decorice

helper library to bind chain of decorators in guice

You have a chain of decorators (D2 -> D1 -> D0) to bind with Guice.

interface Foo { /* .... * }

class D2 implements Foo {
    D2(Foo decorated /* ... */) {/* ... */}
    /* ... */
}

class D1 implements Foo {
    D1(Foo decorated /* ... */) {/* ... */}
    /* ... */
}

class D0 implements Foo { /* ... */ }

Guice does not offer much syntactic sugar to help with binding such chain. (inspired by an answer posted on stackoverflow and [a blog] (http://www.mikevalenty.com/configuring-decorators-with-google-guice/) post) decorice complements Guice by helping you bind the chain with less boilerplate.

First, on each decorator, annotate the constructor parameter associated with the decorated instance with the @DecorateBy annotation passing the decorator class name as an attribute to the annotation (the decorator is oblivious to the concrete class it decorates at runtime):

class D2 implements Foo {
    D2(@DecoratedBy(D2.class) Foo decorated /* ... */) {/* ... */}
    /* ... */
}

class D1 implements Foo {
    D1(@DecoratedBy(D1.class) Foo decorated /* ... */) {/* ... */}
    /* ... */
}

Later, you bind the chain in a Module with:

install(new DecoratorModule() {{
    bind(Foo.class)
            .to(D0.class)
            .decoratedBy(
                    D2.class,
                    D1.class);
}});

The order of the classes on the call to the decoratedBy method defines the order of decorations.

Binding annotations, scopes, and keys are supported:

bind(Foo.class)
        .annotatedWith(SomeAnnotation.class)
        .to(D0.class);
install(new DecoratorModule() {{
    bind(Foo.class)
            .annotatedWith(SomeOtherAnnotation.class)
            .to(Key.get(Foo.class, SomeAnnotation.class))
            .decoratedBy(
                    D2.class,
                    D1.class)
            .in(Singleton.class);
}});

Limitations: does not support generics (yet)

Compatible with Guice 3.0