Casting a Spring's Proxy object to the actual runtime class

Question

I'm using Spring, at one point I would like to cast the object to its actual runtime implementation.

Example:

Class MyClass extends NotMyClass {
    InterfaceA a;
    InterfaceA getA() { return a; }

    myMethod(SomeObject o) { ((ImplementationOfA) getA()).methodA(o.getProperty()); }
}

That yells a ClassCastException since a is a $ProxyN object. Although in the beans.xml I injected a bean which is of the class ImplementationOfA .

EDIT 1 I extended a class and I need to call for a method in ImplementationOfA. So I think I need to cast. The method receives a parameter.

EDIT 2

I better rip off the target class:

private T getTargetObject(Object proxy, Class targetClass) throws Exception {
    while( (AopUtils.isJdkDynamicProxy(proxy))) {
        return (T) getTargetObject(((Advised)proxy).getTargetSource().getTarget(), targetClass);
    }
    return (T) proxy; // expected to be cglib proxy then, which is simply a specialized class
}

I know it is not very elegant but works.

All credits to http://www.techper.net/2009/06/05/how-to-acess-target-object-behind-a-spring-proxy/ Thank you!

This is bad practice, the actual implementation class shouldn't be relevant. However, it is possible, depending on how is your proxy being created. — skaffman, May 12 '11 at 10:03
If you need to call a method on `ImplementationOfA`, then add that method to the `InterfaceA` interface, or define a second interface and add the method to that. — skaffman, May 12 '11 at 10:32
Well, I know it is not ideal, but the class I'm extending implements an Interface, and due to application requirements I cannot modify neither InterfaceA nor NotMyClass. — ssedano, May 12 '11 at 10:42
just a note: `while` does not loop in above code, `if` is enough. — igr, May 31 '13 at 11:06

Roberto Rosin · Answer 1 · 2019-10-02T18:24:56.523

14

Now you can use

AopTestUtils.getTargetObject(proxy)

.

The implementation is the same of @siulkilulki sugestion, but it's on Spring helper

edited Oct 02 '19 at 18:24

answered Sep 30 '19 at 21:05

Roberto Rosin

141
1
4

siulkilulki · Answer 2 · 2016-06-21T14:15:47.530

For me version from EDIT 2 didn't worked. Below one worked:

@SuppressWarnings({"unchecked"})
protected <T> T getTargetObject(Object proxy) throws Exception {
    while( (AopUtils.isJdkDynamicProxy(proxy))) {
        return (T) getTargetObject(((Advised)proxy).getTargetSource().getTarget());
    }
    return (T) proxy; // expected to be cglib proxy then, which is simply a specialized class
}

Usage:

    UserServicesImpl serviceImpl = getTargetObject(serviceProxy);
    serviceImpl.setUserDao(userDAO);

score -1 · Answer 3 · edited Jul 13 '19 at 01:10

Basically when you use AOP in Spring, Spring build a Proxy for you. You have two option:

when you apply an aspect on a bean that implements an interface, in this case Spring use JdkDynamicProxy
when your spring bean don't implements any interface and if you have cglib 2.2 in you classpath, consider that from spring 3.2.x you have cglib in the spring container by default, spring use a special proxy called CGLibProxy.

The key point here is that when an aspect is applied on your bean Spring will instance a proxy and if you try to perform a cast you will get an exception.

I hope tha this can help you

Casting a Spring's Proxy object to the actual runtime class

3 Answers3

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