Guice, Injecting TypeLiteral<T> when using @AssistedInject

Question

This works:

public static class SomeGenericType<T> { private TypeLiteral<T> type; @Inject public SomeGenericType(TypeLiteral<T> type) { this.type = type; } public Class<? super T> getType() { return type.getRawType(); } }

Guice automatically injects the TypeLiteral representing String when I do:

@Inject SomeGenericType<String> foo;

But when trying the same thing with Assisted Inject:

public static interface FooFactory<T> { Foo<T> create(String name); } public static class Foo<T> { @AssistedInject public Foo(TypeLiteral<T> type, @Assisted String name) { ....

My Module looking like this:

public static class TestMod extends AbstractModule { @Override protected void configure() { install(new FactoryModuleBuilder().build(new TypeLiteral<FooFactory<String>>(){})); } }

I get an exception while installing the module:

TypeLiteral<T> cannot be used as a Key, it is not fully specified.

It's certainly the TypeLiteral that I'm trying to Inject that is the problem, as the generic factory does work fine when I remove it.

So, I'll probably just roll my own factory for the moment, but I'm curious to whether this should work? Is it a matter of using the FactoryModuleBuilder slightly differently?

Ryan Nelson · Accepted Answer · 2012-04-19 16:21:07Z

How are you accessing the instance of FooFactory? I built the variation on your code below and it worked for me:

public class AnotherGuiceTest { public static void main( String[] args ) { Injector i = Guice.createInjector( new TestMod() ); FooFactory<String> ff = i.getInstance( Key.get( new TypeLiteral<FooFactory<String>>() {} ) ); ff.create( "myname" ); } } interface FooFactory<T> { Foo<T> create( String name ); } class Foo<T> { @Inject public Foo( TypeLiteral<T> type, @Assisted String name ) { System.out.println( type.getRawType() ); System.out.println( name ); } } class TestMod extends AbstractModule { @Override protected void configure() { install( new FactoryModuleBuilder().build( new TypeLiteral<FooFactory<String>>() {} ) ); } }

Outputs:

class java.lang.String myname

Note I used a regular @Inject annotation rather than @AssistedInject which I think is for multiple constructors in a factory. This also works if you inject the instance directly:

public class AnotherGuiceTest { public static void main( String[] args ) { Injector i = Guice.createInjector( new TestMod() ); AppClass ac = i.getInstance( AppClass.class ); } } class AppClass { @Inject public AppClass( FooFactory<String> fooFactory ) { fooFactory.create( "test" ); } }

Outputs:

class java.lang.String test

Aha.. so it was a setup problem. Thanks for taking the time to test it & answer. Turns out it was because I had a jar from GIN involved, guice-assistedinject-snapshot.jar instead of guice-assistedinject-3.0.jar (side note, regular assisted inject does seem to work with this jar, just not with generics)

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