Spring Data Jpa 多表之间的关系和操作多表的步骤（多对多）

Spring Data Jpa 多表之间的关系和操作多表的步骤（多对多）

多对多操作
案例： 用户和角色（多对多关系）
用户：User
角色：Role

分析步骤：

1. 明确表关系
   多对多关系
2. 确定表关系（描述 外键 | 中间表）
   中间表
3. 编写而实体类，再实体类中描述表关系（包含关系）
   用户：包含角色的集合
   角色：包含用户的集合
4. 配置映射关系

案例

具体代码
pom文件

<?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.itcast</groupId>
    <artifactId>jpa-day03-manytomany</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <spring.version>4.2.4.RELEASE</spring.version>
        <hibernate.version>5.0.7.Final</hibernate.version>
        <slf4j.version>1.6.6</slf4j.version>
        <log4j.version>1.2.12</log4j.version>
        <c3p0.version>0.9.1.2</c3p0.version>
        <mysql.version>5.1.6</mysql.version>
    </properties>
    <dependencies>
        <!-- junit单元测试 -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.9</version>
            <scope>test</scope>
        </dependency>

        <!-- spring beg -->
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>1.6.8</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aop</artifactId>
            <version>${
     spring.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${
     spring.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context-support</artifactId>
            <version>${
     spring.version}</version>
        </dependency>

        <!--     Spring对ORM框架的支持包   -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-orm</artifactId>
            <version>${
     spring.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-beans</artifactId>
            <version>${
     spring.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-core</artifactId>
            <version>${
     spring.version}</version>
        </dependency>

        <!-- spring end -->

        <!-- hibernate beg -->
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>${
     hibernate.version}</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>${
     hibernate.version}</version>
        </dependency>
        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-validator</artifactId>
            <version>5.2.1.Final</version>
        </dependency>
        <!-- hibernate end -->

        <!-- c3p0 beg -->
        <dependency>
            <groupId>c3p0</groupId>
            <artifactId>c3p0</artifactId>
            <version>${
     c3p0.version}</version>
        </dependency>
        <!-- c3p0 end -->

        <!-- log end -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>${
     log4j.version}</version>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>${
     slf4j.version}</version>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>${
     slf4j.version}</version>
        </dependency>
        <!-- log end -->


        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>${
     mysql.version}</version>
        </dependency>

        <!--    Spring data jpa 坐标    -->
        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-jpa</artifactId>
            <version>1.9.0.RELEASE</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>${
     spring.version}</version>
        </dependency>

        <!-- el beg 使用spring data jpa 必须引入 -->
        <dependency>
            <groupId>javax.el</groupId>
            <artifactId>javax.el-api</artifactId>
            <version>2.2.4</version>
        </dependency>

        <dependency>
            <groupId>org.glassfish.web</groupId>
            <artifactId>javax.el</artifactId>
            <version>2.2.4</version>
        </dependency>
        <!-- el end -->
    </dependencies>


</project>

实体类
User

package cn.itcast.domain;

import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;

/**
 * @author JiangDong
 * @date 2020/7/20 - 11:27
 */
@Entity
@Table(name = "sys_user")
public class User {
     

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "user_id")
    private Long userId;
    @Column(name = "user_name")
    private String userName;
    @Column(name = "age")
    private Integer age;

    /**
     * 配置用户到角色的多对多关系
     *  配置多对多关系
     *      1.声明表关系
     *      @ManyToMany(targetEntity = Role.class) // 多对多
     *      targetEntity 代表丢放的实体类字节码
     *
     *      2.配置中间表（包含两个外键）
     *      @JoinTable
     *          name:中间表名称
     *          joinColumns: 配置当前对象在中间表的外键
     *              @JoinColumn的数组
     *                  name: 外键名
     *                  reverserJoinColumns: 配置对方对象在中间表的外键
     *          inverseJoinColumns：配置对方对象在中间表的外键
     *
     */
    @ManyToMany(targetEntity = Role.class,cascade = CascadeType.ALL)
    @JoinTable(name = "sys_user_role",
        // joinColumns,当前对象再中间表中的外键
        joinColumns = {
     @JoinColumn(name = "sys_user_id",referencedColumnName = "user_id")},
            // inverseJoinColumns,对方对象在中间表中的外键
            inverseJoinColumns = {
     @JoinColumn(name = "sys_role_id",referencedColumnName = "role_id")}
    )
    private Set<Role> roles = new HashSet<Role>();

