SpringDataJPA之关联关系

我会带着你远行 2022-01-30 08:43 298阅读 0赞

本文介绍下SpringDataJPA怎么处理关联关系

# 关联关系处理 #

## 1.一对一 ##

用户和角色设置一对一关系，通过外键关联。

### pojo设置 ###

创建 Users 实体

@Entity
    @Table(name="t_users")
    public class Users implements Serializable{ 
    	@Id
    	//strategy=GenerationType.IDENTITY 自增长
    	@GeneratedValue(strategy=GenerationType.IDENTITY)
    	@Column(name="userid")
    	private Integer userid;
    	
    	@Column(name="username")
    	private String username;
    	
    	@Column(name="userage")
    	private Integer userage;
    	
    	public Roles getRoles() { 
    		return roles;
    	}
    	public void setRoles(Roles roles) { 
    		this.roles = roles;
    	}
    	@OneToOne
    	//@JoinColumn：就是维护一个外键
    	@JoinColumn(name="roles_id")
    	private Roles roles;
    	
    	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;
    	}
    	@Override
    	public String toString() { 
    		return "Users [userid=" + userid + ", username=" + username + ",userage=" + userage + "]";
    	}
    }

创建 Roles 实体

@Entity
    @Table(name="t_roles")
    public class Roles { 
    	@Id
    	@GeneratedValue(strategy=GenerationType.IDENTITY)
    	@Column(name="roleid")
    	private Integer roleid;
    	
    	@Column(name="rolename")
    	private String rolename;
    	
    	@OneToOne(mappedBy="roles")
    	private Users users;
    	public Users getUsers() { 
    		return users;
    	}
    	public void setUsers(Users users) { 
    		this.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;
    	}
    }

### 关联关系操作 ###

/** * 一对一关联关系测试 * @author Administrator * */
    @RunWith(SpringJUnit4ClassRunner.class)
    @ContextConfiguration("classpath:applicationContext.xml")
    public class OneToOneTest { 
    	@Autowired
    	private UsersDao usersDao;
    	/** * 添加用户同时添加角色 */
    	@Test
    	public void test1(){ 
    		//创建角色
    		Roles roles = new Roles();
    		roles.setRolename("管理员");
    		//创建用户
    		Users users = new Users();
    		users.setUserage(30);
    		users.setUsername("赵小刚");
    		//建立关系
    		users.setRoles(roles);
    		roles.setUsers(users);
    		//保存数据
    		this.usersDao.save(users);
    	}
    	/** * 根据用户 ID 查询用户，同时查询用户角色 */
    	@Test
    	public void test2(){ 
    		Users users = this.usersDao.findOne(13);
    		System.out.println("用户信息："+users);
    		Roles roles = users.getRoles();
    		System.out.println(roles);
    	}
    }

## 2.一对多 ##

从角色到用户的一对多的关联关系  
角色：一方  
用户：多方

### pojo ###

@Entity
    @Table(name="t_users")
    public class Users implements Serializable{ 
    	@Id
    	//strategy=GenerationType.IDENTITY 自增长
    	@GeneratedValue(strategy=GenerationType.IDENTITY)
    	@Column(name="userid")
    	private Integer userid;
    	
    	@Column(name="username")
    	private String username;
    	
    	@Column(name="userage")
    	private Integer userage;
    	
    	@ManyToOne()
    	@JoinColumn(name="roles_id")
    	private Roles roles;
    	
    	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;
    	}
    	@Override
    	public String toString() { 
    		return "Users [userid=" + userid + ", username=" + username + ",userage=" + userage + "]";
    	}
    }

@Entity
    @Table(name="t_roles")
    public class Roles { 
    	@Id
    	@GeneratedValue(strategy=GenerationType.IDENTITY)
    	@Column(name="roleid")
    	private Integer roleid;
    	
    	@Column(name="rolename")
    	private String rolename;
    	
    	@OneToMany(mappedBy="roles")
    	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;
    	}
    	@Override
    	public String toString() { 
    		return "Roles [roleid=" + roleid + ", rolename=" + rolename + "]";
    	}
    }

