JPA关系映射系列五:many-to-many 关联表存在额外字段关系映射
2018-03-06 16:15
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SpringDataJPA是Spring Data的一个子项目,通过提供基于JPA的Repository极大的减少了JPA作为数据访问方案的代码量,你仅仅需要编写一个接口集成下SpringDataJPA内部定义的接口即可完成简单的CRUD操作。
本篇文章引导你通过
JDK 1.8 或更高版本
Maven 3 或更高版本
MySQL Server 5.6
Spring Data JPA
Spring Boot
MySQL
![](https://oscdn.geek-share.com/Uploads/Images/Content/202003/13/518fd17501e5ee7d0c3bab8ed6727f0e.png)
目录结构
![](https://raw.githubusercontent.com/longfeizheng/longfeizheng.github.io/master/images/jpa/spring-data-jpa10.png)
pom.xml
多对多关联
![](https://raw.githubusercontent.com/longfeizheng/longfeizheng.github.io/master/images/jpa/spring-data-jpa11.png)
db.sql
实体类
Book
Publisher
BookPublisher
TABLE:使用表保存id值
IDENTITY:identitycolumn
SEQUENCR :sequence
AUTO:根据数据库的不同使用上面三个
Spring Data JPA Repository
BookRepository
PublisherRepository
application.yml
BookRepositoryTest
从我的 github 中下载,https://github.com/longfeizheng/jpa-example/tree/master/many-to-many-extra-columns
![](https://oscdn.geek-share.com/Uploads/Images/Content/201908/20/ad0722f2c91fc4ca0dcf2e43efa9cd01.png)
???关注微信小程序java架构师历程 上下班的路上无聊吗?还在看小说、新闻吗?不知道怎样提高自己的技术吗?来吧这里有你需要的java架构文章,1.5w+的java工程师都在看,你还在等什么?
前言
本篇文章引导你通过Spring Boot,
Spring Data JPA和
MySQL实现
many-to-many关联表存在额外字段下关系映射。
准备
JDK 1.8 或更高版本Maven 3 或更高版本
MySQL Server 5.6
技术栈
Spring Data JPASpring Boot
MySQL
目录结构
![](https://oscdn.geek-share.com/Uploads/Images/Content/202003/13/518fd17501e5ee7d0c3bab8ed6727f0e.png)
父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>cn.merryyou</groupId> <artifactId>jpa-example</artifactId> <version>1.0-SNAPSHOT</version> <modules> <module>one-to-one-foreignkey</module> <module>one-to-one-primarykey</module> <module>one-to-many</module> <module>many-to-many</module> <module>many-to-many-extra-columns</module> </modules> <packaging>pom</packaging> <dependencyManagement> <dependencies> <dependency> <groupId>io.spring.platform</groupId> <artifactId>platform-bom</artifactId> <version>Brussels-SR6</version> <type>pom</type> <scope>import</scope> </dependency> </dependencies> </dependencyManagement> </project>
多对多关联映射
目录结构
![](https://raw.githubusercontent.com/longfeizheng/longfeizheng.github.io/master/images/jpa/spring-data-jpa10.png)
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"> <parent> <artifactId>jpa-example</artifactId> <groupId>cn.merryyou</groupId> <version>1.0-SNAPSHOT</version> </parent> <modelVersion>4.0.0</modelVersion> <artifactId>many-to-many-extra-columns</artifactId> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-jpa</artifactId> </dependency> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <scope>runtime</scope> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> </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> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>3.6.1</version> <configuration> <source>1.8</source> <target>1.8</target> </configuration> </plugin> </plugins> </build> </project>
多对多关联
book.id和
publisher.id多对多关联表
book_publisher还存在
published_data字段
![](https://raw.githubusercontent.com/longfeizheng/longfeizheng.github.io/master/images/jpa/spring-data-jpa11.png)
db.sql
CREATE DATABASE IF NOT EXISTS `jpa_manytomany_extracolumns` /*!40100 DEFAULT CHARACTER SET utf8 */; USE `jpa_manytomany_extracolumns`; -- -- Table structure for table `book` -- DROP TABLE IF EXISTS `book`; /*!40101 SET @saved_cs_client = @@character_set_client */; /*!40101 SET character_set_client = utf8 */; CREATE TABLE `book` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(255) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=20 DEFAULT CHARSET=utf8; /*!40101 SET character_set_client = @saved_cs_client */; -- -- Table structure for table `publisher` -- DROP TABLE IF EXISTS `publisher`; /*!40101 SET @saved_cs_client = @@character_set_client */; /*!40101 SET character_set_client = utf8 */; CREATE TABLE `publisher` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(255) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=21 DEFAULT CHARSET=utf8; -- -- Table structure for table `book_publisher` -- DROP TABLE IF EXISTS `book_publisher`; /*!40101 SET @saved_cs_client = @@character_set_client */; /*!40101 SET character_set_client = utf8 */; CREATE TABLE `book_publisher` ( `book_id` int(10) unsigned NOT NULL, `publisher_id` int(10) unsigned NOT NULL, `published_date` datetime DEFAULT NULL, PRIMARY KEY (`book_id`,`publisher_id`), KEY `fk_bookpublisher_publisher_idx` (`publisher_id`), CONSTRAINT `fk_bookpublisher_book` FOREIGN KEY (`book_id`) REFERENCES `book` (`id`) ON DELETE CASCADE ON UPDATE CASCADE, CONSTRAINT `fk_bookpublisher_publisher` FOREIGN KEY (`publisher_id`) REFERENCES `publisher` (`id`) ON DELETE CASCADE ON UPDATE CASCADE ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
