Pegar ID (primary key) usando Reflection

protected Class<?> getPrimaryKeyDeclaringClass(){
		   Class<?> type = entity.getClass();
		   
		    for (Field f : type.getDeclaredFields()) {
		        if (f.getAnnotation(Id.class) != null) {
		        	return f.getDeclaringClass();
		        }
		    }
		    
		    return null;		
	}



			//FIX-ME need to change this :(
			@SuppressWarnings("unchecked")
			@Override
			public T getRowData(String key) {				
				return getBaseService().findOne(  (PK) getPrimaryKeyDeclaringClass().cast(key) );
			}
			
			
			@SuppressWarnings("unchecked")
			@Override
			public Object getRowKey(T obj) {
				   PK id = null;
				   Class<?> type = obj.getClass();
				   
				    for (Field f : type.getDeclaredFields()) {
				        if (f.getAnnotation(Id.class) != null) {
				            String name = f.getName();
				            String method = "get" + name.substring(0, 1).toUpperCase() + name.substring(1);
				            try {
				                Method m = type.getDeclaredMethod(method, (Class<?>) null);
				                id = (PK) m.invoke(obj, (Object []) null);
				            } catch (Exception e) {
				                e.printStackTrace();
				            }
				        }
				    }
				    
				    return id;
			}