如何用初级的JavaWeb知识写一个较简单的网站(三)

版权声明：原创文章，但可以转载哦~ https://blog.csdn.net/Jarvenman/article/details/72969653

废话不多说，我们继续上次的进度，这次我们来做文章模块

跟用户模块相似，我们先来写实体类，在com.software.entities包里new出来一个Article.java

代码就不再贴出来了，要不篇幅太长了，很简单就是声明一下属性然后添加get和set方法。接下来来写ArticleDao.java，里面包含增删改查查全部等方法

public class ArticleDao {

    /**
     * 新增文章
     * @param article
     */
    public static void insert(Article article) {
        Connection conn = DB.getConnection();
        String sql = "INSERT INTO `t_article` VALUES (null, ?, ?, ?, ?, ?, ?)";
        PreparedStatement pstmt = DB.preparedStmt(conn, sql);
        try {
            pstmt.setString(1, article.getTitle());
            pstmt.setString(2, article.getAuthor());
            pstmt.setString(3, article.getContent());
            pstmt.setInt(4, article.getClickTimes());
            pstmt.setString(6, article.getType());
            pstmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }

        DB.close(pstmt);
        DB.close(conn);
    }

    /**
     * 根据id删除文章
     * @param id
     */
    public static void delById(int id) {
        String sql = "DELETE FROM `t_article` WHERE `id` = " + id;
        Connection conn = DB.getConnection();
        Statement stmt = DB.createStmt(conn);
        try {
            stmt.executeUpdate(sql);
        } catch (SQLException e) {
            e.printStackTrace();
        }

        DB.close(stmt);
        DB.close(conn);
    }

    /**
     * 更新文章
     * @param article
     */
    public static void update(Article article) {
        Connection conn = DB.getConnection();
        String sql = "UPDATE `t_article` SET `title` = ?, `author` = ?, `content` = ?,"
                        + " `click_times` = ?, `publish_time` = ?, `type` = ? WHERE `id` = ?";
        PreparedStatement pstmt = DB.preparedStmt(conn, sql);
        try {
            pstmt.setString(1, article.getTitle());
            pstmt.setString(2, article.getAuthor());
            pstmt.setString(3, article.getContent());
            pstmt.setInt(4, article.getClickTimes());
            pstmt.setDate(5, (Date) article.getPublishTime());
            pstmt.setString(6, article.getType());
            pstmt.setInt(7, article.getId());
            pstmt.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }

        DB.close(pstmt);
        DB.close(conn);
    }

    /**
     * 根据id查找文章
     * @param id
     */
    public static Article queryById(int id) {
        Article article = null;
        String sql = "SELECT * FROM `t_article` WHERE `id` = " + id;
        Connection conn = DB.getConnection();
        Statement stmt = DB.createStmt(conn);
        ResultSet rs = null;
        try {
            rs = stmt.executeQuery(sql);
            if(rs.next()) {
                article.setId(rs.getInt("id"));
                article.setTitle(rs.getString("title"));
                article.setAuthor(rs.getString("author"));
                article.setContent(rs.getString("content"));
                article.setClickTimes(rs.getInt("click_times"));
                article.setPublishTime(rs.getDate("publish_time"));
                article.setType(rs.getString("type"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }

        DB.close(rs);
        DB.close(stmt);
        DB.close(conn);

        return article;
    }

    /**
     * 查找全部文章
     * @return
     */
    public static List<Article> listAll() {
        List<Article> articleList = new ArrayList<>();
        String sql = "SELECT * FROM `t_article`";
        Connection conn = DB.getConnection();
        Statement stmt = DB.createStmt(conn);
        ResultSet rs = DB.executeQuery(stmt, sql);
        try {
            while(rs.next()) {
                int id = rs.getInt("id");
                String title = rs.getString("title");
                String author = rs.getString("author");
                String content = rs.getString("content");
                int clickTimes = rs.getInt("click_times");
                Date publishTime = rs.getDate("publish_time");
                String type = rs.getString("type");

