RESTEasy client that should use generics
I managed to get RESTEasy to work with generics (both lists and single objects) and parse the response to JAXB annotated classes by using the following code that uses reflection:

&lt;T&gt; List&lt;T&gt; getList(String path, List&lt;String[]&gt; params, final Class&lt;T&gt; clazz) {
    GenericType&lt;List&lt;T&gt;&gt; type = getListType(clazz);
    Response entity = getEntity(path, params);
    return entity.readEntity(type);
}

&lt;T&gt; T getObject(String path, List&lt;String[]&gt; params, final Class&lt;T&gt; type) {
    Response entity = getEntity(path, params);
    return (T)entity.readEntity(new GenericType(type) {});
}

private &lt;T&gt; GenericType&lt;List&lt;T&gt;&gt; getListType(final Class&lt;T&gt; clazz) {
    ParameterizedType genericType = new ParameterizedType() {
        public Type[] getActualTypeArguments() {
            return new Type[]{clazz};
        }

        public Type getRawType() {
            return List.class;
        }

        public Type getOwnerType() {
            return List.class;
        }
    };
    return new GenericType&lt;List&lt;T&gt;&gt;(genericType) { };
}