概括guice的機器人腿與多重綁定的例子

Question

我有這個用例非常類似於Guice的機器人腿的例子，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註釋。

我期望將所有這些「腿」收集在一個java.util.Set中，並帶有Guice的Multibindings擴展。

從技術上講，在一個PrivateModule中，我想直接將一個實現公開爲Multibindings擴展提供的一組元素。我只是不知道該怎麼做。

參考，代碼示例，請參閱機器人腿例子在這裏：http://code.google.com/p/google-guice/wiki/FrequentlyAskedQuestions#How_do_I_build_two_similar_but_slightly_different_trees_of_objec

---

這裏是我的精確用例：

我有以下幾點：

// 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); 
    } 
} 

由於我在談論擴展罐，起初我不認識它們，我甚至不知道它們中有多少個：我需要將MyModule加載到j.u.ServiceLoader，每個模塊應該定義一個MyInterface實現（這兩個部分都可以）。

問題是讓所有的MyInterface實現在一個集合（在MyManager）。我怎樣才能做到這一點？

---

解決方案，完全基於傑西的回答是：

// 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); 
} 

這讓我不強迫「顧客」來擴展PrivateModule，而是使用任何模塊實現，如果MyModule的是擴展的接口模塊。

Answer 1

看起來您需要跳過一些環節來從私有模塊中提示綁定，以便它們可以位於頂層注入器的多重綁定中。

這應該工作：

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); 
    } 
} 

這個解決辦法是必要的，因爲multibindings需要在頂層注射器的情況發生。但私有模塊綁定對於該注入器不可見，所以您需要公開它們。