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前段时间在学习sentinel和dubbo的时候，很好奇它们对应的控制台为何可以实现代码无侵入 动态的添加/删除功能

看过 @Async、@Transactionnal相关源码的朋友应该知道，这是基于动态代理去实现了，既然如此那我们是否可以实现动态的去添加/删除动态代理呢

答案是 YES，下面就来实现一个动态的添加/删除动态代理的功能，它的源码很简单，但这会打开你的新世界

动态代理后你想干嘛都行，干什么不是这里的重点，重点是控制它干和不干，所以为了简单的我就在返回值上做了点文章

先来看效果图

一、理论

在开始写代码之前，先来了解几个基本的理论知识 （重要‼️）

key	value
advice	动态代理之后要干什么，其实就是这个 advice的定义，本质上就是 Interceptor（实际上也是，因为Interceptor 继承了 advice）
pointcut	不可能对所有的方法都强加上 advice（可以但没必要），所以 pointcut 就是定义拦截的规则（可以对使用了某个注解进行拦截，也可以用表达式去匹配）
advisor	简单理解为 它就是包含了advice 和 pointcut 的类
advised	代理后生成的代理对象，它维护了一个 List advisors，从而实现功能叠加

原理就是先把bean转换成 advised，然后添加/删除 advisor，就实现了动态的动态代理 （最重要的一句话）

也可以添加/删除 advice，但这就对bean的所有方法都代理了，在大多数情况下这不是我们想要了，比如 @Async 是想添加在哪个方法上，哪个方法就异步，而不是全部的方法都异步

advisor，advice 这俩玩意不熟悉的时候，很容易看错，我开始就是，排查半天

advised.addAdvisor();
advised.addAdvice();

二、核心代码

2-1、自定义操作类型枚举

public enum OperateEventEnum {ADD("add"),DELETE("delete");private String value;OperateEventEnum(String value) {this.value = value;}public String getValue() {return value;}
}

2-2、自定义 Advisor

import org.aopalliance.aop.Advice;
import org.aopalliance.intercept.MethodInterceptor;
import org.springframework.aop.Pointcut;
import org.springframework.aop.aspectj.AspectJExpressionPointcut;
import org.springframework.aop.support.AbstractPointcutAdvisor;
import org.springframework.aop.support.ComposablePointcut;
import org.springframework.aop.support.annotation.AnnotationMatchingPointcut;import java.lang.annotation.Annotation;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Set;public class XdxAdvisor extends AbstractPointcutAdvisor {private final Advice advice;private final Pointcut pointcut;// 基于注解的 pointcutpublic XdxAdvisor(Class<? extends Annotation>  annotationClass, MethodInterceptor interceptor) {this.advice = interceptor;this.pointcut = buildPointcut(annotationClass);}// 基于表达式的 pointcutpublic XdxAdvisor(String expression, MethodInterceptor interceptor) {this.advice = interceptor;this.pointcut = buildPointcut(expression);}/*** 直接复制的 @Async 构建 pointcut的代码* @param annotationType* @return*/private Pointcut buildPointcut(Class<? extends Annotation> annotationType) {Set<Class<? extends Annotation>> annotationTypes = new LinkedHashSet(2);annotationTypes.add(annotationType);ComposablePointcut result = null;AnnotationMatchingPointcut mpc;for(Iterator var3 = annotationTypes.iterator(); var3.hasNext(); result = result.union(mpc)) {Class<? extends Annotation> asyncAnnotationType = (Class)var3.next();Pointcut cpc = new AnnotationMatchingPointcut(asyncAnnotationType, true);mpc = new AnnotationMatchingPointcut((Class)null, asyncAnnotationType, true);if (result == null) {result = new ComposablePointcut(cpc);} else {result.union(cpc);}}return (Pointcut) (result != null ? result : Pointcut.TRUE);}private Pointcut buildPointcut(String expression) {AspectJExpressionPointcut tmpPointcut = new AspectJExpressionPointcut();tmpPointcut.setExpression(expression);return  tmpPointcut;}@Overridepublic Pointcut getPointcut() {return pointcut;}@Overridepublic Advice getAdvice() {return advice;}//    private Pointcut buildPointcut(Class<? extends Annotation> annotationTypes) {
//
//        AnnotationClassFilter classFilter = new AnnotationClassFilter(annotationTypes, true);
//        return new ComposablePointcut(classFilter);
//    }}

