Guice

Guice

(from Google Bob Lee's IoC)
Dependency Injection, DI
Inversion of Control, IoC

It's another IoC container, which like a cousin of Spring IoC.

• Spring uses xml, provide IoC, Aop and peripheral service;[*]Guice uses Annotatin, each has their strongpoint, it's hard to say which one is better

Just use them in proper place !

Usage 1:

//1) 
public interface MyService {
    void myMethod();
}

//2)
public class MyServiceImpl implements MyService {
    public void myMethod() {
        System.out.println("Hello, World!");
    }
}

//3) Add annotation of "@Inject"
public class Client {
    //If define @Inject for this field, the set method isn't required
    MyService service;

    @Inject
    void setService(MyService service) {
        this.service = service;
    }

    public void myMethod() {
        service.myMethod();
    }
}

//4) Like Spring's beans.xml
public class MyModule implements Module {
    public void configure(Binder binder) {
        binder.bind(MyService.class).to(MyServiceImpl.class).in(Scopes.SINGLETON);
    }
}

//5) 
public class Test {
    public static void main(String[] args) {
        //IoC Container, the heart of the Guice framework
        Injector injector = Guice.createInjector(new MyModule());
        
        Client client = injector.getInstance(Client.class);
        client.myMethod();
    }
}

Usage 2:

//1)
@ImplementedBy(MyServiceImpl.class)
public interface MyService {
    void myMethod();
}

//2)
public class MyServiceImpl implements MyService {
    public void myMethod() {
        System.out.println("Hello, World!");
    }
}

//3)
public class Client {
    @Inject
    private MyService service;

    public void myMethod() {
        service.myMethod();
    }
}

//4)
public class MyModule implements Module {
    public void configure(Binder binder) {}
}

//5) Test

Note: Some code snippet are from Robbin's Blog.