无法出现数据列表，控制台里不报错-慕课网

无法出现数据列表，控制台里不报错

来源：2-5 数据展示

124839

2016-09-08 16:07

package servlet;

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

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import bean.Message;

/**
 * @author 570
 *
 */
public class ListServlet extends HttpServlet {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {      
        try {          
            String command = req.getParameter("command");//从页面拿到参数
            String description =req.getParameter("description");   
            Class.forName("com.mysql.jdbc.Driver");
            Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb?characterEncoding=utf8&useSSL=true","root","root");
            //String sql ="SELECT ID,COMMAND,DESCRIPTION,CONTENT FROM imooc_mybatis_list";          
            //where 1=1 用于语句拼接。。不明所以
            StringBuilder sql = new StringBuilder("select ID,COMMAND,DESCRIPTION,CONTENT from imooc_mybatis_list where 1=1");         
            PreparedStatement ps = conn.prepareStatement(sql.toString());       
            //多条件查询时，利用List做缓冲，保存查询参数，然后再循环赋值
            List<String> paramer = new ArrayList<String>();
            //语句拼接如果查询的指令非空且非空字符串则执行语句拼接查询
            if (command!=null&&!"".equals(command.trim())) {
                sql.append("and COMMAND=?");
                paramer.add(command);
            }            
            if (description!=null&&!"".equals(description.trim())) {
                sql.append("and DESCRIPTION like '%' ? '%'");
                paramer.add(description);
            }
            //把页面上的语句拿给要送到数据库查询的ps中
            for (int i = 0; i < paramer.size(); i++) {
                ps.setString(i+1, paramer.get(i));
            }
            
            ResultSet rs = ps.executeQuery();
            List<Message> messageList = new ArrayList<Message>();           
            while (rs.next()) {
                Message message = new Message();
                messageList.add(message);
                message.setId(rs.getString("ID"));
                message.setCommand(rs.getString("COMMADN"));
                message.setDescription(rs.getString("DESCRIPTION"));
                message.setContent(rs.getString("CONTENT"));                
            }         
            req.setAttribute("messageList", messageList);           
        } catch (ClassNotFoundException e) {            
            e.printStackTrace();
        } catch (SQLException e) {            
            e.printStackTrace();
        }        
        req.getRequestDispatcher("/WEB-INF/jsp/list.jsp").forward(req, resp);
    }  
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        
        this.doGet(req, resp);
    }   
}

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
        <meta http-equiv="X-UA-Compatible"content="IE=9; IE=8; IE=7; IE=EDGE" />
        <title>内容列表页面</title>
        <link href= "<%=basePath %>resource/css/all.css" rel="stylesheet" type="text/css" />
    </head>
    <body style="background: #e1e9eb;">
        <form action="<%=basePath %>list" id="mainForm" method="post">
            <div class="right">
                <div class="current">当前位置：<a href="javascript:void(0)" style="color:#6E6E6E;">内容管理</a> &gt; 内容列表</div>
                <div class="rightCont">
                    <p class="g_title fix">内容列表 <a class="btn03" href="#">新 增</a>&nbsp;&nbsp;&nbsp;&nbsp;<a class="btn03" href="#">删 除</a></p>
                    <table class="tab1">
                        <tbody>
                            <tr>
                                <td  width="90" align="right">查询指令</td>
                                <td>
                                    <input name="command" type="text" class="allInput" value=""/>
                                </td>
                                <td  width="90" align="right">描述</td>
                                <td>
                                    <input name="description" type="text" class="allInput" value=""/>
                                </td>
                                <td width="85" align="right"><input type="submit" class="tabSub" value="查 询" /></td>
                               </tr>
                        </tbody>
                    </table>
                    <div class="zixun fix">
                        <table class="tab2" width="100%">
                            <tbody>
                                <tr>
                                    <th><input type="checkbox" id="all" onclick="#"/></th>
                                    <th>序号</th>
                                    <th>指令名称</th>
                                    <th>描述</th>
                                    <th>操作</th>
                                </tr>
                                <c:forEach items="${messageList}" var="message" varStatus="status">
                                    <tr <c:if test="${status.index%2!=0}"> style="background-color:#ECF6EE;"</c:if>>
                                    <td><input type="checkbox" /></td>
                                    <td>${status.index+1}</td>
                                    <td>${message.command}</td>
                                    <td>${message.description}</td>
                                    <td>${message.content}</td>
                                    <td>
                                        <a href="#">修改</a>&nbsp;&nbsp;&nbsp;
                                        <a href="#">删除</a>
                                    </td>
                                </tr>
                                </c:forEach>
                            </tbody>
                        </table>

写回答关注

4回答

一起去看海咯

2016-10-23 21:00:46

第一张图第五十二行错了
sql语法拼写错误，前段时间也遇到了，不过解决了
if (description!=null&&!"".equals(description.trim())) {
sql.append("and DESCRIPTION like ? ");
paramer.add("%"+description+"%");
}

0 0
Uauslman

2016-09-16 10:52:19

是不是数据库名称错误。

0 0
124839

2016-09-08 16:12:47

这个问题出现有两天了，我一直没解决就把课程往下听了，其中有几行诗下面课中的代码。不过自己感觉应该不影响页面显示列表的问题。另外我的数据表中是有值的。。不清楚哪里出了问题，还请大神们不吝解答

0 0
124839

2016-09-08 16:09:07

由于不能超过20000字我把jsp中后面的标签删了。。本身jsp页面编译器不现实错误

0 0

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