今天接着昨天的内容：目标:使用反射知识取到配置在xml文件中的类回顾昨天的内容:为了不配置多个servlet,而采用一个ActionServlet来处理很多个请求,但是单一的Servlet中存在大量的if….else if的判断，不利于开发维护，也不满足“分”的思想如何解决？
终于正式进入J2ee的细节部分了，首当其冲的当然是Servlet和Jsp了，上篇曾经提到过J2ee只是一个规范和指南，定义了一组必须要遵循的接口，核心概念是组件和容器。曾经有的人问我Servlet的Class文件是哪里来的？
包含的模块：本文分为十九个模块，分别是：Java 基础、容器、多线程、反射、对象拷贝、Java Web 、异常、网络、设计模式、Spring/Spring MVC、Spring Boot/Spring Cloud、Hibernate、MyBatis、RabbitMQ、Kafka、
DispatcherServlet其实是Servlet接口的实现类，它的本质其实就是一个Servlet。DispatcherServlet继承图在讲DispatcherServlet之前，首先介绍一下Servlet的生命周期。Servlet的生命周期1.
Each incoming request requires a thread for the duration of that request. If more simultaneous requests are received than can be handled by the currently available request processing threads， additional threads will be created up to the configured maximum . If still more simultaneous requests are received， they are stacked up inside the server socket created by the Connector， up to the configured maximum . Any further simultaneous requests will receive “connection refused” errors， until resources are available to process them.
