springboot jpa 至 many to many的级联关系
一.说明
角色和菜单时多对多关系 *角色是多方;菜单也是多方;
在roles:
@ManyToMany(cascade=CascadeType.ALL,fetch=FetchType.EAGER)
//@JoinTable:映射中间表
//joinColumns:当前表中的主键所关联的中间表中的外键字段
//inverseJoinColumns:关联menus表的外键叫什么
@JoinTable(name="tb_roles_menus",joinColumns=@JoinColumn(name="role_id"),inverseJoinColumns=@JoinColumn(name="caidan_id"))
private Set<Menus> menusSet = new HashSet<Menus>();
在meuns:
@ManyToMany(mappedBy="menusSet",cascade=CascadeType.ALL ) private Set<Roles> rolesSet = new HashSet<>();
加载树形结构,使用关闭懒加载fetch=FetchType.EAGER
在数据库中取值的时候,如果使用懒加载,就会只取出一层节点的数据,然后关闭session,这样再去取下一层级的数据的时候就会报出错误:session is closed
如果是EAGER,那么表示取出这条数据时,它关联的数据也同时取出放入内存中
如果是LAZY,那么取出这条数据时,它关联的数据并不取出来,在同一个session中,什么时候要用,就什么时候取(再次访问数据库)。
但是,在session外,就不能再取了。用EAGER时,因为在内存里,所以在session外也可以取。
二.新建工程
2.1 新建pom文件:
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13</version>
<scope>test</scope>
</dependency>
<!-- springBoot的启动器 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- 添加junit环境的jar包 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
</dependency>
<!-- springBoot的启动器 -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<!-- mysql -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
<!-- druid连接池 -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.1.10</version>
</dependency>
</dependencies>
2.2 新建Menus文件:
package com.ljf.spring.boot.demo.jpa.relation.model;
import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;
/**
* @ClassName: Menus
* @Description: 角色和菜单时多对多关系
* 角色是多方;菜单也是多方;
*
* @Author: liujianfu
* @Date: 2020/08/30 17:39:24
* @Version: V1.0
**/
@Entity
@Table(name="tb_menus")
public class Menus {
@Id
@GeneratedValue(strategy= GenerationType.IDENTITY)
@Column(name="menus_id")
private Integer menusId;
@Column(name="menus_name")
private String menusName;
@Column(name="menus_url")
private String menusUrl;
@Column(name="father_id")
private Integer fatherId;
@ManyToMany(mappedBy="menusSet",cascade=CascadeType.ALL )
private Set<Roles> rolesSet = new HashSet<>();
public Integer getMenusId() {
return menusId;
}
public void setMenusId(Integer menusId) {
this.menusId = menusId;
}
public String getMenusName() {
return menusName;
}
public void setMenusName(String menusName) {
this.menusName = menusName;
}
public String getMenusUrl() {
return menusUrl;
}
public void setMenusUrl(String menusUrl) {
this.menusUrl = menusUrl;
}
public Integer getFatherId() {
return fatherId;
}
public void setFatherId(Integer fatherId) {
this.fatherId = fatherId;
}
public Set<Roles> getRolesSet() {
return rolesSet;
}
public void setRolesSet(Set<Roles> rolesSet) {
this.rolesSet = rolesSet;
}
}
2.3 新建Roles文件:
package com.ljf.spring.boot.demo.jpa.relation.model;
import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;
/**
* @ClassName: Roles
* @Description: 用户和角色是1:1关系 ;角色和用户是1:n关系;
* * 角色是少的一方,所以配置@OneToMany
* @Author: liujianfu
* @Date: 2020/08/21 12:19:35
* @Version: V1.0
**/
@Entity
@Table(name="tb_roles")
public class Roles {
@Id
@GeneratedValue(strategy= GenerationType.IDENTITY)
@Column(name="role_id")
private Integer roleId;
@Column(name="role_name")
private String roleName;
@OneToMany(mappedBy="roles",cascade=CascadeType.ALL,fetch=FetchType.LAZY) //见Users实体中的roles属性,要保持一致
private Set<Users> usersSet = new HashSet<>();
@ManyToMany(cascade=CascadeType.ALL)
//@JoinTable:映射中间表
//joinColumns:当前表中的主键所关联的中间表中的外键字段
//inverseJoinColumns:关联menus表的外键叫什么
@JoinTable(name="tb_roles_menus",joinColumns=@JoinColumn(name="role_id"),inverseJoinColumns=@JoinColumn(name="caidan_id"))
