SpringDataJPA之关联关系-阿里云开发者社区

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);
    }
  } 
}

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SpringDataJPA之关联关系

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