Spring 高级 常见的Bean 后处理器

一、代码

package com.mangoubiubiu.show.a04;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import javax.annotation.Resource;


public class Bean1 {

    private static final Logger log = LoggerFactory.getLogger(Bean1.class);

    private Bean2 bean2;

    @Autowired
    public void setBean2(Bean2 bean2){
        log.info("@Autowired 生效：{}",bean2);
        this.bean2=bean2;
    }


    private Bean3 bean3;

    public void setBean3(Bean3 bean3){
        log.info("@Resource 生效:{}",bean3);
        this.bean3=bean3;
    }


    private String home;

    @Autowired
    public void setHomeAutowired(@Value("${JAVA_HOME}") String home){
        log.info("Autowired@Value 生效:{}",home);
        this.home = home;
    }

    @Resource
    public void setHomeResource(@Value("${JAVA_HOME}") String home){
        log.info("Resource@Value 生效:{}",home);
        this.home = home;
    }

    @PostConstruct
    public void initPostConstruct(){
        log.info("@PostConstruct 生效");
    }

    @PreDestroy
    public void initPreDestroy(){
        log.info("@PreDestroy 生效");
    }


    @Override
    public String toString() {
        return "Bean1{" +
                "bean2=" + bean2 +
                ", bean3=" + bean3 +
                ", home='" + home + '\'' +
                '}';
    }
}

package com.mangoubiubiu.show.a04;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;


@Component
public class Bean2 {
}

package com.mangoubiubiu.show.a04;

import org.springframework.stereotype.Component;


@Component
public class Bean3 {
}

二、AutowiredAnnotationBeanPostProcessor

package com.mangoubiubiu.show.a04;

import org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor;
import org.springframework.context.annotation.CommonAnnotationBeanPostProcessor;
import org.springframework.context.annotation.ContextAnnotationAutowireCandidateResolver;
import org.springframework.context.support.GenericApplicationContext;

public class A04Application {

    public static void main(String[] args) {
        // GenericApplicationContext 是一个【干净】的容器
        GenericApplicationContext context = new GenericApplicationContext();
        context.registerBean("bean1",Bean1.class);
        context.registerBean("bean2",Bean2.class);
        context.registerBean("bean3",Bean3.class);
        //自动装配后选者的解析器
        context.getDefaultListableBeanFactory().setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());
        //不给名字就会把包名类名做为添加名称
        context.registerBean(AutowiredAnnotationBeanPostProcessor.class);//解析@Autowired 与 @Value
//        context.registerBean(CommonAnnotationBeanPostProcessor.class);//@Resource、@PostConstruct、@PreDestroy

        //初始化容器
        context.refresh();
        //销毁容器
        context.close();
    }


}

三、CommonAnnotationBeanPostProcessor 

package com.mangoubiubiu.show.a04;

import org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor;
import org.springframework.context.annotation.CommonAnnotationBeanPostProcessor;
import org.springframework.context.annotation.ContextAnnotationAutowireCandidateResolver;
import org.springframework.context.support.GenericApplicationContext;

public class A04Application {

    public static void main(String[] args) {
        // GenericApplicationContext 是一个【干净】的容器
        GenericApplicationContext context = new GenericApplicationContext();
        context.registerBean("bean1",Bean1.class);
        context.registerBean("bean2",Bean2.class);
        context.registerBean("bean3",Bean3.class);
        //自动装配后选者的解析器
        context.getDefaultListableBeanFactory().setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());
        //不给名字就会把包名类名做为添加名称
//        context.registerBean(AutowiredAnnotationBeanPostProcessor.class);//解析@Autowired 与 @Value
        context.registerBean(CommonAnnotationBeanPostProcessor.class);//@Resource、@PostConstruct、@PreDestroy

        //初始化容器
        context.refresh();
        //销毁容器
        context.close();
    }


}

四、ConfigurationPropertiesBindingPostProcessor 

package com.mangoubiubiu.show.a04;

import org.springframework.boot.context.properties.ConfigurationProperties;

@ConfigurationProperties(prefix = "java")
public class Bean4 {
    private String home;
    private String version;
    public String getHome() {
        return home;
    }
    public void setHome(String home) {
        this.home = home;
    }
    public String getVersion() {
        return version;
    }
    public void setVersion(String version) {
        this.version = version;
    }
}

package com.mangoubiubiu.show.a04;

import org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor;
import org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor;
import org.springframework.context.annotation.CommonAnnotationBeanPostProcessor;
import org.springframework.context.annotation.ContextAnnotationAutowireCandidateResolver;
import org.springframework.context.support.GenericApplicationContext;

public class A04Application {

    public static void main(String[] args) {
        // GenericApplicationContext 是一个【干净】的容器
        GenericApplicationContext context = new GenericApplicationContext();
        context.registerBean("bean1",Bean1.class);
        context.registerBean("bean2",Bean2.class);
        context.registerBean("bean3",Bean3.class);
        context.registerBean("bean4",Bean4.class);

        //自动装配后选者的解析器
        context.getDefaultListableBeanFactory().setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());
        //不给名字就会把包名类名做为添加名称
//        context.registerBean(AutowiredAnnotationBeanPostProcessor.class);//解析@Autowired 与 @Value
//        context.registerBean(CommonAnnotationBeanPostProcessor.class);//@Resource、@PostConstruct、@PreDestroy
//        ConfigurationPropertiesBindingPostProcessor.register(context.getDefaultListableBeanFactory());  //解析 @ConfigurationProperties
        //初始化容器
        context.refresh();
        System.out.println(context.getBean("bean4"));

        //销毁容器
        context.close();
    }
}

没有取到值 也就是说@ConfigurationProperties 并未生效

添加后处理器发现生效了

 

 

二、总结

1. @Autowired 等注解的解析属于 bean 生命周期阶段（依赖注入, 初始化）的扩展功能，这些扩展功能由 bean 后处理器来完成
2. 每个后处理器各自增强什么功能

• AutowiredAnnotationBeanPostProcessor 解析 @Autowired 与 @Value ----执行时机 在依赖注入阶段解析@Autowired 与 @Value
• CommonAnnotationBeanPostProcessor 解析 @Resource、@PostConstruct、@PreDestroy ----执行时机 在依赖注入阶段负责解析 @Resource，初始化前解析@PostConstruct，销毁前负责解析@PreDestroy
• ConfigurationPropertiesBindingPostProcessor 解析 @ConfigurationProperties ----执行时机 初始前执行属性绑定