Synthesizing parameterized types for binding

[Tim Boudreau]

I'm working on Guice bindings for MongoDB's new async driver.  The goal is to be able to call, e.g.

mongoModule.bindCollection("myCollection", MyDocument.class)

and then be able to inject

@Named("myCollection") MongoCollection<MyDocument>

I have this working just fine, but I'm actually implementing the JDK's ParameterizedType to do it (code below).

Any reason this is a bad way to go about it, or that this approach might explode on some future version of Guice?  It appears to work fine - things are injected as they should be - but implementing ParameterizedType is a little out-there.

I did this for the older MongoDB driver by forcing the caller to pass a TypeLiteral, which is a bit ugly since they're also passing the type parameter as a Class object.  So this results in a nicer API.

Thanks,

Tim

                MongoTypedCollectionProvider<T> typedProvider = new MongoTypedCollectionProvider<T>(dbProvider, collection, type, knownProvider, opts, inits);

                Type t = new FakeType<>(type);

                Key<MongoCollection<T>> key = (Key<MongoCollection<T>>) Key.get(t, Names.named(bindingName));

                binder.bind(key).toProvider(typedProvider);

    static class FakeType<T> implements ParameterizedType {

        private final Class<T> genericType;

        public FakeType(Class<T> genericType) {

            this.genericType = genericType;

        }

        @Override

        public String getTypeName() {

            return MongoCollection.class.getName();

        }

        @Override

        public Type[] getActualTypeArguments() {

            return new Type[]{genericType};

        }

        @Override

        public Type getRawType() {

            return MongoCollection.class;

        }

        @Override

        public Type getOwnerType() {

            return null;

        }

    }

[Stuart McCulloch]

You could use Guice’s Types class to generate the parameterized type:

https://google.github.io/guice/api-docs/latest/javadoc/com/google/inject/util/Types.html#newParameterizedType-java.lang.reflect.Type-java.lang.reflect.Type…-

For example:

Types.newParameterizedType( MongoCollection.class, MyDocument.class );

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