从调用返回另一个代理的Java.lang.reflect.Proxy在赋值时导致ClassCastException

Question

所以我正在玩geotools,我想我会代理他们的一个数据访问类,并跟踪它们在代码中的使用方式.

我编写了一个动态代理并在其中包含了一个FeatureSource(接口),并且很高兴.然后我想看看一些由featureSource返回,以及在传递对象,因为FeatureSource做的主要工作是返回的FeatureCollection(FeatureSource类似于一个SQL数据源,并以的FeatureCollection SQL语句).

在我的InvocationHandler我刚刚通过的调用底层对象,打印出目标类/方法/指定参数和结果,我去了,但是对于返回的FeatureCollection(另一个接口)调用,我裹着该对象在我的代理服务器(在相同的类,但一个新的实例,应该不重要吗？)并返回它.BAM!Classcast异常:

java.lang.ClassCastException: $Proxy5 cannot be cast to org.geotools.feature.FeatureCollection  
    at $Proxy4.getFeatures(Unknown Source)  
    at MyClass.myTestMethod(MyClass.java:295)  

调用代码:

FeatureSource<SimpleFeatureType, SimpleFeature> featureSource = ... // create the FS
featureSource = (FeatureSource<SimpleFeatureType, SimpleFeature>) FeatureSourceProxy.newInstance(featureSource, features);
featureSource.getBounds();// ok
featureSource.getSupportedHints();// ok

DefaultQuery query1 = new DefaultQuery(DefaultQuery.ALL);
FeatureCollection<SimpleFeatureType, SimpleFeature> results = featureSource.getFeatures(query1); //<- explosion here

代理人:

public class FeatureSourceProxy  implements java.lang.reflect.InvocationHandler {

private Object target;
private List<SimpleFeature> features;

public static Object newInstance(Object obj, List<SimpleFeature> features) {
return java.lang.reflect.Proxy.newProxyInstance(
    obj.getClass().getClassLoader(), 
    obj.getClass().getInterfaces(), 
    new FeatureSourceProxy(obj, features)
);
}

private FeatureSourceProxy(Object obj, List<SimpleFeature> features) {
this.target = obj;
this.features = features;
}

public Object invoke(Object proxy, Method m, Object[] args)throws Throwable{
Object result = null;
try {
    if("getFeatures".equals(m.getName())){ 
        result = interceptGetFeatures(m, args);
    }
    else{
        result = m.invoke(target, args);
    }
} 
catch (Exception e) {
    throw new RuntimeException("unexpected invocation exception: " +  e.getMessage(), e);
} 
return result;
}

private Object interceptGetFeatures(Method m, Object[] args) throws Exception{
    return newInstance(m.invoke(target, args), features);
}

}

是否有可能从代理接口动态返回接口代理,或者我做错了什么？干杯!

Answer 1

Class.getInterfaces()仅返回类实现的DIRECTLY接口.您需要一个传递闭包来获取所有接口.

UPDATE

例:

private static Class<?>[] getInterfaces(Class<?> c) {
    List<Class<?>> result = new ArrayList<Class<?>>();
    if (c.isInterface()) {
        result.add(c);
    } else {
        do {
            addInterfaces(c, result);
            c = c.getSuperclass();
        } while (c != null);
    }
    for (int i = 0; i < result.size(); ++i) {
        addInterfaces(result.get(i), result);
    }
    return result.toArray(new Class<?>[result.size()]);
}

private static void addInterfaces(Class<?> c, List<Class<?>> list) {
    for (Class<?> intf: c.getInterfaces()) {
        if (!list.contains(intf)) {
            list.add(intf);
        }
    }
}

您可能还需要"解开"作为参数传递的代理.