细节知多少 - spring boot aop过程解析之阶段三 CglibAopProxy或JdkDynamicAopProxy生成Proxy代理类阶段

2019-05-28 spring spring, spring aop, springboot 0 评论字数统计: 4.1k(字) 阅读时长: 19(分)

此篇是细节知多少-spring boot aop过程解析系列的第三篇，即第三阶段

spring boot的aop实现分为三个阶段

AnnotationAwareAspectJAutoProxyCreator加载(初始化和实例化)阶段
AnnotationAwareAspectJAutoProxyCreator使用post-process基于@Aspect验证beanName或beanClass是否可以生成Proxy代理类阶段
CglibAopProxy或JdkDynamicAopProxy生成Proxy代理类阶段

上两个阶段的内容参见：
spring boot aop过程解析之阶段一：AnnotationAwareAspectJAutoProxyCreator加载(初始化和实例化)
spring boot aop过程解析之阶段二：判断beanName或beanClass是否生成Proxy代理类

这篇我们说下阶段三：CglibAopProxy或JdkDynamicAopProxy生成Proxy代理类阶段。

带着问题学习

带着问题学习往往起到更好的效果

问题：

1	1. 什么时候什么位置在真实对象方法前后加上代理逻辑的

前提

实际工作中，我们都写过@Aspect的代码吧。我们这里定义一个，便于后面知识点阐述

@Aspect
@Component
public class TimeFeeAspect {

    @Pointcut("execution(* com.yy..rest..*(..))")
    public void cut(){}

    @Before("cut()")
    public void doTimeFeeIntercepter(JoinPoint joinPoint) throws Throwable {
        System.out.println("args:" + joinPoint.getArgs());
        System.out.println("target" + joinPoint.getTarget().toString());
    }

}

package com.yy.rest;
@RestController
@RequestMapping("/user")
public class UserController {

    @RequestMapping("/test")
    public String test() {
        return "success";
    }
}

同上一篇一样，我们定义一个Aspect类，目的是对com.yy..rest包下所有的方法的访问都被切面切入，也就是要走doTimeFeeIntercepter()方法。同时，在com.yy.rest包下定义了一个类：UserController，充当目标类：targetClass，声明了一个方法：test()，从而在访问这个方法时，会被doTimeFeeIntercepter()方法切入

下面我们通过debug追踪源码，了解实现原理。

生成Proxy代理类入口

从上一篇 spring boot aop过程解析之阶段二：判断beanName或beanClass是否生成Proxy代理类，我们可以知道，当判断beanName或beanClass可以生成Proxy代理类时，就进行生成proxy代理类的操作了。如下图

AbstractAutoProxyCreator类
public Object postProcessBeforeInstantiation(Class<?> beanClass, String beanName) {
    ······
    if (beanName != null) {
        Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(beanClass, beanName, targetSource);
        Object proxy = createProxy(beanClass, beanName, specificInterceptors, targetSource);
        return proxy;
    }
}

AbstractAutoProxyCreator类
public Object postProcessAfterInitialization(Object bean, String beanName) {
  ······
  return wrapIfNecessary(bean, beanName, cacheKey);
}
protected Object wrapIfNecessary(Object bean, String beanName, Object cacheKey) {
  ······
  Object[] specificInterceptors = getAdvicesAndAdvisorsForBean(bean.getClass(), beanName, null);
  if (specificInterceptors != DO_NOT_PROXY) {
      Object proxy = createProxy(bean.getClass(), beanName, specificInterceptors, new SingletonTargetSource(bean));
      this.proxyTypes.put(cacheKey, proxy.getClass());
      return proxy;
  }

    return bean;
}

从上代码，我们知道AbstractAutoProxyCreator类的postProcessBeforeInstantiation()和postProcessAfterInitialization()方法都可以生成proxy代理类。都是调用的this.createProxy(..)`方法，这就是生成Proxy代理类入口，代码如下

protected Object createProxy(Class<?> beanClass, String beanName, Object[] specificInterceptors, TargetSource targetSource) {
    ProxyFactory proxyFactory = new ProxyFactory(); //(1)
    proxyFactory.copyFrom(this);

    if (!proxyFactory.isProxyTargetClass()) {
        // 检查时通过接口还是目标类创建proxy代理类，true表示通过标类创建
        if (shouldProxyTargetClass(beanClass, beanName)) {
            proxyFactory.setProxyTargetClass(true);
        }
        else {
            evaluateProxyInterfaces(beanClass, proxyFactory);
        }
    }