private Set<Menus> menusSet = new HashSet<Menus>();
public Integer getRoleId() {
return roleId;
}
public void setRoleId(Integer roleId) {
this.roleId = roleId;
}
public String getRoleName() {
return roleName;
}
public void setRoleName(String roleName) {
this.roleName = roleName;
}
public Set<Users> getUsersSet() {
return usersSet;
}
public void setUsersSet(Set<Users> usersSet) {
this.usersSet = usersSet;
}
public Set<Menus> getMenusSet() {
return menusSet;
}
public void setMenusSet(Set<Menus> menusSet) {
this.menusSet = menusSet;
}
}
2.4 新建repository文件:
package com.ljf.spring.boot.demo.jpa.relation.repostory;
import com.ljf.spring.boot.demo.jpa.relation.model.Roles;
import com.ljf.spring.boot.demo.jpa.relation.model.Users;
import org.springframework.data.jpa.repository.JpaRepository;
public interface RoleMenusRespository extends JpaRepository<Roles,Integer> {
}
2.5 application配置文件:
#spring的配置mysql
spring.datasource.driverClassName=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/test_db?serverTimezone=UTC
spring.datasource.username=root
spring.datasource.password=root
#ali
spring.datasource.type=com.alibaba.druid.pool.DruidDataSource
spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true
2.6 junit单元测试:
package com.ljf.spring.boot.demo.jpa.relation;
/**
* @ClassName: ManyToManyTest
* @Description: TODO
* @Author: liujianfu
* @Date: 2020/08/30 18:10:07
* @Version: V1.0
**/
import com.ljf.spring.boot.demo.jpa.relation.model.Menus;
import com.ljf.spring.boot.demo.jpa.relation.model.Roles;
import com.ljf.spring.boot.demo.jpa.relation.model.Users;
import com.ljf.spring.boot.demo.jpa.relation.repostory.RoleMenusRespository;
import com.ljf.spring.boot.demo.jpa.relation.repostory.UserRespository;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
/**
* SpringBoot测试类
*@RunWith:启动器
*SpringJUnit4ClassRunner.class:让junit与spring环境进行整合
*
*@SpringBootTest(classes={App.class}) 1,当前类为springBoot的测试类
*@SpringBootTest(classes={App.class}) 2,加载SpringBoot启动类。启动springBoot
*
*junit与spring整合 @Contextconfiguartion("classpath:applicationContext.xml")
*/
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest(classes={App.class}) //springboot的启动类
public class ManyToManyTest {
@Autowired
RoleMenusRespository ur;
/**
*创建多对多的关系
*/
@Test
public void oneToManySave(){
//创建角色对象
Roles r = new Roles();
r.setRoleName("项目经理");
//创建菜单对象
Menus menus = new Menus();
menus.setMenusName("xxxx管理系统");
menus.setMenusUrl("/uuuu");
menus.setFatherId(0);
Menus menus2 = new Menus();
menus2.setMenusName("电商管理系统");
menus2.setMenusUrl("/xmgl");
menus2.setFatherId(0);
//关联
r.getMenusSet().add(menus);
r.getMenusSet().add(menus2);
menus.getRolesSet().add(r);
menus2.getRolesSet().add(r);
//保存
ur.save(r);
}
}
2.7 查看:
2.7 查询:需要在roles的@manytomany的加载策略进行修改,@ManyToMany(cascade=CascadeType.ALL,fetch=FetchType.EAGER)
打印:
Hibernate: select roles0_.role_id as role_id1_1_0_, roles0_.role_name as role_nam2_1_0_, menusset1_.role_id as role_id1_2_1_, menus2_.menus_id as caidan_i2_2_1_, menus2_.menus_id as menus_id1_0_2_, menus2_.father_id as father_i2_0_2_, menus2_.menus_name as menus_na3_0_2_, menus2_.menus_url as menus_ur4_0_2_ from tb_roles roles0_ left outer join tb_roles_menus menusset1_ on roles0_.role_id=menusset1_.role_id left outer join tb_menus menus2_ on menusset1_.caidan_id=menus2_.menus_id where roles0_.role_id=?
项目经理
m:电商管理系统
m:xxxx管理系统
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