                Article article = new Article();
                article.setId(id);
                article.setTitle(title);
                article.setAuthor(author);
                article.setContent(content);
                article.setClickTimes(clickTimes);
                article.setPublishTime(publishTime);
                article.setType(type);

                articleList.add(article);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }

        DB.close(rs);
        DB.close(stmt);
        DB.close(conn);

        return articleList;
    }
}

封装好之后开始套页，我们需要展示所有article的页面首先就是首页index.jsp。所以这就涉及到一个问题：要运行首页之前，肯定要先运行查找所有文章的servlet，所以我们来写一下查找所有文章的servlet

我们的大致思想是这样的：先运行articleList这个servlet，然后将得到的articleList放到session中去，再跳转到columnList，同样将得到的columnList放到session，最后再跳转到index.jsp，在index.jsp中将所有的Article和Column读出来

这里我们在articleList中还写了一个分页，下面我把分页的基本思想给大家介绍一下：

对于一个文章列表，如果其中只有几个文章，那么没有问题，但是如果其中包含了成百上千个的文章，想要在一个页面展示出来显然不太现实，用户体验度也极差，所以这就引出来了分页这个概念。

如果我们要做分页，我们有这样的两种想法：第一种，是我先一次性把所有的文章全部查找出来，然后再根据用户所选的页码，来判断我应该显示哪些。这样做的话显然会比较麻烦，每次用户重新选择页码，都需要把所有文章都找出来一遍。那我们不禁就想到了第二种方法：我根据用户所选的页码，做一个计算，计算出需要查找出第几条到第几条数据，然后再去数据库中进行查询操作。这样做显然是合理的，也是高效率的，所以这就引出来sql语句中的limit关键字。
limit关键字的用法是这样的：在sql语句的后面加上”limit startNo , pageSize”，startNo是从哪条记录开始查询，pageSize是查询多少条数据。我们来看个例子，就直接以我们的这个项目为例，我们在ArticleDao里面添加一个方法listByNum()

/**
     * 分页查找全部文章
     * @return
     */
    public static List<Article> listByNum(int pageNo, int pageSize, String column) {
        List<Article> articleList = new ArrayList<>();
        int startNo = (pageNo-1)*pageSize ;
        String sql = "SELECT * FROM `t_article`";
        if(column != "null") {
            sql += " WHERE `type` = '" + column + "'";
        }
        sql += " ORDER BY `id` DESC LIMIT " + startNo + ", " + pageSize;

        Connection conn = DB.getConnection();
        Statement stmt = DB.createStmt(conn);
        ResultSet rs = DB.executeQuery(stmt, sql);
        try {
            while(rs.next()) {
                int id = rs.getInt("id");
                String title = rs.getString("title");
                String author = rs.getString("author");
                String content = rs.getString("content");
                int clickTimes = rs.getInt("click_times");
                Date publishTime = rs.getDate("publish_time");
                String type = rs.getString("type");

                Article article = new Article();
                article.setId(id);
                article.setTitle(title);
                article.setAuthor(author);
                article.setContent(content);
                article.setClickTimes(clickTimes);
                article.setPublishTime(publishTime);
                article.setType(type);

                articleList.add(article);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }

        DB.close(rs);
        DB.close(stmt);
        DB.close(conn);

        return articleList;
    }

这里startNo的计算方法就是(pageNo - 1) * pageSize，注意第一条数据在这里是记做第零条的哈

这里提一下，我们的第一种方法也是可以的。我们后面的一个分页用的就是第一种方法，采用的是前台的BootStrap，这里就不做过多介绍了

所以这样我们就可以在ArticleList.java里面调用这个方法了。我们来贴一个ArticleList.java的代码，

/**
 * 
 */
package com.software.servlet;

import java.io.IOException;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

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 javax.servlet.http.HttpSession;

import com.software.Dao.ArticleDao;
import com.software.entities.Article;
import com.software.util.DB;

/**
 * 查找所有文章servlet
 * @author lw
 * @time 2017年6月10日下午9:02:54
 */

@WebServlet(name="articleList", value="/articleList")
public class ArticleList extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        List<Article> articleList = new ArrayList<>();
        //文章类型
        String column = request.getParameter("column");
        if(column==null) {
            column = "null";
        }


        //第几页
        String strPageNo = request.getParameter("pageNo");
        int pageNo = 0;
        if(strPageNo == null || strPageNo.trim().equals("")) {
            pageNo = 1;
        } else {
            pageNo = Integer.parseInt(strPageNo.trim());
        }

