springIOC: Scopes

The Spring framework supports following five scopes, three of which are available only if we use a web-aware ApplicationContext:

Scope	Description
Singleton	This scopes the bean definition to a single instance per Spring IOC container (default)
Prototype	This scopes a single bean definition to have any number of object instances
Request	This scopes a bean definition to the HTTP request
Session	This scopes a bean definition to HTTP session
Global-session	This scopes a bean definition to a global session. Suitable for portlet kind of applications

The Singleton scope:If scope is set to Singleton, the Spring IOC container creates exactly one instance of the object defined by that bean definition. This single instance is stored in a cache of such singleton beans and all subsequent requests and references for that named bean returns the cached object.

The prototype scope:If scope is set to prototype, the Spring IoC container creates new bean instance of the object every time a request for that specific bean is made.

Bean class

package myspring;

public class HelloWorld {

private String message;

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

}

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

}

Spring Scope  Test class

package myspring;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MainApp {

public static void main(String[] args) {

ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");

HelloWorld objA = (HelloWorld) context.getBean("helloWorld"); objA.setMessage("I'm object A"); objA.getMessage();

HelloWorld objB = (HelloWorld) context.getBean("helloWorld"); objB.getMessage(); } }

Singleton Scope  Beans file

<beans …..

<bean id="helloWorld" class=“myspring.HelloWorld" scope="singleton">

</bean>

</beans>

Prototype Scope  Beans file

<beans …..

<bean id="helloWorld" class=“mysprin.HelloWorld" scope=“prototype">

</bean>

</beans>