Spring Data JPA处理一对一、一对多、多对多关系映射

柔情只为你懂 2021-12-07 12:57 338阅读 0赞

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",joinColumns=@JoinColumn(name="role_id"),inverseJoinColumns=@JoinColumn(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);
    		}
    	}
    	
    	
    }