If I'm correct, we're not suppose to investigate and discuss the implementation details of RI. Sounds it is violate our independent implemenation's goal.
Best Regards Sean, Xiao Xia Qiu 2009/7/8 oleg babul <oleg...@gmail.com>: > To find entry in the HashMap RI performs: > 1) Check that entry.hash==key.hashCode() (entry - hash map entry) > 2) Check that entry.key == key or (key!=null && key.eqauls(entry.key)) > > hm.get(proxyInstance); returns !=null object because entry.key == key > in the 2) and equals doesn't perform. > > Oleg > > On Wed, Jul 8, 2009 at 8:34 AM, Regis<xu.re...@gmail.com> wrote: >> Jim Yu wrote: >>> >>> 2009/6/18 Regis <xu.re...@gmail.com> >>> >>>> Jim Yu wrote: >>>> >>>>> 2009/6/18 Regis <xu.re...@gmail.com> >>>>> >>>>> Jim Yu wrote: >>>>>> >>>>>> Hi all, >>>>>>> >>>>>>> There is an interesting edge case in HashMap. If we use a proxy object >>>>>>> as >>>>>>> the key to put something into HashMap, we will fail to retrieve the >>>>>>> value >>>>>>> by >>>>>>> using that key. But RI works well for this case. Here is a test case >>>>>>> below >>>>>>> to present the problem. I found the root cause of the failure for our >>>>>>> HashMap is that proxyInstance.equals(proxyInstance) returns false >>>>>>> which >>>>>>> sounds strange but appears work correctly as both Harmony and RI >>>>>>> behave >>>>>>> so. >>>>>>> >>>>>>> It's very interesting behaviors, seems like RI did it intended, are >>>>>> >>>>>> there >>>>>> any cases we need proxyInstance.equals(proxyInstance) return false? >>>>>> >>>>> >>>>> I think it is reasonable to return false here since spec mentioned for >>>>> proxy >>>>> instance that "An invocation of the hashCode, equals, or toString >>>>> methods >>>>> declared in java.lang.Object on a proxy instance will be encoded and >>>>> dispatched to the invocation handler's invoke method" So the meaning of >>>>> equals method seems has been changed by the invoke here: ) >>>>> >>>>> >>>>>> I suspect RI has made some special approaches to match the key when >>>>>> the >>>>>> >>>>>>> key >>>>>>> is a proxy object. So I would be inclined to follow RI's behavior in >>>>>>> this >>>>>>> case. Any thoughts here? >>>>>>> >>>>>>> I think if proxyInstance.equals(proxyInstance) return false is >>>>>> >>>>>> reasonable, >>>>>> we should do some tricks to make HashMap work with Proxy. And does >>>>>> Proxy >>>>>> object work well with other collections which used equals to retrieve >>>>>> object >>>>>> from collection? >>>>>> >>>>>> >>>>> Agree. I have made a patch to do the trick so as to follow RI's >>>>> behavior. >>>>> >>>> The patch looks good for me, applied at r786015, please verify. >>> >>> >>> Verified at r786379. Thanks, Regis. >>> >>>> >>>> >>>>> >>>>>> I have raised a JIRA at >>>>>>> >>>>>>> https://issues.apache.org/jira/browse/HARMONY-6237for this issue. >>>>>>> >>>>>>> >>>>>>> public interface MockInterface { >>>>>>> public String mockMethod(); >>>>>>> } >>>>>>> >>>>>>> public class MockClass implements MockInterface { >>>>>>> public String mockMethod() { >>>>>>> return "This is a mock class."; >>>>>>> } >>>>>>> } >>>>>>> >>>>>>> import java.lang.reflect.InvocationHandler; >>>>>>> import java.lang.reflect.Method; >>>>>>> import java.lang.reflect.Proxy; >>>>>>> import java.util.HashMap; >>>>>>> import java.util.Map; >>>>>>> >>>>>>> public class TestProxy implements InvocationHandler { >>>>>>> >>>>>>> Object obj; >>>>>>> >>>>>>> public TestProxy(Object o) { >>>>>>> obj = o; >>>>>>> } >>>>>>> >>>>>>> public Object invoke(Object proxy, Method m, Object[] args) >>>>>>> throws Throwable { >>>>>>> >>>>>>> Object result = null; >>>>>>> >>>>>>> try { >>>>>>> >>>>>>> result = m.invoke(obj, args); >>>>>>> >>>>>>> } catch (Exception e) { >>>>>>> e.printStackTrace(); >>>>>>> } finally { >>>>>>> } >>>>>>> return result; >>>>>>> } >>>>>>> >>>>>>> public static void main(String[] argv) throws Exception { >>>>>>> >>>>>>> MockInterface proxyInstance = (MockInterface) >>>>>>> Proxy.newProxyInstance( >>>>>>> MockInterface.class.getClassLoader(), >>>>>>> new Class[] { MockInterface.class }, new TestProxy( >>>>>>> new MockClass())); >>>>>>> >>>>>>> Map hm = new HashMap(); >>>>>>> >>>>>>> hm.put(proxyInstance, "Value"); >>>>>>> >>>>>>> Object o = hm.get(proxyInstance); >>>>>>> >>>>>>> System.out.println("Value got for proxy object key:" + o); >>>>>>> >>>>>>> System.out.println(proxyInstance.equals(proxyInstance)); >>>>>>> >>>>>>> } >>>>>>> } >>>>>>> >>>>>>> Output >>>>>>> Harmony: >>>>>>> Value got for proxy object key:null >>>>>>> false >>>>>>> >>>>>>> RI: >>>>>>> Value got for proxy object key:Value >>>>>>> false >>>>>>> >>>>>>> >>>>>>> -- >>>>>> >>>>>> Best Regards, >>>>>> Regis. >>>>>> >>>>>> >>>>> >>>>> >>>> -- >>>> Best Regards, >>>> Regis. >>>> >>> >>> >>> >> >> I found this patch involve serious performance regression. Because >> Proxy.isProxyClass() synchronized on a instance "proxyCache", which is a >> static field of Proxy, so all HashMap.get() will contend for this lock. So >> is there other way to test whether a class is Proxy class or >> Proxy.isProxyClass() could avoid to use lock of static field? >> >> >> -- >> Best Regards, >> Regis. >> >
