Spring interface injection example

According to Variants of DI in spring

DI exists in two major variants, Constructor-based dependency injection and Setter-based dependency injection.

Also see Interface injection is not implemented in Spring clearly states it.

So there are only two variants of DI. So if documentation says nothing about interface injection, its clear that its not there. Those who believe that interface injection is done by providing setter method in interface answer me:

1. Why spring ref doc left mention of interface injection?
2. Why can't interface injection via providing setter method NOT considered as setter injection itself. Why create special term for that when introduction of interface doesn't affect anything, I mean its still configured the same way. If they were different then how can one find it via seeing the config. Shouldn't it be transparent that in config and not seeing the impl that actually configured class implements some interface ?
3. Just like Instantiation using an instance factory method and Instantiation using an static factory method, some bean attributes should clarify the interface injection?

With interface injection an interface explicitly defines the point where a dependency can be set:

interface InjectPerson {
    public void injectHere(Person p);
}

class Company implements InjectPerson {
   Person injectedPerson; 

   public void injectHere(Person p) {
        this.injectedPerson = p;
    }
}

Hi I tried with a very simple approach that may clarify your answer.

following is the code that i have built on using two interfaces and and two bean classes.

first interface with name Job.

public interface Job {
    public void setmyJob(String myJob);
    public String getmyJob();
}

and one class to implement this interface with name as MyJob

public class MyJob implements Job {
    public String myJob;

    public MyJob() {
        System.out.println("From MyJob default Constructor and the ID= "+this);
    }

    public void setmyJob(String myJob) {
        this.myJob=myJob;
    }

    public String getmyJob() {
        return myJob;
    }
}

In the next step i created another Interface with name as Service

public interface Service {
    public void setJob(Job job);
    public Job getJob();
}

and then again another class to implement this Service Interface.

public class MyService implements Service {

    public Job job;

    public void setJob(Job job) {
        this.job=job;
        System.out.println("Hello from Myservice: Job ID="+job);
    }

    public Job getJob() {
        return job;
    }
}

then i created on main class with the main function and written the code as follows:

import org.springframework.beans.factory.BeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MainApplication {

    public static void main(String...a) {

        BeanFactory beanfactory=new ClassPathXmlApplicationContext("Beans.xml");

        MyService myservice=(MyService)beanfactory.getBean("myservice");
        System.out.println("Before print");
        System.out.println(myservice.getJob().getmyJob());
    }
}

in my Beans.xml file i mentioned the code as follows and it worked.

 <?xml version="1.0" encoding="UTF-8"?>
 <beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://www.springframework.org/schema/beans
 http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">


    <bean id="myjob" class="MyJob">
        <property name="myJob" value="My First String"/>
    </bean>

    <bean id="myservice" class="MyService">
        <property name="job" ref="myjob"/>
    </bean>
</beans>

I have also reffered to another online tutorials and then got this kind of solution. please let me know if you have any problem with this code. it is working for me.