三十 SpringBoot整合Spring Data JPA-关联映射

一、建立一对多的双向关联关系

角色与用户的一对多的关联关系。

角色：一方

用户：多方

1.1 实体类

package com.bjsxt.pojo;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

@Entity
@Table(name = "t_users")
public class Users {
	@Id
	@GeneratedValue(strategy = GenerationType.IDENTITY)
	@Column(name = "id")
	private Integer id;
	@Column(name = "name")
	private String name;
	@Column(name = "age")
	private Integer age;
	@Column(name = "address")
	private String address;
	
	@ManyToOne(cascade=CascadeType.PERSIST)
	// @JoinColumn用来维护一个外键
	@JoinColumn(name = "role_id")
	private Roles 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 Integer getAge() {
		return age;
	}

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

	public String getAddress() {
		return address;
	}

	public void setAddress(String address) {
		this.address = address;
	}
	

	public Roles getRole() {
		return role;
	}

	public void setRole(Roles role) {
		this.role = role;
	}

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

}

package com.bjsxt.pojo;

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.OneToMany;
import javax.persistence.Table;

@Entity
@Table(name = "t_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="role")
	private Set<Users> users = new HashSet<>();

	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> getUsers() {
		return users;
	}

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

	@Override
	public String toString() {
		return "Roles [roleId=" + roleId + ", roleName=" + roleName + "]";
	}

}

1.2 添加测试类

 

package com.bjsxt.dao;

import java.util.Optional;

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;

import com.bjsxt.App;
import com.bjsxt.pojo.Roles;
import com.bjsxt.pojo.Users;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest(classes=App.class)
public class OneToManyTest {
	@Autowired
	private UsersRepository usersRepository;

	/**
	 * 一对多关联关系的添加
	 */
	@Test
	public void testOneToManySave() {
		// 创建一个用户
		Users user = new Users();
		user.setAddress("深圳");
		user.setAge(56);
		user.setName("牟牟");
		
		// 创建一个角色
		Roles role = new Roles();
		role.setRoleName("管理员");
		
		// 关联
		role.getUsers().add(user);
		user.setRole(role);
		
		// 保存 需要user中role添加cascade=CascadeType.PERSIST
		usersRepository.save(user);
	}
	
	/**
	 * 一对多关联关系的查询
	 */
	@Test
	public void testOneToManyFind() {
		Optional<Users> optional = usersRepository.findById(6);
		Users users = optional.get();
		System.out.println(users);
		Roles role = users.getRole();
		System.out.println(role);
	}

}
2019-04-12 11:50:11.311  INFO 15664 --- [           main] com.bjsxt.dao.OneToManyTest              : Started OneToManyTest in 13.297 seconds (JVM running for 15.593)
Hibernate: insert into t_roles (role_name) values (?)
Hibernate: insert into t_users (address, age, name, role_id) values (?, ?, ?, ?)
2019-04-12 11:50:11.923  INFO 15664 --- [       Thread-2] o.s.s.concurrent.ThreadPoolTaskExecutor  : Shutting down ExecutorService 'applicationTaskExecutor'

2019-04-12 12:00:44.510  INFO 14292 --- [           main] com.bjsxt.dao.OneToManyTest              : Started OneToManyTest in 11.759 seconds (JVM running for 14.402)
Hibernate: select users0_.id as id1_1_0_, users0_.address as address2_1_0_, users0_.age as age3_1_0_, users0_.name as name4_1_0_, users0_.role_id as role_id5_1_0_, roles1_.role_id as role_id1_0_1_, roles1_.role_name as role_nam2_0_1_ from t_users users0_ left outer join t_roles roles1_ on users0_.role_id=roles1_.role_id where users0_.id=?
Users [id=6, name=牟牟, age=56, address=深圳]
Roles [roleId=1, roleName=管理员]
2019-04-12 12:00:44.836  INFO 14292 --- [       Thread-2] o.s.s.concurrent.ThreadPoolTaskExecutor  : Shutting down ExecutorService 'applicationTaskExecutor'

二、建立多对多的双向关联关系

角色与菜单的多对多的关联关系。

角色：多方

用户：多方

2.1 实体

package com.bjsxt.pojo;

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.OneToMany;
import javax.persistence.Table;

@Entity
@Table(name = "t_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 = "role")
	private Set<Users> users = new HashSet<>();

