Spring中bean的范围

Spring中有5种bean的范围：

5 types of bean scopes supported :

1. singleton – Return a single bean instance per Spring IoC container 这个范围也是默认的
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. *

P.S * means only valid in the context of a web-aware Spring ApplicationContext

我们看个关于singleton and prototype.的例子：

public class CustomerService 
{
	String message;
 
	public String getMessage() {
		return message;
	}
 
	public void setMessage(String message) {
		this.message = message;
	}
}

1. Singleton example

<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-2.5.xsd">
 
       <bean id="customerService" 
            class="com.mkyong.customer.services.CustomerService" />
 
</beans>

　　运行：

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());
    }
}

　　输出为：

Message : Message by custA
Message : Message by custA

2. Prototype example

<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-2.5.xsd">
 
   <bean id="customerService" class="com.mkyong.customer.services.CustomerService" 
         scope="prototype"/>
 
</beans>

　　运行输出为：

Message : Message by custA
Message : null

也可以使用注解来做这些事情：

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;
	}
}

　　

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