使用Multibinding概括guice的机器人腿示例

Question

我有这个用例非常类似于Guice的机器人腿例子,除了我不知道我有多少"腿".因此,我无法使用机器人腿示例所需的注释.

我期望在带有Guice的Multibindings扩展的java.util.Set中收集所有这些"leg".

从技术上讲,在PrivateModule中,我想直接将实现作为Multibindings扩展提供的集合的元素公开.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robot-legs示例:http://code.google.com/p/google-guice/wiki/FrequentlyAskedQuestions#How_do_I_build_two_similar_but_slightly_different_trees_of_objec

---

这是我的确切用例:

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);
  }
}

因为我说的是扩展罐,我起初并不知道它们,我甚至不知道它们中有多少存在:我需要加载MyModules j.u.ServiceLoader并且每个模块应该定义一个MyInterface实现(这两个部分是好).

问题是将所有MyInterface实现都放在一个集合中(in MyManager).我怎样才能做到这一点？

---

解决方案,完全基于Jesse的答案:

// 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);
}

这允许我不强制"客户"扩展PrivateModule,而是使用任何模块实现,如果MyModule是扩展Module的接口.

Answer 1

看起来你需要跳过一些箍来促进来自私有模块的绑定,这样它们就可以进入顶级注入器的多重绑定.

这应该工作:

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);
  }
}

这种解决方法是必要的,因为多绑定需要在顶级注入器处进行.但是私有模块绑定对于该注入器是不可见的,因此您需要公开它们.