    public Set<Role> getRoles() {
     
        return roles;
    }

    public void setRoles(Set<Role> roles) {
     
        this.roles = roles;
    }

    public Long getUserId() {
     
        return userId;
    }

    public void setUserId(Long userId) {
     
        this.userId = userId;
    }

    public String getUserName() {
     
        return userName;
    }

    public void setUserName(String userName) {
     
        this.userName = userName;
    }

    public Integer getAge() {
     
        return age;
    }

    public void setAge(Integer age) {
     
        this.age = age;
    }
}

Role

package cn.itcast.domain;

import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;

/**
 * @author JiangDong
 * @date 2020/7/20 - 11:27
 */
@Entity
@Table(name = "sys_role")
public class Role {
     

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "role_id")
    private Long roleId;
    @Column(name = "role_name")
    private String roleName;

    // 配置多对多
    @ManyToMany(mappedBy = "roles")  // 放弃维护权
//    @JoinTable(name = "sys_user_role",
//            // joinColumns,当前对象再中间表中的外键
//            joinColumns = {@JoinColumn(name = "sys_role_id",referencedColumnName = "role_id")},
//            // inverseJoinColumns,对方对象在中间表中的外键
//            inverseJoinColumns = {@JoinColumn(name = "sys_user_id",referencedColumnName = "user_id")}
//    )
    private Set<User> users = new HashSet<User>();

    public Set<User> getUsers() {
     
        return users;
    }

    public void setUsers(Set<User> users) {
     
        this.users = users;
    }

    public Long getRoleId() {
     
        return roleId;
    }

    public void setRoleId(Long roleId) {
     
        this.roleId = roleId;
    }

    public String getRoleName() {
     
        return roleName;
    }

    public void setRoleName(String roleName) {
     
        this.roleName = roleName;
    }

    @Override
    public String toString() {
     
        return "Role{" +
                "roleId=" + roleId +
                ", roleName='" + roleName + '\'' +
                '}';
    }
}

dao接口
RoleDao

package cn.itcast.dao;

import cn.itcast.domain.Role;
import cn.itcast.domain.User;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;

/**
 * @author JiangDong
 * @date 2020/7/20 - 11:33
 */
public interface RoleDao extends JpaRepository<Role,Long>, JpaSpecificationExecutor<Role> {
     
}

UserDao

package cn.itcast.dao;

import cn.itcast.domain.User;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;

/**
 * @author JiangDong
 * @date 2020/7/20 - 11:32
 */
public interface UserDao extends JpaRepository<User,Long>, JpaSpecificationExecutor<User> {
     
}

applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:jdbc="http://www.springframework.org/schema/jdbc" xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:jpa="http://www.springframework.org/schema/data/jpa" xmlns:task="http://www.springframework.org/schema/task"
       xsi:schemaLocation="
		http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
		http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
		http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc.xsd
		http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd
		http://www.springframework.org/schema/data/jpa
		http://www.springframework.org/schema/data/jpa/spring-jpa.xsd">

<!--    spring 和 Spring data 的配置-->
    <!--1. 创建entityManagerFactory对象交给Spring容器管理    -->
    <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">

        <property name="dataSource" ref="dataSource" />
        <!--配置的扫描的包（实体类所在的包） -->
        <property name="packagesToScan" value="cn.itcast.domain" />
        <!-- jpa的实现厂家 -->
        <property name="persistenceProvider">
            <bean class="org.hibernate.jpa.HibernatePersistenceProvider"/>
        </property>