        //每页几篇文章
        String strPageSize = request.getParameter("pageSize");
        int pageSize = 0;
        if(strPageSize == null || strPageSize.trim().equals("")) {
            pageSize = 5;
        } else {
            pageSize = Integer.parseInt(strPageSize);
        }

        Connection conn = DB.getConnection();
        String sql = "SELECT count(*) FROM `t_article`";

        Statement stmtCount = DB.createStmt(conn);
        ResultSet rsCount = DB.executeQuery(stmtCount, sql);
        int totalNum = 0;

        try {
            if(rsCount.next()) {
                totalNum = rsCount.getInt(1);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }

/*
总页数的计算方法，如果totalNum/pageSize能整除，就是totalNum/pageSize，如果不能整除，就是totalNum/pageSize + 1
*/
        int totalPages = totalNum % pageSize == 0 ? totalNum / pageSize : totalNum / pageSize + 1;
        //防止不合法输入       
        if(pageNo > totalPages) {
            pageNo = totalPages;
        }

        HttpSession session = request.getSession();

        session.setAttribute("totalPages", totalPages);
        session.setAttribute("pageNo", pageNo);
        session.setAttribute("pageSize", pageSize);

        //调用listByNum方法
        articleList = ArticleDao.listByNum(pageNo, pageSize, column);

        session.setAttribute("articleList", articleList);
        response.sendRedirect("columnList");
    }

}

最后在index.jsp里面用session读出来

<div style="border-bottom: 1px solid rgb(228, 228, 228);">
                        <p class="article_title" id="article_recommend_title" style="display:inline">
                        最新文章</p>
                        <form action="articleList" method="post" style="display:inline">
                        <%--设置每页显示几条--%>
                        <span style="margin-left:450px;color:#37acd3;display:inline-block;font-size:15px;">显示</span>
                            <select class="form-control" name="pageSize" style="border:1px solid #37acd3;width:60px;height:30px;">

                                <option>5</option>
                                <option>10</option>
                                <option>15</option>
                                <option>20</option>
                            </select>
                            <span style="color:#37acd3;display:inline-block;font-size:15px;">条</span>
                            <input type="submit" value="提交" style="display:inline;width:70px;">
                        </form>
                        </div>
                        <ul>

                        <c:forEach items="${sessionScope.articleList}" var="article">
                            <li>
                                <div class="articleCtx clearfix">
                                    <a href="detail?id=${article.id}">
                                        ${article.title}
                                        <span style="float: right;">
                                        ${article.publishTime}
                                        </span>
                                    </a>
                                </div>
                            </li>
                        </c:forEach>

                        </ul>


                        <div class="pageNum fr clearfix">
                        <%
                        System.out.println("totalPages = " + session.getAttribute("totalPages"));
                        System.out.println("pageNo = " + session.getAttribute("pageNo"));
                         %>
                         <%--共几页，第几页--%>
                        <span style="float:left;">共${sessionScope.totalPages}页，第${sessionScope.pageNo}页</span>
                        <div style="float:right;">
                            <a href="articleList?pageNo=${sessionScope.pageNo-1}&${sessionScope.pageSize}">上一页</a>

                            <a href="articleList?pageNo=${sessionScope.pageNo+1}&${sessionScope.pageSize}">下一页</a>
                        </div>
                        </div>

                    </div>

                </div>

这样，主页中就可以从数据库中读出来所有的article啦~

然后我们开始写文章的添加，其实很简单，如果大家是按照前面的操作步骤一步步来的话已经清除熟路了。先设置跳转页面，然后提交到servlet，最后请求转发或者请求重定向回index.jsp

我们直接贴代码

首先是index.jsp中的链接，用了一个<c:choose>标签

<c:choose>
        <c:when test="${sessionScope.username == null}">
            <a href="login.jsp">登陆</a>
            <a href="register.jsp">注册</a>
        </c:when>
        <c:otherwise>
            欢迎您， ${sessionScope.username}  <br>
            <a href="new_article.jsp">写文章</a>
            <a href="logout">退出登录</a>
            <c:if test="${sessionScope.username eq 'admin'}">
                <a href="back/production/user_manage.jsp">去往后台管理页面</a>
            </c:if>
        </c:otherwise>
    </c:choose>

