HttpServlet

HttpServlet

1) 是一个Servlet，继承自GenericServlet，针对于HTTP协议所定制。

2）在service（）方法中直接把ServletRequest和ServletReponse,转为HttpServletRequest和HttpServletReponse.

    并调用了重载的service(HttpServletRequest,HttpServletReponse)。在service(HttpServletRequest,HttpServletReponse)

    中获取了请求方式：request.getMethod()，根据请求方式又创建了doXXX()方法。

3）实际开发中，直接继承HttpServlet，并根据请求方式复写doXXX()方法接口。

4）优势：  直接由针对性的覆盖doxxx()方法

                  直接使用HttpServletRequest，HttpServletReponse，不再需要进行强转。

package com.sa.servlet;import java.io.IOException;import java.io.InputStream;import java.io.PrintWriter;import java.util.Arrays;import java.util.Enumeration;import java.util.Map;import javax.servlet.Servlet;import javax.servlet.ServletConfig;import javax.servlet.ServletContext;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class LoginServlet2 extends HttpServlet {     /** *  */private static final long serialVersionUID = 1L;public void doPost(HttpServletRequest request, HttpServletResponse response)throws IOException {// TODO Auto-generated method stub        String user=request.getParameter("login");        String password=request.getParameter("password");        ServletContext servletContext=request.getServletContext();        String user2=servletContext.getInitParameter("user");        String password2=servletContext.getInitParameter("password");        PrintWriter writer=response.getWriter();        if(user.equals(user2)&&password.equals(password2)){                      writer.println("hello,"+user);        }else{        writer.println("sorry,"+user);        }}}