[WINK-363] Failure to find array entity providers (such as ByteArrayProvider) in Java 7

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.2
• Fix Version/s: 1.3
• Component/s: Providers

Environment

Linux, Java 1.7.0-b147

• Assignee: Unassigned
• Reporter: Georg Sander
• Created: 02/Mar/12 11:53
• Updated: 13/Jul/13 20:13
• Resolved: 02/Aug/12 00:36

Description

The ByteArrayProvider is properly registered and is found through ProvidersRegistry in Java 6,but not in Java 7. The effect is a consequence of Java bug http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5041784 which got fixed in Java 7. It can also affect other array entity providers.

Explanation:

ProvidersRegistry collects the providers for the target type byte[] by checking whether the provider type and the target type are assignable. The corresponding utilities are in GenericsUtils. To determine the provider type, GenericsUtil.getGenericInterfaceParamType retrieves the type from the generic interfaces of ByteArrayProvider. The type parameters in the generic interfaces are represented as java.lang.reflect.Type in Java 6 but as java.lang.Class in Java 7. As consequence, the method GenericsUtils.isAssignableFrom fails to see that the type parameter is an array, hence it returns that byte[] is not assignable to the retrieved type of ByteArrayProvider.

Here is a simple Java program that explains the difference between Java 6 and Java 7.

In Java 6, the output is:

Type Parameter byte[]
Type Parameter class class sun.reflect.generics.reflectiveObjects.GenericArrayTypeImpl
Is Generic Array true

In Java 7, the output is:

Type Parameter class [B
Type Parameter class class java.lang.Class
Is Generic Array false

import java.lang.reflect.GenericArrayType;

import java.lang.reflect.ParameterizedType;

import java.lang.reflect.Type;

public class Test
{

  public static void main(String[] args) {
    Class cls = ByteArrayProvider.class;
    Type[] interfaces = cls.getGenericInterfaces();
    for (Type type : interfaces) {
      if (type instanceof ParameterizedType) {
        ParameterizedType pType = (ParameterizedType)type;
        Type t = pType.getActualTypeArguments()[0];
        System.err.println("Type Parameter " + t);
        System.err.println("Type Parameter class " + t.getClass());
        System.err.println("Is Generic Array " + (t instanceof GenericArrayType));
      }
    }
  }
}

interface MessageBodyWriter<T> { }

class ByteArrayProvider implements MessageBodyWriter<byte[]> { }

I suggest the following fix in GenericsUtils (tested locally in Wink 1.1.3):

GenericsUtils.isAssignableFrom

    public static boolean isAssignableFrom(Type type, Class<?> cls) {
        if (cls.isArray()) {
            if (type instanceof GenericArrayType) {
                GenericArrayType genericArray = (GenericArrayType)type;
                Class<?> componentType = cls.getComponentType();
                return isAssignableFrom(genericArray.getGenericComponentType(), componentType);
            }
            else if ((type instanceof Class<?>) && ((Class<?>)type).isArray()) {
                Class<?> componentType1 = ((Class<?>)type).getComponentType();
                Class<?> componentType2 = cls.getComponentType();
                return isAssignableFrom(componentType1, componentType2);
            }
        } else {
            if (type instanceof GenericArrayType == false) {
                Class<?> classType = getClassType(type, null);
                if (classType == Object.class || classType.isAssignableFrom(cls)) {
                    return true;
                }
            }
        }
        return false;
    }