Spring系列(八)Spring生命周期中BeanPostProcessor接口用法
今天给大家介绍BeanPostProcessor接口用法,希望对大家能有所帮助!
1、BeanPostProcessor 概念介绍
BeanPostProcessor接口通常被称为Bean的后置处理器,它是Spring中定义的接口,可以在Spring容器的创建过程中(主要在Bean初始化前后进行工作)回调BeanPostProcessor中定义的两个方法。 2、BeanPostProcessor接口方法
postProcessBeforeInitialization :在每一个bean对象的初始化方法调用之前回调。
postProcessAfterInitialization :在每个bean对象的初始化方法调用之后被回调。
说明 :以上两个方法的返回值都不能为null,否则在后续的初始化方法会报空指针或者通过getBean()方法无法获取Bean对象。主要原因是如果返回值为null的情况下以上两个方法从Spring容器获取bean实例,没有再次放入Spring容器中去,这样容器中就没有了。 2.1 BeanPostProcessor源码内容package org.springframework.beans.factory.config; import org.springframework.beans.BeansException; import org.springframework.lang.Nullable; public interface BeanPostProcessor { @Nullable default Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { return bean; } @Nullable default Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { return bean; } } 3、BeanPostProcessor 接口的作用
可以Spring容器中完成bean实例化、配置以及其他初始化方法前后根据业务的场景增加相应的逻辑处理。典型的案例AOP的实现。 4、代码示例4.1 新建Person.java 类文件package com.spring.bean; public class Person { private String name; private Integer age; private String address; public Person(String name, Integer age, String address) { this.name = name; this.age = age; this.address = address; } public Person() { } public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } @Override public String toString() { return "Person{" + "name="" + name + """ + ", age="" + age + """ + ", address="" + address + """ + "}"; } } 4.2、新建MyBeanPostProcessor.javapackage com.spring.bean; import org.springframework.beans.BeansException; import org.springframework.beans.factory.config.BeanPostProcessor; import org.springframework.stereotype.Component; @Component public class MyBeanPostProcessor implements BeanPostProcessor { /** * 实例化、依赖注入完毕,在调用显示的初始化之前完成一些自定义的初始化逻辑 * 方法返回值不能为null * 返回null那么在后续初始化方法会报空指针异常或者通过getBean()方法获取不到bena实例 * 如果设置为null情况下,后置处理器从Spring IoC容器中取出bean实例对象没有再次放回IoC容器中 */ public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException { System.out.println("postProcessBeforeInitialization执行了"+beanName); return bean; } /** * 实例化、依赖注入、初始化完成后时执行 * 方法返回值也不能为null * 如果返回null那么在后续初始化方法将报空指针异常或者通过getBean()方法获取不到bena实例对象 * 如果设置为null情况下,后置处理器从Spring IoC容器中取出bean实例对象没有再次放回IoC容器中 */ public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException { System.out.println("postProcessAfterInitialization"+beanName); return bean; } } 4.3、新建TestBeanPostProcessorConfig.java 配置类package com.spring.config; import com.spring.bean.UserInfo; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; import org.springframework.context.annotation.FilterType; import org.springframework.stereotype.Component; import org.springframework.stereotype.Controller; @Configuration @ComponentScan(value = "com.spring.bean",includeFilters = { @ComponentScan.Filter(type = FilterType.ANNOTATION , classes = {Component.class, Controller.class} ), @ComponentScan.Filter(type = FilterType.ASSIGNABLE_TYPE , classes = {UserInfo.class} ), }) public class TestBeanPostProcessorConfig { } 4.4、新建测试类 TestBeanPostProcessor.javapackage com.spring.test; import com.spring.config.TestBeanPostProcessorConfig; import org.springframework.context.annotation.AnnotationConfigApplicationContext; public class TestBeanPostProcessor { public static void main(String[] args) { AnnotationConfigApplicationContext annotationContext = new AnnotationConfigApplicationContext(TestBeanPostProcessorConfig.class); } }
输出结果: postProcessBeforeInitialization执行了testBeanPostProcessorConfig postProcessAfterInitializationtestBeanPostProcessorConfig UserInfo构造器执行了 postProcessBeforeInitialization执行了userInfo PostConstruct 初始化方法执行 postProcessAfterInitializationuserInfo Process finished with exit code 0