案例需求：编写Servlet，当浏览器发送systemTime.do请求时，返回yyyy-MM-dd hh:mm:ss格式的日期字符串并在浏览器中显示。

案例实现：

●  Servlet对应的Java类源代码：

package com.xdl.servlet;

import java.io.IOException;

import java.io.PrintWriter;

import java.text.SimpleDateFormat;

import java.util.Date;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class XdlSystemTime extends HttpServlet {

    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest req,

         HttpServletResponse resp) throws ServletException, IOException {

         // 获取系统当前时间    yyyy-MM-dd  hh:mm:ss

         Date date = new Date();

         SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd  hh:mm:ss");

         String dateStr = sdf.format(date);

         //写给浏览器

         PrintWriter  pw =  resp.getWriter();

         pw.write("<h1>" + dateStr + "</h1>");

         pw.close();

    }

}

●  web.xml配置

<servlet>

    <servlet-name>XdlSystemTime</servlet-name>

    <servlet-class>com.xdl.servlet.XdlSystemTime</servlet-class>

</servlet>

<servlet-mapping>

    <servlet-name>XdlSystemTime</servlet-name>

    <url-pattern>/systemTime.do</url-pattern>

</servlet-mapping>