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+":"+""+title+"";

页面下方有新增留言的链接，点击后跳转到写留言页面

新增留言

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

登录界面

昵称：

密码：

记住密码

board-title.jsp

留言板

${lists}

新增留言

boarrd-write.jsp

标题:

内容:

board-message.jsp

留言详情

用户名：${name}

标题：${title}

内容：${text}

时间：${date}

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 messages = new ArrayList();

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+":"+""+title+"";

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 + "
";

}

else{

lists = list + "
";

}

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 messages = new ArrayList();

//获取列表

messages = (List)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脚本之家。