question on prototype scope of a bean

[Mark Curlette]

Hello,

I am new to Spring and I have question regarding to the prototype scope of a bean.
I have a simple program, and i have a simple bean called helloworld which has a prototype scope.
Even though its scope defined as prototype; it did not created a new instance each times the bean is called.
I thought it should create a new instance every time it is called.
I was running this program in eclipse.

Here is my simple code. Please help me to point out my errors if you could.

Many thanks in advance.

package com.du;

public class HelloWorld {
	   private String message;

	   public void setMessage(String message){
	      this.message  = message;
	   }

	   public void getMessage(){
	      System.out.println("Your Message : " + message);
	   }
	}

package com.du;

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

public class MainApp {
   public static void main(String[] args) {
	   
	  ApplicationContext context = null;
	  try {
       context =  new ClassPathXmlApplicationContext("Beans.xml");

      HelloWorld obj1 = (HelloWorld) context.getBean("helloWorld");

      obj1.getMessage();
      
	  HelloWorld obj2 = (HelloWorld) context.getBean("helloWorld");
	  
	  obj2.getMessage ();
	  }
	  finally {}
	  
	
   }
}

<?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="helloWorld" class="com.du.HelloWorld" scope="prototype">
       <property name="message" value="Hello World world!!!!"/>
   </bean>

</beans>

and the result when i ran the program:

INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@305f6ed4: startup date [Wed Mar 20 14:52:19 EDT 2013]; root of context hierarchy
Mar 20, 2013 2:52:19 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions
INFO: Loading XML bean definitions from class path resource [Beans.xml]
Mar 20, 2013 2:52:19 PM org.springframework.beans.factory.support.DefaultListableBeanFactory preInstantiateSingletons
INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@27d8f985: defining beans [helloWorld]; root of factory hierarchy
Your Message : Hello World world!!!!
Your Message : Hello World world!!!!

I don't know why its showed the same message twice as it was singleton. I thought it should shown Hello world on the first line and null on the second line.

[Bill Gorder]

Its going to print it twice you have it defined in your bean

   <bean id="helloWorld" class="com.du.HelloWorld" scope="prototype">  
       <property name="message" value="Hello World world!!!!"/>  
   </bean> 

What proto-type does is it does not use a singleton. That bean is created new each time you ask for it. To prove this add a default constructor to your HelloWorld object

	public HelloWorld(){
		System.out.println("constructor called");
	}

You will see that the constructor is called twice. Once each time you get the bean. Now if you remove the prototype it will only print once. This is because it is instantiated only once as a singleton and you get that same instance on each request.