    Advisor[] advisors = buildAdvisors(beanName, specificInterceptors);//(2)
    proxyFactory.addAdvisors(advisors);
    proxyFactory.setTargetSource(targetSource);
    customizeProxyFactory(proxyFactory);

    proxyFactory.setFrozen(this.freezeProxy);
    if (advisorsPreFiltered()) {
        proxyFactory.setPreFiltered(true);
    }

    return proxyFactory.getProxy(getProxyClassLoader());
}

首先创建了一个ProxyFactory，看名字就知道含义：proxy的工厂。注意这句代码proxyFactory.copyFrom(this)，其中的this为AnnotationAwareAspectJAutoProxyCreator对象，还记得吗，spring项目初始化时，aop相关实例化xxxProxyAutoConfiguration就是AnnotationAwareAspectJAutoProxyCreator类，他的proxyTargetClass和exposeProxy等属性通过proxyFactory.copyFrom(this)传递给proxyFactory属性。
然后通过buildAdvisors(beanName, specificInterceptors)方法构建advisor,看他的specificInterceptors参数，往上追溯可以知道是post-process方法传递进来的，结合spring boot aop过程解析之阶段二：判断beanName或beanClass是否生成Proxy代理类，我们可以知道specificInterceptors之一就是InstantiationModelAwarePointcutAdvisorImpl实例。所以生成的advisors包含InstantiationModelAwarePointcutAdvisorImpl实例，同时将advisors赋值给proxyFactory.addAdvisors(advisors)。接下来，通过proxyFactory.getProxy(getProxyClassLoader())生成proxy代理类

生成Proxy代理类

看下proxyFactory.getProxy(getProxyClassLoader())内部实现

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2
3

public Object getProxy(ClassLoader classLoader) {
    return createAopProxy().getProxy(classLoader);
}

只有一行代码，但是确包含很多内容，createAopProxy()是一部分；getProxy(classLoader)是另一部分

先说createAopProxy()，看内部实现

ProxyFactory类
protected final synchronized AopProxy createAopProxy() {
    return getAopProxyFactory().createAopProxy(this);
}

public AopProxyFactory getAopProxyFactory() {
    // aopProxyFactory = new DefaultAopProxyFactory()
    return this.aopProxyFactory;
}

// DefaultAopProxyFactory类
public AopProxy createAopProxy(AdvisedSupport config) throws AopConfigException {
    if (config.isOptimize() || config.isProxyTargetClass() || hasNoUserSuppliedProxyInterfaces(config)) {
        Class<?> targetClass = config.getTargetClass();
        if (targetClass.isInterface() || Proxy.isProxyClass(targetClass)) {
            return new JdkDynamicAopProxy(config);
        }
        return new ObjenesisCglibAopProxy(config);
    }
    else {
        return new JdkDynamicAopProxy(config);
    }
}

createAopProxy方法正式创建xxxAopProxy了，到底是创建Jdk动态代理还是cglib动态代理呢，看条件，条件之一proxyTargetClass的值是我们所能控制的，因为可以在我们的项目启动类中加入类似
@EnableAspectJAutoProxy(proxyTargetClass = true, exposeProxy = true)的配置。这是全局设置。还有每次创建proxy的设置：shouldProxyTargetClass(beanClass, beanName)，逻辑为beanName有没有接口，有接口proxyTargetClass=false；没有接口，proxyTargetClass=true。对于我们开头定义的UserController，由于没有接口，所以生成代理时是cglib代理，即new ObjenesisCglibAopProxy(config)，看其及父类构造函数

public CglibAopProxy(AdvisedSupport config){
    this.advised = config;
    this.advisedDispatcher = new AdvisedDispatcher(this.advised);
}

