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自学编程网。
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