07点睛Spring4.1-BeanPostProcessor

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7.1 BeanPostProcessor

• spring通过BeanPostProcessor接口可以对所有bean或者指定的某些bean的初始化前后对bean的检查或者修改提供支持;
• 使用postProcessBeforeInitialization和postProcessAfterInitialization对bean进行操作;
• postProcessBeforeInitialization和postProcessAfterInitialization返回值是bean;

7.2 示例

7.2.1 处理全部bean

7.2.1.1 新建两个测试用的bean

package com.wisely.beanpostprocessor;

import org.springframework.stereotype.Service;

@Service
public class DemoNormal1Service {

}

package com.wisely.beanpostprocessor;

import org.springframework.stereotype.Service;

@Service
public class DemoNormal2Service {

}

7.2.1.2 编写处理所有bean的BeanPostProcessor

package com.wisely.beanpostprocessor;

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

@Component
public class DemoAllBeanPostProcessor implements BeanPostProcessor{

    public Object postProcessBeforeInitialization(Object bean, String beanName)
            throws BeansException {
        System.out.println("在 DemoAllBeanPostProcessor的"
        +postProcessBeforeInitialization方法里处理bean: " + beanName
        +" bean的类型为:"+bean.getClass());
        return bean;
    }

    public Object postProcessAfterInitialization(Object bean, String beanName)
            throws BeansException {
        System.out.println("在 DemoAllBeanPostProcessor的"+
        postProcessAfterInitialization方法里处理bean: " + beanName
        +" bean的类型为:"+bean.getClass());
        return bean;
    }

}

7.2.1.3 测试

package com.wisely.beanpostprocessor;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class Main {

    public static void main(String[] args) {
        AnnotationConfigApplicationContext context =  
                 new AnnotationConfigApplicationContext("com.wisely.beanpostprocessor");
        context.close();

    }

}

输出结果为:

在 DemoAllBeanPostProcessor的postProcessBeforeInitialization方法里处理bean:
demoNormal1Service bean的类型为:class com.wisely.beanpostprocessor.DemoNormal1Service
在 DemoAllBeanPostProcessor的postProcessAfterInitialization方法里处理bean:
demoNormal1Service bean的类型为:class com.wisely.beanpostprocessor.DemoNormal1Service
在 DemoAllBeanPostProcessor的postProcessBeforeInitialization方法里处理bean:
demoNormal2Service bean的类型为:class com.wisely.beanpostprocessor.DemoNormal2Service
在 DemoAllBeanPostProcessor的postProcessAfterInitialization方法里处理bean:
demoNormal2Service bean的类型为:class com.wisely.beanpostprocessor.DemoNormal2Service

7.2.2 处理指定的bean

7.2.2.2 新建指定处理的bean

已经给os和num属性赋值,将在BeanPostProcessor的实现类对类的属性进行修改

package com.wisely.beanpostprocessor;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;

@Service
public class DemoSelectedService {
    @Value("#{systemProperties['os.name']}")
    private String os;
    @Value("123")
    private Long num;

    public String getOs() {
        return os;
    }

    public void setOs(String os) {
        this.os = os;
    }

    public Long getNum() {
        return num;
    }

    public void setNum(Long num) {
        this.num = num;
    }


}

7.2.2.3 编写指定bean的BeanPostProcessor

packagecom.wisely.beanpostprocessor;

importorg.springframework.beans.BeansException;
importorg.springframework.beans.factory.config.BeanPostProcessor;
importorg.springframework.stereotype.Component;
@Component

public class DemoSelectedBeanPostProcessor implements BeanPostProcessor {

    public Object postProcessBeforeInitialization(Objectbean, StringbeanName)
            throwsBeansException {
        if(bean instanceof DemoSelectedService){
            ((DemoSelectedService) bean).setOs("Linux");
            System.out.println("在DemoSelectedBeanPostProcessor的"+"postProcessBeforeInitialization中将os从windows修改成了Linux" );
        }
        return bean;
    }

    public Object postProcessAfterInitialization(Objectbean, StringbeanName)
            throwsBeansException {
        if(bean instanceof DemoSelectedService){
            ((DemoSelectedService) bean).setNum(456);
            System.out.println("在DemoSelectedBeanPostProcessor的"+"postProcessBeforeInitialization中将num从123修改成了456" );
        }
        return bean;
    }

}

7.2.2.4 测试

package com.wisely.beanpostprocessor;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class Main {

    public static void main(String[] args) {
        AnnotationConfigApplicationContext context =
                 new  AnnotationConfigApplicationContext("com.wisely.beanpostprocessor");
        DemoSelectedService dss = context.getBean(DemoSelectedService.class);
        System.out.println("os确实被修改成了"+dss.getOs());
        System.out.println("num确实被修改成了"+dss.getNum());
        context.close();

    }

}

输出结果

在DemoSelectedBeanPostProcessor的postProcessBeforeInitialization中将os从windows修改成了Linux
在DemoSelectedBeanPostProcessor的postProcessBeforeInitialization中将num从123修改成了456
os确实被修改成了Linux
num确实被修改成了123

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