AdvisedSupport是proxyFactory的父类，CglibAopProxy拥有一个AdvisedSupport类型的advised属性，而这个advised拥有advisors、proxyTargetClass、exposeProxy等，所以CglibAopProxy就等于有了advisors、proxyTargetClass、exposeProxy。

aopProxy已经创建了，下面说另一部分：getProxy(classLoader)，看内部代码

CglibAopProxy类
public Object getProxy(ClassLoader classLoader) {
    Class<?> rootClass = this.advised.getTargetClass();
    Class<?> proxySuperClass = rootClass;
    // 这里判断rootClass是否是Cglib代理所产生的类（内部判断rootClass的className是否包含$$）
    if (ClassUtils.isCglibProxyClass(rootClass)) {
        proxySuperClass = rootClass.getSuperclass();
        Class<?>[] additionalInterfaces = rootClass.getInterfaces();
        for (Class<?> additionalInterface : additionalInterfaces) {
            this.advised.addInterface(additionalInterface);
        }
    }

    // 方法校验，final方法不能被代理，记录日志
    validateClassIfNecessary(proxySuperClass, classLoader);

    // Configure CGLIB Enhancer...
    Enhancer enhancer = createEnhancer();
    if (classLoader != null) {
        enhancer.setClassLoader(classLoader);
        if (classLoader instanceof SmartClassLoader &&
                ((SmartClassLoader) classLoader).isClassReloadable(proxySuperClass)) {
            enhancer.setUseCache(false);
        }
    }
    enhancer.setSuperclass(proxySuperClass);
    enhancer.setInterfaces(AopProxyUtils.completeProxiedInterfaces(this.advised));
    enhancer.setNamingPolicy(SpringNamingPolicy.INSTANCE);
    enhancer.setStrategy(new ClassLoaderAwareUndeclaredThrowableStrategy(classLoader));

    Callback[] callbacks = getCallbacks(rootClass);
    Class<?>[] types = new Class<?>[callbacks.length];
    for (int x = 0; x < types.length; x++) {
        types[x] = callbacks[x].getClass();
    }
    // fixedInterceptorMap only populated at this point, after getCallbacks call above
    enhancer.setCallbackFilter(new ProxyCallbackFilter(
            this.advised.getConfigurationOnlyCopy(), this.fixedInterceptorMap, this.fixedInterceptorOffset));
    enhancer.setCallbackTypes(types);

    // Generate the proxy class and create a proxy instance.
    return createProxyClassAndInstance(enhancer, callbacks);
}

getProxy()方法会创建一个Enhancer对象，这个工具类负责生成代理类的class，只不过这个class不是文本的形式，而是在内存中。Enhancer`会被赋值生成proxy代理类是用于的属性，说下这些属性即作用

superclass：目标类
Interfaces：目标类和代理类的接口
namingPolicy：生成代理类名称策略, 如”xxx\$\$EnhancerBySpringCGLIB$$d2e4a5ae”这个文本形式就是namingPolicy生成的
strategy：生成代理类class策略
callbackFilter：设置对不同方法执行不同的回调逻辑，或者根本不执行回调

callBackTypes：都会赋值给Enhancer对象用于生成Proxy代理类。callBackTypes就是aop interceptor，CGLIB中对于方法的拦截是通过将自定义的拦截器（实现MethodInterceptor接口）加入Callback中并在调用代理时直接激活拦截器中的intercept方法来实现的，DynamicAdvisedInterceptor继承自MethodInterceptor，而包含AspectJMethodBeforeAdvice的advised属性又封装在DynamicAdvisedInterceptor中，DynamicAdvisedInterceptor又赋值到callBack。所以当我们curl访问目标类方法时会被proxy代理类的拦截器拦截，继而会走切面的AspectJMethodBeforeAdvice对象的方法执行切面逻辑。下面就详细下CallbackTypes，看getCallbacks方法代码，如下

private Callback[] getCallbacks(Class<?> rootClass) throws Exception {
    // Parameters used for optimization choices...
    boolean exposeProxy = this.advised.isExposeProxy();
    boolean isFrozen = this.advised.isFrozen();
    boolean isStatic = this.advised.getTargetSource().isStatic();