	// fetch必须加，不加执行测试类会异常，org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.bjsxt.pojo.Roles.menus, could not initialize proxy - no Session
	@ManyToMany(cascade=CascadeType.PERSIST, fetch=FetchType.EAGER)
	// @JoinTable：用来映射中间表
	// @JoinColumn用来维护一个外键,即所关联的中间表中的外键字段
	// inverseJoinColumns 中间表另一侧的外键字段
	@JoinTable(name = "t_roles_menus", joinColumns = @JoinColumn(name = "role_id"), 
		inverseJoinColumns = @JoinColumn(name = "menus_id"))
	private Set<Menus> menus = new HashSet<>();

	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> getUsers() {
		return users;
	}

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

	public Set<Menus> getMenus() {
		return menus;
	}

	public void setMenus(Set<Menus> menus) {
		this.menus = menus;
	}

	@Override
	public String toString() {
		return "Roles [roleId=" + roleId + ", roleName=" + roleName + "]";
	}

}
package com.bjsxt.pojo;

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
@Table(name = "t_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;
	
	// mappedBy指定的是roles中的menus对象
	@ManyToMany(mappedBy="menus")
	private Set<Roles> roles = 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;
	}

	@Override
	public String toString() {
		return "Menus [menusId=" + menusId + ", menusName=" + menusName + ", menusUrl=" + menusUrl + ", fatherId="
				+ fatherId + "]";
	}
}

2.2 创建role的dao

package com.bjsxt.dao;

import org.springframework.data.jpa.repository.JpaRepository;

import com.bjsxt.pojo.Roles;

public interface RolesRepository extends JpaRepository<Roles, Integer> {

}

2.3 创建测试类

package com.bjsxt.dao;

import java.util.Optional;
import java.util.Set;

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;

import com.bjsxt.App;
import com.bjsxt.pojo.Menus;
import com.bjsxt.pojo.Roles;

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest(classes=App.class)
public class ManyToManyTest {
	
	@Autowired
	private RolesRepository rolesRepository;

	@Test
	public void testManyToManySave() {
		// 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("xxx管理系统");
		menus.setFatherId(0);
		
		Menus menus2 = new Menus();
		menus2.setMenusName("项目管理");
		menus2.setFatherId(1);
		// 关联
		r.getMenus().add(menus);
		r.getMenus().add(menus2);
		menus.getRoles().add(r);
		menus2.getRoles().add(r);
		// 保存
		rolesRepository.save(r);
	}
	
	/**
	 * org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: 
	 * com.bjsxt.pojo.Roles.menus, could not initialize proxy - no Session
	 * 原因是没加在roles对象的menus字段中加fetch=FetchType.EAGER 
	 */
	@Test
	public void testManyToManyFind() {
		Optional<Roles> optional = rolesRepository.findById(2);
		Roles roles = optional.get();
		System.out.println(roles);
		Set<Menus> menus = roles.getMenus();
		for (Menus menu : menus) {
			System.out.println(menu);
		}
	}
}
2019-04-12 14:01:54.860  INFO 10904 --- [           main] com.bjsxt.dao.ManyToManyTest             : Started ManyToManyTest in 13.322 seconds (JVM running for 15.792)
Hibernate: insert into t_roles (role_name) values (?)
Hibernate: insert into t_menus (father_id, menus_name, menus_url) values (?, ?, ?)
Hibernate: insert into t_menus (father_id, menus_name, menus_url) values (?, ?, ?)
Hibernate: insert into t_roles_menus (role_id, menus_id) values (?, ?)
Hibernate: insert into t_roles_menus (role_id, menus_id) values (?, ?)
2019-04-12 14:01:55.441  INFO 10904 --- [       Thread-2] o.s.s.concurrent.ThreadPoolTaskExecutor  : Shutting down ExecutorService 'applicationTaskExecutor'

Hibernate: select roles0_.role_id as role_id1_1_0_, roles0_.role_name as role_nam2_1_0_, menus1_.role_id as role_id1_2_1_, menus2_.menus_id as menus_id2_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 t_roles roles0_ left outer join t_roles_menus menus1_ on roles0_.role_id=menus1_.role_id left outer join t_menus menus2_ on menus1_.menus_id=menus2_.menus_id where roles0_.role_id=?
Roles [roleId=2, roleName=项目经理]
Menus [menusId=1, menusName=项目管理, menusUrl=null, fatherId=1]
Menus [menusId=2, menusName=xxx管理系统, menusUrl=null, fatherId=0]
2019-04-12 14:08:25.906  INFO 16268 --- [       Thread-2] o.s.s.concurrent.ThreadPoolTaskExecutor  : Shutting down ExecutorService 'applicationTaskExecutor'

 

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