToMany(cascade = {CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH})
+    @JoinTable(name = "post_category",
+            joinColumns = @JoinColumn(name = "post_id"),
+            inverseJoinColumns = @JoinColumn(name = "category_id")
+    )
+    private Set<Category> categories = new HashSet<>();
+
+    // getters and setters
+
+    public Post(String title) {
+        this.title = title;
+    }
+
+    public Post() {
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public void setId(Long id) {
+        this.id = id;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public Set<Category> getCategories() {
+        return categories;
+    }
+
+    public void setCategories(Set<Category> categories) {
+        this.categories = categories;
+    }
+}

persistence-modules/spring-jpa-2/src/test/java/com/baeldung/manytomanyremoval/BidirectionalRemovalUnitTest.java

@@ -0,0 +1,78 @@
+package com.baeldung.manytomanyremoval;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+import org.springframework.transaction.annotation.Transactional;
+
+import javax.persistence.EntityManager;
+
+@ExtendWith(SpringExtension.class)
+@ContextConfiguration(classes = TestContextConfig.class)
+@DirtiesContext(classMode = DirtiesContext.ClassMode.BEFORE_EACH_TEST_METHOD)
+@Transactional
+class BidirectionalRemovalUnitTest {
+
+    @Autowired
+    private EntityManager entityManager;
+
+    @BeforeEach
+    void init() {
+        Author author1 = new Author("Erich Gamma");
+        Author author2 = new Author("John Vlissides");
+        Author author3 = new Author("Ralph Johnson");
+        Author author4 = new Author("Richard Helm");
+
+        Book book = new Book();
+        book.setTitle("GOF Java");
+        book.addAuthor(author1);
+        book.addAuthor(author2);
+        book.addAuthor(author3);
+        book.addAuthor(author4);
+        entityManager.persist(book);
+
+        Book book2 = new Book();
+        book2.setTitle("A Lost Age");
+        book2.addAuthor(author3);
+        entityManager.persist(book2);
+    }
+
+    @Test
+    void givenEntities_whenRemoveFromOwner_thenRemoveAssociation() {
+        Author author = (Author) entityManager
+                .createQuery("SELECT author from Author author where author.name = ?1")
+                .setParameter(1, "Ralph Johnson")
+                .getSingleResult();
+
+        Book book1 = entityManager.find(Book.class, 1L);
+        Book book2 = entityManager.find(Book.class, 2L);
+
+        book1.removeAuthor(author);
+        entityManager.persist(book1);
+
+        Assertions.assertEquals(3, book1.getAuthors().size());
+        Assertions.assertEquals(1, book2.getAuthors().size());
+    }
+
+    @Transactional
+    @Test
+    void givenEntities_whenRemoveFromNotOwner_thenRemoveAssociation() {
+        Author author = (Author) entityManager
+                .createQuery("SELECT author from Author author where author.name = ?1")
+                .setParameter(1, "Ralph Johnson")
+                .getSingleResult();
+        Book book1 = entityManager.find(Book.class, 1L);
+        Book book2 = entityManager.find(Book.class, 2L);
+
+        entityManager.remove(author);
+
+        Assertions.assertEquals(3, book1.getAuthors().size());
+        Assertions.assertEquals(0, book2.getAuthors().size());
+    }
+}
+

persistence-modules/spring-jpa-2/src/test/java/com/baeldung/manytomanyremoval/TestContextConfig.java

@@ -0,0 +1,12 @@
+package com.baeldung.manytomanyremoval;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.PropertySource;
+
+@Configuration
+@PropertySource("classpath:/manytomanyremoval/test.properties")
+@ComponentScan("com.baeldung.manytomanyremoval")
+public class TestContextConfig {
+
+}

persistence-modules/spring-jpa-2/src/test/java/com/baeldung/manytomanyremoval/UnidirectionalRemovalUnitTest.java

@@ -0,0 +1,55 @@
+package com.baeldung.manytomanyremoval;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+import org.springframework.transaction.annotation.Transactional;
+
+import javax.persistence.EntityManager;
+
+@ExtendWith(SpringExtension.class)
+@ContextConfiguration(classes = TestContextConfig.class)
+@DirtiesContext(classMode = DirtiesContext.ClassMode.BEFORE_EACH_TEST_METHOD)
+@Transactional
+class UnidirectionalRemovalUnitTest {
+
+    @Autowired
+    private EntityManager entityManager;
+
+    @BeforeEach
+    void init() {
+        Category category1 = new Category("JPA");
+        Category category2 = new Category("Persistence");
+
+        Post post1 = new Post("Many-to-Many Relationship");
+        post1.getCategories().add(category1);
+        post1.getCategories().add(category2);
+
+        Post post2 = new Post("Entity Manager");
+        post2.getCategories().add(category1);
+
+        entityManager.persist(post1);
+        entityManager.persist(post2);
+
+        Assertions.assertEquals(2, post1.getCategories().size());
+        Assertions.assertEquals(1, post2.getCategories().size());
+    }
+
+    @Test
+    void givenEntities_whenRemove_thenRemoveAssociation() {
+        Post post1 = entityManager.find(Post.class, 1L);
+        Post post2 = entityManager.find(Post.class, 2L);
+        Category category = entityManager.find(Category.class, 1L);
+
+        post1.getCategories().remove(category);
+
+        Assertions.assertEquals(1, post1.getCategories().size());
+        Assertions.assertEquals(1, post2.getCategories().size());
+    }
+
+}

persistence-modules/spring-jpa-2/src/test/resources/manytomanyremoval/test.properties

@@ -0,0 +1,11 @@
+spring.datasource.url=jdbc:h2:mem:mydb;MODE=LEGACY;
+spring.datasource.driverClassName=org.h2.Driver
+spring.datasource.username=sa
+spring.datasource.password=
+
+hibernate.dialect=org.hibernate.dialect.H2Dialect
+hibernate.hbm2ddl.auto=none
+spring.jpa.show-sql=true
+spring.jpa.hibernate.dialect=org.hibernate.dialect.H2Dialect
+spring.jpa.hibernate.ddl-auto=create-drop
+