2-3、动态添加/删除advisor 工具类

import org.springframework.aop.Advisor;
import org.springframework.aop.framework.Advised;
import org.springframework.aop.framework.ProxyFactory;
import org.springframework.aop.framework.ProxyProcessorSupport;
import org.springframework.aop.support.AopUtils;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.support.DefaultListableBeanFactory;
import org.springframework.context.annotation.Configuration;@Configuration
public class DynamicProxy extends ProxyProcessorSupport implements BeanFactoryAware {private DefaultListableBeanFactory beanFactory;public void operateAdvisor(XdxAdvisor advisor, OperateEventEnum operateEventEnum) {// 循环每一个beanfor (String beanDefinitionName : beanFactory.getBeanDefinitionNames()) {Object bean = beanFactory.getBean(beanDefinitionName);// 判断当前bean是否匹配if (!isEligible(bean, advisor)) {continue;}// 判断当前bean是不是已经是代理对象了，是就直接进行 Advisor 操作if (bean instanceof Advised) {Advised advised = (Advised) bean;if(operateEventEnum == OperateEventEnum.DELETE) {advised.removeAdvisor(advisor);}else if(operateEventEnum == OperateEventEnum.ADD){advised.addAdvisor(advisor);}continue;}// 生成 Advisor 的代理对象ProxyFactory proxyFactory = new ProxyFactory();proxyFactory.addAdvisor(advisor);proxyFactory.setTarget(bean);ClassLoader classLoader = this.getProxyClassLoader();Object proxy = proxyFactory.getProxy(classLoader);// 销毁之前的bean，把新的bean注入到容器beanFactory.destroySingleton(beanDefinitionName);beanFactory.registerSingleton(beanDefinitionName, proxy);}}@Overridepublic void setBeanFactory(BeanFactory beanFactory) throws BeansException {this.beanFactory = (DefaultListableBeanFactory) beanFactory;}/*** 复制的 @Async 的匹配逻辑*/private boolean isEligible(Object bean, Advisor advisor) {return AopUtils.canApply(advisor, bean.getClass());}
}

1. 添加的时候其实可以指定位置的，如果有需要的话，本身存储的就是List有序的
2. @Async每次添加的时候 pos = 0 ，因为异步要先开启呀

void addAdvisor(int pos, Advisor advisor) throws AopConfigException;void addAdvice(int pos, Advice advice) throws AopConfigException;

