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;

	@Autowired
	public void setDog(Dog dog) {
		System.out.println("@Autowired生效：" + dog);
		this.dog = dog;
	}

	private String home;

	@Autowired
	public 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Bean
		genericApplicationContext.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;

	@Resource
	public 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Bean
		genericApplicationContext.registerBean("person", Person.class);

		genericApplicationContext.registerBean("cat", Cat.class);

		// 解析@Resource @PostConstruct @PreDestroy
		genericApplicationContext.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@ConfigurationProperties
		ConfigurationPropertiesBindingPostProcessor.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