注入被注入類

我在我的應用程序中使用Google guice進行依賴注入。我有一個類的結構就是這樣，注入被注入類

的例子是從here

這是我的接口採取

package com.journaldev.di.services; 

@ImplementedBy(EmailService.class) 
public interface MessageService { 

    boolean sendMessage(String msg, String receipient); 
}

，我將實現在此

package com.journaldev.di.services; 

import javax.inject.Singleton; 

//import com.google.inject.Singleton; 

@Singleton 
public class EmailService implements MessageService { 

    public boolean sendMessage(String msg, String receipient) { 
     //some fancy code to send email 
     System.out.println("Email Message sent to "+receipient+" with message="+msg); 
     return true; 
    } 
}

如果我注射t EmailService在這裏。

package com.journaldev.di.consumer; 

import javax.inject.Inject; 

import com.journaldev.di.services.MessageService; 

public class MyApplication { 

    private MessageService service; 

    @Inject 
    public void setService(MessageService svc){ 
     this.service=svc; 
    } 

    public boolean sendMessage(String msg, String rec){ 
     //some business logic here 
     return service.sendMessage(msg, rec); 
    } 
}

如果假設我EmailService類這個樣子，

package com.journaldev.di.services; 

import javax.inject.Singleton; 

//import com.google.inject.Singleton; 

@Singleton 
public class EmailService implements MessageService { 
    public EmailService(int someValue) { 
     FancyEmailService fancyEmailService = new FancyEmailService(someValue); 
    } 
    public boolean sendMessage(String msg, String receipient) { 
     fancyEmailService.doSomething(); 
     System.out.println("Email Message sent to "+receipient+" with message="+msg); 
     return true; 
    } 
}

爲了檢驗上述EmailService代碼，我需要注入FancyEmailService不是從構造函數實例化。如何將FancyEmailService注入EmailService代碼？並且仍然能夠將EmailService注入到MyApplication中。

來源

2017-04-18 Balaraj V

你需要看看這些 -和https://github.com/google/guice/wiki/ProvidesMethods

public class GuiceTestModule extends AbstractModule { 

    @Override 
    protected void configure() { 
     bind(Integer.class) 
     .annotatedWith(Names.named("fancy")) 
     .toInstance(10); 
    } 

    @Provides 
    FancyEmailService fancyEmailServiceProvider(@Named("fancy") int i){ 
     return new FancyEmailService(i); 
    } 

}

我FancyEmailService & EMailService分別如下。

public class FancyEmailService { 

    private final int i; 

    public FancyEmailService(int i){ 
     this.i = i; 
    } 

    public void doSomething(){ 
     System.out.println("i is injected with " + i); 
    } 

} 

@Singleton 
public class EmailService implements MessageService { 

    private FancyEmailService fancyEmailService; 

    @Inject 
    public EmailService(@Named("fancy") int someValue){ 
     fancyEmailService = new FancyEmailService(someValue); 
    } 

    public boolean sendMessage(String msg, String receipient) { 
     //some fancy code to send email 
     System.out.println("Email Message sent to "+receipient+" with message="+msg); 
     fancyEmailService.doSomething(); 
     return true; 
    } 
}

允許測試

public class GuiceTest { 

    public static void main(String[] args) { 


     Injector injector = Guice.createInjector(new GuiceTestModule()); 

     MyApplication appn = injector.getInstance(MyApplication.class); 
     appn.sendMessage("msg", "guru"); 
    } 

}

輸出：

Email Message sent to guru with message=msg 
i is injected with 10

EmailService也可以寫成使用@Provides

@Singleton 
public class EmailService implements MessageService { 

    private FancyEmailService fancyEmailService; 

    @Inject 
    public EmailService(FancyEmailService fes){ 
     fancyEmailService = fes; 
    } 

    public boolean sendMessage(String msg, String receipient) { 
     //some fancy code to send email 
     System.out.println("Email Message sent to "+receipient+" with message="+msg); 
     fancyEmailService.doSomething(); 
     return true; 
    } 
}

這種方式

來源

2017-04-18 21:25:46 vins

注入被注入類

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