    // Choose an "aop" interceptor (used for AOP calls).
    Callback aopInterceptor = new DynamicAdvisedInterceptor(this.advised);

    // Choose a "straight to target" interceptor. (used for calls that are
    // unadvised but can return this). May be required to expose the proxy.
    Callback targetInterceptor;
    if (exposeProxy) {
        targetInterceptor = isStatic ?
                new StaticUnadvisedExposedInterceptor(this.advised.getTargetSource().getTarget()) :
                new DynamicUnadvisedExposedInterceptor(this.advised.getTargetSource());
    }
    else {
        targetInterceptor = isStatic ?
                new StaticUnadvisedInterceptor(this.advised.getTargetSource().getTarget()) :
                new DynamicUnadvisedInterceptor(this.advised.getTargetSource());
    }

    // Choose a "direct to target" dispatcher (used for
    // unadvised calls to static targets that cannot return this).
    Callback targetDispatcher = isStatic ?
            new StaticDispatcher(this.advised.getTargetSource().getTarget()) : new SerializableNoOp();

    Callback[] mainCallbacks = new Callback[] {
            aopInterceptor,  // for normal advice
            targetInterceptor,  // invoke target without considering advice, if optimized
            new SerializableNoOp(),  // no override for methods mapped to this
            targetDispatcher, this.advisedDispatcher,
            new EqualsInterceptor(this.advised),
            new HashCodeInterceptor(this.advised)
    };

    Callback[] callbacks;
}

可以看到，mainCallbacks是最终生成的callbacks，包含7个callback，属于几类，分别说下

DynamicAdvisedInterceptor：核心的aop interceptor，aspect的AspectJMethodBeforeAdvice就被赋值在这里。访问业务方法时就会先访问DynamicAdvisedInterceptor的intercept方法，详情看此方法
StaticUnadvisedExposedInterceptor：用于没有advice chain的静态目标
SerializableNoOp 什么操作也不做，代理类直接调用被代理的方法不进行拦截

Dispatcher 每次调用都会重新加载被代理的对象
···
下面看下getProxy方法createProxyClassAndInstance方法，这个方法创建proxy class并实例化为instance，看下内部代码

protected Object createProxyClassAndInstance(Enhancer enhancer, Callback[] callbacks) {
    // 创建class
    Class<?> proxyClass = enhancer.createClass();
    // 实例化proxyClass为instance
    Object proxyInstance = proxyInstance = objenesis.newInstance(proxyClass, enhancer.getUseCache());
    ((Factory) proxyInstance).setCallbacks(callbacks);
    return proxyInstance;
}

private Object createHelper() {
    Object key = KEY_FACTORY.newInstance(this.superclass != null ? this.superclass.getName() : null, ReflectUtils.getNames(this.interfaces), this.filter == ALL_ZERO ? null : new WeakCacheKey(this.filter), this.callbackTypes, this.useFactory, this.interceptDuringConstruction, this.serialVersionUID);
    Object result = super.create(key);
    return result;
}

protected Object create(Object key) {
    ClassLoader loader = this.getClassLoader();
    Map<ClassLoader, AbstractClassGenerator.ClassLoaderData> cache = CACHE;
    AbstractClassGenerator.ClassLoaderData data = (AbstractClassGenerator.ClassLoaderData)cache.get(loader);
    // 此处又使用了双重检查机制(double check and synchronized)来避免锁竞争，这个机制在java和spring中多次使用
    if (data == null) {
        synchronized(AbstractClassGenerator.class) {
            data = (AbstractClassGenerator.ClassLoaderData)cache.get(loader);
            if (data == null) {
                data = new AbstractClassGenerator.ClassLoaderData(loader);
            }
        }
    }
    this.key = key;
    // 获取class
    Object obj = data.get(this, this.getUseCache());
    return obj instanceof Class ? this.firstInstance((Class)obj) : this.nextInstance(obj);
}

