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141 lines
5.8 KiB
141 lines
5.8 KiB
# Spring AOP 如何生效
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- Author: [HuiFer](https://github.com/huifer)
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- 源码阅读仓库: [SourceHot-Spring](https://github.com/SourceHot/spring-framework-read)
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## 解析
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- 在使用 Spring AOP 技术的时候会有下面这段代码在xml配置文件中出现,来达到 Spring 支持 AOP
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```xml
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<aop:aspectj-autoproxy/>
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```
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- 源码阅读目标找到了,那么怎么去找入口或者对这句话的标签解析方法呢?项目中使用搜索
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这样就找到了具体解析方法了
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### `org.springframework.aop.config.AspectJAutoProxyBeanDefinitionParser`
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- 类图
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```java
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@Override
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@Nullable
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public BeanDefinition parse(Element element, ParserContext parserContext) {
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// 注册 <aop:aspectj-autoproxy/>
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AopNamespaceUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(parserContext, element);
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// 子类解析
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extendBeanDefinition(element, parserContext);
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return null;
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}
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```
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```java
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/**
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* 注册 <aop:aspectj-autoproxy/>
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* @param parserContext
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* @param sourceElement
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*/
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public static void registerAspectJAnnotationAutoProxyCreatorIfNecessary(
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ParserContext parserContext, Element sourceElement) {
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// 注册或者升级bean
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BeanDefinition beanDefinition = AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(
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parserContext.getRegistry(), parserContext.extractSource(sourceElement));
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// proxy-target-class 和 expose-proxy 标签处理
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useClassProxyingIfNecessary(parserContext.getRegistry(), sourceElement);
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// 注册组件并且交给监听器
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registerComponentIfNecessary(beanDefinition, parserContext);
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}
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```
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- `org.springframework.aop.config.AopConfigUtils.registerAspectJAnnotationAutoProxyCreatorIfNecessary(org.springframework.beans.factory.support.BeanDefinitionRegistry, java.lang.Object)`
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```java
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@Nullable
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public static BeanDefinition registerAspectJAnnotationAutoProxyCreatorIfNecessary(
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BeanDefinitionRegistry registry, @Nullable Object source) {
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// 注册或者升级 AspectJ
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return registerOrEscalateApcAsRequired(AnnotationAwareAspectJAutoProxyCreator.class, registry, source);
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}
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```
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- `org.springframework.aop.config.AopConfigUtils.registerOrEscalateApcAsRequired`
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```java
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/**
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* 注册或者升级 bean
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* @param cls 类
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* @param registry 注册器
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* @param source 源类
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* @return
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*/
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@Nullable
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private static BeanDefinition registerOrEscalateApcAsRequired(
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Class<?> cls, BeanDefinitionRegistry registry, @Nullable Object source) {
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Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
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// 判断注册器是否包含org.springframework.aop.config.internalAutoProxyCreator
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if (registry.containsBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME)) {
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// 获取注册器
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BeanDefinition apcDefinition = registry.getBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME);
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// 创建新的bean对象
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if (!cls.getName().equals(apcDefinition.getBeanClassName())) {
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int currentPriority = findPriorityForClass(apcDefinition.getBeanClassName());
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int requiredPriority = findPriorityForClass(cls);
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if (currentPriority < requiredPriority) {
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apcDefinition.setBeanClassName(cls.getName());
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}
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}
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// 即将创建的Bean对象和当前的注册器相同返回null
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return null;
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}
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RootBeanDefinition beanDefinition = new RootBeanDefinition(cls);
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beanDefinition.setSource(source);
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// 设置加载顺序
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beanDefinition.getPropertyValues().add("order", Ordered.HIGHEST_PRECEDENCE);
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beanDefinition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
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// 注册bean定义
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registry.registerBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME, beanDefinition);
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return beanDefinition;
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}
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```
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### org.springframework.aop.config.AopNamespaceUtils.useClassProxyingIfNecessary
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```java
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/**
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* proxy-target-class 和 expose-proxy 标签处理
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*/
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private static void useClassProxyingIfNecessary(BeanDefinitionRegistry registry, @Nullable Element sourceElement) {
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if (sourceElement != null) {
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// 处理 proxy-target-class
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boolean proxyTargetClass = Boolean.parseBoolean(sourceElement.getAttribute(PROXY_TARGET_CLASS_ATTRIBUTE));
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if (proxyTargetClass) {
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AopConfigUtils.forceAutoProxyCreatorToUseClassProxying(registry);
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}
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// 处理 expose-proxy
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boolean exposeProxy = Boolean.parseBoolean(sourceElement.getAttribute(EXPOSE_PROXY_ATTRIBUTE));
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if (exposeProxy) {
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AopConfigUtils.forceAutoProxyCreatorToExposeProxy(registry);
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}
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}
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}
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```
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- `org.springframework.aop.config.AopConfigUtils.forceAutoProxyCreatorToUseClassProxying`
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```java
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public static void forceAutoProxyCreatorToUseClassProxying(BeanDefinitionRegistry registry) {
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if (registry.containsBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME)) {
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BeanDefinition definition = registry.getBeanDefinition(AUTO_PROXY_CREATOR_BEAN_NAME);
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definition.getPropertyValues().add("proxyTargetClass", Boolean.TRUE);
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}
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}
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```
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- `forceAutoProxyCreatorToExposeProxy`方法就不贴出代码了,操作和`forceAutoProxyCreatorToUseClassProxying`一样都是将读取到的数据放入bean对象作为一个属性存储
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## 总结
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- 实现`org.springframework.beans.factory.xml.BeanDefinitionParser`接口的类,多用于对xml标签的解析,并且入口为`parse`方法,如果是一个bean对象通常会和Spring监听器一起出现 |