Spring BeanPostProcessor接口使用详解

2024-07-13 10:15:57

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Spring中提供了很多PostProcessor供开发者进行拓展，例如：BeanPostProcessor、BeanFactoryPostProcessor、BeanValidationPostProcessor等一系列后处理器。他们的使用方式大多类似，了解其中一个并掌握他的使用方式，其他的可以触类旁通。

这里以BeanPostProcessor为例展示其使用方式。

BeanPostProcessor接口提供了两个供开发者自定义的方法：postProcessBeforeInitialization、postProcessAfterInitialization。

postProcessBeforeInitialization：该方法主要针对spring在bean初始化时调用初始化方法前进行自定义处理。

postProcessAfterInitialization：该方法主要针对spring在bean初始化时调用初始化方法后进行自定义处理。

示例代码：

/** * 测试bean */public class Cat {  private String name;  private int age;  public void say() {    System.out.println("name:" + name);    System.out.println("age:" + age);  }  public String getName() {    return name;  }  public void setName(String name) {    this.name = name;  }  public int getAge() {    return age;  }  public void setAge(int age) {    this.age = age;  }}

/** * 自定义后处理器 */public class CatBeanPostProcessor implements BeanPostProcessor {  @Nullable  @Override  public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {    if (bean instanceof Cat) {      //输出原始属性      Cat cat = (Cat) bean;      cat.say();      return bean;    }    return bean;  }  @Nullable  @Override  public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {    if (bean instanceof Cat) {      //修改属性值，并返回      Cat cat = (Cat) bean;      cat.setName("hello maomi");      cat.setAge(3);      return cat;    }    return bean;  }}

/** * 运行 */public class Run {  public static void main(String[] args) {    ApplicationContext applicationContext = new ClassPathXmlApplicationContext("spring-bean.xml");    Cat cat = (Cat) applicationContext.getBean("cat");    cat.say();  }}

xml配置信息

  <!--配置bean并初始化-->  <bean id="cat" class="com.source.postprocessor.Cat" >    <property name="name" value="HelloKitty" />    <property name="age" value="1" />  </bean>  <bean id="catBeanPostProcessor" class="com.source.postprocessor.CatBeanPostProcessor" />

输出结果：

name:HelloKitty
age:1
name:hello maomi
age:3

可以看到通过后处理器处理过后的bean信息已经改变。最后，看看源码中如何调用自定义实现的。

在初始化bean方法中：AbstractAutowireCapableBeanFactory.java

  /**  * 初始化bean  */ protected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {   //省略部分无关代码   Object wrappedBean = bean;   //初始化前   if (mbd == null || !mbd.isSynthetic()) {     wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);   }   try {     //调用初始化方法初始化bean     invokeInitMethods(beanName, wrappedBean, mbd);   }   catch (Throwable ex) {     throw new BeanCreationException(         (mbd != null ? mbd.getResourceDescription() : null),         beanName, "Invocation of init method failed", ex);   }   //初始化后   if (mbd == null || !mbd.isSynthetic()) {     wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);   }   return wrappedBean; } //postProcessBeforeInitialization方法调用 @Override public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)     throws BeansException {   Object result = existingBean;   for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {     //调用自定义postProcessBeforeInitialization方法     Object current = beanProcessor.postProcessBeforeInitialization(result, beanName);     if (current == null) {       return result;     }     result = current;   }   return result; } //postProcessAfterInitialization方法调用 @Override public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)     throws BeansException {   Object result = existingBean;   for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {     //自定义postProcessAfterInitialization方法调用     Object current = beanProcessor.postProcessAfterInitialization(result, beanName);     if (current == null) {       return result;     }     result = current;   }   return result; }

以上就是spring对自定义方法实现的调用过程。希望对大家的学习有所帮助，也希望大家多多支持VeVb武林网。

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