Hibernate Annotatoin - How to Join Three Tables with many to many relationship

问题

1. I have 3 Entity USER, APPLICATION, and ROLE .

   1. I want there IDs to be joined in a table named USER_APP_ROLE(user_ID, application_ID, role_ID) with many to many relationship between them.
   2. Reason I want this structure is- I have requirement of allowing the user to work on multiple application with multiple roles.
   3. I have done the following codes:

   User.java @ManyToMany (targetEntity=Role.class) @JoinTable(name="USER_APPLICATION_ROLE", joinColumns=@JoinColumn(name="USER_ID"), inverseJoinColumns=@JoinColumn(name="ROLE_ID")) private Collection roles;

     @ManyToMany (targetEntity=Application.class)
     @JoinTable(name="USER_APPLICATION_ROLE",
     joinColumns=@JoinColumn(name="USER_ID"),
     inverseJoinColumns=@JoinColumn(name="APPLICATION_ID"))
     private Collection<Application> applications;
   
     Role.java
     @ManyToMany(mappedBy="roles", targetEntity=User.class)
     private Collection<User> users = new ArrayList<User>();
   
     Application.java
     @ManyToMany(mappedBy="applications", targetEntity=User.class)
     private Collection<User> users = new ArrayList<User>();
   

   1. When I tried to run the following test:

   user.getRoles().add(role1); user.getRoles().add(role2);

   role1.getUsers().add(user); role1.getUsers().add(user);

   role2.getUsers().add(user); role2.getUsers().add(user);

   user.getApplications().add(app1); user.getApplications().add(app2);

   app1.getUsers().add(user); app2.getUsers().add(user);

   ......

   session.beginTransaction(); session.save(user); session.save(role1); session.save(role2); session.save(app1); session.save(app2);

   I get the following error:
   
   
   
         Hibernate: select seq_cm_user.nextval from dual
          Hibernate: select seq_role.nextval from dual
   Hibernate: select seq_role.nextval from dual
   Hibernate: select seq_application.nextval from dual
   Hibernate: select seq_application.nextval from dual
   Hibernate: insert into CM_USER (EMAIL, FIRST_NAME, LAST_NAME, MIDDLE_NAME, USERNAME, ID) values (?, ?, ?, ?, ?, ?)
   Hibernate: insert into CM_ROLE (DESCRIPTION, ID) values (?, ?)
   Hibernate: insert into CM_ROLE (DESCRIPTION, ID) values (?, ?)
   Hibernate: insert into CM_APPLICATION (CODE, DESCRIPTION, ID) values (?, ?, ?)
   Hibernate: insert into CM_APPLICATION (CODE, DESCRIPTION, ID) values (?, ?, ?)
   Hibernate: insert into USER_APPLICATION_ROLE (USER_ID, APPLICATION_ID) values (?, ?)
   Hibernate: insert into USER_APPLICATION_ROLE (USER_ID, APPLICATION_ID) values (?, ?)
   Exception in thread "main" org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch update
       at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:96)
       at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:66)
       at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:275)
       at org.hibernate.jdbc.AbstractBatcher.prepareStatement(AbstractBatcher.java:114)
       at org.hibernate.jdbc.AbstractBatcher.prepareStatement(AbstractBatcher.java:109)
       at org.hibernate.jdbc.AbstractBatcher.prepareBatchStatement(AbstractBatcher.java:244)
       at org.hibernate.persister.collection.AbstractCollectionPersister.recreate(AbstractCollectionPersister.java:1179)
       at org.hibernate.action.CollectionRecreateAction.execute(CollectionRecreateAction.java:58)
       at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:273)
       at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:265)
       at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:188)
       at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:321)
       at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:51)
       at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1216)
       at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:383)
       at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:133)
       at com.hp.gdas.capman.HibernateTest.main(HibernateTest.java:73)
   Caused by: java.sql.BatchUpdateException: ORA-01400: cannot insert NULL into ("SYSTEM"."USER_APPLICATION_ROLE"."ROLE_ID")
   
       at oracle.jdbc.driver.DatabaseError.throwBatchUpdateException(DatabaseError.java:343)
       at oracle.jdbc.driver.OraclePreparedStatement.executeBatch(OraclePreparedStatement.java:10657)
       at org.hibernate.jdbc.BatchingBatcher.doExecuteBatch(BatchingBatcher.java:70)
       at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:268)
       ... 14 more
   

   6.I might have doing this in wrong direction.Please help and suggest me any alternative if i m totally doing in wrong way.Any help is appreciated.

thanks.

回答1:

It seems that you want the USER_APPLICATION_ROLE table to contain the assignment of a Role to a User in an Application. But that's not what your mapping does. What it does is use this table to contain the roles of a user (ignoring the application), and also the applications of a user (ignoring the role).

Your mapping is thus wrong. You need to map the USER_APPLICATION_ROLE table as an entity, since it's not a pure join table between two entities. You could name it UserApplicationRole for example. A User would have a OneToMany association with UserApplicationRole. UserApplicationRole would have a ManyToOne association with User, as well as with Role and with Application. And I strongly suggest you to add an automatically generated ID column to this table, just like for all your entities.

来源：https://stackoverflow.com/questions/20918513/hibernate-annotatoin-how-to-join-three-tables-with-many-to-many-relationship