public Object get(AbstractClassGenerator gen, boolean useCache) {
    if (!useCache) {
        // 生成代理类
        return gen.generate(this);
    } else {
        Object cachedValue = this.generatedClasses.get(gen);
        return gen.unwrapCachedValue(cachedValue);
    }
}

protected V createEntry(final K key, KK cacheKey, Object v) {
    FutureTask task = new FutureTask(new Callable<V>() {
            public V call() throws Exception {
                // 异步执行下面的generate()方法
                return LoadingCache.this.loader.apply(key);
            }
        });
    }
    task.run();
    return ask.get();
}

// future新起了一个线程来完成这个生成逻辑
protected Class generate(AbstractClassGenerator.ClassLoaderData data) {
    String className;
    synchronized(classLoader) {
        // 声明代理类的名字
        className = this.generateClassName(data.getUniqueNamePredicate());
    }
    // 使用指定策略生成代理类字节流数组
    byte[] b = this.strategy.generate(this);
    className = ClassNameReader.getClassName(new ClassReader(b));
    // 生成代理类
    gen = ReflectUtils.defineClass(className, b, classLoader, protectionDomain);

    return gen;
}

private String generateClassName(Predicate nameTestPredicate) {
    // 使用指定的name生成政策生成代理类的名字
    return this.namingPolicy.getClassName(this.namePrefix, this.source.name, this.key, nameTestPredicate);
}

public String getClassName(String prefix, String source, Object key, Predicate names) {
    if (prefix == null) {
        prefix = "org.springframework.cglib.empty.Object";
    } else if (prefix.startsWith("java")) {
        prefix = "$" + prefix;
    }

    String base = prefix + "$$" + source.substring(source.lastIndexOf(46) + 1) + this.getTag() + "$$" + Integer.toHexString(STRESS_HASH_CODE ? 0 : key.hashCode());
    String attempt = base;

    for(int var7 = 2; names.evaluate(attempt); attempt = base + "_" + var7++) {
    }

    return attempt;
}

上述代码着重贴了proxy代理类的名字的生成过程，这是平时你debug代理类时常看见的名字。所以了解名字的生成过程有助于你理解更深层的东西。

生成的class文件我们可以输出到.class

到这，proxy代理类的生成过程就说完了，整个过程生成的代理类都是在内存的，我们可以通过设置，将内存中生成的代理类class字节码输出到硬盘的.class文件中，输出到.class的方法见文末扩展部分

package com.yy.rest;

import **

public class UserController$$EnhancerBySpringCGLIB$$bd9c2334 extends UserController implements SpringProxy, Advised, Factory {
    private boolean CGLIB$BOUND;
    public static Object CGLIB$FACTORY_DATA;
    private static final ThreadLocal CGLIB$THREAD_CALLBACKS;
    private static final Callback[] CGLIB$STATIC_CALLBACKS;
    private MethodInterceptor CGLIB$CALLBACK_0;
    private MethodInterceptor CGLIB$CALLBACK_1;
    private NoOp CGLIB$CALLBACK_2;
    private Dispatcher CGLIB$CALLBACK_3;
    private Dispatcher CGLIB$CALLBACK_4;
    private MethodInterceptor CGLIB$CALLBACK_5;
    private MethodInterceptor CGLIB$CALLBACK_6;
    private static Object CGLIB$CALLBACK_FILTER;
    private static final Method CGLIB$test$0$Method;
    private static final MethodProxy CGLIB$test$0$Proxy;
    private static final Object[] CGLIB$emptyArgs;
    private static final Method CGLIB$queryOne$1$Method;
    private static final MethodProxy CGLIB$queryOne$1$Proxy;
    private static final Method CGLIB$hello$2$Method;
    private static final MethodProxy CGLIB$hello$2$Proxy;
    private static final Method CGLIB$equals$3$Method;
    private static final MethodProxy CGLIB$equals$3$Proxy;
    private static final Method CGLIB$toString$4$Method;
    private static final MethodProxy CGLIB$toString$4$Proxy;
    private static final Method CGLIB$hashCode$5$Method;
    private static final MethodProxy CGLIB$hashCode$5$Proxy;
    private static final Method CGLIB$clone$6$Method;
    private static final MethodProxy CGLIB$clone$6$Proxy;

