java web实现简单留言板功能

本文实例为大家分享了java web实现简单留言板的具体代码，供大家参考，具体内容如下

一、目标

用户可以登录并记住密码进入留言板，添加留言，点击留言列表中的标题可显示该条留言全部内容。

二、相关知识

1、使用Cookie实现自动登录

用户第一次登录网站，服务器将用户名和密码以Cookie的形式发送到客户端。当客户之后再次访问该网站时，浏览器自动将Cookie文件中的用户名和密码随请求一起发送到服务器，服务器从Cookie中取出用户名和密码并且通过验证。

2、java类的定义与使用

定义java类时注意属性的定义、构造方法的重写，定义两个方法，一个是访问方法（getter），一个是修改方法（setter）。

三、实现思路

1、登录

输入用户名、密码登录，对应检测登录BoardLoginServlet
可实现记住登录信息 Cookie实现
登录成功显示留言板标题列表页面board-title.jsp，登录失败返回登录页面

2、显示留言标题

标题列表为上下文变量lists，其中标题为链接，点击可显示留言具体信息界面（跳转到MessageServlet处理）。

list = username+":"+"<a href='MessageServlet?title="+title+"'target='_parent'>"+title+"</a>";

页面下方有新增留言的链接，点击后跳转到写留言页面

<a href="board-write.jsp" rel="external nofollow" rel="external nofollow" >新增留言</a>

3、添加留言

输入标题、内容 post给WriteServlet

4、显示留言具体信息

在MessageServlet中遍历查找留言并传递变量，显示留言信息在board-message.jsp

四、代码实现

board-login.jsp

<form action="board.do" method="post">
 <br>
 <h1 class="text" >登录界面</h1>
   昵称：<input type="text" name="username" value="${cookie.username.value}"/><br>
   密码：<input type="password" name="password" value="${cookie.password.value}"/><br><br>
   <input type="checkbox" name="check" value="check"/>记住密码<br> <br>
   <input type="submit" value="登录"/>
   <input type="reset" value="取消"/>
</form>

board-title.jsp

<h2>留言板</h2>
 ${lists}
<a href="board-write.jsp" rel="external nofollow" rel="external nofollow" >新增留言</a>

boarrd-write.jsp

<form action="write.do" method="post">
 标题:<input type="text" name="title"/><br>
 内容:<input type="text" name="text"/><br>
 <input type="submit"/>
</form>

board-message.jsp

<h2>留言详情</h2>
 用户名：${name}<br>
 标题：${title}<br>
 内容：${text}<br>
 时间：${date}<br>

Message.java（将留言信息存储在Message类中）

package board;

import java.util.Date;

public class Message {
 private String title;//标题
 private String time;//时间
 private String username;//用户名
 private String text;//内容
 public Message(){}
 //初始化
 public Message(String title,String time,String username,String text){
  this.title = title;
  this.time = time;
  this.username = username;
  this.text = text;
 }

 public String getTitle(){
  return title;
 }
 public String getUsername(){
  return username;
 }
 public String getTime(){
  return time;
 }
 public String getText(){
  return text;
 }
}

BoardLoginServlet.java（用Cookie登录）

package board;

import javax.servlet.ServletException;
import javax.servlet.http.*;
import java.io.IOException;

@javax.servlet.annotation.WebServlet(name = "BoardLoginServlet",urlPatterns = "/board.do")
public class BoardLoginServlet extends HttpServlet {

