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Guice: Fast and Light Dependency Injection Container

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Guice is a new open-source Dependency Injection framework for Java 5 that is closing in on a 1.0 release. Guice is a very annotation-driven, lightweight framework that provides an alternative to Spring, for a certain set of features.

Guice, which is the depenecy injection engine in XWork, focuses on being small, fast, and requiring minimal code to use. The simple example from the Users’ Guide is:

With Guice, you implement modules. Guice passes a binder to your module, and your module uses the binder to map interfaces to implementations. The following module tells Guice to map Service to ServiceImpl in singleton scope:

public class MyModule implements Module {
 protected void configure(Binder binder) {
  binder.bind(Service.class)
  .to(ServiceImpl.class)
  .in(Scopes.SINGLETON);
  }
}

A module tells Guice what we want to inject. Now, how do we tell Guice where we want it injected? With Guice, you annotate constructors, methods and fields with @Inject.

public class Client {
  private final Service service;

  @Inject
 public Client(Service service) {
  this.service = service;
  }

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

The @Inject annotation makes it clear to a programmer editing your class which members are injected.For Guice to inject Client, we must either directly ask Guice to create an instance for us, or some other class must have Client injected into it.

Bob Lee, one of the project leads of Guice, has written a comparison piece of Spring and Guice.  In it he notes that Guice and Spring look very different, as Guice is focused on annotations.  Guice can be configured with strings, as in Spring, but they don't encourage it.  Guice requires Java 5 and supports generic types. 

Update:  Guice 1.0 has been released.

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Community comments

  • Congrats

    by Gavin King /

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    Congrats on this work, there's some really good ideas there :-)

  • struts2

    by Matt Giacomini /

    Your message is awaiting moderation. Thank you for participating in the discussion.

    Hey guys,

    This sounds interesting. Any links to where I can find any Guice+Struts2 integration docs/examples?

    Thanks,

    ~Matt

  • comparison to hivemind + tapestry ioc

    by Kristian Marinkovic /

    Your message is awaiting moderation. Thank you for participating in the discussion.

    i don't want to start a flame war, but how does Guice compare to Hivemind 2 (in beta) and Tapestry IOC (part of Tapestry 5). Both are fast and rely heavily on annotations too. Tapestry IOC for example is much more "lightweight" as it does not require to implement an interface for a module at all. Also Tapestry IOC configurations (returning new services) are much more natural to plain old java code :)

    g,
    kris

  • Re: comparison to hivemind + tapestry ioc

    by Jesse Kuhnert /

    Your message is awaiting moderation. Thank you for participating in the discussion.

    I think that there is enough room in this space still to have different implementations running around. It'll keep everything nice & honest in what is still arguably a fairly new programming paradigm for java. I for one am glad to see multiple versions that we can all learn from and evolve with. Er something like that anyways ;) Besides, we probably don't want to mess with Bob too much.heh...

  • Re: comparison to hivemind + tapestry ioc

    by Twice Tshwenyane /

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    +1
    As much as i like Spring, i don't think it's good for innovation if there is no competition. So hopefully there will be 1 or 2 things for Spring to learn or give them new ideas.
    Apart from that i think Spring is still very much useable and easy especially with tools like SpringIDE.

  • This framework, or somethign like it, should be in the JDK

    by Weiqi Gao /

    Your message is awaiting moderation. Thank you for participating in the discussion.

    I have always felt that an DI container should be included in the JDK. I have thought about suggesting that Spring's DI container be "standardized" but feared that such a suggestion would be perceived as a sabotage against Interface21.

    On a very practical level, I would feel a lot better to do an

    import java.lang.inject.Inject;


    than

    import com.google.inject.Inject;


    in my components.

    On a reuse level, this could eliminate the duplications in some of the half serious dependency injection frameworks in many other frameworks.

  • Re: struts2

    by Bob Lee /

    Your message is awaiting moderation. Thank you for participating in the discussion.

    There's a small example Struts 2 application in the repos and we talk about it in the user's guide.

  • Re: This framework, or somethign like it, should be in the JDK

    by Bob Lee /

    Your message is awaiting moderation. Thank you for participating in the discussion.

    Keep an eye on JSR 299. :)

  • Re: comparison to hivemind + tapestry ioc

    by Bob Lee /

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    Doesn't Hivemind use string identifiers? Also, "module" is the Guice equivalent of a configuration file. Guice does not require interfaces.

    Regarding performance, I have a small benchmark here. If you submit a Hivemind implementation, I'll happily include it.

  • I Like What I See

    by Steve Tekell /

    Your message is awaiting moderation. Thank you for participating in the discussion.

    I think the same things in Spring as you and Guice look like a great alternative, well for DI anyway. Sometimes I think Spring is the new Struts in it's domain. It has similar timing and popularity, and as time progesses it sure seams like there must be something much, much better. I'll be curious to see if Guice will be able to foster a community and the like to make it a viable long term alternative for rest of us.

    Congrats on 1.0!

    looking forward to many more,

    Steve

  • should say

    by Steve Tekell /

    Your message is awaiting moderation. Thank you for participating in the discussion.

    I (think that I) dislike the same things in Spring....

  • Pulga is so simple

    by Leandro Cruz /

    Your message is awaiting moderation. Thank you for participating in the discussion.

    I have implemented a small avalon container called pulga (only 20k, small set of dependencies).

    Pulga works like an object factory (like pico), using annotations (@Dependency) and conventions. Here is an example:

    //Create a component
    public class MyComponentImpl implements MyComponent
    {


    @Dependency
    private SomeOtherComponent ref;

    }

    public class MyTest extends TestCase
    {

    @Dependency
    private MyComponent ref;

    public void testComponent()
    {
    assertTrue(ref instanceof MyComponentImpl);
    }

    }

    More information at: black-beans.com.br:8088/xingu

  • Re: This framework, or somethign like it, should be in the JDK

    by Brent Baxter /

    Your message is awaiting moderation. Thank you for participating in the discussion.

    JSR 299 looks interesting, and I for one would welcome the idea of a managed "web bean" for data driven web apps. What I fear based on the public material available on the JCP web site is that this will be too closely bound to JSF. Can we be sure that any implementation of JSR 299 does not require the use of JSF on the web tier?

  • Guice is cool! Mentawai IOC support is very similar!

    by Sergio Oliveira /

    Your message is awaiting moderation. Thank you for participating in the discussion.

    I like the programmatic approach used by Guice to configure modules. We have been using programmatic configuration since the start in Mentawai.

    Check how you can do IoC and Auto-wiring with Mentawai very easily, with no need for an external IOC framework. You are always free to use a external framework, but check this first:

    recipes.mentaframework.org/posts/list/8.page

    recipes.mentaframework.org/posts/list/14.page

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