Maybe this has been answered before, but I wasn't able to find it in
the archives. Or, maybe it is in the Guice book, but mine is still in
the ordering process...
Here's the class I want to inject dependencies into:
public class ProcessorImpl<T> implements Processor<T>
{
private final Subprocessor<T> subprocessor;
@Inject
public ProcessorImpl(Subprocessor<T> subprocessor)
{
super();
this.subprocessor = subprocessor;
}
public T process(List<T> list)
{
...
}
}
The constructor wants a Subprocessor<T>. However, I cannot figure out
how (or if it is possible) to bind a parameterized type. The best I've
come up with is this module:
public static class MyModule implements Module
{
public void configure(final Binder binder)
{
binder.bind(new TypeLiteral<Processor<String>>(){}).to(new
TypeLiteral<ProcessorImpl<String>>(){});
binder.bind(new TypeLiteral<Subprocessor<String>>()
{}).to(new TypeLiteral<StringConcater>(){});
}
}
and then this main() method:
public static void main(final String[] argv)
{
final Injector injector = Guice.createInjector(new
MyModule());
injector.getInstance(Key.get(new
TypeLiteral<Processor<String>>(){}));
}
My thoughts here were that, by asking guice for a Processor<String>
(which is bound to ProcessorImpl<String>), the T is now the concrete
type String, so guice should be looking for a binding for
Subprocessor<String>. But, I get this error:
1) Error at
example07_generics.ProcessorImpl.<init>(ProcessorImpl.java:15):
Binding to example07_generics.Subprocessor<T> not found. No bindings
to that type were found.
And now I'm stuck, because I can't create a TypeLiteral with
parameterized types, only concrete ones. I can work around the problem
with another Gafter-ish trick and make a little shim class of concrete
type:
public class ProcessorStringImpl extends ProcessorImpl<String>
{
@Inject
public ProcessorStringImpl(final Subprocessor<String>
subprocessor)
{
super(subprocessor);
}
}
and then tweaking the module a bit:
public static class MyModule implements Module
{
public void configure(final Binder binder)
{
binder.bind(new TypeLiteral<Processor<String>>(){}).to(new
TypeLiteral<ProcessorStringImpl>(){});
binder.bind(new TypeLiteral<Subprocessor<String>>()
{}).to(new TypeLiteral<StringConcater>(){});
}
}
Is this the best way to work around the issue? If so, can it be added
to the recipes page?
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