Spring Data JPA处理一对一、一对多、多对多关系映射

程序员文章站 2022-04-23 23:49:32

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1.一对一的关联
一对一关联可以把外键放在任何一放，假设Users和Roles是一对一的关系，代码如下
Users.java

package per.czt.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.OneToOne;
import javax.persistence.Table;

@Entity
@Table(name="t_users")
public class Users {
	@Id
	@GeneratedValue(strategy=GenerationType.IDENTITY)
	@Column(name="user_id")
	private Integer userid;
	@Column(name="user_name")
	private String username;
	@Column(name="user_age")
	private Integer userage;
	
	@OneToOne(cascade=CascadeType.PERSIST)
	@JoinColumn(name="roles_id")
	private Roles roles;
	public Users() {
		// TODO Auto-generated constructor stub
	}
	public Integer getUserid() {
		return userid;
	}
	public void setUserid(Integer userid) {
		this.userid = userid;
	}
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public Integer getUserage() {
		return userage;
	}
	public void setUserage(Integer userage) {
		this.userage = userage;
	}
	public Roles getRoles() {
		return roles;
	}
	public void setRoles(Roles roles) {
		this.roles = roles;
	}
	@Override
	public String toString() {
		return "Users [userid=" + userid + ", username=" + username + ", userage=" + userage + "]";
	}
}

Roles.java

package per.czt.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.OneToOne;
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;
	@OneToOne(mappedBy="roles",cascade=CascadeType.PERSIST)
	private Users users;
	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 Roles() {
		super();
		// TODO Auto-generated constructor stub
	}

	public Users getUsers() {
		return users;
	}

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

	@Override
	public String toString() {
		return "Roles [roleid=" + roleid + ", rolename=" + rolename + ", users=" + users + "]";
	}

	
	

}

测试类

package per.czt.test;
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 per.czt.dao.UsersDao;
import per.czt.pojo.Roles;
import per.czt.pojo.Users;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(value="classpath:applicationContext.xml")
public class AssociationOneToOneTest {
	
	@Autowired
	private UsersDao usersDao;
	
	@Test

	public void test1() {
	   //创建角色
		Roles roles=new Roles();
		roles.setRolename("admin");
		//创建用户
		Users users=new Users();
		users.setUserage(13);
		users.setUsername("张晓萌");
		//建立关联
		users.setRoles(roles);
		roles.setUsers(users);
		//保存对象
		this.usersDao.save(users);
		//this.usersDao.save(users);
		
		
	}
	@Test
	public void test2() {
		Users users=usersDao.findOne(22);
		System.out.println(users);
		System.out.println(users.getRoles());
	}

}

2.一对多关系
假设角色和用户是一对多的关系，一个角色对于多个用户，一个用户只能有一个角色
Roles.java

package per.czt.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_roles4")
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")
	private Set<Users> users=new HashSet<Users>();	

	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 Roles() {
		super();
		// TODO Auto-generated constructor stub
	}


	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 + "]";
	}

	
	
	

}

Users.java

package per.czt.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_users4")
public class Users {
	@Id
	@GeneratedValue(strategy=GenerationType.IDENTITY)
	@Column(name="user_id")
	private Integer userid;
	@Column(name="user_name")
	private String username;
	@Column(name="user_age")
	private Integer userage;
	
	@ManyToOne(cascade=CascadeType.PERSIST)//开启级联操作
	@JoinColumn(name="roles_id")
	private Roles roles;
	
	
	public Users() {
		// TODO Auto-generated constructor stub
	}
	public Integer getUserid() {
		return userid;
	}
	public void setUserid(Integer userid) {
		this.userid = userid;
	}
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public Integer getUserage() {
		return userage;
	}
	public void setUserage(Integer userage) {
		this.userage = userage;
	}
	
	public Roles getRoles() {
		return roles;
	}
	public void setRoles(Roles roles) {
		this.roles = roles;
	}
	@Override
	public String toString() {
		return "Users [userid=" + userid + ", username=" + username + ", userage=" + userage + "]";
	}
}

