Hierarchical lookup

[Mariano Gonzalez]

Hello,

I want to perform a hierarchical lookup. Suppose I have the following code:

bind(Apple.class).in(Singleton.class);
bind(Banana.class).in(Singleton.class);
bind(Grape.class).in(Singleton.class);

Now suppose that Apple and Grape implement the JuiceFactory interface, which Banana does not.

How do I programmatically lookup all the JuiceFactory instances? In Spring there's a getBeansOfType() method which allows for any random hierarchical queries, I'm wondering how to achieve the same with Guice. Reason why I need this is that my modules will be pluggable so I don't know the fruits I'll be handling before hand. Also, I might later want to do a lookup by the HasSeed interface, where I also expect the Apple and Grape instances to be returned, so MultiBinder is not really an option.

Thanks! 

[Stephan Classen]

Multibindings are the way Guice is implementing plug-in mechanism.

The best I can think of is having a single SetBinder and add all pluggable classes there.
Then implement your own methods which iterate over all binded classes and filter for the criteria you need.

class Fruity {

@Inject Set<Object> fruits;

Set<HasSeed> getAllFruitsWithSeed() {
    Set<HasSeed> result = new HashSet<>();
    for (Object candidate : fruits) {
        if (candidate instanceof HasSeed) {
            result.add((HasSeed) candidate);
        }
    }
}

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