Spring(十二):IOC容器中Bean的生命周期方法
IOC容器中Bean的生命周期方法
1)Spring IOC容器可以管理Bean的声明周期,Spring允许在Bean生命周期的特定点执行定制的任务。
2)Spring IOC容器对Bean的生命周期进行管理的过程:
--- 通过构造器或工厂方法创建Bean实例;
--- 为Bean的属性设置值和对其他Bean的引用;
--- Bean可以使用
--- 当容器关闭是,调用Bean的销毁方法
3)在Bean的声明里设置init-method和destroy-method属性,为Bean指定初始化和销毁方法。
演示:
第一步:创建一个Java Project,并导入以下包:
第二步:在src下添加com.dx.spring.beans.cycle.Member.java和spring bean配置文件bean-cycle.xml
Member.java
package com.dx.spring.beans.cycle; public class Member { public Member() { System.out.println("Member constructor ... "); } private String name; public void setName(String name) { System.out.println("setName " + name); this.name = name; } public void initMethod() { System.out.println("init method"); } public void destroyMethod() { System.out.println("despose method"); } }
注意:Member中的initMethod和destroyMethod两个方法名字是任意的。
bean-cycle.xml
<?xml version="1.0" encoding="UTF-8"?> <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.xsd"> <bean id="member" class="com.dx.spring.beans.cycle.Member" init-method="initMethod" destroy-method="destroyMethod"> <property name="name" value="member1"></property> </bean> </beans>
第三步:使用IOC容器管理Bean并关闭IOC容器查看打印日志:
package com.dx.spring.beans.cycle; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Main { public static void main(String[] args) { ClassPathXmlApplicationContext ctx = new ClassPathXmlApplicationContext("bean-cycle.xml"); Member member = (Member) ctx.getBean("member"); System.out.println(member); ctx.close(); // 关闭IOC容器 } }
打印信息如下:
信息: Loading XML bean definitions from class path resource [bean-cycle.xml] Member constructor ... setName member1 init method com.dx.spring.beans.cycle.Member@4f7d0008 May 24, 2018 9:41:33 PM org.springframework.context.support.ClassPathXmlApplicationContext doClose 信息: Closing org.springframework.context.support.ClassPathXmlApplicationContext@4bf558aa: startup date [Thu May 24 21:41:33 CST 2018]; root of context hierarchy despose method
创建Bean后置处理器
1)Bean后置处理器允许在调用初始化方法前后对Bean进行额外的处理;
2)Bean后置处理器对IOC容器里的所有Bean实例逐一进行处理,而非单一实例。其经典应用是:检查Bean属性的正确性或根据特定的标准更改Bean的属性。
3)对Bean后置处理器而言,需要实现abstract interface org.springframework.beans.factory.config.BeanPostProcessor抽象接口。在初始化方法被调用前后,Spring将把每个Bean实例分别传递给上述接口的以下两个方法:
演示:
第一步:添加com.dx.spring.beans.cycle.MyBeanPostProcessor.java使其实现抽象接口类BeanPostProcessor
package com.dx.spring.beans.cycle; import org.springframework.beans.BeansException; import org.springframework.beans.factory.config.BeanPostProcessor; public class MyBeanPostProcessor implements BeanPostProcessor { @Override public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { System.out.println("postProcessBeforeInitialization:" + beanName + "," + bean); return BeanPostProcessor.super.postProcessBeforeInitialization(bean, beanName); } @Override public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { System.out.println("postProcessAfterInitialization" + beanName + "," + bean); return BeanPostProcessor.super.postProcessAfterInitialization(bean, beanName); } }
第二步:修改spring-cycle.xml配置文件
<?xml version="1.0" encoding="UTF-8"?> <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.xsd"> <bean id="member" class="com.dx.spring.beans.cycle.Member" init-method="initMethod" destroy-method="destroyMethod"> <property name="name" value="member1"></property> </bean> <!-- 注意:这里不需要指定id --> <bean class="com.dx.spring.beans.cycle.MyBeanPostProcessor"></bean> </beans>
第三步:执行Main测试,查看打印信息:
信息: Loading XML bean definitions from class path resource [bean-cycle.xml] Member constructor ... setName member1 postProcessBeforeInitialization:member,com.dx.spring.beans.cycle.Member@1a968a59 init method postProcessAfterInitializationmember,com.dx.spring.beans.cycle.Member@1a968a59 com.dx.spring.beans.cycle.Member@1a968a59 May 24, 2018 9:46:07 PM org.springframework.context.support.ClassPathXmlApplicationContext doClose 信息: Closing org.springframework.context.support.ClassPathXmlApplicationContext@4bf558aa: startup date [Thu May 24 21:46:06 CST 2018]; root of context hierarchy despose method
基础才是编程人员应该深入研究的问题,比如:
1)List/Set/Map内部组成原理|区别
2)mysql索引存储结构&如何调优/b-tree特点、计算复杂度及影响复杂度的因素。。。
3)JVM运行组成与原理及调优
4)Java类加载器运行原理
5)Java中GC过程原理|使用的回收算法原理
6)Redis中hash一致性实现及与hash其他区别
7)Java多线程、线程池开发、管理Lock与Synchroined区别
8)Spring IOC/AOP 原理;加载过程的。。。
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