        <!--jpa的供应商适配器 -->
        <property name="jpaVendorAdapter">
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
                <!--配置是否自动创建数据库表 -->
                <property name="generateDdl" value="false" />
                <!--指定数据库类型 -->
                <property name="database" value="MYSQL" />
                <!--数据库方言：支持的特有语法 -->
                <property name="databasePlatform" value="org.hibernate.dialect.MySQLDialect" />
                <!--是否显示sql -->
                <property name="showSql" value="true" />
            </bean>
        </property>

        <!--jpa的方言 ：高级的特性 -->
        <property name="jpaDialect" >
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaDialect" />
        </property>


        <!--
            注入jpa的配置信息
            加载jpa的基本配置信息和jpa实现方式（hibernate）的配置信息
            hibernate.hbm2ddl.auto  : 自动创建数据库表
        -->
        <property name="jpaProperties">
            <props>
                <prop key="hibernate.hbm2ddl.auto">update</prop>
            </props>
        </property>

    </bean>

    <!--2. 创建数据库连接池    -->
    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <property name="user" value="root"/>
        <property name="password" value=""/>
        <property name="jdbcUrl" value="jdbc:mysql://localhost:3308/itheima_spring_data_jpa"/>
        <property name="driverClass" value="com.mysql.jdbc.Driver"/>
    </bean>

    <!--3.整合spring data jpa    -->
    <jpa:repositories base-package="cn.itcast.dao" transaction-manager-ref="transactionManager" entity-manager-factory-ref="entityManagerFactory">
    </jpa:repositories>

    <!--4.配置事务管理器    -->
    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactory"/>
    </bean>

    <!--5.声明式事务    -->

    <!--6.配置包扫描    -->
    <context:component-scan base-package="cn.itcast"/>
</beans>

测试类代码

package cn.itcast.test;

import cn.itcast.dao.RoleDao;
import cn.itcast.dao.UserDao;
import cn.itcast.domain.Role;
import cn.itcast.domain.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.annotation.Rollback;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.transaction.annotation.Transactional;

/**
 * @author JiangDong
 * @date 2020/7/20 - 15:28
 */
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath*:applicationContext.xml")
public class ManyToManyTest {
     

    @Autowired
    private UserDao userDao;

    @Autowired
    private RoleDao roleDao;


    /**
     * 保存一个用户  保存一个角色
     *
     * 多对多放弃维护权， 被动的一方放弃
     */
    @Test
    @Transactional
    @Rollback(false)
    public void testAdd(){
     
        User user = new User();
        user.setUserName("小李");

        Role role = new Role();
        role.setRoleName("Java程序员");

        //配置用户到角色关系,可以为中间表中的数据进行维护
        user.getRoles().add(role);

        //配置角色到用户关系,可以为中间表中的数据进行维护
        role.getUsers().add(user);

        userDao.save(user);
        roleDao.save(role);
    }

    /**
     * 测试级联添加（保存一个用户的同时，保存用户的关联角色）
     */
    @Test
    @Transactional
    @Rollback(false)
    public void testCascadeAdd(){
     
        User user = new User();
        user.setUserName("小李");

        Role role = new Role();
        role.setRoleName("Java程序员");

        //配置用户到角色关系,可以为中间表中的数据进行维护
        user.getRoles().add(role);

        //配置角色到用户关系,可以为中间表中的数据进行维护
        role.getUsers().add(user);

        userDao.save(user);

    }

    /**
     * 删除id为 1 的用户 ，同时删除他的关联对象
     */
    @Test
    @Transactional
    @Rollback(false)
    public void testCascadeRemove(){
     
        //查询1号用户
       User user = userDao.findOne(1l);

       //删除用户
        userDao.delete(user);
    }
}

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