JPA關係對映系列五：many-to-many 關聯表存在額外欄位關係對映

niocoder發表於2018-03-06

SpringDataJPA是Spring Data的一個子專案，通過提供基於JPA的Repository極大的減少了JPA作為資料訪問方案的程式碼量，你僅僅需要編寫一個介面整合下SpringDataJPA內部定義的介面即可完成簡單的CRUD操作。

前言

本篇文章引導你通過Spring Boot，Spring Data JPA和MySQL實現many-to-many關聯表存在額外欄位下關係對映。

準備

JDK 1.8 或更高版本
Maven 3 或更高版本
MySQL Server 5.6

技術棧

Spring Data JPA
Spring Boot
MySQL

目錄結構

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>

多對多關聯對映

目錄結構

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>

多對多關聯

book.id 和 publisher.id 多對多關聯表book_publisher還存在published_data欄位

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;

實體類

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宣告此物件對映到資料庫的資料表，通過它可以為實體指定表(talbe),目錄(Catalog)和schema的名字。該註釋不是必須的，如果沒有則系統使用預設值(實體的短類名)。
@Id 宣告此屬性為主鍵。該屬性值可以通過應該自身建立，但是Hibernate推薦通過Hibernate生成
@GeneratedValue 指定主鍵的生成策略。
1. TABLE：使用表儲存id值
2. IDENTITY：identitycolumn
3. SEQUENCR ：sequence
4. AUTO：根據資料庫的不同使用上面三個
@Column 宣告該屬性與資料庫欄位的對映關係。
@OneToMany 一對多關聯關係
@ManyToMany 多對多關聯關係
@JoinColumn 指定關聯的欄位
@JoinTable 參考

Spring Data JPA Repository

BookRepository

public interface BookRepository extends JpaRepository<Book, Integer> {
}

PublisherRepository

public interface PublisherRepository extends JpaRepository<Publisher, Integer> {
}

Spring Data JPA包含了一些內建的Repository，實現了一些常用的方法：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());
    }

}

程式碼下載

從我的 github 中下載，https://github.com/longfeizheng/jpa-example/tree/master/many-to-many-extra-columns

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前言

準備

技術棧

目錄結構

父pom.xml

多對多關聯對映

目錄結構

pom.xml

多對多關聯

實體類

Book

Publisher

BookPublisher

Spring Data JPA Repository

BookRepository

PublisherRepository

application.yml

BookRepositoryTest

程式碼下載

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