这里通过一个完整的例子展示如何通过 JPA 对两张表（多对多关联，关联表带扩展字段）进行增删改查操作。
前提
- JDK 8+
- Maven 3+
表结构
例子
创建 Maven 项目
pom.xml
<?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>org.lewis.demos</groupId>
<artifactId>jpa-manytomany-extracolumns-springboot-h2</artifactId>
<version>1.0</version>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.2.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>src/main/resources/application.properties
## DATASOURCE Settings
#spring.datasource.driver-class-name:org.h2.Driver
#spring.datasource.password:demo
#spring.datasource.url:jdbc:h2:tcp://127.0.0.1/~/jpa-h2
#spring.datasource.username:demo
## JPA Settings
spring.jpa.generate-ddl:true
spring.jpa.hibernate.ddl-auto:update
#spring.jpa.hibernate.dialect:org.hibernate.dialect.H2Dialect
spring.jpa.properties.hibernate.format_sql:false
spring.jpa.show-sql:truesrc/main/java/hello/Application.java
创建实体
src/main/java/hello/domain/Book.java
package hello;
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);
}
}src/main/java/hello/domain/Author.java
package hello.domain;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import java.io.Serializable;
import java.util.Set;
@Entity
public class Author implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue
private Integer id;
private String name;
@OneToMany(mappedBy = "author")
private Set<BookAuthor> bookAuthors;
public Author() {
super();
}
public Author(String name) {
super();
this.name = name;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Set<BookAuthor> getBookAuthors() {
return bookAuthors;
}
public void setBookAuthors(Set<BookAuthor> bookAuthors) {
this.bookAuthors = bookAuthors;
}
@Override
public String toString() {
return String.format("Author [id=%s, name=%s]", id, name);
}
}src/main/java/hello/domain/BookAuthor.java
package hello.domain;
import javax.persistence.*;
import java.io.Serializable;
import java.util.Date;
@Entity(name = "BOOK_AUTHOR")
public class BookAuthor implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@ManyToOne
@JoinColumn(name = "BOOK_ID")
private Book book;
@Id
@ManyToOne
@JoinColumn(name = "AUTHOR_ID")
private Author author;
@Column(name = "FINISH_DATE")
private Date finishDate;
public BookAuthor() {
super();
}
public BookAuthor(Book book, Author author) {
super();
this.book = book;
this.author = author;
}
public BookAuthor(Book book, Author author, Date finishDate) {
super();
this.book = book;
this.author = author;
this.finishDate = finishDate;
}
public Book getBook() {
return book;
}
public void setBook(Book book) {
this.book = book;
}
public Author getAuthor() {
return author;
}
public void setAuthor(Author author) {
this.author = author;
}
public Date getFinishDate() {
return finishDate;
}
public void setFinishDate(Date finishDate) {
this.finishDate = finishDate;
}
@Override
public String toString() {
return String.format("BookAuthor [book=%s, author=%s, finishDate=%s]", book.getName(), author.getName(), finishDate);
}
}创建 Repository
src/main/java/hello/repository/BookRepository.java
package hello.repository;
import hello.domain.Book;
import org.springframework.data.jpa.repository.JpaRepository;
import java.util.List;
public interface BookRepository extends JpaRepository<Book, Integer> {
Book findByName(String name);
List<Book> findByNameContaining(String name);
}src/main/java/hello/repository/AuthorRepository
package hello.repository;
import hello.domain.Author;
import org.springframework.data.jpa.repository.JpaRepository;
import java.util.List;
public interface AuthorRepository extends JpaRepository<Author, Integer> {
Author findByName(String name);
List<Author> findByNameContaining(String name);
}单元测试
编写单元测试
src/test/java/hello/BookRepositoryTests.java
package hello;
import hello.domain.Author;
import hello.domain.Book;
import hello.domain.BookAuthor;
import hello.repository.AuthorRepository;
import hello.repository.BookRepository;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
import org.springframework.test.context.junit4.SpringRunner;
import java.util.Arrays;
import java.util.Date;
import static org.assertj.core.api.Assertions.assertThat;
@RunWith(SpringRunner.class)
@DataJpaTest
public class BookRepositoryTests {
@Autowired
private BookRepository bookRepository;
@Autowired
private AuthorRepository authorRepository;
@Before
public void init() {
Book spring = new Book("Spring in Action");
Book springboot = new Book("Spring Boot in Action");
Author lewis = new Author("Lewis");
