Spring中Bean的初始化过程

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

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

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   version = "1.0"   encoding = "UTF-8" ?>
>
< 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()...