[jboss-user] [JBoss Seam] - Re: Further extending an EntityHome

[matt.drees]

"damianharvey" wrote : Bingo. Cheers Matt. Worked a treat. Your first suggestion worked first time (always nice).
  | 
Cool

"damianharvey" wrote : 
  | Does anyone know what behaviour that the block of code in the Home object is trying to avoid? ie: why not just take the class rather than throw the exception?
  | 
I think perhaps you misread that code.  I'll post it here for reference:

  |    public Class<E> getEntityClass()
  |    {
  |       if (entityClass==null)
  |       {
  |          Type type = getClass().getGenericSuperclass();
  |          if (type instanceof ParameterizedType)
  |          {
  |             ParameterizedType paramType = (ParameterizedType) type;
  |             entityClass = (Class<E>) paramType.getActualTypeArguments()[0];
  |          }
  |          else
  |          {
  |             throw new IllegalArgumentException("Could not guess entity class by reflection");
  |          }
  |       }
  |       return entityClass;
  |    }
  | 

EntityHome needs to know what your entity's class is, so that it can create a new instance when needed.  What it does is check to see if you've set an entity class (which is usually, I imagine, only done if this Home was created by xml in components.xml).  If you haven't, it tries to guess the class by looking at the type parameter of the home instance's superclass.  

In your case, the superclass wasn't EntityHome, but BookingHome, which has no type parameter.  So, it couldn't get the class and threw an exception.

Make sense?

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