然后是new_article.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8" import="com.software.entities.*"%>
<%@ page isELIgnored = "false" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <!-- Meta, title, CSS, favicons, etc. -->
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">


    <title>Gentelella Alela! | </title>
    <!-- Bootstrap -->
    <link href="back/vendors/bootstrap/dist/css/bootstrap.min.css" rel="stylesheet">
    <!-- Font Awesome -->
    <link href="back/vendors/font-awesome/css/font-awesome.min.css" rel="stylesheet">
    <!-- NProgress -->
    <link href="back/vendors/nprogress/nprogress.css" rel="stylesheet">
    <!-- iCheck -->
    <link href="back/vendors/iCheck/skins/flat/green.css" rel="stylesheet">
    <!-- bootstrap-wysiwyg -->
    <link href="back/vendors/google-code-prettify/bin/prettify.min.css" rel="stylesheet">
    <!-- Select2 -->
    <link href="back/vendors/select2/dist/css/select2.min.css" rel="stylesheet">
    <!-- Switchery -->
    <link href="back/vendors/switchery/dist/switchery.min.css" rel="stylesheet">
    <!-- starrr -->
    <link href="back/vendors/starrr/dist/starrr.css" rel="stylesheet">
    <!-- bootstrap-daterangepicker -->
    <link href="back/vendors/bootstrap-daterangepicker/daterangepicker.css" rel="stylesheet">

    <!-- Custom Theme Style -->
    <link href="back/build/css/custom.min.css" rel="stylesheet">
    <link href="js/simditor/styles/simditor.css" rel="stylesheet">

    <style>
        .col-md-6 {
            width: 66%;
            }
            .col-md-3 {
            width: 20%;
            }
    </style>
  </head>

        <!-- page content -->
        <div class="right_col" role="main">
          <div class="">
            <div class="clearfix"></div>
            <div class="row">
            <div class="col-md-12 col-sm-12 col-xs-12">
                <div class="x_panel">
                  <div class="x_title">
                    <h2>文章添加</h2>

                    <div class="clearfix"></div>
                  </div>
                  <div class="x_content">
                    <br />
                    <form id="demo-form2" data-parsley-validate class="form-horizontal form-label-left" action="newArticle" method="post">

                    <div class="form-group">
                        <label class="control-label col-md-3 col-sm-3 col-xs-12" for="">标题
                        </label>
                        <div class="col-md-6 col-sm-6 col-xs-12">
                          <input type="text" id="last-name" name="title" required="required" class="form-control col-md-7 col-xs-12">
                        </div>
                     </div>

                      <div class="form-group">
                        <label class="control-label col-md-3 col-sm-3 col-xs-12" for="">作者
                        </label>
                        <div class="col-md-6 col-sm-6 col-xs-12">
                          <p class="form-control col-md-7 col-xs-12" style="margin:0px;">${sessionScope.username}</p>
                        </div>
                      </div>

                     <div class="form-group">
                        <label class="control-label col-md-3 col-sm-3 col-xs-12" for="">归属栏目
                        </label>
                        <div class="col-md-6 col-sm-6 col-xs-12">
                          <select class="form-control" name="column">
                              <c:forEach items="${sessionScope.columnList}" var="column">
                                <option>
                                    ${column.name}
                                </option>
                              </c:forEach>
                          </select>
                      </div>
                      </div>

                      <div class="form-group">
                        <label class="control-label col-md-3 col-sm-3 col-xs-12" rows="3">内容
                        </label>
                        <div class="col-md-6 col-sm-6 col-xs-12">
              <!-- 插件开始 -->            
                <textarea id="editor" placeholder="这里输入内容" name="content"autofocus></textarea>  
 <!--插件结束-->

                  <br />

                        </div>
                      </div>
                      <div class="ln_solid"></div>
                      <div class="form-group">
                        <div class="col-md-6 col-sm-6 col-xs-12 col-md-offset-3">
                          <button class="btn btn-primary" type="reset">重置</button>
                          <button type="submit" class="btn btn-success">提交</button>
                        </div>
                      </div>

                    </form>
                  </div>
                </div>
              </div>
            </div>

