Is there something like getInstaceOnlyIfCreated on the Injector?

[David Leonhartsberger]

I was wondering If I can check on the Injector if an instance of some class/interface was already or 

have a method that does only return the instance if it was already created.

Why I need this:

In the shutdown of my integration tests I clean up all instances in the Service that I am testing.

In most of the tests however some dependencies (TimeoutManager)  are never instaniated but will now in the shutdown code only to destroy them right afterwards, this takes some time and causes exceptions and a lot of confusing output in the test log.

     /**

     * Called by junit after each integration test.

     */

    @After

    public final void afterIntegrationTest() {

        

     if (service != null) {

         service.destroy();

     }

            

           // more shutdow

    }

private void tryCloseInstances() {

               // current code 

        TimeoutManager timeoutManager = injector.getInstance(TimeoutManager.class);

        AutoCloseables.tryClose(timeoutManager);

              // what i would like to do               

          TimeoutManager timeoutManager = injector.getInstanceOnlyIfCreated(TimeoutManager.class);

          AutoCloseables.tryCloseIfNotNull(timeoutManager);

    }

Br

David L. 

[Sam Berlin]

There's no way to do this in the injector, because "creation" of an object depends on the scope.  However, you could build something using a ProvisionListener and some knowledge of your object graph and capture instances as they're created.

sam

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[Nate Bauernfeind]

In my opinion, you have a few options:

1) You can create a class (and inject it) that optionally injects all of the things you might shutdown, a la something like this:

class TestShutdownHelper {
    @Inject(optional = true) public TimeoutManager timeoutManager = null;
    ...
 
    public void cleanUp() {
      AutoCloseables.tryCloseIfNotNull(timeoutManager);
      // ...
    }
}

2) Or you could change the way that you do injection for things you want to be able to close and inject them with OptionalBinder:

http://google.github.io/guice/api-docs/latest/javadoc/com/google/inject/multibindings/OptionalBinder.html

You could then pull out Optional<TimeoutManager> instead (this is likely to be lots more overhead esp. if you're doing it only for tests).

3) And my last suggestion would be to use MulitBinder and have bind each of your Closeable classes to a Set<Closeable> -- then pull out the set from the injector, iterate, and close each bound instance.

https://github.com/google/guice/wiki/Multibindings

Nate

On Fri, Oct 10, 2014 at 9:48 AM, David Leonhartsberger <leoz...@gmail.com> wrote:

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