Spring中Bean的初始化过程

技术2022-05-20 42

Quotes: http://kantery.javaeye.com/blog/342206

在传统的Java应用中，Bean的生命周期非常简单。Java的关键词new用来实例化Bean（或许他是非序列化的）。这样就够用了。相反，Bean 的生命周期在Spring容器中更加细致。理解Spring Bean的生命周期非常重要，因为你或许要利用Spring提供的机会来订制Bean的创建过程。 1. 容器寻找Bean的定义信息并且将其实例化。 2.受用依赖注入，Spring按照Bean定义信息配置Bean的所有属性。 3.如果Bean实现了BeanNameAware接口，工厂调用Bean的setBeanName()方法传递Bean的ID。 4.如果Bean实现了BeanFactoryAware接口，工厂调用setBeanFactory()方法传入工厂自身。 5.如果BeanPostProcessor和Bean关联，那么它们的postProcessBeforeInitialzation()方法将被调用。 6.如果Bean指定了init-method方法，它将被调用。 7.最后，如果有BeanPsotProcessor和Bean关联，那么它们的postProcessAfterInitialization()方法将被调用。到这个时候，Bean已经可以被应用系统使用了，并且将被保留在Bean Factory中知道它不再需要。有两种方法可以把它从Bean Factory中删除掉。 1.如果Bean实现了DisposableBean接口，destory()方法被调用。 2.如果指定了订制的销毁方法，就调用这个方法。 Bean在Spring应用上下文的生命周期与在Bean工厂中的生命周期只有一点不同，唯一不同的是，如果Bean实现了ApplicationContextAwre接口，setApplicationContext()方法被调用。举例：（这里只是演示Bean工厂的例子）我这里用的是spring-1.2.6，由于版本原因吧，这里演示的不是很好! 1.HelloWorld.java

Java代码 package com.spring.lifecycle; import org.springframework.beans.BeansException; import org.springframework.beans.factory.BeanFactory; import org.springframework.beans.factory.BeanFactoryAware; import org.springframework.beans.factory.BeanNameAware; import org.springframework.beans.factory.DisposableBean; import org.springframework.beans.factory.InitializingBean; import org.springframework.beans.factory.config.BeanPostProcessor; public class HelloWorld implements BeanNameAware,BeanFactoryAware, BeanPostProcessor,InitializingBean,DisposableBean{ private String hello; public void setBeanName(String arg0) { System.out.println("调用BeanNameAware的setBeanName()..." ); } public String getHello() { return hello; } public void setHello(String hello) { this .hello = hello; System.out.println("调用setHello()..." ); } public void customInit() { System.out.println("调用customInit()..." ); } public void customDestroy() { System.out.println("调用customDestroy()..." ); } public Object postProcessAfterInitialization(Object arg0, String arg1) throws BeansException { System.out.println("调用BeanPostProcessor的postProcessAfterInitialization()..." ); return null ; } public Object postProcessBeforeInitialization(Object arg0, String arg1) throws BeansException { System.out.println("调用BeanPostProcessor的postProcessBeforeInitialization()..." ); return null ; } public void destroy() throws Exception { System.out.println("调用DisposableBean的destory()..." ); } public void afterPropertiesSet() throws Exception { System.out.println("调用InitializingBean的afterPropertiesSet()..." ); } public void setBeanFactory(BeanFactory arg0) throws BeansException { System.out.println("调用BeanFactoryAware的setBeanFactory()..." ); } } package com.spring.lifecycle; import org.springframework.beans.BeansException; import org.springframework.beans.factory.BeanFactory; import org.springframework.beans.factory.BeanFactoryAware; import org.springframework.beans.factory.BeanNameAware; import org.springframework.beans.factory.DisposableBean; import org.springframework.beans.factory.InitializingBean; import org.springframework.beans.factory.config.BeanPostProcessor; public class HelloWorld implements BeanNameAware,BeanFactoryAware, BeanPostProcessor,InitializingBean,DisposableBean{ private String hello; public void setBeanName(String arg0) { System.out.println("调用BeanNameAware的setBeanName()..." ); } public String getHello() { return hello; } public void setHello(String hello) { this.hello = hello; System.out.println("调用setHello()..." ); } public void customInit() { System.out.println("调用customInit()..."); } public void customDestroy() { System.out.println("调用customDestroy()..."); } public Object postProcessAfterInitialization(Object arg0, String arg1) throws BeansException { System.out.println("调用BeanPostProcessor的postProcessAfterInitialization()..."); return null; } public Object postProcessBeforeInitialization(Object arg0, String arg1) throws BeansException { System.out.println("调用BeanPostProcessor的postProcessBeforeInitialization()..."); return null; } public void destroy() throws Exception { System.out.println("调用DisposableBean的destory()..."); } public void afterPropertiesSet() throws Exception { System.out.println("调用InitializingBean的afterPropertiesSet()..."); } public void setBeanFactory(BeanFactory arg0) throws BeansException { System.out.println("调用BeanFactoryAware的setBeanFactory()..."); } }

2.测试程序

Java代码 package com.spring.springtest; import junit.framework.TestCase; import org.springframework.beans.factory.BeanFactory; import org.springframework.context.support.ClassPathXmlApplicationContext; import com.spring.lifecycle.HelloWorld; public class TestLifeCycle extends TestCase { private BeanFactory bf; protected void setUp() throws Exception { bf = new ClassPathXmlApplicationContext( "applicationContext.xml" ); } public void testLifeCycle() throws Exception { HelloWorld hello = (HelloWorld) bf.getBean("helloWorld" ); assertEquals("hello world!" , hello.getHello()); hello.destroy(); } } package com.spring.springtest; import junit.framework.TestCase; import org.springframework.beans.factory.BeanFactory; import org.springframework.context.support.ClassPathXmlApplicationContext; import com.spring.lifecycle.HelloWorld; public class TestLifeCycle extends TestCase { private BeanFactory bf; protected void setUp() throws Exception { bf = new ClassPathXmlApplicationContext("applicationContext.xml"); } public void testLifeCycle() throws Exception { HelloWorld hello = (HelloWorld) bf.getBean("helloWorld"); assertEquals("hello world!", hello.getHello()); hello.destroy(); } }

3.applicationContext.xml

Xml代码 <? xml version = "1.0" encoding = "UTF-8" ?> <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd"> < beans > < bean id = "helloWorld" class = "com.spring.lifecycle.HelloWorld" init-method = "customInit" destroy-method = "customDestroy" > < property name = "hello" value = "hello world!" > </ property > </ bean > </ beans > <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd"> <beans> <bean id="helloWorld" class="com.spring.lifecycle.HelloWorld" init-method="customInit" destroy-method="customDestroy"> <property name="hello" value="hello world!"></property> </bean> </beans>

4.运行结果：

引用调用setHello()... 调用BeanNameAware的setBeanName()... 调用BeanFactoryAware的setBeanFactory()... 调用InitializingBean的afterPropertiesSet()... 调用customInit()... 调用DisposableBean的destory()...

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