GIN frequently asked questions

How about adding Where do I get gin.jar from and what is aopalliance.jar

You have to build gin.jar for the moment. Im in the middle of that troublesome procedure right now.

If I'm not running a GWT-RPC server, will I still be able to use Gin? It seems as though it's essentially compiled in and only has the Java dependency at compile-time, but I would just like to make sure.

You don't need to run a GWT/Java/Guice server, all GWT client code will work with Gin, regardless of its server.

Building gin.jar works fine. I having trouble locating documentation on how to use it on in the client under Eclipse. My code compiles and tests just fine, however, when I try to run the Eclipse Web Application with Ginjector code in the client it breaks:

ERROR? No source code is available for type com.google.gwt.inject.client.Ginjector; did you forget to inherit a required module?

@jSlim180,

It looks like you're forgetting to inherit the GIN GWT module. You need to add the following to your GWT module file:

<inherits name="com.google.gwt.inject.Inject" />

@jSlim180, Have had the same error. I guess it should be added to this FAQ because it is not clear. In order to add GIN to your project you should add 3 files to build path: 1) gin.jar 2) guice.jar (from guice distro) 3) aopalliance.jar (from guice distro)

I can't build the GIN jar, when will you propose it ? Can someone propose it somewhere please ?

Someone's providing nightly builds: http://code.google.com/p/google-gin/issues/detail?id=45#c3

It is possible to use GIN and GUICE with an application with GWT and JSON ? thanks for your answer.

Currently, in my project, I'm using replace-with to handle some specific implementations for gecko1_8. But with gin, I haven't found any way to do it.

The scenario is like, I have RegisterPanel?, and its subclasses RegisterPanelStandard? for other browsers and RegisterPanelGecko? for firefox.

I have Module.java

public class Module extends AbstractGinModule
{
    @Override
    protected void configure()
    {
        bind(RegisterPanel.class).to(RegisterPanelStandard .class);
    }
}

and ModuleGecko?.java

public class ModuleGecko extends Module 
{
    @Override
    protected void configure()
    {
        super.configure();
        bind(RegisterPanel.class).to(RegisterPanelGecko .class);
    }
}

and Injector.java

@GinModules(Module.class)
public interface Injector extends Ginjector
{
    RegisterPanel getRegisterPanel();
}

and in myproject.gwt.xml, I added the following,

<replace-with class="com.topcmm.client.ModuleGecko">
    <when-type-is class="com.topcmm.client.Module"></when-type-is>
    <when-property-is name="user.agent" value="gecko1_8"></when-property-is>
</replace-with>

But I found it doesn't work for me. Anyone can explain it or how can I make it work?

Appreciate for any comments!

Hey everyone,

We are trying to split out our codebase into multiple GWT modules with GIN for dependency injections. A need arose for different Ginjectors to inherit from other Ginjectors.

We found that this works:

@GinModules(ParentModule.class)
public interface ParentInjector extends ChildInjector, Ginjector{
	public SomeClass getSomeClass();
}

and then the ChildInjector? is like this:

@GinModules(ChildModule.class)
public interface ChildInjector extends Ginjector{
	public SomeOtherClass getSomeOtherClass();
}

Now, we can get the SomeOtherClass? instance by instantiating the parent Ginjector:

ParentInjector injector = GWT.create(ParentInjector.class);
SomeOtherClass socInstance = injector.getSomeOtherClass();

This works fine, but I'm wondering whether we're overlooking any major issues this could cause?

Any comments are appreciated!

@vkubushyn i'm having the exact same problem.

How does lazy instantiation works with jin?

Can I inject a parametrized type to a class using jin? I tried several approaches but I get error

Sorry for answering a question in the comments but....

@arashbi Lazy instantiation works fine. You can see this by adding some sort of message, such as Window.alert("XXX"), to the constructor of a class created by gin. You will see that the message only appears when the injector.xxx() method is called. By printing out hashCodes you can also check that Singleton etc. works as you expect.

For parameterized types use the TypeLiteral? class, take a look at the Guice documentation for this.

While working on a gin module in development mode, I often get the "Deferred binding result type 'A' should not be abstract" error. After restarting the development console, it's gone. Just a hint in case you run into this one as well.

Debian, 2.6.26-2 Firefox 3.6.13 GWT 2.1.1 GIN 1.0

I have a question to Gin team:

In Guice, I specify the module when I am creating an injector. This is fine because I can create two injectors with different modules, for testing purposes.

In Gin, I must specify the module to use in the Injector interface via @GinModules?. So I cannot create two instances of the injector with different modules. This creates a dependency from an interface to the implementation and defeats the whole purpose of dependency injection.

Is there a way around it?

There are two ways to reuse Ginjectors. The classic way is to subclass them, i.e. if the ginjector with all your methods is A, then have 2 (n) ginjectors B and C, each of which extend A but which define different gin modules.

Another way to easily swap the gin module names is to use GWT properties, which was recently implemented. Take a look at http://code.google.com/p/google-gin/source/browse/trunk/src/com/google/gwt/inject/client/GinModules.java for some more documentation.