Question

I have two entities, Entity1 and Entity2, on a one to many relationship. On Entity1 I have a map which contains entries.

The code I use to persist a new Entity1 with some Entity2 on the map is like this:

   Entity1 e1 = new Entity1();      Entity2 e2 = null;      e1.setE2s(new HashMap<String, Entity2>());    for (String key : someKeySet()){       e2 = new Entity2();       e2.setCode(key);                             e2.setSwhon(true);               e2.setE1(e1);       e1.getE2s(key, e2);              em.persist(e1.getE2s().get(key));               }            em.persist(e1);     em.flush(); 

and here is a exctract of the entities:

@Entity @Table(name = 'wm_Entities1')   public class Entity1 implements Serializable {      private static final long serialVersionUID = 6592708276573465599L;      private Map<String, Entity2> e2s;    private Long id;      @Id      @GeneratedValue(strategy=GenerationType.TABLE)      public long getId() {       return id;      }      public void setId(long id) {       this.id = id;      }      public void setE2s(Map<String, Entity2> e2s){         this.e2s = e2s;    }           @OneToMany(mappedBy = 'e1', fetch = FetchType.EAGER)      public Map<String, Entity2> getE2s() {       return e2s;      }   } 

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@Entity @Table(name = 'wm_Entities2') public class Entity2 implements Serializable {       private static final long serialVersionUID = -6131765066573346790L;      private long id;     private Entity1 e1;     @Id     @GeneratedValue(strategy=GenerationType.TABLE)     public long getId() {         return id;     }      public void setId(long id) {         this.id = id;     }     @ManyToOne()     @JoinColumn(name='e1_id')     public Entity1 getE1() {         return this.e1;     }     public void setE1(Entity1 e1) {         this.e1 = e1;     } } 

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This seems to work fine since it inserts both entities on the pg database, but the catch is that it is not creating-saving the MapKey of the e2 on the database (theoretically JPA generates this key), so when I get the e1 back, and I try to get the e2s map from it, I have a:

javax.ejb.EJBException: org.hibernate.HibernateException: null index column for collection:

How can I get this MapKey saved??

Note: I’m using JavaEE with JPA/Hibernate, running over JBoss 4.2, with PGSQL DB.

Answer 1

There are some oddities in your code… But it seems that you should add a @MapKey annotation in Entity1:

(snippet) @OneToMany(mappedBy = 'e1', fetch = FetchType.EAGER) @MapKey(name='iCantFigureTheRightPropertyName') public Map<String, Entity2> getE2s() {       return e2s;   }