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='https://www.haobala.com/bcjs/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 >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='https://www.haobala.com/bcjs/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好吧啦网。