Google Guice, Interceptors and PrivateModules - module

Question

New poster here, hope I don't brake any rules :)
I am using PrivateModule in google-guice in order to have multiple DataSource's for the same environment. But I am having a hard time getting MethodInterceptor's to work inside the private modules.
Below is a simple test case that explains the "problem".
A simple service class would be:
interface Service {
String go();
}
class ServiceImpl implements Service {
#Override #Transactional
public String go() {
return "Test Case...";
}
}
The MyModule class would be:
class MyModule extends AbstractModule {
#Override
protected void configure() {
install(new PrivateModule() {
#Override
protected void configure() {
bind(Service.class).to(ServiceImpl.class);
bindInterceptor(
Matchers.any(),
Matchers.annotatedWith(Transactional.class),
new MethodInterceptor() {
#Override
public Object invoke(MethodInvocation i)
throws Throwable {
System.out.println("Intercepting: "
+ i.getMethod().getName());
return i.proceed();
}
});
expose(Service.class);
}
});
}
}
And the final test case:
public class TestCase {
#Inject Service service;
public TestCase() {
Guice.createInjector(new MyModule()).injectMembers(this);
}
public String go() {
return service.go();
}
public static void main(String[] args) {
TestCase t = new TestCase();
System.out.println(t.go());
}
}
You would expect the output to be:
Intercepting: go
Test Case...
But it doesn't happen, the interceptor is not used, ant only Test Case... is output.
If I bind/expose the ServiceImpl instead of the interface then it works.
Thanks in advance,
Regards,
LL

Answer 1

Well... I figured it out shortly after I posted the question :)
The problem is that you also need to expose() the ServiceImpl class.
So the bind/expose would be.
bind(ServiceImpl.class); // ServiceImpl annotated with #Singleton
bind(Service.class).to(ServiceImpl.class);
expose(ServiceImpl.class);
expose(Service.class);
Regards,
LL

Answer 2

You need to explicitly bind ServiceImpl in the private module. The problem with your existing code is that it inherits the binding for ServiceImpl from the parent module. From the PrivateModule docs,
Private modules are implemented using parent injectors. When it can satisfy their dependencies, just-in-time bindings will be created in the root environment. Such bindings are shared among all environments in the tree.
Adding this line should fix the problem:
bind(ServiceImpl.class);