Servlet的应用（含过滤器）

朱雀 2022-02-03 03:27 249阅读 0赞

# #

## **要求：** ##

1、使用MVC(JavaBean + JSP + Servlet)模式实现实验三的功能，具体要求如下：

(1) login.jsp：登录页面(假定合法的用户名均以“ahpu\_”开头，密码均为“123”)，其提交到名为LoginServlet的Servlet。

(2) 在LoginServlet中检查用户名和密码，若合法则转发到messageBoard.jsp。

(3) messageBoard.jsp：留言板页面，其提交到名为MessageServlet的Servlet。

(4) 在MessageServlet中将留言信息对应的Message对象加入application，并转发到showMessage.jsp。

(5) showMessage.jsp：留言列表页面，其以表格呈现application中所有的留言。

(6) 编写名为LoginChecker的过滤器(Filter)实现“若未经过登录，则禁止访问除login.jsp和LoginServlet之外的所有URL”的功能。

## web.xml(配置) ##

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
             version="4.0">
    
        
        <servlet>
            <servlet-name>LoginServlet</servlet-name>
            <servlet-class>servlet.LoginServlet</servlet-class>
        </servlet>
        <servlet-mapping>
            <servlet-name>LoginServlet</servlet-name>
            <url-pattern>/login</url-pattern>
        </servlet-mapping>
    
        
        <servlet>
            <servlet-name>MessageServlet</servlet-name>
            <servlet-class>servlet.MessageServlet</servlet-class>
        </servlet>
        <servlet-mapping>
            <servlet-name>MessageServlet</servlet-name>
            <url-pattern>/Message</url-pattern>
        </servlet-mapping>
    
        
        <filter>
            <filter-name>loginChecker</filter-name>
            <filter-class>filter.LoginChecker</filter-class>
            <init-param>
                <param-name>encoding</param-name>
                <param-value>utf-8</param-value>
            </init-param>
            <init-param>
                <param-name>loginPage</param-name>
                <param-value>/login.jsp</param-value>
            </init-param>
            <init-param>
                <param-name>LoginServlet</param-name>
                <param-value>/login</param-value>
            </init-param>
        </filter>
        <filter-mapping>
            <filter-name>loginChecker</filter-name>
            <url-pattern>/*</url-pattern>
        </filter-mapping>
    </web-app>

## Message.java ##

package bean;
    
    /**
     * @Author: WQ
     * @Date: 2019/4/28 15:23
     * @Version
     */
    public class Message {
        private String who;
        private String title;
        private String content;
        private String when;
    
        public String getWho() {
            return who;
        }
    
        public void setWho(String who) {
            this.who = who;
        }
    
        public String getTitle() {
            return title;
        }
    
        public void setTitle(String title) {
            this.title = title;
        }
    
        public String getContent() {
            return content;
        }
    
        public void setContent(String content) {
            this.content = content.replace("<", "<").replace(">", ">").replace("\"", """);
        }
    
        public String getWhen() {
            return when;
        }
    
        public void setWhen(String when) {
            this.when = when;
        }
    }

## login.jsp ##

<%--
      Created by IntelliJ IDEA.
      User: 19855
      Date: 2019/4/28
      Time: 15:05
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page language="java" pageEncoding="UTF-8"%>
    
    <!DOCTYPE html>
    <html>
    <head>
        <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" />
        <title>登录</title>
    </head>
    
    <body class="container mt-3">
    
    <%
        String err = (String)request.getAttribute("LOGIN_ERR");
        if(err != null) {
            out.write("<div class='alert alert-danger'>" + err + "</div>");
        }
    %>
    <form action="login" method="post">
        <div class="card border-success">
            <div class="card-header bg-success">登录信息</div>
            <div class="card-body">
                <div class="form-group">
                    <label>用户名</label>
                    <input type="text" class="form-control" name="username"/>
                </div>
                <div class="form-group">
                    <label>密码</label>
                    <input type="password" class="form-control" name="password"/>
                </div>
            </div>
            <div class="card-footer">
                <input type="submit" class="btn btn-primary float-right" value="登录" />
                <input type="reset" class="btn btn-danger float-right mr-3" value="重置" />
            </div>
        </div>
    </form>
    </body>
    </html>

## LoginServlet.java ##

package servlet;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    import java.io.IOException;
    
    /**
     * @Author: WQ
     * @Date: 2019/4/28 15:07
     * @Version
     */
    public class LoginServlet extends HttpServlet {
        @Override
        protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            String name = request.getParameter("username");
            String psw = request.getParameter("password");
            boolean success = false; // 登录是否成功
            HttpSession session = request.getSession();
    
            if (name == null || !name.startsWith("ahpu_") || name.length() < 6 || name.length() > 12) {
                request.setAttribute("LOGIN_ERR", "用户名格式错误");
            } else if (!"123".equals(psw)) {
                request.setAttribute("LOGIN_ERR", "密码错误");
            } else {
                success = true;
            }
    
            if (!success) {
                request.getRequestDispatcher("login.jsp").forward(request, response); // 转发到登录界面
            } else {
                session.setAttribute("LOGIN_USER", name); // 保存用户名到session
                request.getRequestDispatcher("messageBoard.jsp").forward(request,response);
            }
    
