Guice動態綁定，獲取實例

Question

我是新的依賴注入& Guice in Java。我有一個動態注入合適對象的問題。

例如：

public class Main { 
    public static void main(String[] args) { 
     Injector injector = Guice.createInjector(new MyModule()); 

     StudentStore studentStore = injector.getInstance(StudentStore.class); 
     RegisterService registerService = injector.getInstance(RegisterService.class); 

     registerService.register("First User"); 
     registerService.register("Second User"); 

     //Now I would like to use OfflineRegisterService.class - is it good idea to do it here? 
     registerService = injector.getInstance(OfflineRegisterService.class); 

     registerService.register("Third User"); 
     registerService.register("Fourth User"); 

     System.out.println(studentStore.size()); 
    } 
} 

它的工作原理，但它是做最好的主意？

public class MyModule extends AbstractModule { 
    @Override 
    protected void configure() { 
     bind(StudentStore.class).to(MemoryStudentStore.class); 
     bind(RegisterService.class).to(OnlineRegisterService.class); 
    } 
} 

Answer 1

至於Guice，你的解決方案是好的。爲了代碼可讀性，我會爲離線代碼創建一個新的局部變量。所以你總是知道你正在使用哪一個：

public class Main { 
    public static void main(String[] args) { 
     Injector injector = Guice.createInjector(new MyModule()); 

     final StudentStore studentStore = injector.getInstance(StudentStore.class); // final prevents reassignment 
     // do some stuff 

     //Now I would like to use OfflineRegisterService.class - is it good idea to do it here? 
     final offlineRegisterService = injector.getInstance(OfflineRegisterService.class); // final too 

     offlineRegisterService.register("Third User"); 
     offlineRegisterService.register("Fourth User"); 

     System.out.println(studentStore.size()); 
    } 
}