使用 Multibinding 泛化 guice 的機器人腿示例

Question

我有這個與 Guice 的機器人腿示例非常相似的用例，除了我不知道我有多少“腿”。 因此我不能使用機器人腿示例所需的注釋。

我希望將所有這些“腿”收集在帶有 Guice 的 Multibindings 擴展的 java.util.Set 中。

從技術上講，在 PrivateModule 中，我想將實現直接公開為將由 Multibindings 擴展提供的集合的元素。 我只是不知道該怎么做。

有關參考和代碼示例，請參見此處的機器人腿示例： http://code.google.com/p/google-guice/wiki/FrequentlyAskedQuestions#How_do_I_build_two_similar_but_slightly_different_trees_of_objec

---

這是我的精確用例：

我有以下內容：

// 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);
  }
}

由於我說的是擴展jars，所以一開始我並不認識它們，我什至不知道它們有多少個：我需要用juServiceLoader加載MyModule並且每個模塊都應該定義一個MyInterface實現（這些兩部分都可以）。

問題是將所有MyInterface實現放在一組中（在MyManager中）。 我怎樣才能做到這一點？

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解決方案，完全基於傑西的回答：

// 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);
}

這允許我不強制“客戶”擴展 PrivateModule，而是在 MyModule 是擴展 Module 的接口時使用任何模塊實現。

Answer 1

看起來您需要跳過一些環節來促進來自私有模塊的綁定，以便它們可以在頂級注入器的多重綁定中。

這應該有效：

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);
  }
}

這種解決方法是必要的，因為多重綁定需要在頂級注入器中發生。 但是該注入器看不到私有模塊綁定，因此您需要公開它們。