2-4、提供测试的 Controller

import cn.hutool.core.text.CharSequenceUtil;
import com.xdx97.cli.dynamic.DynamicProxy;
import com.xdx97.cli.dynamic.OperateEventEnum;
import com.xdx97.cli.dynamic.XdxAdvisor;
import com.xdx97.cli.dynamic.annotation.XdxAnnotation;
import org.aopalliance.intercept.MethodInterceptor;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import javax.annotation.Resource;
import java.lang.annotation.Annotation;
import java.util.HashMap;
import java.util.Map;@RestController
@RequestMapping("/advisor")
public class AdvisorController {@Resourceprivate DynamicProxy dynamicProxy;private static Map<String, XdxAdvisor> xdxAdvisorMap = new HashMap<>();@GetMapping(value = "/add")public String add(String interceptorClass, String expression, String annotationClass) throws Exception {if(CharSequenceUtil.isAllBlank(expression, annotationClass) || CharSequenceUtil.isBlank(interceptorClass)) {return "the parameter is abnormal";}if (xdxAdvisorMap.containsKey(interceptorClass + annotationClass) || xdxAdvisorMap.containsKey(interceptorClass + expression)) {return "advisor already exists";}MethodInterceptor methodInterceptor =  (MethodInterceptor) Class.forName(interceptorClass).getDeclaredConstructor().newInstance();XdxAdvisor xdxAdvisor;// 以注解为主，有注解就用注解if (CharSequenceUtil.isNotBlank(annotationClass)) {Class<? extends Annotation> aClass = (Class<? extends Annotation>) Class.forName(annotationClass);xdxAdvisor = new XdxAdvisor(aClass, methodInterceptor);xdxAdvisorMap.put(interceptorClass + annotationClass, xdxAdvisor);} else {xdxAdvisor = new XdxAdvisor(expression, methodInterceptor);xdxAdvisorMap.put(interceptorClass + expression, xdxAdvisor);}dynamicProxy.operateAdvisor(xdxAdvisor, OperateEventEnum.ADD);return "advisor add success" ;}@GetMapping(value = "/delete")public String delete(String interceptorClass, String expression, String annotationClass) {if(CharSequenceUtil.isAllBlank(expression, annotationClass) || CharSequenceUtil.isBlank(interceptorClass)) {throw new IllegalArgumentException("参数异常");}if (!xdxAdvisorMap.containsKey(interceptorClass + annotationClass) && !xdxAdvisorMap.containsKey(interceptorClass + expression)) {return "advisor not exists";}// 以注解为主，有注解就用注解StringBuilder advisorKey = new StringBuilder(interceptorClass);if (CharSequenceUtil.isNotBlank(annotationClass)) {advisorKey.append(annotationClass);} else {advisorKey.append(expression);}XdxAdvisor xdxAdvisor = xdxAdvisorMap.get(advisorKey.toString());dynamicProxy.operateAdvisor(xdxAdvisor, OperateEventEnum.DELETE);xdxAdvisorMap.remove(advisorKey.toString());return "advisor delete success";}/*** 用来测试效果的fun* @return*/@GetMapping(value = "/fun")@XdxAnnotationpublic String fun() {return "my fun";}
}

三、测试

上面的代码就已经完成了动态的动态代理，是不是很简单？或许你现在还有点懵，别担心下面的测试，会让你脉动回来

要实现两种动态代理

1. 基于表达式，（不会写表达式？没关系，AI助你）
2. 基于注解的

3-1、自定义注解

细心的朋友可能已经发现了在AdvisorController.fun() 方法上面已经携带了这个注解

import java.lang.annotation.*;@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface XdxAnnotation {
}

这个注解也可以用在类上面哦，这样会把所有方法都拦截

3-2、自定义拦截器

拦截到之后总得干点什么，这里我在返回值上做文章，因为这样测试的时候效果最显著了

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;public class OneInterceptor implements MethodInterceptor {@Overridepublic Object invoke(MethodInvocation invocation) throws Throwable {Object result = invocation.proceed();return result + " 增强One";}
}public class TwoInterceptor implements MethodInterceptor {@Overridepublic Object invoke(MethodInvocation invocation) throws Throwable {Object result = invocation.proceed();return result + " 增强Two";}
}

定义2个拦截器，是为了一个给注解拦截用，一个给表达式拦截用，方便观察

3-3、测试

查看代理结果

curl --location --request GET 'http://127.0.0.1:9897/advisor/fun'

添加注解的代理

curl --location --request GET 'http://127.0.0.1:9897/advisor/add?interceptorClass=com.xdx97.cli.dynamic.inteceptor.OneInterceptor&annotationClass=com.xdx97.cli.dynamic.annotation.XdxAnnotation'

添加表达式代理

curl --location --request GET 'http://127.0.0.1:9897/advisor/add?interceptorClass=com.xdx97.cli.dynamic.inteceptor.TwoInterceptor&expression=execution(* com.xdx97.cli.AdvisorController.fun(..))' 

删除注解代理

curl --location --request GET 'http://127.0.0.1:9897/advisor/delete?interceptorClass=com.xdx97.cli.dynamic.inteceptor.OneInterceptor&annotationClass=com.xdx97.cli.dynamic.annotation.XdxAnnotation' 

删除表达式代理

curl --location --request GET 'http://127.0.0.1:9897/advisor/delete?interceptorClass=com.xdx97.cli.dynamic.inteceptor.TwoInterceptor&expression=execution(* com.xdx97.cli.AdvisorController.fun(..))'

四、源码获取

1. 关注公众号：小道仙97
2. 回复：dynamicProxy