使用Hibernate映射多对多关联时，将额外的属性添加到中间表中 [英] Add extra property to intermediary table when mapping many-to-many association with Hibernate

问题描述

在数据库中，我有以下三个表，其中 User 和 Profile 具有多对多关系，并且加入 User_Profile 如下：

  User User_Profile配置文件
 ---- ------------ ------- 
 user_id user_id profile_id 
 user_name profile_id profile_description 
 user_time 
  

Class UserHbm 和 ProfileHbm 使用：

  @Entity 
 @Table（name =User）
 public class UserHbm {
 
 @Id 
 @GeneratedValue（generator =id-generator）
 @GenericGenerator（name =id-generator，
 strategy =com。 xx.xxx.XXXSequenceGenerator，
参数= {@Parameter（name =sequenceName，value =User）}）
 @Column（name =user_id）
 private long用户名; 
 
 @Column 
 private String user_name; 
 
 @Column 
私人日期user_time; 
 
 @ManyToMany（cascade = CascadeType.REFRESH，fetch = FetchType.EAGER）
 @JoinTable（name =User_Profile，
 joinColumns = {@JoinColumn（name =identityProfileID ）}，
 inverseJoinColumns = {@ JoinColumn（name =profile_id）}）
 private Set< ProfileHbm> profiles = new HashSet< ProfileHbm>（）; 
 
 //不相关的其他代码
 
} 
 
 @Entity 
 @Table（name =Profile）
 public class ProfileHbm {
 
 @Id 
 @GeneratedValue（generator =id-generator）
 @GenericGenerator（name =id-generator，
 strategy = com.xx.xxx.XXXSequenceGenerator，
 parameters = {@Parameter（name =sequenceName，value =Profile）}）
 @Column（name =profile_id）
私人长profile_id; 
 
 @Column 
 private String profile_description; 
 
 //不相关的其他代码
 
} 
  

到目前为止，一切都很好，直到出现新的需求：将 user_time 放入 User_Profile 中，以使模式看起来像：

  User User_Profile配置文件
 ---- ------------  - ----- 
 user_id user_id profile_id 
 user_name profile_id profile_description 
 user_time user_time 
  

任何人都可以告诉我如何做到这一点？

我是否需要创建另一个中介 HBM 要做到这一点？

解决方案

解决方案是为UserProfile连接表创建一个新实体。设置一个从用户实体到新的UserProfile实体的OneToMany关系，以及从Profile到User_Profile的OneToMany。

你必须创建一个adda l class，假设UserProfilePk为由user_id和profile_id组成的组合索引的User_Profile实体。

$ pre
$ @
$ public class UserProfilePk {
@ManyToOne
private User

@ManyToOne
私人资料
}

然后，您必须将该类用于User_Profile索引：

  @Entity 
 public class UserProfile { 
 @EmbeddedId 
私人UserProfilePk pk; 
 
 @Column（name =user_time）
 private user userTime; 
 
 
  

你的课程User：

  @Entity 
 public class User {
 @Id 
 private Long id; 
 
私人字符串名称; 
 
私人日期userTime; 
 
 @OneToMany（mappedBy =pk.user，cascade = CascadeType.ALL）
 private Set< UserProfile>的UserProfiles; 
} 
  

和课程档案：

  @Entity 
 public class Profile {
 @Id 
 private Long id; 
 
私人字符串描述; 
 
 @OneToMany（mappedBy =pk.profile）
 private Set< UserProfile>的UserProfiles; 
} 
  

下面的代码保存用户和关联的配置文件： p>

  Configuration configuration = new Configuration（）; 
 configuration.configure（hibernate.cfg.xml）; 
 ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder（）。applySettings（configuration.getProperties（））。build（）; 
 SessionFactory sessionFactory = configuration.buildSessionFactory（serviceRegistry）; 
 Session session = sessionFactory.getCurrentSession（）; 
 
 User user = new User（）; 
 user.setId（1l）; 
 user.setName（Scott）; 
 user.setUserTime（new Date（））; 
档案档案=新档案（）; 
 profile.setId（1l）; 
 profile.setDescription（some user）; 
 
 Transaction tx = session.beginTransaction（）; 
 session.save（profile）; 
 
