使用多重绑定推广 guice 的机器人腿示例

Question

我有这个用例，它与Guice的机器人腿示例非常相似，只是我不知道我有多少条"腿"。因此，我不能使用机器人腿示例所需的注释。

我希望在java.util.Set中使用Guice的Multibindings扩展集所有这些"分支"。

从技术上讲，在PrivateModule中，我希望将实现直接公开为将由Multibindings扩展提供的集合的元素。我只是不知道该怎么做。

有关参考和代码示例，请参阅此处的机器人腿示例:http://code.google.com/p/google-guice/wiki/FrequentlyAskedQuestions#How_do_I_build_two_similar_but_slightly_different_trees_of_objec

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下面是我精确的用例:

我有以下内容:

// Main application
public interface MyTree {...}
public interface MyInterface {
  public MyTree getMyTree() {}
}
public abstract class MyModule extends PrivateModule {}
public class MyManager {
  @Inject MyManager (Set<MyInterface> interfaces){ this.interfaces = interfaces }
}
public class MainModule extends AbstractModule {
  public void configure () {
    // Install all MyModules using java.util.ServiceLoader.
  }
}

// In expansion "square.jar"
public class SquareTree implements MyTree {...}
public class SquareImplementation implements MyInterface {
  @Inject SquareImplementation (MyTree tree) { this.tree = tree; }
  public MyTree getMyTree () { return this.tree; }
}
public class SquareModule extends MyModule { // correctly defined as a ServiceLoader's service.
  public void configure () {
    // How to make this public IN a multibinder's set?
    bind(MyInterface.class).to(SquareImplementation.class);
    // Implementation specific to the Squareimplementation.
    bind(MyTree.class).to(SquareTree.class);
  }
}
// In expansion "circle.jar"
public class CircleTree implements MyTree {...}
public class CircleImplementation implements MyInterface {
  @Inject CircleImplementation (MyTree tree) { this.tree = tree; }
  public MyTree getMyTree () { return this.tree; }
}
public class CircleModule extends MyModule { // correctly defined as a ServiceLoader's service.
  public void configure () {
    // How to make this public IN a multibinder's set?
    bind(MyInterface.class).to(CircleImplementation.class);
    // Implementation specific to the Circle implementation.
    bind(MyTree.class).to(CircleTree.class);
  }
}

因为我说的是扩展jar，我一开始不知道它们，我甚至不知道它们中有多少存在:我需要用j.u.ServiceLoader加载MyModule s，每个模块应该定义一个MyInterface实现(这两个部分是ok的)。

问题是将所有MyInterface实现放在一个集合中(在MyManager中)。我该怎么做呢?

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解决方案，完全基于Jesse的回答:

// Create the set binder.
Multibinder<MyInterface> interfaceBinder = Multibinder.newSetBinder(binder(), MyInterface.class, MyBinding.class);
// Load each module that is defined as a service.
for (final MyModule module : ServiceLoader.load(MyModule.class)) {
  // Generate a key with a unique random name, so it doesn't interfere with other bindings.
  final Key<MyInterface> myKey = Key.get(MyInterface.class, Names.named(UUID.randomUUID().toString()));
  install(new PrivateModule() {
    @Override protected void configure() {
      // Install the module as part of a PrivateModule so they have full hands on their own implementation.
      install(module);
      // Bind the unique named key to the binding of MyInterface.
      bind(myKey).to(MyInterface.class);
      // Expose the unique named binding
      expose(myKey);
    }
  });
  // bind the unique named binding to the set
  interfaceBinder.addBinding().to(myKey);
}

这允许我不强迫"客户"扩展PrivateModule，而是使用任何模块实现，如果MyModule是一个扩展module的接口。

Answer 1

看起来你需要跳过一些环节才能从私有模块中提交绑定，这样它们就可以在顶级注入器的多绑定中使用了。

这个应该可以工作:

public class SquareModule extends AbstractModule { // does not extend PrivateModule
  @Overide public void configure() {
    // this key is unique; each module needs its own!
    final Key<MyInterface> keyToExpose
        = Key.get(MyInterface.class, Names.named("square"));
    install(new PrivateModule() {
      @Override public void configure() {
        // Your private bindings go here, including the binding for MyInterface.
        // You can install other modules here as well!
        ...
        // expose the MyInterface binding with the unique key
        bind(keyToExpose).to(MyInterface.class);
        expose(keyToExpose);
      }
    });
    // add the exposed unique key to the multibinding
    Multibinder.newSetBinder(binder(), MyInterface.class).addBinding().to(keyToExpose);
  }
}

这个解决方法是必要的，因为多绑定需要在顶层注入器中进行。但是私有模块绑定对这个注入器是不可见的，所以你需要把它们暴露出来。