JavaWeb-(04)-创建Servlet会话--学生登陆一起聊天

1.掌握创建Servlet会话方法
熟悉掌握Servlet会话跟踪技术
理解 Servlet 通信方法
掌握创建Servlet程序以访问上下文状态方法
了解开发Servlet程序以修改上下文状态步骤

2.要求使用Servlet编写聊天程序完成如下功能:
用户输入一个昵称后,可以参加聊天,该昵称用于聊天应用程序的用户名
用户通过在一个文本框中输入发送的消息后点击命令按钮参与聊天
用户应看见所有参与聊天的人和他们的全部聊天记录。没有其他的权限控制
用户应能够使用中文聊天

UserServlet 生成用户界面接受用户输入昵称
在这里插入图片描述

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package sise.com.cn;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Vector;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 *
 * @author Liugx
 */
public class UserServlet extends HttpServlet {

    /**
     * Processes requests for both HTTP <code>GET</code> and <code>POST</code>
     * methods.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=GBK");
        request.setCharacterEncoding("GBK");
        try (PrintWriter out = response.getWriter()) {
            /* TODO output your page here. You may use following sample code. */
            out.println("<!DOCTYPE html>");
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet UserServlet</title>");            
            out.println("</head>");
            out.println("<body>");
            out.println("<h1>Servlet UserServlet at " + request.getContextPath() + "</h1>");
         
            
            out.println("<h3>我的聊天器，进入聊天系统....");
            out.println("<br><br>");
            ServletContext context = getServletContext();
            //判断用户列表书否纯在；
            if(context.getAttribute("userlist") == null){
                Vector aduser = new Vector();
                context.setAttribute("userlist", aduser);
            }
            
            //判断用户信息列表存在；
            if(context.getAttribute("messagelist") == null){
                Vector message = new Vector();
                context.setAttribute("messagelist",message);
            }
            out.println("<form method='post' action='/ServletSessionApp/MainServlet'>");
            out.println("昵称<input type='text' name='uname'/>");
            out.println("<input type=submit value='登陆'/>");
            out.println("</form>");
            out.println("");
            
            out.println("</body>");
            out.println("</html>");
            out.close();
        }
    }

    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /**
     * Handles the HTTP <code>GET</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Handles the HTTP <code>POST</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Returns a short description of the servlet.
     *
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

}

2.MainServlet读出 Servlet上下文中保存的用户列表向量，如果向量为 null，则新建一个向量，并在用户列表向量中添加用户

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package sise.com.cn;

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

/**
 *
 * @author Liugx
 */
public class MainServlet extends HttpServlet {

    /**
     * Processes requests for both HTTP <code>GET</code> and <code>POST</code>
     * methods.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=GBK");
        request.setCharacterEncoding("GBK");
        try (PrintWriter out = response.getWriter()) {
            /* TODO output your page here. You may use following sample code. */
            out.println("<!DOCTYPE html>");
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet MainServlet</title>");            
            out.println("</head>");
            out.println("<body>");
            //out.println("<h1>Servlet MainServlet at " + request.getContextPath() + "</h1>");
           
            out.println("<h3>进入聊天系统。。。");
            ServletContext context = getServletContext();
            Vector vc = (Vector)context.getAttribute("userlist");
            String username = request.getParameter("uname");
            vc.add(username);
            RequestDispatcher view = request.getRequestDispatcher("/MessageServlet?uname="+username);
            view.forward(request, response);
          
            out.println("</body>");
            out.println("</html>");
            out.close();
        }
    }

    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /**
     * Handles the HTTP <code>GET</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Handles the HTTP <code>POST</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Returns a short description of the servlet.
     *
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

}

3.MessageServlet显示了一个文本框和一个命令按钮，以输入要通过聊天应用程序发送的消息
使用request.setCharacterEncoding(“GBK”)处理中文

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package sise.com.cn;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Vector;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 *
 * @author Liugx
 */
public class MessageServlet extends HttpServlet {

    /**
     * Processes requests for both HTTP <code>GET</code> and <code>POST</code>
     * methods.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=GBK");
        request.setCharacterEncoding("GBK");
        try (PrintWriter out = response.getWriter()) {
            /* TODO output your page here. You may use following sample code. */
            out.println("<!DOCTYPE html>");
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet MessageServlet</title>");
            out.println("</head>");
            out.println("<body>");
         //   out.println("<h1>Servlet MessageServlet at " + request.getContextPath() + "</h1>");
            
            ServletContext context = getServletContext();
            //获取表单信息
            String usr = request.getParameter("uname");
            String str = request.getParameter("message");
            Vector hsh = (Vector)context.getAttribute("messagelist");
            if(str != null){
                hsh.add(usr + ":" +str);
            }
            
            out.println("<iframe frameborder=0 height=400 marginheight=0 marginwidth=0"+
                    "scrolling=auto src='/ServletSessionApp/DisplayServlet' width='100%' height='80%'>");
            
            out.println("</iframe>");
            out.println("<form method='post' action='/ServletSessionApp/MessageServlet?uname="+usr+"'>");
            out.println("<hr>");
            out.println("输入信息：<input type='text' name='message' />");
            out.println("<input type=submit value='发送' />");
            out.println("</form>");
            
            out.println("</body>");
            out.println("</html>");
        }
    }

    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /**
     * Handles the HTTP <code>GET</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Handles the HTTP <code>POST</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Returns a short description of the servlet.
     *
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

}

4.DisplayServlet 显示所有的聊天消息
UserList显示所有的聊天用户

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package sise.com.cn;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Vector;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 *
 * @author Liugx
 */
public class DisplayServlet extends HttpServlet {

    /**
     * Processes requests for both HTTP <code>GET</code> and <code>POST</code>
     * methods.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=GBK");
        request.setCharacterEncoding("GBK");
        try (PrintWriter out = response.getWriter()) {
            /* TODO output your page here. You may use following sample code. */
            ServletContext context = getServletContext();
            
            out.println("<!DOCTYPE html>");
            out.println("<html>");
            out.println("<head>");
            
            out.println("<meta http-equiv='refresh' content='3' />");
            out.println("<title>Servlet DisplayServlet</title>");            
            out.println("</head>");
            out.println("<body>");
            out.println("<h1>Servlet DisplayServlet at " + request.getContextPath() + "</h1>");
            
            out.println("内容");
            //显示聊天信息
            Vector hab = (Vector)context.getAttribute("messagelist");
            out.println("<textarea name='info' rows='9'>");
            for(int i=0;i<hab.size();i++){
                out.println(hab.get(i));
            }
            out.println("</textarea>");

//显示用户列表
            out.println("用户列表");
            out.println("<textarea name='user' rows='9'>");
            Vector vc = (Vector)context.getAttribute("userlist");
            for(int i=0;i<vc.size();i++){
                if(vc.get(i) != null)
                    out.println(vc.get(i));
            }
            out.println("</textarea>");
 
            
            
            out.println("</body>");
            out.println("</html>");
            out.close();
        }
    }

    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /**
     * Handles the HTTP <code>GET</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Handles the HTTP <code>POST</code> method.
     *
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        processRequest(request, response);
    }

    /**
     * Returns a short description of the servlet.
     *
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

}

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JavaWeb-(04)-创建Servlet会话--学生登陆一起聊天

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