在 Guice 中使用命名注入

Question

I'm using Guice for dependency injection and I'm a bit confused. There are two Named annotations in different packages:

com.google.inject.name.Named and javax.inject.Named (JSR 330?).

I'm eager to depend on javax.inject.* . Code sample:

import javax.inject.Inject;
import javax.inject.Named;

public class MyClass
{
    @Inject
    @Named("APrefix_CustomerTypeProvider")
    private CustomerTypeProvider customerTypeProvider;
}

In my naming module I may have the following line:

bind(CustomerTypeProvider.class).annotatedWith(...).toProvider(CustomerTypeProviderProvider.class);

The question: I'm curious what should I put where the dots are? I would expect something like com.google.inject.name.Names.named("APrefix_CustomerTypeProvider") but this one returns com.google.inject.name.Named while I need the one in javax.inject .

CustomerTypeProviderProvider.class.getAnnotation(javax.inject.Named.class) also does not fit well because the CustomerTypeProviderProvider (ignore the stupid name, legacy issue) is not annotated.

Answer 1

As mentioned on the Guice wiki, both work the same . You shouldn't worry about that. It is even recommended to use javax.inject.* when available, just as you prefer too (bottom of the same page).

import com.google.inject.AbstractModule;
import com.google.inject.Guice;
import com.google.inject.name.Names;
import javax.inject.Inject;

public class Main {
  static class Holder {
    @Inject @javax.inject.Named("foo")
    String javaNamed;
    @Inject @com.google.inject.name.Named("foo")
    String guiceNamed;
  }

  public static void main(String[] args) {
    Holder holder = Guice.createInjector(new AbstractModule(){
      @Override
      protected void configure() {
        // Only one injection, using c.g.i.Names.named("").
        bind(String.class).annotatedWith(Names.named("foo")).toInstance("foo");
      }

    }).getInstance(Holder.class);
    System.out.printf("javax.inject: %s%n", holder.javaNamed);
    System.out.printf("guice: %s%n", holder.guiceNamed);
  }
}

Prints:

java.inject: foo
guice: foo