Failure to find array entity providers (such as ByteArrayProvider) in Java 7
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Key: WINK-363
URL: https://issues.apache.org/jira/browse/WINK-363
Project: Wink
Issue Type: Bug
Components: Providers
Affects Versions: 1.1.3
Environment: Linux, Java 1.7.0-b147
Reporter: Georg Sander
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[]> { }
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I suggest the following fix in GenericsUtils (tested locally in Wink 1.1.3):
public static boolean isAssignableFrom(Type type, Class<?> cls) {
if (cls.isArray()) {
if (type instanceof GenericArrayType) {
// JDK 6 case
GenericArrayType genericArray = (GenericArrayType)type;
Class<?> componentType = cls.getComponentType();
return isAssignableFrom(genericArray.getGenericComponentType(),
componentType);
}
else if ((type instanceof Class<?>) && ((Class<?>)type).isArray()) {
// JDK 7 case
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;
}
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