Author mark = new Author("Mark");
Author peter = new Author("Peter");
BookAuthor springLewis = new BookAuthor(spring, lewis, new Date());
BookAuthor springMark = new BookAuthor(spring, mark, new Date());
BookAuthor springbootLewis = new BookAuthor(springboot, lewis, new Date());
BookAuthor springbootPeter = new BookAuthor(springboot, peter, new Date());
spring.getBookAuthors().addAll(Arrays.asList(springLewis, springMark));
springboot.getBookAuthors().addAll(Arrays.asList(springbootLewis, springbootPeter));
authorRepository.save(Arrays.asList(lewis, mark, peter));
bookRepository.save(Arrays.asList(spring, springboot));
}
@After
public void deleteAll() {
// 删除所有书籍和关联关系，但不删除作者
bookRepository.deleteAll();
// 删除所有作者，如果书籍和作者存在关联，则删除报错
authorRepository.deleteAll();
}
@Test
public void findAll() {
assertThat(bookRepository.findAll()).hasSize(2);
assertThat(authorRepository.findAll()).hasSize(3);
}
@Test
public void findByName() {
assertThat(bookRepository.findByName("Spring in Action")).isNotNull();
assertThat(authorRepository.findByName("Lewis")).isNotNull();
}
@Test
public void findByNameContaining() {
assertThat(bookRepository.findByNameContaining("Spring")).hasSize(2);
assertThat(authorRepository.findByNameContaining("e")).hasSize(2);
}
@Test
public void margeBook() {
Book book = bookRepository.findByName("Spring in Action");
assertThat(book).isNotNull();
book.setName("Spring in Action (4th Edition)");
assertThat(bookRepository.findByName("Spring in Action")).isNull();
assertThat(bookRepository.findByName("Spring in Action (4th Edition)")).isNotNull();
}
@Test
public void deleteBook() {
Book book = bookRepository.findByName("Spring Boot in Action");
assertThat(book).isNotNull();
bookRepository.delete(book);
assertThat(bookRepository.findAll()).hasSize(1);
assertThat(bookRepository.findByName("Spring Boot in Action")).isNull();
assertThat(authorRepository.findAll()).hasSize(3);
assertThat(authorRepository.findByName("Peter")).isNotNull();
}
@Test
public void clearAuthor() {
Book book = bookRepository.findByName("Spring in Action");
assertThat(book).isNotNull();
book.getBookAuthors().clear();
assertThat(bookRepository.findAll()).hasSize(2);
assertThat(bookRepository.findByName("Spring in Action").getBookAuthors()).isEmpty();
assertThat(authorRepository.findAll()).hasSize(3);
}
@Test
public void removeAuthor() {
Book book = bookRepository.findByName("Spring Boot in Action");
assertThat(book).isNotNull();
Author author = authorRepository.findByName("Peter");
assertThat(author).isNotNull();
book.getBookAuthors().removeIf(bookAuthor -> bookAuthor.getAuthor().equals(author));
assertThat(bookRepository.findAll()).hasSize(2);
assertThat(bookRepository.findByName("Spring Boot in Action").getBookAuthors()).hasSize(1);
assertThat(authorRepository.findAll()).hasSize(3);
assertThat(authorRepository.findByName("Peter")).isNotNull();
}
@Test
public void removeAllautors() {
Book book = bookRepository.findByName("Spring in Action");
assertThat(book).isNotNull();
book.getBookAuthors().removeAll(book.getBookAuthors());
assertThat(bookRepository.findAll()).hasSize(2);
assertThat(bookRepository.findByName("Spring in Action").getBookAuthors()).isEmpty();
assertThat(authorRepository.findAll()).hasSize(3);
}
@Test
public void plusAuthor() {
Book book = bookRepository.findByName("Spring in Action");
assertThat(book).isNotNull();
Author author = authorRepository.findByName("Jacob");
assertThat(author).isNull();
author = new Author("Jacob");
BookAuthor bookAuthor = new BookAuthor(book, author, new Date());
book.getBookAuthors().add(bookAuthor);
authorRepository.save(author);
assertThat(bookRepository.findByName("Spring in Action").getBookAuthors()).hasSize(3);
assertThat(authorRepository.findAll()).hasSize(4);
assertThat(authorRepository.findByName("Jacob")).isNotNull();
}
@Test
public void deleteAuthor() {
Book book = bookRepository.findByName("Spring Boot in Action");
assertThat(book).isNotNull();
bookRepository.delete(book);
Author author = authorRepository.findByName("Peter");
assertThat(author).isNotNull();
authorRepository.delete(author);
assertThat(authorRepository.findAll()).hasSize(2);
}
@Test
public void deleteAllAuthors() {
bookRepository.deleteAll();
assertThat(bookRepository.findAll()).isEmpty();
assertThat(authorRepository.findAll()).hasSize(3);
authorRepository.deleteAll();
assertThat(authorRepository.findAll()).isEmpty();
}
}执行测试用例
mvn clean test