Spring bean的生命周期详解
bean的生命周期
1.实例化bean 即new
2.按照spring上下文对实例化的bean进行配置 即填充属性,也就是IOC/DI(控制反转,依赖注入)
3.如果这个bean实现了BeanNameAware接口,Spring会调用它实现的setBeanName()方法,参数是bean的ID,即Spring将bean的ID传递给setBeanName()方法。(让bean知道自己是谁,即自己的ID)
4.如果bean实现了BeanFactoryAware接口,Spring将调用setBeanFactory(BeanFactory factory)方法,将BeanFactory容器实例传入;(即知道bean自己属于哪个工厂)
5.如果Bean实现了ApplicationContextAware接口,Spring将调用setApplicationContext(ApplicationContext context)方法,传入Spring上下文。
6.如果Bean实现了BeanPostProcessor接口,将会调用postProcessBeforeInialization(Object obj,String s)方法。BeanPostProcessor经常被用作是Bean内容的更改。
7.如果这个Bean在Spring配置文件中配置了init-method属性会自动调用其配置的初始化方法。
8.如果这个Bean实现了BeanPostProcessor接口,将会调用postAfterInitialization(Object obj,String s)方法
备注:当以上工作完成后就可以使用这个Bean了,这个bean是single的,一般调用同一个ID的bean会是在内容地址相同的实例
9.这个Bean会一直留在应用上下文中(ApplicationContext),直到该应用上下文被销毁。
10.如果这个Bean实现了DisposableBean接口,会调用destroy()方法;如果Bean在Spring配置中配置了destroy-method属性,会自动调用其配置的销毁方法。
在Spring框架中,bean的定义,从编写到配置再到最终的getbean调用,框架都有相应的实现规则,具体如下所述。
bean的定义:
package com.spring.beans; import javax.ejb.Init; import org.springframework.beans.factory.InitializingBean; public class HelloBean implements InitializingBean { public HelloBean() {
System.out.println("构造方法");
} private String name;
private String nullTest; private int age; public String getNullTest() {
return nullTest;
} public void setNullTest(String nullTest) {
this.nullTest = nullTest;
} public String getName() {
return name;
} public void setName(String name) {
this.name = name;
} public int getAge() {
return age;
} public void setAge(int age) {
this.age = age;
} public void prints(String str) {
System.out.println(str + ":hahahah");
} public void init() {
System.out.println("init");
} @Override
public void afterPropertiesSet() throws Exception {
// TODO Auto-generated method stub
System.out.println("initializing");
}
}
BeanPostProcessor定义:
package com.spring.test; import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor; public class BeanPostProcessor_Imp implements BeanPostProcessor { @Override
public Object postProcessAfterInitialization(Object arg0, String arg1)
throws BeansException {
System.out.println("执行后");
return arg0;
} @Override
public Object postProcessBeforeInitialization(Object arg0, String arg1)
throws BeansException {
System.out.println("执行前");
return arg0;
} }
测试类的定义:
package com.spring.test; import java.util.List; import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.core.io.FileSystemResource;
import org.springframework.core.io.Resource; import com.spring.beans.BigBearBean;
import com.spring.beans.HelloBean;
import com.spring.beans.List_Map_Bean;
import com.spring.beans.smallBearBean;
import com.spring.interfaces.Animal; public class HelloTest {
public static void main(String[] args) {
ApplicationContext ctx = new ClassPathXmlApplicationContext(
"hellotest.xml");
HelloBean HB = (HelloBean) ctx.getBean("hello");
HB.prints("王涛");
System.out.println(HB.getName() + "\n------------");
} }
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" xmlns:util="http://www.springframework.org/schema/util"
xmlns:context="http://www.springframework.org/schema/context" xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.0.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.0.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd"> <bean id="hello" class="com.spring.beans.HelloBean" init-method="init">
<property name="name">
<value><![CDATA[<wb<t>]]></value>
</property>
<property name="age" value="23" />
<property name="nullTest">
<value></value>
</property>
</bean>
<bean class="com.spring.test.BeanPostProcessor_Imp"></bean>
</beans>
运行结果:
15:38:12,269 INFO [context.support.ClassPathXmlApplicationContext] Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@61a48515: startup date [Fri Jun 23 15:38:12 CST 2017]; root of context hierarchy
15:38:12,343 INFO [factory.xml.XmlBeanDefinitionReader] Loading XML bean definitions from class path resource [hellotest.xml]
15:38:12,588 INFO [factory.support.DefaultListableBeanFactory] Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@25ff3700: defining beans [hello,com.spring.test.BeanPostProcessor_Imp#0]; root of factory hierarchy
构造方法
执行前
initializing
init
执行后
王涛:hahahah
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