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一、作用

• 1.为bean生命周期的各个阶段提供扩展
• 2.实例化前、实例化后、依赖注入阶段、初始化前、初始化后、销毁之前提供扩展

二、常见的bean后处理器

2.1 AutowiredAnnotationBeanPostProcessor

2.1.1 说明

• 1. 用来解析@Autowired @Value注解

2.1.2 代码示例

package com.learning.bean_processor;public class Dog {
}

package com.learning.bean_processor;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;public class Person {private Dog dog;@Autowiredpublic void setDog(Dog dog) {System.out.println("@Autowired生效：" + dog);this.dog = dog;}private String home;@Autowiredpublic void setHome(@Value("${JAVA_HOME}") String home){System.out.println("@Value生效：" + home);this.home = home;}}

package com.learning.bean_processor;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;/*** Bean后处理器*/
public class BeanProcessorTest {public static void main(String[] args) {GenericApplicationContext genericApplicationContext = new GenericApplicationContext();// 用原始方法注册三个BeangenericApplicationContext.registerBean("person", Person.class);genericApplicationContext.registerBean("dog", Dog.class);genericApplicationContext.getDefaultListableBeanFactory().setAutowireCandidateResolver(new ContextAnnotationAutowireCandidateResolver());// 解析@Autowired @Value注解genericApplicationContext.registerBean(AutowiredAnnotationBeanPostProcessor.class);// 初始化容器// 执行beanFactory后处理器，添加bean后处理器，初始化所有单例genericApplicationContext.refresh();// 销毁容器genericApplicationContext.close();}
}

2.1.3 截图示例

2.2 CommonAnnotationBeanPostProcessor

2.2.1 说明

• 1. 解析@Resource @PostConstruct @PreDestroy

2.2.2 代码示例

package com.learning.bean_processor;public class Cat {
}

package com.learning.bean_processor;import javax.annotation.Resource;public class Person {private Cat cat;@Resourcepublic void setCat(Cat cat) {System.out.println("@Resource：" + cat);this.cat = cat;}}

package com.learning.bean_processor;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;/*** Bean后处理器*/
public class BeanProcessorTest {public static void main(String[] args) {GenericApplicationContext genericApplicationContext = new GenericApplicationContext();// 用原始方法注册三个BeangenericApplicationContext.registerBean("person", Person.class);genericApplicationContext.registerBean("cat", Cat.class);// 解析@Resource @PostConstruct @PreDestroygenericApplicationContext.registerBean(CommonAnnotationBeanPostProcessor.class);// 初始化容器// 执行beanFactory后处理器，添加bean后处理器，初始化所有单例genericApplicationContext.refresh();// 销毁容器genericApplicationContext.close();}
}

2.2.3 截图示例

2.3 ConfigurationPropertiesBindingPostProcessor

2.3.1 说明

• 1. springboot中配置文件属性绑定bean的增强
• 2. 需要引用springboot的包

2.3.2 代码示例

package com.learning.bean_processor;import lombok.Data;
import org.springframework.boot.context.properties.ConfigurationProperties;@Data
@ConfigurationProperties(prefix = "java")
public class JavaProperties {private String home;private String version;}

package com.learning.bean_processor;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;/*** Bean后处理器*/
public class BeanProcessorTest {public static void main(String[] args) {GenericApplicationContext genericApplicationContext = new GenericApplicationContext();// 把springboot中的ConfigurationPropertiesBindingPostProcessor后处理器加到容器中// 解析@ConfigurationPropertiesConfigurationPropertiesBindingPostProcessor.register(genericApplicationContext.getDefaultListableBeanFactory());genericApplicationContext.registerBean("java_home", JavaProperties.class);// 初始化容器// 执行beanFactory后处理器，添加bean后处理器，初始化所有单例genericApplicationContext.refresh();System.out.println(genericApplicationContext.getBean(JavaProperties.class));// 销毁容器genericApplicationContext.close();}
}

2.3.3 截图示例