why does the method invoke() in InvocationHandler have an parameter Object proxy?

Question

When you r checking out that the method invoke(Object proxy, Method method, Object[] args) declaration & the doc statement,you will find that the input parameter proxy

proxy - the proxy instance that the method was invoked on

when I am doing a test on java dynamic proxy,I find this proxy is produced by vm.So I do want to know why the method invoke has this param,which is surely nothing except that is just an object ($proxy0 )but don't have the actual action for our usage?

Answer 1

This very useful if you have single invocation handle for multiple proxy objects. So you can use hash map to store proxy states information. For example - Mokito test framework store proxy invocation history.

Answer 2

if you are chinese ,you can read this article http://rejoy.iteye.com/blog/1627405

he makes a decompliation of $proxy0.class, you should know that $proxy0 extends Proxy

public final class $Proxy0 extends Proxy  
    implements UserService 

and there is a function in $proxy0:

public final void add()  
    {  
        try  
        {  
            //the h(invocationhandler) is in Proxy class,so we need pass this $proxy0 instance to super ,so the super(Proxy) can invoke($proxy0,method,args)
            super.h.invoke(this, m3, null);  
            return;  
        }  
        catch(Error _ex) { }  
        catch(Throwable throwable)  
        {  
            throw new UndeclaredThrowableException(throwable);  
        }  
    }