Spring(四)JavaBean作用范围的配置及生命周期

来源：互联网发布：中国汽车发展历史知乎编辑：程序博客网时间：2024/04/28 08:47

Bean的作用范围有几种：

singleton 在每个Spring Ioc容器中一个Bean定义只有一个对象实例。默认情况下会在容器启动时初始化Bean,但我们可以指定Bean节点的lazy-init="true"来延迟初始化Bean,这样只有第一次获取Bean才会初始化Bean。如：
<bean id=".." class=".." lazy-init="true"/>
如果想对所有Bean都应用延迟初始化，可以在根节点beans设置default-lazy-init="true",如下:
<beans default-lazy-init="true">
prototype 每次从容器获取bean都是新的对象

还有三种是应用在web project中的：request、session、global session

package test.spring.jnit;import org.junit.Test;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import test.spring.service.impl.PersonServiceBean;public class BeanScopeTest {@Testpublic void testScope() {ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml");// -------------------------------------------------PersonServiceBean personServiceBean1 = (PersonServiceBean) applicationContext.getBean("personService");PersonServiceBean personServiceBean2 = (PersonServiceBean) applicationContext.getBean("personService");System.out.println(personServiceBean1 == personServiceBean2);}}

按之前的配置这块代码返回true，但如果改变PersonServiceBean的作用范围

<bean id="personService" class="test.spring.service.impl.PersonServiceBean"scope="prototype"></bean>

就会返回false

<bean id="personService" class="test.spring.service.impl.PersonServiceBean"lazy-init="false" init-method="init" destroy-method="destroy"></bean>

bean的初始化在实例化之后，而销毁即释放资源在Spring容器关闭后

package test.spring.service.impl;import test.spring.service.PersonService;public class PersonServiceBean implements PersonService {public void init(){System.out.println("初始化");}public PersonServiceBean(){System.out.println("现在实例化");}@Overridepublic void save(){System.out.println("=============");}public void destroy() {System.out.println("释放资源");}}

package test.spring.jnit;import org.junit.Test;import org.springframework.context.support.AbstractApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;public class BeanScopeTest {@Testpublic void testScope() {// ApplicationContext applicationContext = new// ClassPathXmlApplicationContext(// "beans.xml");// 如果scope="singleton",现在对bean实例化// System.out.println("-------------------------------");/* * 如果scope="prototype",现在对bean实例化。 * 如果scope="singleton"，通过设置lazy-init="true"延迟实 例化的时间，bean也在此时实例化。 */// PersonServiceBean personServiceBean1 = (PersonServiceBean)// applicationContext// .getBean("personService");// PersonServiceBean personServiceBean2 = (PersonServiceBean)// applicationContext// .getBean("personService");//// System.out.println(personServiceBean1 == personServiceBean2);//// 返回trueAbstractApplicationContext abstractApplicationContext = new ClassPathXmlApplicationContext("beans.xml");abstractApplicationContext.close();}}

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