        }
    }

## messageBoard.jsp ##

<%--
      Created by IntelliJ IDEA.
      User: 19855
      Date: 2019/4/28
      Time: 15:18
      To change this template use File | Settings | File Templates.
    --%>
    <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
    <!DOCTYPE html>
    <html>
    <head>
        <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" />
        <title>编辑留言</title>
    </head>
    
    <body class="container mt-3">
    <form method="post" action="Message">
    
        <div class="card border-primary">
            <div class="card-header bg-primary">编辑留言</div>
            <div class="card-body">
                <div class="form-group">
                    <label>标题</label>
                    <input type="text" class="form-control" name="title"/>
                </div>
                <div class="form-group">
                    <label>内容</label>
                    <textarea class="form-control" name="content"></textarea>
                </div>
            </div>
            <div class="card-footer">
                <input type="submit" class="btn btn-primary float-right" value="提交" />
            </div>
        </div>
    </form>
    </body>
    </html>

## MessageServlet.java ##

package servlet;
    
    import bean.Message;
    
    import javax.servlet.ServletContext;
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    import java.io.IOException;
    import java.io.PrintWriter;
    import java.text.SimpleDateFormat;
    import java.util.ArrayList;
    import java.util.Date;
    import java.util.List;
    
    /**
     * @Author: WQ
     * @Date: 2019/4/28 15:22
     * @Version
     */
    public class MessageServlet extends HttpServlet {
        @Override
        protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            PrintWriter out = response.getWriter();
            HttpSession session = request.getSession();
            ServletContext application = request.getServletContext();
    
            String title = request.getParameter("title");
            String content = request.getParameter("content");
            SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            String time  = sdf.format(new Date());
    
            if (title == null || title.trim().length() < 1 || content == null || content.trim().length() < 1) {
                out.write("<div class='alert alert-danger'>请输入留言的标题和内容</div>");
                return;
            }
    
            Message m = new Message();
            m.setWho((String)session.getAttribute("LOGIN_USER"));
            m.setTitle(title.trim());
            m.setContent(content.trim());
            m.setWhen(time);
    
            List<Message> msgs = (List<Message>)application.getAttribute("MSGS");
            if(msgs == null) { // 首次进入此页面时成立
                msgs = new ArrayList<Message>();
                application.setAttribute("MSGS", msgs);
            }
            msgs.add(m); // 留言信息加入application
            response.sendRedirect("showMessage.jsp");//重定向到showMessage.jsp页面
        }
    
    }

## showMessage.jsp ##

<%--
      Created by IntelliJ IDEA.
      User: 19855
      Date: 2019/4/28
      Time: 15:27
      To change this template use File | Settings | File Templates.
    --%>
    <%@page import="bean.Message"%>
    <%@ page language="java" contentType="text/html; charset=UTF-8" import="java.util.*" pageEncoding="UTF-8"%>
    <!DOCTYPE html>
    <html>
    <head>
        <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" />
        <title>留言列表</title>
    </head>
    
    <body class="container mt-3">
    <%
        List<Message> msgs = (List<Message>)application.getAttribute("MSGS");
    %>
    <div class="card border-info">
        <div class="card-header bg-info">留言列表</div>
        <div class="card-body">
            <table class="table table-striped table-hover">
                <thead>
                <tr>
                    <th scope="col">#</th>
                    <th scope="col">Message from</th>
                    <th scope="col">title</th>
                    <th scope="col">content</th>
                    <th scope="col">time</th>
                </tr>
                </thead>
                <tbody>
                <%
                    int i = 0;
    
                    for(Message msg : msgs){
                        out.write("<tr>");
                        out.write("<td>" + (++i) + "</td>");
                        out.write("<td>" + msg.getWho() + "</td>");
                        out.write("<td>" + msg.getTitle() + "</td>");
                        out.write("<td>" + msg.getContent() + "</td>");
                        out.write("<td>" + msg.getWhen() + "</td>");
                        out.write("</tr>");
                    }
                %>
                </tbody>
            </table>
        </div>
    </div>
    </body>
    </html>

## LoginChecker.java(过滤器) ##

package filter;
    
    import javax.servlet.*;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpSession;
    import java.io.IOException;
    
    /**
     * @Author: WQ
     * @Date: 2019/4/28 15:29
     * @Version
     */
    public class LoginChecker implements Filter {
    
        //FilterConfig可用于访问filter的配置信息
        private FilterConfig config;
        @Override
        public void doFilter(ServletRequest request, ServletResponse response, FilterChain fc) throws IOException, ServletException {
            //获取Filter的配置参数
            String encoding = config.getInitParameter("encoding");
            String loginPage = config.getInitParameter("loginPage");
            String loginServlet = config.getInitParameter("LoginServlet");
            HttpSession session = ((HttpServletRequest)request).getSession();
            //设置request编码用的字符集
            request.setCharacterEncoding(encoding);
            String requestPath = ((HttpServletRequest)request).getServletPath();//获取用户请求地址
            if(session.getAttribute("LOGIN_USER") == null
                && !requestPath.endsWith(loginPage)
                && !requestPath.endsWith(loginServlet)
                && !requestPath.endsWith("index")){
                request.getRequestDispatcher(loginPage).forward(request,response);
            }else{
                fc.doFilter(request,response);//放行
            }
        }
    
        @Override
        public void init(FilterConfig filterConfig) throws ServletException {this.config = filterConfig;}
        @Override
        public void destroy() {this.config = null;}
    }