实体类
Book
@Entity public class Book{ @Id @GeneratedValue(strategy = GenerationType.AUTO) private int id; private String name; @OneToMany(mappedBy = "book", cascade = CascadeType.ALL, orphanRemoval = true) private Set<BookPublisher> bookPublishers; public Book() { } public Book(String name) { this.name = name; bookPublishers = new HashSet<>(); } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Set<BookPublisher> getBookPublishers() { return bookPublishers; } public void setBookPublishers(Set<BookPublisher> bookPublishers) { this.bookPublishers = bookPublishers; } }
Publisher
@Entity public class Publisher { @Id @GeneratedValue(strategy = GenerationType.AUTO) private int id; private String name; @OneToMany(mappedBy = "publisher") private Set<BookPublisher> bookPublishers; public Publisher(){ } public Publisher(String name){ this.name = name; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Set<BookPublisher> getBookPublishers() { return bookPublishers; } public void setBookPublishers(Set<BookPublisher> bookPublishers) { this.bookPublishers = bookPublishers; } }
BookPublisher
@Entity @Table(name = "book_publisher") public class BookPublisher implements Serializable { @Id @ManyToOne @JoinColumn(name = "book_id") private Book book; @Id @ManyToOne @JoinColumn(name = "publisher_id") private Publisher publisher; @Column(name = "published_date") private Date publishedDate; public Book getBook() { return book; } public void setBook(Book book) { this.book = book; } public Publisher getPublisher() { return publisher; } public void setPublisher(Publisher publisher) { this.publisher = publisher; } public Date getPublishedDate() { return publishedDate; } public void setPublishedDate(Date publishedDate) { this.publishedDate = publishedDate; } }
@Table声明此对象映射到数据库的数据表,通过它可以为实体指定表(talbe),目录(Catalog)和schema的名字。该注释不是必须的,如果没有则系统使用默认值(实体的短类名)。
@Id声明此属性为主键。该属性值可以通过应该自身创建,但是Hibernate推荐通过Hibernate生成
@GeneratedValue指定主键的生成策略。
TABLE:使用表保存id值
IDENTITY:identitycolumn
SEQUENCR :sequence
AUTO:根据数据库的不同使用上面三个
@Column声明该属性与数据库字段的映射关系。
@OneToMany一对多关联关系
@ManyToMany多对多关联关系
@JoinColumn指定关联的字段
@JoinTable参考
Spring Data JPA Repository
BookRepository
public interface BookRepository extends JpaRepository<Book, Integer> { }
PublisherRepository
public interface PublisherRepository extends JpaRepository<Publisher, Integer> { }
Spring Data JPA包含了一些内置的
Repository,实现了一些常用的方法:
findone,
findall,
save等。
application.yml
spring: datasource: url: jdbc:mysql://localhost/jpa_manytomany_extracolumns username: root password: admin driver-class-name: com.mysql.jdbc.Driver jpa: show-sql: true properties: hibernate: enable_lazy_load_no_trans: true
BookRepositoryTest
@RunWith(SpringRunner.class) @SpringBootTest @Slf4j public class BookRepositoryTest { @Autowired private BookRepository bookRepository; @Autowired private PublisherRepository publisherRepository; @Test @Transactional public void manyToManyExtraColumnsTest() throws Exception{ Book bookA = new Book("Book One"); Publisher publisherA = new Publisher("Publisher One"); BookPublisher bookPublisher = new BookPublisher(); bookPublisher.setBook(bookA); bookPublisher.setPublisher(publisherA); bookPublisher.setPublishedDate(new Date()); bookA.getBookPublishers().add(bookPublisher); publisherRepository.save(publisherA); bookRepository.save(bookA); // test System.out.println(bookA.getBookPublishers().size()); // update bookA.getBookPublishers().remove(bookPublisher); bookRepository.save(bookA); // test System.out.println(bookA.getBookPublishers().size()); } }
代码下载
从我的 github 中下载,https://github.com/longfeizheng/jpa-example/tree/master/many-to-many-extra-columns![](https://oscdn.geek-share.com/Uploads/Images/Content/201908/20/ad0722f2c91fc4ca0dcf2e43efa9cd01.png)
???关注微信小程序java架构师历程 上下班的路上无聊吗?还在看小说、新闻吗?不知道怎样提高自己的技术吗?来吧这里有你需要的java架构文章,1.5w+的java工程师都在看,你还在等什么?
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