Spring bean scopes example

Spring bean scopes exampleposted on March 26,201 0

By mkyong

In spring, bean scope is used to decide which type of bean instance shocould be return from spring container back to the caller.

5 types of bean scopes supported:

1. Singleton-return a single bean instance per Spring IoC container
2. Prototype-return a new bean instance each time when requested
3. Request-return a single bean instance per HTTP request .*
4. Session-return a single bean instance per http session .*
5. Globalsession-return a single bean instance per global http session .*

In most cases, you may only deal with the spring's core scope-singleton and prototype, and the default scope is Singleton.

P.s * means only valid in the context of a Web-aware spring applicationcontext

Singleton vs prototype

Here's an example to show you what's the different between bean scope:SingletonAndPrototype.

package com.mkyong.customer.services; public class CustomerService {String message; public String getMessage() {return message;} public void setMessage(String message) {this.message = message;}}

1. Singleton example

If no bean scope is specified in bean configuration file, default to Singleton.

<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-2.5.xsd">        <bean id=""             class="com.mkyong.customer.services.CustomerService" /> </beans>

Run it

package com.mkyong.common; import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext; import com.mkyong.customer.services.CustomerService; public class App {    public static void main( String[] args )    {    ApplicationContext context =      new ClassPathXmlApplicationContext(new String[] {"Spring-Customer.xml"});     CustomerService custA = (CustomerService)context.getBean("customerService");    custA.setMessage("Message by custA");    System.out.println("Message : " + custA.getMessage());     //retrieve it again    CustomerService custB = (CustomerService)context.getBean("customerService");    System.out.println("Message : " + custB.getMessage());    }}

Output

Message : Message by custAMessage : Message by custA

Since the bean 'mermerservice' is in singleton scope, the second retrieval by 'custb' will display the message set by 'custa' also, even it's retrieve by a new getbean () method. in Singleton, only a single instance per spring
IOC container, no matter how many times you retrieve it with getbean (), it will always return the same instance.

2. Prototype example

If you want a new 'mermerservice' bean instance, every time you call it, use prototype instead.

<beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans-2.5.xsd">    <bean id="customerService" class="com.mkyong.customer.services.CustomerService"          scope="prototype"/> </beans>

Run it again

Message : Message by custAMessage : null

In prototype scope, you will have a new instance for eachgetBean()Method
Called.

3. Bean scopes Annotation

You can also use annotation to define your bean scope.

package com.mkyong.customer.services; import org.springframework.context.annotation.Scope;import org.springframework.stereotype.Service; @Service@Scope("prototype")public class CustomerService {String message; public String getMessage() {return message;} public void setMessage(String message) {this.message = message;}}

Enable auto component Scanning

<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/beanshttp://www.springframework.org/schema/beans/spring-beans-2.5.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context-2.5.xsd">        <context:component-scan base-package="com.mkyong.customer" /> </beans>

Download source codedownload it-Spring-Bean-Scopes-Example.zip (7 kb) Reference

1. Http://static.springsource.org/spring/docs/2.0.x/reference/beans.html#beans-factory-scopes