[jboss-dev] generic collection item type

[Alexey Loubyansky]

Yes, it does work! Thanks!

I had to add a check that the interface implements the reference before 
calling locateActualType because in case of Comparable<T> and so on I 
would get NPE later. I checked out the trunk but it didn't build. So, 
here is the diff.

        Type[] interfaces = clazz.getGenericInterfaces();
        for (Type intf : interfaces)
-      {
-         Type result;
+      {
+         Class interfaceClass;
           if (intf instanceof Class)
           {
-            Class interfaceClass = (Class) intf;
-            result = locateActualType(reference, parameter, 
interfaceClass, intf);
-            if (result instanceof TypeVariable)
-               result = getParameter(clazz, type, (TypeVariable) result);
+            interfaceClass = (Class) intf;
           }
           else if (intf instanceof ParameterizedType)
           {
              ParameterizedType interfaceType = (ParameterizedType) intf;
-            Class interfaceClass = (Class) interfaceType.getRawType();
+            interfaceClass = (Class) interfaceType.getRawType();
+         }
+         else
+            throw new IllegalStateException("Unexpected type " + 
intf.getClass());
+
+         Type result = null;
+         if (reference.isAssignableFrom(interfaceClass))
+         {
              result = locateActualType(reference, parameter, 
interfaceClass, intf);
              if (result instanceof TypeVariable)
                 result = getParameter(clazz, type, (TypeVariable) result);
           }
-         else
-            throw new IllegalStateException("Unexpected type " + 
intf.getClass());
+
           if (result != null)
              return result;

Adrian wrote:
> On Mon, 2007-07-30 at 14:39 +0200, Alexey Loubyansky wrote:
>> Adrian wrote:
>>> Perhaps we can add that to the ClassInfo model?
>> That would be excellent.
>>
>>> if (classInfo.isCollection())
>>>    typeInfo = classInfo.getComponentType();
>>>
>>> and it would do all the hard work of locating the collection
>>> definition and retrieving the type.
>>>
>>> We could also do something similar for maps, i.e.
>>>
>>> if (classInfo.isMap())
>>> {
>>>    keyType = classInfo.getKeyType();
>>>    valueType = classInfo.getValueType();
>>> }
>> This one too!
>>
> 
> I've implemented this. It was actually easier
> than I thought once I got my head around it. :-)
> 
> See the bottom of IntrospectionTypeInfoFactoryImpl
> 
> The basic idea is to locate the Collection interface
> in the type hierarchy
> then work your way back mapping TypeVariables
> until you reach where the real type is specified.
> 
> Or failing that use the upper bounds of the
> last TypeVariable found.
> 
>> Thanks,
>> Alexey
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