progress bars on guice get-instance call

[Geoff Groos]

Hey guys,

I'm wondering about the best way to go about getting a progress bar on the resolution of guice things.

Rougly speaking, if I have a dependency tree with

RootItem
   -> 1-to-1 instance-of Dependency-1,
   -> 1-to-1 instance-of Dependency-2
        -> 1-to-1 instance-of Grand-Child-Dep-2
   -> 1-to-1 instance-of Dependency-3
        -> 1-to-many instance-of GrandChildDep-3

and dependency-3's ctor looks like this:

public Dep3{
    @Inject
    public Dep3(List<Model> models){
        for(Model model : models){
            GrandChildDep3 deepdep = guiceProvidedFactory.createFor(model);
            //...
        }
    }
}

What would be the best process to make a progress bar for such a system?

I've got an object that I use for serialization that uses a stack to track progress. In this way we can have a tree like structure of tasks, so long as we can get the number of child tasks under any given task.

public NotifyingSerializer extends RealSerializer{

    ProgressBarUpdater updater;

    @Override
    public marshal(...){
        updater.pushNewTask(/*speculate, or use meta about the model, to guess at how many child-tasks this one has*/ 45);
        super.marshall(...);
        updater.popTask();
    }

    //similar for unmarshal
}

I'd like to use this same object for guice tasks.

The best I've been able to do so far is putting the pushTask call in a SPI ProvisionListener, and the corresponding popTask at the end of each constructor.

eg:

binder().bindListener(
        new AbstractMatcher<Binding<?>>() {
            Set<Class> types = ImmutableSet.of(
                    (Class) RootItem.class, Dependency1.class,
                    Dependency2.class, Dependency3.class,
                    GrandChildDep2.class, GrandChildDep3.class);
            @Override public boolean matches(Binding<?> binding) {
                return types.contains(binding.getKey().getTypeLiteral().getRawType());
            }
        },
        new ProvisionListener(){
            Class provisionedType = provision.getBinding().getKey().getTypeLiteral().getRawType();
            //do a filter to find out if this provision is just because of a factory call
            if(provision.getDependenyChain().stream().filter(dep -> dep.getDependency().getKey().getTypeLiteral().getRawType().equals(provisionedTyped)).size() == 1){

                updater.pushTask(/*use static knowledge to figure out how many subtasks this dep will have*/);

            }
        }
);

//...

public Class RootItem{

    @Inject
    public RootItem(Dependency1 dep1, Dependency2 dep2, Dependency3 dep3,
                    /*other misc items*/,
                    ProgressBarUpdater updater){
   
        //... ctor-things
        updater.popTask();
    }

}

This is not a great solution because

• it involves modifying a lot of production code to include the popTask line,
• In the event that the object is resolved without a progress-watching-provision-listener (IE, a component uses guice to resolve the component but doesnt include the provision listener that gives us the progress bars), there will be a popTask call with no prior pushTask call. I could handle this case, but it wouldn't be nice.

What I would really like is one of the following:

• an SPI object that would allow me to get something like onProvisionEnter and onProvisionExit
• a wrapper Provisioner for all provisioners, so it could contain similar code to whats in my above serializer-wrapper

Is there something I'm missing? Is there an existing elegant way to, from withen guice, get a piece of code executed when a component has been constructed?

Thanks for any help,

-Geoff

[Sam Berlin]

You can call provisionInvocation.provision() to manually do the provision.  ProvisionListener lets you hook into the entire provision lifecycle -- if you don't call provision() manually, Guice will do it for you.  You can also call it manually and do stuff before & after the provision.  (Provision == creation of the object & injection of its dependents.)

 sam

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