011_Spring Data JPA多对多关系

最新推荐文章于 2022-07-14 19:17:58 发布

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本文通过实例讲解如何使用Spring Data JPA在Java项目中建立角色和权限之间的多对多关联，包括实体类定义、Repository接口实现和数据库操作演示。

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1. 多对多的关联关系

1.1. 权限和用户是多对多的关联关系

权限类(对应表名: t_auth): 多方

角色类(对应表名: t_role): 多方

权限角色类(对应表名: t_auth_role): 中间表

1.2. 权限表

1.3. 角色表

1.4. 权限角色表

2. 多对多的关联关系例子

2.1. 创建一个名为spring-data-jpa-many2many的Java项目, 同时添加相关jar包, 并添加JUnit能力。

2.2. 新建Role.java

package com.bjbs.pojo;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;
import javax.persistence.Table;

@Entity // 指定该类是实体类
@Table(name = "t_role") // 指定数据库表名(表名和实体类对应)
public class Role implements Serializable {
	private static final long serialVersionUID = 1L;
	
	@Id // 指定为主键
	@GeneratedValue(strategy = GenerationType.IDENTITY) // 指定主键生成策略
	@Column(name = "id") // 指定表中列名(列名和属性名对应)
	private Integer id;

	@Column(name = "name")
	private String name; // 角色名
	
	// fetch=FetchType.EAGER立即加载
	@ManyToMany(cascade=CascadeType.PERSIST, fetch=FetchType.EAGER)
	// @JoinTable: 配置中间表信息
	// joinColumns: 建立当前表在中间表中的外键字段
	@JoinTable(name="t_auth_role", joinColumns=@JoinColumn(name="r_id"), inverseJoinColumns=@JoinColumn(name="a_id"))
	private Set<Auth> auths = new HashSet<Auth>();

	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<Auth> getAuths() {
		return auths;
	}

	public void setAuths(Set<Auth> auths) {
		this.auths = auths;
	}

	@Override
	public String toString() {
		return "Role [id=" + id + ", name=" + name + "]";
	}

}

2.3. 新建Auth.java

package com.bjbs.pojo;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.ManyToMany;
import javax.persistence.Table;

@Entity // 指定该类是实体类
@Table(name = "t_auth") // 指定数据库表名(表名和实体类对应)
public class Auth implements Serializable {
	private static final long serialVersionUID = 1L;

	@Id // 指定为主键
	@GeneratedValue(strategy = GenerationType.IDENTITY) // 指定主键生成策略
	@Column(name = "id") // 指定表中列名(列名和属性名对应)
	private Integer id;

	@Column(name = "name")
	private String name; // 权限名

	@ManyToMany(mappedBy="auths")
	private Set<Role> roles = new HashSet<Role>();

	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<Role> getRoles() {
		return roles;
	}

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

	@Override
	public String toString() {
		return "Auth [id=" + id + ", name=" + name + "]";
	}

}

2.4. 新建RoleRepository.java

package com.bjbs.dao;

import org.springframework.data.jpa.repository.JpaRepository;
import com.bjbs.pojo.Role;

/**
 * 参数一T: 当前需要映射的实体; 参数二 T: 当前映射的实体中的id的类型
 */
public interface RoleRepository extends JpaRepository<Role, Integer> {

}

2.5. 新建TestRoleRepository.java

package com.bjbs.test;

import java.util.Set;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import com.bjbs.dao.RoleRepository;
import com.bjbs.pojo.Role;
import com.bjbs.pojo.Auth;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath:applicationContext.xml")
public class TestRoleRepository {
	@Autowired
	private RoleRepository roleRepository;
	
	@Test
	public void findOne() {
		Role role = roleRepository.findOne(1);
		System.out.println(role);
		Set<Auth> auths = role.getAuths();
		for (Auth auth : auths) {
			System.out.println(auth);
		}
	}
	
	@Test
	public void save() {
		// 创建角色
		Role role = new Role();
		role.setName("张三");
		
		// 创建权限
		Auth auth = new Auth();
		auth.setName("注册用户");
		
		// 建立关系
		role.getAuths().add(auth);
		auth.getRoles().add(role);
		
		// 保存数据
		roleRepository.save(role);
	}
}

2.6. 在src下新建application.properties

spring.datasource.driverClassName=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://192.168.25.138:3306/StudyMybatis?useSSL=true&useUnicode=true&characterEncoding=utf-8&serverTimezone=Asia/Shanghai
spring.datasource.username=root
spring.datasource.password=lyw123456

2.7. 在src下新建applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns="http://www.springframework.org/schema/beans"
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:jpa="http://www.springframework.org/schema/data/jpa"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
	http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
	http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa.xsd
	http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd">
	
	<!-- 配置读取properties文件的工具类 -->
	<context:property-placeholder location="classpath:application.properties" />

	<!-- 配置c3p0数据库连接池 -->
	<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
		<property name="jdbcUrl" value="${spring.datasource.url}" />
		<property name="driverClass" value="${spring.datasource.driverClassName}" />
		<property name="user" value="${spring.datasource.username}" />
		<property name="password" value="${spring.datasource.password}" />
	</bean>

	<!-- Spring整合JPA 配置EntityManagerFactory -->
	<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
		<property name="dataSource" ref="dataSource" />
		<property name="jpaVendorAdapter">
			<bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
				<!-- hibernate相关的属性的注入 -->
				<!-- 配置数据库类型 -->
				<property name="database" value="MYSQL" />
				<!-- 正向工程 自动创建表 -->
				<!-- <property name="generateDdl" value="true" /> -->
				<!-- 显示执行的SQL -->
				<property name="showSql" value="true" />
			</bean>
		</property>
		<!-- 扫描实体的包 -->
		<property name="packagesToScan">
			<list>
				<value>com.bjbs.pojo</value>
			</list>
		</property>
	</bean>

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

	<!-- 配置开启注解事务处理 -->
	<tx:annotation-driven transaction-manager="transactionManager" />

	<!-- 配置springIOC的注解扫描 -->
	<context:component-scan base-package="com.bjbs.service" />

	<!-- Spring Data JPA 的配置 -->
	<!-- base-package: 扫描dao接口所在的包 -->
	<jpa:repositories base-package="com.bjbs.dao" />
</beans>

2.8. 查询角色

2.9. 保存角色