In Spring 3.0 using the tag context:component-scan in xml file, the entry of the class(or bean) defined under the scan tag is automatically created. The example to show use of context:component-scan tag is as below:

Example:-

JavaConfig.java

package com.babita;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;


@Configuration
public class JavaConfig {

    public void printMessage()
    {
        System.out.println("Hello World From Spring 3.0");
    }
}

Now define the below code in app-context.xml

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:component-scan base-package="com.babita"></context:component-scan>
   <context:annotation-config/>


</beans>

Now define the below class to run the code:

MainApp.java

package com.babita;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MainApp {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
         //ApplicationContext context = new AnnotationConfigApplicationContext();
        ApplicationContext context =  new ClassPathXmlApplicationContext(new String[] {"app-context.xml"});
        JavaConfig obj = (JavaConfig) context.getBean("javaConfig");
        obj.printMessage();

    }

}

In Above example we can see that the @Configuration Class JavaConfig.java can be instantiate using the following tag in app-context.xml file.this class(or bean) entry is automatically created in the xml file.

<context:component-scan base-package="com.babita"></context:component-scan> 

Hope this will help you :)