     

    final String CGLIB$test$0() {
        return super.test();
    }

    public final String test() {
        try {
            MethodInterceptor var10000 = this.CGLIB$CALLBACK_0;
            if (var10000 == null) {
                CGLIB$BIND_CALLBACKS(this);
                var10000 = this.CGLIB$CALLBACK_0;
            }
            // var10000实际上是DynamicAdvisedInterceptor类
            return var10000 != null ? (String)var10000.intercept(this, CGLIB$test$0$Method, CGLIB$emptyArgs, CGLIB$test$0$Proxy) : super.test();
        } catch (Error | RuntimeException var1) {
            throw var1;
        } catch (Throwable var2) {
            throw new UndeclaredThrowableException(var2);
        }
    }

    ......
}

这里只列出了test方法的代码，还有很多其他的方法代码，运行你的代码就可以看到全部了

访问业务方法

下面我们看下访问controller方法时是怎样走入代理类的方法的，又怎么进入切面的方法的，最后又是怎么进去目标方法的

在浏览器或者命令行访问链接：http://localhost:20282/user/test。通过下图的调用栈可以看到
20201129083820
首先访问了UserController代理类：UserController\$\$EnhancerBySpringCGLIB$$bd9c2334的方法，从UserController\$\$EnhancerBySpringCGLIB\$\$bd9c2334的源码我们知道，它的test方法内引用了MethodInterceptor类型属性，所以调用了DynamicAdvisedInterceptor.intercept()方法。我们看下这个方法的内部

public Object intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
    try {
       
        oldProxy = AopContext.setCurrentProxy(proxy);
        targetClass = target.getClass();
       
        // 获取MethodInterceptor集合，而相应的MethodInterceptor包含对应的Advice类型属性
        List<Object> chain = this.advised.getInterceptorsAndDynamicInterceptionAdvice(method, targetClass); // (1)
        
        if (chain.isEmpty() && Modifier.isPublic(method.getModifiers())) {
            // 直接调用目标方法
            retVal = methodProxy.invoke(target, argsToUse);
        }
        else {
            // We need to create a method invocation...
            retVal = new CglibMethodInvocation(proxy, target, method, args, targetClass, chain, methodProxy).proceed();// (2)
        }
        retVal = processReturnType(proxy, target, method, retVal);
        return retVal;
    }
    finally {
       AopContext.setCurrentProxy(oldProxy);
    }
}

方法(1)处获取MethodIntercetor集合，从而获取对应的dvice集合，如下图
20201129084042

方法(2)处创建一个CglibMethodInvocation，CglibMethodInvocation拥有一个MethodInterceptor集合，通过proceed()方法执行interceptor chain。所有这里运用了一个设计模式：责任链模式的变种，类似tomcat filter的形式。
具体如下，运行这个链的入口是DynamicAdvisedInterceptor.intercept()。这个方法会获取interceptor集合，然后创建一个CglibMethodInvocation对象，并把interceptor集合传递给CglibMethodInvocation对象的interceptorsAndDynamicMethodMatchers属性，然后调用CglibMethodInvocation对象的proceed()，proceed()会遍历interceptorsAndDynamicMethodMatchers(其实就是interceptor集合)从而执行每个interceptor.invoke(MethodInvocation)自身的逻辑，因为这个时候MethodInvocation会传递给invoke方法，所以每一个invoke方法内部都会执行MethodInvocation.proceed()，从而这样形成了一个链式的调用关系。我们看下链式代码结构