测试类
OneToManyTest.java

package per.czt.test;
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 per.czt.dao.UsersDao;
import per.czt.pojo.Roles;
import per.czt.pojo.Users;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(value="classpath:applicationContext.xml")
public class OneToManyTest {
	
	@Autowired
	private UsersDao usersDao;
	@Test
	public void test1() {
		//创建Roles对象
	
		Roles roles=new Roles();
		roles.setRolename("administrator");
		//创建Users对象
		
		Users users1=new Users();
		users1.setUsername("小孙");
		users1.setUserage(14);
		//建立关联
		
		roles.getUsers().add(users1);
		users1.setRoles(roles);
		//保存
		usersDao.save(users1);
	}
	
	@Test
	public void test2() {
		Users users=usersDao.findOne(5);
		System.out.println(users);
		System.out.println(users.getRoles());
	}
}

3.多对多关系
假设角色和菜单之间是多对多的关系，则会存在一个中间表存储角色id和菜单id，在这里从那一方建立这个表关联都可以，假设从角色表建立关联
Roles.java

package per.czt.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_roles5")
public class Roles {
	@Id
	@GeneratedValue(strategy=GenerationType.IDENTITY)
	@Column(name="role_id")
	private Integer roleid;
	@Column(name="role_name")
	private String rolename;
	
	@ManyToMany(cascade=CascadeType.PERSIST,fetch=FetchType.EAGER)//级联  ， 延迟加载
	@JoinTable(name="t_roles_menus",[email protected](name="role_id"),[email protected](name="menu_id"))
	private Set<Menus> menus=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<Menus> getMenus() {
		return menus;
	}

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

	public Roles() {
		super();
		// TODO Auto-generated constructor stub
	}


	

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

Menus.java

package per.czt.pojo;

import java.util.HashSet;
import java.util.Set;

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.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="fatherid")
	private Integer fatherid;
	
	@ManyToMany(mappedBy="menus",fetch=FetchType.EAGER)// 延迟加载
	private Set<Roles> roles=new HashSet<Roles>();
	
	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> getRoles() {
		return roles;
	}
	public void setRoles(Set<Roles> roles) {
		this.roles = roles;
	}
	@Override
	public String toString() {
		return "Menus [menusid=" + menusid + ", menusname=" + menusname + ", menusurl=" + menusurl + ", fatherid="
				+ fatherid + ", roles=" + roles + "]";
	}
	public Menus() {
		super();
		// TODO Auto-generated constructor stub
	}
	
	

}

ManyToManyTest.java

package per.czt.test;
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 per.czt.dao.RolesDao;
import per.czt.pojo.Menus;
import per.czt.pojo.Roles;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(value="classpath:applicationContext.xml")
public class ManyToManyTest {
	
	@Autowired
	private RolesDao rolesDao;
	
	@Test
	public void test() {
		//创建角色
		Roles roles=new Roles();
		roles.setRolename("超级管理员");
		
		//创建menus
		Menus menus=new Menus();
		menus.setFatherid(1);
		menus.setMenusname("xx管理平台");
		menus.setMenusurl(null);
		
		//创建menus1
		Menus menus1=new Menus();
		menus1.setFatherid(-1);
		menus1.setMenusname("用户管理平台");
		menus1.setMenusurl(null);
		
		//把roles分别与menus1和menus建立关联
		roles.getMenus().add(menus1);
		roles.getMenus().add(menus);
		menus1.getRoles().add(roles);
		menus1.getRoles().add(roles);
		//保存
		rolesDao.save(roles);
	}
	
	@Test
	public void test2() {
		Roles roles=rolesDao.findOne(1);
		System.out.println(roles);
	
		System.out.println(roles.getMenus().size());
		for(Menus menus:roles.getMenus()) {
			System.out.println(menus);
		}
	}
	
	
}

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