          </div>
        </div>
        <!-- /page content -->

        <!-- footer content -->
        <footer>
          <div class="pull-right">
          </div>
          <div class="clearfix"></div>
        </footer>
        <!-- /footer content -->
      </div>
    </div>
    <!-- jQuery -->
    <script src="back/vendors/jquery/dist/jquery.min.js"></script>
    <!-- Bootstrap -->
    <script src="back/vendors/bootstrap/dist/js/bootstrap.min.js"></script>
    <!-- FastClick -->
    <script src="back/vendors/fastclick/lib/fastclick.js"></script>
    <!-- NProgress -->
    <script src="back/vendors/nprogress/nprogress.js"></script>
    <!-- bootstrap-progressbar -->
    <script src="back/vendors/bootstrap-progressbar/bootstrap-progressbar.min.js"></script>
    <!-- iCheck -->
    <script src="back/vendors/iCheck/icheck.min.js"></script>
    <!-- bootstrap-daterangepicker -->
    <script src="back/vendors/moment/min/moment.min.js"></script>
    <script src="back/vendors/bootstrap-daterangepicker/daterangepicker.js"></script>
    <!-- bootstrap-wysiwyg -->
    <script src="back/vendors/bootstrap-wysiwyg/js/bootstrap-wysiwyg.min.js"></script>
    <script src="back/vendors/jquery.hotkeys/jquery.hotkeys.js"></script>
    <script src="back/vendors/google-code-prettify/src/prettify.js"></script>
    <!-- jQuery Tags Input -->
    <script src="back/vendors/jquery.tagsinput/src/jquery.tagsinput.js"></script>
    <!-- Switchery -->
    <script src="back/vendors/switchery/dist/switchery.min.js"></script>
    <!-- Select2 -->
    <script src="back/vendors/select2/dist/js/select2.full.min.js"></script>
    <!-- Parsley -->
    <script src="back/vendors/parsleyjs/dist/parsley.min.js"></script>
    <!-- Autosize -->
    <script src="back/vendors/autosize/dist/autosize.min.js"></script>
    <!-- jQuery autocomplete -->
    <script src="back/vendors/devbridge-autocomplete/dist/jquery.autocomplete.min.js"></script>
    <!-- starrr -->
    <script src="back/vendors/starrr/dist/starrr.js"></script>
    <!-- Custom Theme Scripts -->
    <script src="back/build/js/custom.min.js"></script>
    <!-- <script type="text/javascript" src="js/jquery.min.js"></script> -->
    <script type="text/javascript" src="back/layer/layer.js"></script>

    <script type="text/javascript" src="js/simditor/scripts/jquery.min.js"></script>
    <script type="text/javascript" src="js/simditor/scripts/module.js"></script>
    <script type="text/javascript" src="js/simditor/scripts/uploader.js"></script>
    <script type="text/javascript" src="js/simditor/scripts/hotkeys.js"></script>
    <script type="text/javascript" src="js/simditor/scripts/simditor.js"></script>

    <script type="text/javascript">
        var editor = new Simditor({
            textarea: $('#editor'),
        });
    </script>
  </body>
</html>

这里我是用了一个simditor这样的一个编辑器，这是一个非常轻量级的编辑器，比Ueditor，或者是我在写这个项目的时候有同学想要搞一点骚操作想嵌入的MarkDown编辑器，比起这些编辑器，simditor用起来会非常方便

然后是NewArticle.java

/**
 * 
 */
package com.software.servlet;

import java.io.IOException;

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 javax.servlet.http.HttpSession;

import com.software.Dao.ArticleDao;
import com.software.entities.Article;

/**
 * 添加文章servlet类
 * @author lw
 * @time 2017年6月20日下午3:01:29
 */
@WebServlet(name="newArticle", value="/newArticle")
public class NewArticle extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        request.setCharacterEncoding("utf-8");
        String title = request.getParameter("title");
        HttpSession session = request.getSession();
        String author = (String)session.getAttribute("username");
        String column = request.getParameter("column");
        String content = request.getParameter("content");

        content = content.replaceAll("\n","<br>");

        Article article = new Article();
        article.setTitle(title);
        article.setAuthor(author);
        article.setContent(content);
        article.setType(column);

