Spring AOP 源码探索之链式调用中的 ExposeInvocationInterceptor拦截器作用

系统管理员 2024-03-17 13:07 39阅读 0赞

#### 文章目录 ####

*   *  ExposeInvocationInterceptor
     *   *  示例代码
         *  源码分析
         *   *  extendAdvisors
             *  makeAdvisorChainAspectJCapableIfNecessary
         *  添加扩展拦截器的调用链
         *  作用示例
     *  总结
 *  相关学习路线
 *   *  JAVA资深架构师成长路线->开源框架解读->Spring框架源码解读

### ExposeInvocationInterceptor ###

从英文名字，顾名思义，暴露调用器的[拦截器][Link 1]。  
其就是起了暴露一个调用器作用的拦截器。

*  1、那么其暴露了什么调用器？
 *  2、是如何暴露的，通过什么方法实现？
 *  3、暴露给谁？
 *  4、在什么时候起到拦截作用？

下面带着以上问题，通过示例代码来分析spring [Aop][]源码

#### 示例代码 ####

[Spring AOP 源码探索 之 示例代码][Spring AOP _ _]

#### 源码分析 ####

##### extendAdvisors #####

在初始化完Bean，调用AbstractAutoProcxyCreator的后置处理方法postProcessAfterInitialization的时候，对adivisors进行了扩展，添加了ExposeInvocationInterceptor拦截器  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjIxMzkwMw_size_16_color_FFFFFF_t_70]

##### makeAdvisorChainAspectJCapableIfNecessary #####

实际添加了ExposeInvocationInterceptor拦截器的地方  
作者英文注释：

> /\*\*  
> \* Add special advisors if necessary to work with a proxy chain that contains AspectJ advisors.  
> \* This will expose the current Spring AOP invocation (necessary for some AspectJ pointcut matching)  
> \* and make available the current AspectJ JoinPoint. The call will have no effect if there are no  
> \* AspectJ advisors in the advisor chain.  
> \* @param advisors Advisors available  
> \* @return \{@code true\} if any special \{@link Advisor Advisors\} were added, otherwise \{@code false\}.  
> \*/

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjIxMzkwMw_size_16_color_FFFFFF_t_70 1]

#### 添加扩展拦截器的调用链 ####

方法栈图示  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjIxMzkwMw_size_16_color_FFFFFF_t_70 2]  
完整方法栈

makeAdvisorChainAspectJCapableIfNecessary:44, AspectJProxyUtils (org.springframework.aop.aspectj)
    extendAdvisors:97, AspectJAwareAdvisorAutoProxyCreator (org.springframework.aop.aspectj.autoproxy)
    findEligibleAdvisors:90, AbstractAdvisorAutoProxyCreator (org.springframework.aop.framework.autoproxy)
    getAdvicesAndAdvisorsForBean:70, AbstractAdvisorAutoProxyCreator (org.springframework.aop.framework.autoproxy)
    wrapIfNecessary:346, AbstractAutoProxyCreator (org.springframework.aop.framework.autoproxy)
    postProcessAfterInitialization:298, AbstractAutoProxyCreator (org.springframework.aop.framework.autoproxy)
    applyBeanPostProcessorsAfterInitialization:421, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support)
    initializeBean:1635, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support)
    doCreateBean:553, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support)
    createBean:481, AbstractAutowireCapableBeanFactory (org.springframework.beans.factory.support)
    getObject:312, AbstractBeanFactory$1 (org.springframework.beans.factory.support)
    getSingleton:230, DefaultSingletonBeanRegistry (org.springframework.beans.factory.support)
    doGetBean:308, AbstractBeanFactory (org.springframework.beans.factory.support)
    getBean:197, AbstractBeanFactory (org.springframework.beans.factory.support)
    preInstantiateSingletons:761, DefaultListableBeanFactory (org.springframework.beans.factory.support)
    finishBeanFactoryInitialization:867, AbstractApplicationContext (org.springframework.context.support)
    refresh:543, AbstractApplicationContext (org.springframework.context.support)
    <init>:84, AnnotationConfigApplicationContext (org.springframework.context.annotation)
    main:11, SilasMainClass (org.silas)

#### 作用示例 ####

在代理对象调用方法时起作用。  
[Spring AOP 源码探索 之 方法栈及链式调用解读][Spring AOP _ _ 1]

调用链首先调用此ExposeInvocationInterceptor拦截器的invoke方法，将MethodInvocation mi 设置到  
ThreadLocal invocation 里面  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjIxMzkwMw_size_16_color_FFFFFF_t_70 3]  
以后置通知（@After）拦截器的invoke为例  
org.springframework.aop.aspectj.AspectJAfterAdvice\#invoke  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjIxMzkwMw_size_16_color_FFFFFF_t_70 4]  
在调用通知方法invokeAdviceMethod的时候传了一个参，参数通过调用getJoinPointMatch()方法获得。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjIxMzkwMw_size_16_color_FFFFFF_t_70 5]  
看下getJoinPointMatch()方法源码  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjIxMzkwMw_size_16_color_FFFFFF_t_70 6]  
ExposeInvocationInterceptor.currentInvocation()方法  
从ThreadLocal invocation 里面取出了  
前面通过ExposeInvocationInterceptor实例对象set进去的mi  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjIxMzkwMw_size_16_color_FFFFFF_t_70 7]

### 总结 ###

那么从上面的AspectJAfterAdvice\#invoke方法例子可以知道，ExposeInvocationInterceptor就是用来传递MethodInvocation的。在后续的任何下调用链环节，只要需要用到当前的MethodInvocation就通过ExposeInvocationInterceptor.currentInvocation()静态方法获得。

## 相关学习路线 ##

### [JAVA资深架构师成长路线->开源框架解读->Spring框架源码解读][JAVA_-_-_Spring] ###

[Link 1]: https://so.csdn.net/so/search?q=%E6%8B%A6%E6%88%AA%E5%99%A8&spm=1001.2101.3001.7020
[Aop]: https://so.csdn.net/so/search?q=Aop&spm=1001.2101.3001.7020
[Spring AOP _ _]: https://blog.csdn.net/weixin_42213903/article/details/100577292
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[Spring AOP _ _ 1]: https://blog.csdn.net/weixin_42213903/article/details/100573953
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjIxMzkwMw_size_16_color_FFFFFF_t_70 7]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/15/a87e30d083364fb09ef5915ce7d56358.png
[JAVA_-_-_Spring]: https://blog.csdn.net/weixin_42213903/article/details/99114232