Hidden Features of Google Guice [closed]

Question

Google Guice provides some great dependency injection features.

I came across the @Nullable feature recently which allows you to mark constructor arguments as optional (permitting null) since Guice does not permit these by default:

e.g.

public Person(String firstName, String lastName, @Nullable Phone phone) {     this.firstName = checkNotNull(firstName, "firstName");     this.lastName = checkNotNull(lastName, "lastName");     this.phone = phone; } 

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

What are the other useful features of Guice (particularly the less obvious ones) that people use?

Answer 1

None of 'em are intended to be hidden, but these are my favorite 'bonus features' in Guice:

• Guice can inject a TypeLiteral<T>, effectively defeating erasure.
• TypeLiteral can do generic type resolution: this tells you that get() on a List<String> returns an Iterator<String>.
• Types is a factory for implementations of Java's generic type interfaces.
• Grapher visualizes injectors. If your custom provider implements HasDependencies, it can augment this graph.
• Modules.override() is incredibly handy in a pinch.
• Short syntax for defining parameterized keys: new Key<List<String>>() {}.
• Binder.skipSources() lets you to write extensions whose error messages track line numbers properly.
• The SPI. Elements.getElements() breaks a module into atoms and Elements.getModule() puts them back together.
• If you implement equals() and hashCode() in a Module, you can install that module multiple times without problem.