实现思路

1.登录页面 login.jsp 输入昵称

2.编写一个LoginSevlet，处理登录提交的昵称，保存登录昵称到session（会话变量）
若昵称合法 if(nickname.length()!=0)，跳转到聊天室，不合法回到登录页面

3.编写聊天室页面chatroom.jsp ，是一个框架，把多个页面集成到一个页面中

4.聊天内容显示message.jsp，不断自动刷新标签内设置响应头,用${上下文变量}显示聊天内容

5.input.jsp（不刷新）输入聊天内容文本框text，点击发送聊天内容按钮时，将把文本框的聊天信息提交给ChatServlet处理。下方有超链接可退出聊天室。

退出聊天室

6.ChatServlet：检测聊天信息合法性，把聊天信息加入到ServletContext变量（字符串）中，（每次都将xx:xxxx加入上下文字符串）
判断是否存在该变量，存在则直接读取现有聊天内容，把数据加入进去后，重新写回上下文变量

7.实现拍一拍功能（目的：学习如何进行链接操作）
每个人名做成一个链接，访问某一个servlet，该servlet可以在聊天信息（上下文变量）里添加一行，xx拍了yyy一下，跳转回message.jsp
问题：链接里应该包含yyy参数，servlet？nick=yyy

say = ""+nickname+""+":"+text;

8.多人聊天实现：多种类型浏览器

关键代码

login.jsp

昵称：
 

input.jsp

 
 




 退出聊天室

message.jsp

一起来聊天吧
${says}

LoginServlet.java

package chatting;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "LoginServlet2",urlPatterns = {"/login.do"})
public class LoginServlet2 extends HttpServlet {
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 //避免乱码
 response.setContentType("text/html;charset=utf-8");
 request.setCharacterEncoding("utf-8");
 //nickname保存用户昵称
 String nickname = request.getParameter("nickname");
 //nickname存储到session变量中
 HttpSession session = request.getSession();
 session.setAttribute("nickname",nickname);
 //对nickname进行合法性判断
 if(nickname.length()!=0){
 //昵称合法，则进入聊天室页面
  request.getRequestDispatcher("/chatroom.jsp").forward(request,response);
 }
 else{
 //昵称不合法，返回登陆页面
  request.getRequestDispatcher("/login.jsp").forward(request,response);
 }

 }

 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 }
}

ChatServlet.java

package chatting;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.util.Vector;

@WebServlet(name = "ChatServlet",urlPatterns = "/input.do")
public class ChatServlet extends HttpServlet {
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 //防止乱码
 request.setCharacterEncoding("utf-8");
 response.setContentType("text/html;charset=utf-8");
 HttpSession session = request.getSession();
 String text = request.getParameter("text");
 //text存储聊天信息，并进行合法性判断
 if (text.length()!=0) {
  String say =new String();
  //获取session中的昵称
  String nickname = (String)session.getAttribute("nickname");
  //将昵称作为链接，并传参
  say = ""+nickname+""+":"+text;
  String says = new String();
  //将昵称和聊天信息一起放在上下文变量
  ServletContext context = getServletContext();
  if(context.getAttribute("says")!=null){
  says = context.getAttribute("says") + say + "
";
  }
  else{
  says = say + "
";
  }
  context.setAttribute("says", says);
  request.setAttribute("says", says);
 }
 //转发
 RequestDispatcher dispatcher = request.getRequestDispatcher("/input.jsp");
 dispatcher.forward(request, response);
 }

 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {


 }
}

NickServlet.java

package chatting;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "NickServlet",urlPatterns = "/NickServlet")
public class NickServlet extends HttpServlet {
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

 }

 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 response.setContentType("text/html;charset=UTF-8");
 request.setCharacterEncoding("utf-8");
 //将拍一拍放到上下文变量says中 一起输出

 HttpSession session = request.getSession();
 //nickname存储当前用户昵称
 String nickname = (String)session.getAttribute("nickname");
 //name存储连接中传递的参数，即被拍的用户昵称
 String name = java.net.URLDecoder.decode(request.getParameter("nickname"),"UTF-8");
 String pick = nickname+"拍了拍"+name+"
";

 ServletContext context = request.getServletContext();
 String says = context.getAttribute("says")+pick;
 context.setAttribute("says",says);

 RequestDispatcher dispatcher = request.getRequestDispatcher("/chatroom.jsp");
 dispatcher.forward(request, response);
 }
}