/** * Resolve the type arguments of the given generic interface against the given target class which * is assumed to implement the generic interface and possibly declare concrete types for its type * variables. * * @param clazz the target class to check against * @param genericIfc the generic interface or superclass to resolve the type argument from * @return the resolved type of each argument, with the array size matching the number of actual * type arguments, or <code>null</code> if not resolvable */ public static Class<?>[] resolveTypeArguments(Class<?> clazz, Class<?> genericIfc) { return doResolveTypeArguments(clazz, clazz, genericIfc); }
private static Class<?>[] doResolveTypeArguments( Class<?> ownerClass, Class<?> classToIntrospect, Class<?> genericIfc) { while (classToIntrospect != null) { if (genericIfc.isInterface()) { Type[] ifcs = classToIntrospect.getGenericInterfaces(); for (Type ifc : ifcs) { Class<?>[] result = doResolveTypeArguments(ownerClass, ifc, genericIfc); if (result != null) { return result; } } } else { Class<?>[] result = doResolveTypeArguments( ownerClass, classToIntrospect.getGenericSuperclass(), genericIfc); if (result != null) { return result; } } classToIntrospect = classToIntrospect.getSuperclass(); } return null; }
private static Class<?>[] doResolveTypeArguments( Class<?> ownerClass, Type ifc, Class<?> genericIfc) { if (ifc instanceof ParameterizedType) { ParameterizedType paramIfc = (ParameterizedType) ifc; Type rawType = paramIfc.getRawType(); if (genericIfc.equals(rawType)) { Type[] typeArgs = paramIfc.getActualTypeArguments(); Class<?>[] result = new Class[typeArgs.length]; for (int i = 0; i < typeArgs.length; i++) { Type arg = typeArgs[i]; result[i] = extractClass(ownerClass, arg); } return result; } else if (genericIfc.isAssignableFrom((Class<?>) rawType)) { return doResolveTypeArguments(ownerClass, (Class<?>) rawType, genericIfc); } } else if (ifc != null && genericIfc.isAssignableFrom((Class<?>) ifc)) { return doResolveTypeArguments(ownerClass, (Class<?>) ifc, genericIfc); } return null; }