从头认识Spring-1.5 Bean的作用域

这一章节我们来讨论一下Bean的作用域。

1.Bean的作用域

singleton:单例

prototype:任意次创建

request:每次请求创建一个，仅在web里面有效

session:每个session创建一个，仅在web里面有效

global-session:在全局session里面，每个bean一个实例

上面的几个作用域我们一般使用singleton和prototype，而且以singleton为主

2.singleton和prototype的对比

（1）domain

package com.raylee.my_new_spring.my_new_spring.ch01.topic_1_5;

public class Chief {
	private final int id = index++;

	public int getId() {
		return id;
	}

	private static int index = 0;

}

特别说明：这里我使用了id来记录每一个实例的id

（2）test

package com.raylee.my_new_spring.my_new_spring.ch01.topic_1_5;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = {
		"/com/raylee/my_new_spring/my_new_spring/ch01/topic_1_5/ApplicationContext-test.xml" })
public class ChiefTest {

	@Autowired
	private ApplicationContext applicationContext;

	@Test
	public void testChief() {
		for (int i = 0; i < 3; i++) {
			Chief chief = applicationContext.getBean(Chief.class);
			System.out.println("chief id:" + chief.getId());
		}
	}
}

（3）配置

当是singleton时

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:aop="http://www.springframework.org/schema/aop"
	xsi:schemaLocation="
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd
		http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.1.xsd
		http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsd
		http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.0.xsd
		http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">
	<bean id="chief"
		class="com.raylee.my_new_spring.my_new_spring.ch01.topic_1_5.Chief" />
</beans>

测试输出：

chief id:0
chief id:0
chief id:0

从输出可以看见，每次从容器拿出来的都是同一个Bean

当是prototype时

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:context="http://www.springframework.org/schema/context"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx"
	xmlns:aop="http://www.springframework.org/schema/aop"
	xsi:schemaLocation="
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
		http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd
		http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.1.xsd
		http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsd
		http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.0.xsd
		http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">
	<bean id="chief"
		class="com.raylee.my_new_spring.my_new_spring.ch01.topic_1_5.Chief"
		scope="prototype" />
</beans>

测试输出：

chief id:0
chief id:1
chief id:2

从输出可以看见，每次从容器拿出来的不是同一个Bean，而是重新创建一次

总结：这一章节简单介绍了Bean的作用域。

目录：http://blog.csdn.net/raylee2007/article/details/50611627

我的github：https://github.com/raylee2015/my_new_spring