MethodInvocation类
public Object proceed() throws Throwable {
    // 链式调用终结点
    if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {
        return invokeJoinpoint();
    }
    // 从interceptor集合中获取一个interceptor
    Object interceptorOrInterceptionAdvice =
            this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);
    // 调用这个interceptor.invoke方法，开始走链了
    return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
}
MethodInterceptor类
public interface MethodInterceptor extends Interceptor {
    
    Object invoke(MethodInvocation invocation) throws Throwable;
}

MethodInterceptor实现类
public Object invoke(MethodInvocation mi) throws Throwable {
    // 又调回MethodInvocation.proceed()方法
    return mi.proceed();
}

以上就是链式调用的代码结构，现在通过结构流程图的方法更直观的看下
todo

因为这里我们只有一个interceptor，所以只执行它了，如下图
20201129084156

从图中我们知道，调用了MethodBeforeAdvice.before()方法，MethodBeforeAdvice持有aspectJAdviceMethod属性，这个aspectJAdviceMethod其实就TimeFeeAspect.doTimeFeeIntercepter()方法，所以before方法会进去我们定义的Aspect切面，从而实现了切入方法的功能

spring aop 关键词

现在我们走了一遍spring aop生成代理类的逻辑和代码实现方式，感觉门清了。但千万不要忽略时间老人的魔力，不久的以后你可能没有这么清晰的记忆了，一些点可能已经忘记了。这个时候关键词会给你指引和作为回忆的钥匙
spring aop 关键词

AdvisedSupport

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2
3

1. Base class for AOP proxy configuration managers
2. ProxyConfig的子类，又是ProxyFactory的父类
3. 包含Advisor，而advisor又包含advice

2.AbstractAutoProxyCreator

1
2
3

1. 前后置方法生成代理类逻辑
2. postProcessBeforeInstantiation()
3. postProcessAfterInitialization()

3.InstantiationModelAwarePointcutAdvisor

1
2
3

看名字知道他是一个advisor，是它携带者pointcut和advice，从abstractAutoProxyCreater的后置方法传递给到ProxyFacatory，再传递到CglibMethodInvocation中
1. 包含pointcut(expression)
2. 包含advice：TimeFeeAspect.doTimeFeeIntercepter

MethodInterceptor内部类DynamicAdvisedInterceptor

1	DynamicAdvisedInterceptor是interceptor责任链模式的开始处。代理类把它切入到真实对象方法前后，执行切入功能

MethodBeforeAdvice

扩展 - jvm内存中生成的代理类class字节码输出到硬盘.class文件

以下两种方法的代码放在main方法中

方法一

该设置用于输出cglib动态代理产生的类
System.setProperty(DebuggingClassWriter.DEBUG_LOCATION_PROPERTY, "/Users/xx/skyler");

该设置用于输出jdk动态代理产生的类，输出的文件路径为your project下。如我的项目是java_example, $ProxyX.class在java_example/com/sun/proxy/下
System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles", "true");

方法二

writeProxyClass2File("/Users/xx/skyler/project/mytest/java_example/target/classes/com/yy/example/pattern_mode/structure/proxy/dynamic_proxy/spring_aop/$Proxy2.class");

/**
  * 将内存中的$ProxyX对象生成$ProxyX.class文件存放到指定的硬盘位置
  *
  * @param outPath 存放到的硬盘位置
  */
public static void writeProxyClass2File(String outPath) {
    byte[] bytes = ProxyGenerator.generateProxyClass("$Proxy2", new Class[]{House.class});
    try (OutputStream outputStream = new FileOutputStream(new File(outPath))) {
        outputStream.write(bytes);
        outputStream.flush();
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

本文链接： https://yaoyuanyy.github.io/2019/05/28/细节知多少 - spring boot aop动态代理解析之阶段三/

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skyler

Web Developer