注入被注入类

我在我的应用程序中使用Google guice进行依赖注入。我有一个类的结构就是这样，注入被注入类

的例子是从here

这是我的接口采取

package com.journaldev.di.services; 

@ImplementedBy(EmailService.class) 
public interface MessageService { 

    boolean sendMessage(String msg, String receipient); 
}

，我将实现在此

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在这里。

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); 
    } 
}

如果假设我EmailService类这个样子，

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; 
    } 
}

为了检验上述EmailService代码，我需要注入FancyEmailService不是从构造函数实例化。如何将FancyEmailService注入EmailService代码？并且仍然能够将EmailService注入到MyApplication中。

来源

2017-04-18 Balaraj V

你需要看看这些 -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分别如下。

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; 
    } 
}

允许测试

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"); 
    } 

}

输出：

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

EmailService也可以写成使用@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; 
    } 
}

这种方式

来源

2017-04-18 21:25:46 vins

注入被注入类

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