Inject into a being injected class

[Balaraj V]

I'm using Google Guice for dependency injection in my application. I have a
class structure like this,

Example is taken from here
<http://www.journaldev.com/2403/google-guice-dependency-injection-example-tutorial>


This is my interface,

package com.journaldev.di.services;
@ImplementedBy(EmailService.class)public interface MessageService {

boolean sendMessage(String msg, String receipient);}

Which I will implement here

package com.journaldev.di.services;
import javax.inject.Singleton;
//import com.google.inject.Singleton;
@Singletonpublic 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;
}}

If I inject EmailService here.

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);
}}

If suppose my EmailService class looked like this,

package com.journaldev.di.services;
import javax.inject.Singleton;
//import com.google.inject.Singleton;
@Singletonpublic 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;
}}

In order to test the above EmailService code, I need to inject
FancyEmailService than instantiating from the constructor. How do I inject
FancyEmailService into EmailService code? and still be able to inject
EmailService into MyApplication.

I posted the same question in Stackoverflow could not find any answers.

[Stephan Classen]

You would need to bind the dependencies of your fancy email service. If those are configuration values like "url", "port" or similiar I recommend looking ate some of the 3rd party extensions which allow you to easily bind values from a properties file to a @Named singleton.

Maybe you find something at the apache onami project.

Post by Balaraj V
I'm using Google Guice for dependency injection in my application. I have a
class structure like this,
Example is taken from here
<http://www.journaldev.com/2403/google-guice-dependency-injection-example-tutorial>
This is my interface,
package com.journaldev.di.services;
@ImplementedBy(EmailService.class)public interface MessageService {
boolean sendMessage(String msg, String receipient);}
Which I will implement here
package com.journaldev.di.services;
import javax.inject.Singleton;
//import com.google.inject.Singleton;
@Singletonpublic 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;
}}
If I inject EmailService here.
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);
}}
If suppose my EmailService class looked like this,
package com.journaldev.di.services;
import javax.inject.Singleton;
//import com.google.inject.Singleton;
@Singletonpublic 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;
}}
In order to test the above EmailService code, I need to inject
FancyEmailService than instantiating from the constructor. How do I inject
FancyEmailService into EmailService code? and still be able to inject
EmailService into MyApplication.
I posted the same question in Stackoverflow could not find any answers.
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