 UserProfilePk pk = new UserProfilePk（）; 
 pk.setProfile（profile）; 
 pk.setUser（user）; 
 
 UserProfile userProfile = new UserProfile（）; 
 userProfile.setPk（pk）; 
 userProfile.setUserTime（new Date（））; 
 
设置< UserProfile> ups = new HashSet<>（）; 
 ups.add（userProfile）; 
 user.setUserProfiles（ups）; 
 
 session.save（user）; 
 tx.commit（）; 
  

In database, I have following three tables, where User and Profile have many-to-many relationship and joined with User_Profile as follow:

User                User_Profile            Profile
----                ------------            ------- 
user_id             user_id                 profile_id
user_name           profile_id              profile_description
user_time

Class UserHbm and ProfileHbm are used:

@Entity
@Table(name = "User")
public class UserHbm {

    @Id
    @GeneratedValue(generator = "id-generator")
    @GenericGenerator(name = "id-generator",
            strategy = "com.xx.xxx.XXXSequenceGenerator", 
            parameters = { @Parameter(name = "sequenceName", value = "User") })
    @Column(name = "user_id")
    private long user_id;   

    @Column
    private String user_name; 

    @Column
    private Date user_time; 

    @ManyToMany(cascade = CascadeType.REFRESH, fetch = FetchType.EAGER)
    @JoinTable(name="User_Profile", 
            joinColumns = { @JoinColumn(name = "identityProfileID") },
            inverseJoinColumns={@JoinColumn(name="profile_id")})
    private Set<ProfileHbm> profiles = new HashSet<ProfileHbm>();

    //irrelevant other codes

}

@Entity
@Table(name = "Profile")
public class ProfileHbm {

    @Id
    @GeneratedValue(generator = "id-generator")
    @GenericGenerator(name = "id-generator",
            strategy = "com.xx.xxx.XXXSequenceGenerator", 
            parameters = { @Parameter(name = "sequenceName", value = "Profile") })
    @Column(name = "profile_id")
    private long profile_id;    

    @Column 
    private String profile_description;   

    //irrelevant other codes

}

So far, everything is fine until a new requirement comes up: put user_time into User_Profile so that the schema looks like:

User                User_Profile            Profile
----                ------------            ------- 
user_id             user_id                 profile_id
user_name           profile_id              profile_description
user_time           user_time

Could anyone could show me how to achieve this?

Do I have to create another intermediary HBM to do this?

解决方案

A solution is to create a new entity for UserProfile join table.
Set a OneToMany relationship from User entity to new UserProfile entity and a OneToMany from Profile to User_Profile.
You will have to create an additional class, let say UserProfilePk, for the User_Profile entity for the composite index composed of user_id and profile_id.

@Embeddable
public class UserProfilePk {
  @ManyToOne
  private User

  @ManyToOne
  private Profile
}

Then you have to use that class for the User_Profile index:

@Entity
public class UserProfile {
  @EmbeddedId
  private UserProfilePk pk;

  @Column(name = "user_time")
  private Date userTime;

}

Your class User:

@Entity
public class User {
  @Id
  private Long id;

  private String name;

  private Date userTime;

  @OneToMany(mappedBy = "pk.user", cascade=CascadeType.ALL)
  private Set<UserProfile> userProfiles;
}

And the class Profile:

@Entity
public class Profile {
  @Id
  private Long id;

  private String description;

  @OneToMany(mappedBy = "pk.profile")
  private Set<UserProfile> userProfiles;
}

And here below the code to save a User and an associated Profile:

Configuration configuration = new Configuration();
configuration.configure("hibernate.cfg.xml");
ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();
SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);
Session session = sessionFactory.getCurrentSession();

User user = new User();
user.setId(1l);
user.setName("Scott");
user.setUserTime(new Date());
Profile profile = new Profile();
profile.setId(1l);
profile.setDescription("some user");

Transaction tx = session.beginTransaction();     
session.save(profile);

UserProfilePk pk = new UserProfilePk();
pk.setProfile(profile);
pk.setUser(user);

UserProfile userProfile = new UserProfile();
userProfile.setPk(pk);
userProfile.setUserTime(new Date());

Set<UserProfile> ups = new HashSet<>();
ups.add(userProfile);    
user.setUserProfiles(ups);

session.save(user);
tx.commit();

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