How do i return a proxied object from provider ?

[lei wang]

I want to add an interceptor to a 3rd party class. Since it does not have a no-arg constructor, I'd have to use a provider to create an instance. But it seems that provider returns a raw object (no proxy), and I can't intercept it. Do i miss something? How can I add an interceptor to a class without no-arg constructor ? Here is a snippet..

class Foo {

    public Foo(int value) {...}

    public void exec() {...}

}

class Bar {

     public void bar() {...}

}

class FooBarModule extends AbstractModule {

    protected void configure() {

        bind(Foo.class).toProvider(FooProvider.class);

        bind(Bar.class);

         bindInterceptor(Matchers.subclassesOf(Foo.class).or(Matchers.subclassesOf(Bar.class)), Matchers.any(), new FooBarInterceptor());

    }

}

class FooMain {

    public static void main(String[] args) {

       Injector injector = Guice.createInjector(new FooModule());

       Foo fooObj = injector.getInstance(Foo.class);

       fooObj.exec();           // FooBarInterceptor is NOT triggered, because fooObj is a raw object.

       Bar barObj = injector.getInstance(Bar.class);

       barObj.bar();             // FooBarInterceptor is triggeredas expected. barObj is a Guice proxied object

}

[lei wang]

class FooProvider implements Provider<Foo> {

    public Foo get() {

        return new Foo(10);

[Thomas Broyer]

Could you maybe create a Foo subclass?

class SubFoo extends Foo {

  public SubFoo() {

    super(10);

  }

}

…

bind(Foo.class).to(SubFoo.class);

bindInterceptor(…)…

[lei wang]

If I have to, that would be one option.

But I am wondering why Guice does not add a proxy to the objects which are returned from a Provider. After all, Guice calls Provider.get(), and it does have a chance to add a proxy. Because I get the object through injector.getInstance(), it is confusing that some have proxies, and some don't depending on they are created behind scene.

[Thomas Broyer]

AFAIK, Guice doesn't create a proxy, it synthesizes a subclass that overrides matched methods and then instantiate them instead of the original class.

[lei wang]

Sorry I might use the term "proxy" loosely. What I meant is that - if an object is instantiated by Guice (not through a Provider), the object is enhanced by Guice, and the string rep of the object has $$EnhancerByGuice$$.... But if an object is created by a Provider, it is not enhanced by Guice.

Is there an API to make a provider-instantiated object to be "enhanced by Guice" ?

Thank you very much for your responses.