Spring中JavaBean的预处理和后处理

首先要知道在Spring中BeanFactory

在BeanFactory中JavaBean的生命周期分为实例化、初始化、使用和销毁四个阶段

实例化：调用BeanFactory的getBean()方法，在中期会创建JavaBean的实例对象，并根据指定的XML自动收集JavaBean的定义信息，通过<constructor-arg>标签为JavaBean构造方法阐述初始化JavaBean的实例对象

初始化：容器按照JavaBean的定义初始化JavaBean的所有属性和依赖关系。

使用：可直接通过getBean(）方法获得并使用JavaBean的实例对象。

销毁：关闭容器时会销毁所有的javabean

JavaBean的预处理和后处理。通过实现BeanPostProcessor接口来对JavaBean是初始化之前调用还是初始化之后调用

例如：在本例子中定义了一个TempWorker类记录员工信息。LogFile中存储所有员工信息保存在workList中。在applicationContext.xml中在workList加入了3个worker。其中worker1赋值完整。如果不创建BeanPostProcessorExample运行之后未赋值的值为空。创建了BeanPostProcessorExample之后可以在logFile这个bean实例化之后根据我们的代码把为赋值的地方赋值

TempWorker:

package com;

public class TempWorker implements Worker{
    private String name;
    private String workType;
    private int pay;
    
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getWorkType() {
        return workType;
    }

    public void setWorkType(String workType) {
        this.workType = workType;
    }
    
    
    

    public int getPay() {
        return pay;
    }

    public void setPay(int pay) {
        this.pay = pay;
    }

    public void printInfo() {
        System.out.println("\nName:"+name);
        System.out.println("Work Type:"+workType);
        System.out.println("Pay:"+pay);


    }

}

logFile:

package com;

import java.util.ArrayList;
import java.util.List;

public class logFile {
    private List workList=new ArrayList();

    public List getWorkList() {
        return workList;
    }

    public void setWorkList(List workList) {
        this.workList = workList;
    }
    
}

applicationContext:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN"
"http://www.springframework.org/dtd/spring-beans-2.0.dtd">
<beans>
    <bean id="log" class="com.logFile">
        <property name="workList">
            <list>
                <ref bean="worker1"/>
                <ref bean="worker2"/>
                <ref bean="worker3"/>
            </list>
        </property>
    </bean>
    <bean id="worker1" class="com.TempWorker">
        <property name="name">
            <value>Michle</value>
        </property>
        <property name="pay">
            <value>1000</value>
        </property>
        
    </bean>
    <bean id="worker2" class="com.TempWorker">
        <property name="name">
            <value>Michle</value>
        </property>
        <property name="workType">
            <value>Regular</value>
        </property>
        <property name="pay">
            <value>8000</value>
        </property>
        
    </bean>
    <bean id="worker3" class="com.TempWorker">
        <property name="name">
            <value>Lucy</value>
        </property>
        
        
    </bean>
    
</beans>

test:

package com;
import java.util.Iterator;
import java.util.List;

import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;

import com.Worker;
import com.logFile;


public class test {
    public static void main(String args[]){
        ApplicationContext ctx=new  FileSystemXmlApplicationContext("src/applicationContext.xml");
        //XmlBeanFactory bf=new XmlBeanFactory(rs);
        logFile log=(logFile) ctx.getBean("log");
        List workerlist=log.getWorkList();
        System.out.println("All workers:");
        Iterator it=workerlist.iterator();
        while(it.hasNext()){
            Worker worker=(Worker) it.next();
            worker.printInfo();
        }
        
    }
}

Result:

加入BeanPostProcessorExample

package com;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;

public class BeanPostProcessorExample implements BeanPostProcessor{

    public Object postProcessAfterInitialization(Object bean, String beanName)
            throws BeansException {
         if(bean instanceof TempWorker){
             TempWorker tempworker=(TempWorker) bean;
             if(tempworker.getPay()<=800){
                 tempworker.setPay(800);
             }
             if(tempworker.getWorkType()==null||tempworker.getWorkType().equals("")){
                 tempworker.setWorkType("Temp");
             }
             return tempworker;
         }
        return bean;
    }

    public Object postProcessBeforeInitialization(Object bean, String beanName)
            throws BeansException {
        // TODO Auto-generated method stub
        return bean;
    }

}

test:

package com;

import java.util.Iterator;
import java.util.List;

import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.context.support.FileSystemXmlApplicationContext;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;

public class TakeIn {
    public static void main(String args[]){
        Resource rs = new ClassPathResource("applicationContext.xml");
        XmlBeanFactory bf = new XmlBeanFactory(rs);
        BeanPostProcessorExample bp=new BeanPostProcessorExample();
        bf.addBeanPostProcessor(bp);
        logFile log=(logFile) bf.getBean("log");
        List workerlist=log.getWorkList();
        System.out.println("All workers:");
        Iterator it=workerlist.iterator();
        while(it.hasNext()){
            Worker worker=(Worker) it.next();
            worker.printInfo();
        }
    }
}

结果：