// 执行目标方法时 会先执行
org.springframework.aop.framework.CglibAopProxy
.DynamicAdvisedIntercepto
.intercept(Object proxy, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
Object oldProxy = null;
boolean setProxyContext = false;
Class targetClass = null;
Object target = null;
try {
if (this.advised.exposeProxy) {
// Make invocation available if necessary.
// 如果需要，使调用可用
oldProxy = AopContext.setCurrentProxy(proxy);
setProxyContext = true;
}
// May be null. Get as late as possible to minimize the time we
// "own" the target, in case it comes from a pool...
//可能为空。尽量晚到，把我们的时间减到最少
//“拥有”目标，以防它来自一个池…
target = getTarget();
if (target != null) {
targetClass = target.getClass();
}
//获取目标方法拦截器链
List
CglibMethodInvocation.proceed() 方法的执行过程
org.springframework.aop.framework.ReflectiveMethodInvocation
.proceed() throws Throwable {
// We start with an index of -1 and increment early.
if (this.currentInterceptorIndex == this.interceptorsAndDynamicMethodMatchers.size() - 1) {
// 利用反射去执行目标方法
return invokeJoinpoint();
}
// 从方法拦截器链中获取一个方法拦截器 从下表 0 递增
Object interceptorOrInterceptionAdvice =
this.interceptorsAndDynamicMethodMatchers.get(++this.currentInterceptorIndex);
if (interceptorOrInterceptionAdvice instanceof InterceptorAndDynamicMethodMatcher) {
// Evaluate dynamic method matcher here: static part will already have
// been evaluated and found to match.
//评估动态方法匹配器这里:静态部分将已经评估并找到匹配。
InterceptorAndDynamicMethodMatcher dm =
(InterceptorAndDynamicMethodMatcher) interceptorOrInterceptionAdvice;
if (dm.methodMatcher.matches(this.method, this.targetClass, this.arguments)) {
return dm.interceptor.invoke(this);
}
else {
// Dynamic matching failed.
// Skip this interceptor and invoke the next in the chain.
//动态匹配失败。跳过这个拦截器并调用链中的下一个。
return proceed();
}
}
else {
// It's an interceptor, so we just invoke it: The pointcut will have
// been evaluated statically before this object was constructed.
// 它是一个拦截器，所以我们只是调用它:切入点将在构造这个对象之前被静态地计算。
return ((MethodInterceptor) interceptorOrInterceptionAdvice).invoke(this);
}
网上关于SQL优化的教程很多，但是比较杂乱。近日有空整理了一下，写出来跟大家分享一下，其中有错误和不足的地方，还请大家纠正补充。
这篇文章我花费了大量的时间查找资料、修改、排版，希望大家阅读之后，感觉好的话推荐给更多的人，让更多的人看到、纠正以及补充。
1.对查询进行优化，要尽量避免全表扫描，首先应考虑在 where 及 order by 涉及的列上建立索引。
2.应尽量避免在 where
Zookeeper类是Zookeeper提供给用户访问Zookeeper service的主要API，它包含了如下几个内部类
首先分析它的内部类，从WatchRegistration开始，为指定的znode path注册一个Watcher，
/**
* Register a watcher for a particular p
何为部分应用函数？
Partially applied function: A function that’s used in an expression and that misses some of its arguments.For instance, if function f has type Int => Int => Int, then f and f(1) are p