### 操作 ###

/** * 一对多的关联关系测试 * @author Administrator * */
    @RunWith(SpringJUnit4ClassRunner.class)
    @ContextConfiguration("classpath:applicationContext.xml")
    public class OneToManyTest { 
    @Autowired
    private UsersDao usersDao;
    	/** * 添加用户同时添加角色 */
    	@Test
    	public void test1(){ 
    		//创建角色
    		Roles roles = new Roles();
    		roles.setRolename("管理员");
    		//创建用户
    		Users users =new Users();
    		users.setUserage(30);
    		users.setUsername("小王");
    		//建立关系
    		roles.getUsers().add(users);
    		users.setRoles(roles);
    		//保存数据
    		this.usersDao.save(users);
    	}
    	/** * 根据用户 ID 查询用户信息，同时查询角色 */
    	@Test
    	public void test2(){ 
    		Users users = this.usersDao.findOne(14);
    		System.out.println("用户姓名："+users.getUsername());
    		Roles roles = users.getRoles();
    		System.out.println(roles);
    	}
    }

## 3.多对多 ##

一个角色可以拥有多个菜单，一个菜单可以分配多个角色。多对多的关联关系  
角色：多方  
菜单：多方

### Pojo ###

@Entity
    @Table(name="t_roles")
    public class Roles { 
    	@Id
    	@GeneratedValue(strategy=GenerationType.IDENTITY)
    	@Column(name="roleid")
    	private Integer roleid;
    	
    	@Column(name="rolename")
    	private String rolename;
    	
    	@ManyToMany
    	//@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_roles_menus",joinColumns=@JoinColumn(name="role_id"),inverseJoinColumns=@JoinColumn(name="menu_id"))
    	private Set<Menus> menus = new HashSet<>();
    	
    	public Set<Menus> getMenus() { 
    		return menus;
    	}
    	public void setMenus(Set<Menus> menus) { 
    		this.menus = 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;
    	}
    	@Override
    	public String toString() { 
    		return "Roles [roleid=" + roleid + ", rolename=" + rolename + "]";
    	}
    }

@Entity
    @Table(name="t_menus")
    public class Menus { 
    	@Id
    	@GeneratedValue(strategy=GenerationType.IDENTITY)
    	@Column(name="menusid")
    	private Integer menusid;
    	
    	@Column(name="menusname")
    	private String menusname;
    	
    	@Column(name="menusurl")
    	private String menusurl;
    	
    	@Column(name="fatherid")
    	private Integer fatherid;
    	
    	@ManyToMany(mappedBy="menus")
    	private Set<Roles> roles = new HashSet<>();
    	
    	public Set<Roles> getRoles() { 
    		return roles;
    	}
    	public void setRoles(Set<Roles> roles) { 
    		this.roles = 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;
    	}
    	@Override
    	public String toString() { 
    		return "Menus [menusid=" + menusid + ", menusname=" + menusname+ ", menusurl=" + menusurl + ", fatherid="+ fatherid + "]";
    	}
    }

### 操作 ###

/** * 多对多关联关系测试 * @author Administrator * */
    @RunWith(SpringJUnit4ClassRunner.class)
    @ContextConfiguration("classpath:applicationContext.xml")
    public class ManyToManyTest { 
    	@Autowired
    	private RolesDao rolesDao;
    	/** * 添加角色同时添加菜单 */
    	@Test
    	public void test1(){ 
    		//创建角色对象
    		Roles roles = new Roles();
    		roles.setRolename("超级管理员");
    		//创建菜单对象 XXX 管理平台 --->用户管理
    		Menus menus = new Menus();
    		menus.setMenusname("XXX 管理平台");
    		menus.setFatherid(-1);
    		menus.setMenusurl(null);
    		//用户管理菜单
    		Menus menus1 = new Menus();
    		menus1.setMenusname("用户管理");
    		menus1.setFatherid(1);
    		menus1.setMenusurl(null);
    		//建立关系
    		roles.getMenus().add(menus);
    		roles.getMenus().add(menus1);
    		menus.getRoles().add(roles);
    		menus1.getRoles().add(roles);
    		//保存数据
    		this.rolesDao.save(roles);
    	}
    	/** * 查询 Roles */
    	@Test
    	public void test2(){ 
    		Roles roles = this.rolesDao.findOne(3);
    		System.out.println("角色信息："+roles);
    		Set<Menus> menus = roles.getMenus();
    		for (Menus menus2 : menus) { 
    			System.out.println("菜单信息："+menus2);
    		}
    	} 
    }

搞定~