        ArticleDao.insert(article);

        response.sendRedirect("articleList");
    }

}

这里可以看到我最后请求重定向到了articleList这个servlet，而没有重定向到index.jsp，这是因为我在添加文章之后，文章列表肯定有所更新，所以我需要重新获取一下articleList，来更新一下session中的文章列表

删、改这些操作我们在前面的模块都已经说过了，Article模块中也是大同小异，这里我们说一下过滤器

过滤器是什么我就不再说了，如果有不了解的同学可以去翻一翻资料。过滤器多数会用于字符编码方式的统一、或者是对没有权限进入页面的用户进行阻止。在我们这个项目里，分为前台普通用户可视页面和后台管理页面，那么问题就在于，如果作为一个普通用户，当我输入后台管理页面的网址时，肯定是不能进入这个页面的，所以，我们这个项目的过滤器主要就是这个作用。

我们过滤器的代码放在了项目src/com.software.filter这个包里面，右键新建一个类，实现Filter接口并重写方法。我们filter的主要功能实现的代码都写在doFilter里面，这里我们直接把代码贴出来

package com.software.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

/**
 * 后台页面登录验证过滤器
 * @author lw
 * @time 2017年6月27日上午11:16:40
 */
public class BackFilter implements Filter {

    /* (non-Javadoc)
     * @see javax.servlet.Filter#destroy()
     */
    @Override
    public void destroy() {
        // TODO Auto-generated method stub

    }

    /* (non-Javadoc)
     * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)
     */
    @Override
    public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain chain)
            throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest)arg0;
        HttpServletResponse response = (HttpServletResponse)arg1;

        HttpSession session = request.getSession();
        String username = (String)session.getAttribute("username");
        if((username != null && username =="admin" )) {
            chain.doFilter(request, response);
        } else {
            response.sendRedirect("/Software_Party/error.jsp");
        }
    }

    /* (non-Javadoc)
     * @see javax.servlet.Filter#init(javax.servlet.FilterConfig)
     */
    @Override
    public void init(FilterConfig arg0) throws ServletException {
        // TODO Auto-generated method stub

    }

}

然后，我们还需要在web.xml里对filter进行配置，代码如下

<filter>
        <filter-name>backFilter</filter-name>
        <filter-class>com.software.filter.BackFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>backFilter</filter-name>
        <url-pattern>/back/*</url-pattern>
    </filter-mapping>

这里是完成了一个类和路径的一一对应关系意味着：所有路径为/back/（代表所有文件）的页面都会被com.software.filter.BackFilter这个类，或者说这个过滤器处理。
再说一下这个过滤器，BackFilter.java的代码

在doFilter方法中，前两行代码是先将ServletRequest和ServletResponse强制转换成HttpServletRequet和HttpServleteResponse，然后从session中取出用户的username，如果username不为空，并且username为”admin”，那么，放行。否则，请求重定向到error.jsp

以下是error.jsp的代码

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%String path = request.getContextPath();String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";%>

<!DOCTYPE html>
<html>
  <head>
    <base href="<%=basePath%>">

    <title>My JSP 'error.jsp' starting page</title>

    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  </head>

  <body>
    对不起，您没有权限进行此操作<br>
    如想进行此操作，请联系超级管理员<br>
    <a href="index.jsp">返回首页</a>
  </body>
</html>

截止到目前为止，这个项目就大致成型了。其中运用了jsp、servlet、以及过滤器filter等JavaWeb开发的基本知识。其实在我测试这个项目的时候，发现在这个项目里面也存在很多bug，其中比较严重的就是分页那里，比如当我选择了每页有10条，然后当我选择下一页的时候，就会发现每页又变成了5条。其实这个bug也不难调，只是当时由于时间不够，忙着项目验收以及期末考试，所以就匆匆结项了。大家可以尝试修改一下。

这三篇博客的时间拖延比较长，最后这一篇是已经一个月之后写的了，所以有一些地方说的不是很清楚，或者有一些遗漏。我相信博客中也有一些错误的地方，也欢迎大家指出。jsp+servlet的开发模式也只是JavaWeb中最基础的一部分，企业中也很少有人会使用这种模式了，它还是我们JavaWeb中的基础，很多东西还是要以它们作为基础的。