IllegalArgumentException: expecting IdClass mapping

Question

During deploying my app I occurs on that exception. I have a lot of class in my app and I dont know where I must to place @IdClass and what does this exception

Answer 1

@IdClass annotation is used to define the Class that contains the id. i.e. This is generally used in case defining a compound key. i.e. a key composite of more than one attribute. If that is the case, than this is how we do. take a look at following example.. we define a class as IdClass and use @Id's to define varrious Ids for thisIdClass`.

Example :

@Entity
@IdClass(AssignedRoleId.class)
public class AssignedRole
{
  @Id
  @ManyToOne
  private User userId;

  @Id
  @ManyToOne  
  private Role roleId;

  private Date dateAssigned;
}

Hope this helps.