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

 }
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  response.setContentType("text/html;charset = utf-8");
  request.setCharacterEncoding("UTF-8");
  HttpSession session=request.getSession();
  String username = request.getParameter("username").trim();
  String password = request.getParameter("password").trim();
  session.setAttribute("username",username);
  if (!(username.equals("admin") &&password.equals("admin"))&&!(username.equals("123") &&password.equals("123"))) {
   response.sendRedirect("board-login.jsp");
  } else {

   if ((request.getParameter("check") != null) && (request.getParameter("check").equals("check"))) {
    Cookie nameCookie = new Cookie("username", username);
    Cookie pswdCookie = new Cookie("password", password);
    nameCookie.setMaxAge(60 * 60);
    pswdCookie.setMaxAge(60 * 60);
    nameCookie.setPath("/");
    pswdCookie.setPath("/");
    response.addCookie(nameCookie);
    response.addCookie(pswdCookie);
    String value1 = "", value2 = "";
    Cookie cookie = null;
    Cookie[] cookies = request.getCookies();
    if (cookies != null) {
     for (int i = 0; i < cookies.length; i++) {
      cookie = cookies[i];
      if (cookie.getName().equals("username"))
       value1 = cookie.getValue();
      if (cookie.getName().equals("password"))
       value2 = cookie.getValue();
     }
     if (value1.equals("admin") && value2.equals("admin")||value1.equals("123") && value2.equals("123")) {
      response.sendRedirect("board-title.jsp");
     } else {
      response.sendRedirect("board-login.jsp");
     }

    }
   }
   else
   {
    response.sendRedirect("board-title.jsp");
   }
  }

 }
}

WriteServlet.java（新增留言）

package board;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

@WebServlet(name = "WriteServlet",urlPatterns = "/write.do")
public class WriteServlet extends HttpServlet {
 //messages列表中存放Message类对象
 public List<Message> messages = new ArrayList<Message>();
 protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  response.setContentType("text/html;charset=utf-8");
  ServletContext context = request.getServletContext();
  HttpSession session = request.getSession();
  //用户名存储到session中
  String username =(String)session.getAttribute("username");
  String title = request.getParameter("title");
  String text = request.getParameter("text");
  //获取当前时间
  SimpleDateFormat formatter= new SimpleDateFormat("yyyy-MM-dd 'at' HH:mm:ss");
  Date date = new Date(System.currentTimeMillis());
  String time = formatter.format(date);
 //在messages列表中添加留言对象
  messages.add(new Message(title,time,username,text));
  context.setAttribute("messages",messages);

  String list = new String();
  //list中存放留言用户名+留言标题，标题为链接，可跳转到留言具体信息，并传参title
  list = username+":"+"<a href='MessageServlet?title="+title+"'target='_parent'>"+title+"</a>";
  String lists = new String();
  //将留言标题列表信息存到上下文对象
  if(context.getAttribute("lists")!=null){
   lists = context.getAttribute("lists") + list + "<br>";
  }
  else{
   lists = list + "<br>";
  }
  context.setAttribute("lists", lists);
  request.setAttribute("lists", lists);
 //转发
  RequestDispatcher dispatcher = request.getRequestDispatcher("/board-title.jsp");
  dispatcher.forward(request, response);

 }

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

 }
}

MessageServlet.java

package board;

import com.sun.net.httpserver.HttpContext;

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 java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;

@WebServlet(name = "MessageServlet",urlPatterns = "/MessageServlet")
public class MessageServlet 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");
  ServletContext context = request.getServletContext();
  List<Message> messages = new ArrayList<Message>();
  //获取列表
  messages = (List<Message>)context.getAttribute("messages");
  //获取链接中的参数title
  String title =request.getParameter("title");
  String name = new String();
  String date = new String();
  String text = new String();
 //遍历列表，查找该title的具体信息
  for(Message message : messages){
   if((message.getTitle()).equals(title)){
    name = message.getUsername();
    date = message.getTime();
    text = message.getText();
    title = message.getTitle();
    request.setAttribute("name",name);
    request.setAttribute("title",title);
    request.setAttribute("text",text);
    request.setAttribute("date",date);
    break;
   }
  }
  //将留言信息转发到board-message.jsp
  RequestDispatcher dispatcher = request.getRequestDispatcher("/board-message.jsp");
  dispatcher.forward(request, response);

 }
}

（以上仅为部分代码）

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持我们。