没有查询到数据
来源：3-2 分类管理表现层
Wchisper
2019-07-26 19:14:27
package com.coke.cake.global;
import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
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.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
/*
*需求困难：
* 1：如果每一次请求都写一个servlet过会非常复杂
* 2：如果我们想统一的处理这些servlet也是没有办法同意的
* 新的解决思路：
* 我们将所有的用户请求，交给一个servlet来处理，这个servlet并不做任何的请求处理。
* 但是它根据我们的请求(通过前台传递的url分辨出哪一个servlet进行处理)，让它告诉程序，哪
* 一个servlet进行处理
* */
public class GlobalController extends GenericServlet {
public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
/*
* url分析:
* 以 ".do" 为后缀结尾的交给我们这个servlet出理
* /Login.do 不是前台和后台 ：默认一个servlet login
* /Cake/detail.do detail
* /admin/Cake/add.do add
* */
//强制转换得到HttpServletXxx 下的request/response
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) res;
//获取url的路径格式
String path = request.getServletPath();
System.out.println(path);
System.out.println("---------------");
//判断传过来的是后台页面还是前台页面或者登录页面
if (path.indexOf("/admin") != -1) {
//代表path是后台页面
path = path.substring(7);
} else {
path = path.substring(1);
}
/*
* 经过上面判断后url
* login.do
* cake/detail.do 类名:cakeServlet 方法名:detail
* cake/add.do 类名:cakeServlet 方法名：add
* */
int index = path.indexOf("/");
String className = null;
String methodName = null;
if (index != -1) {
className = "com.coke.cake.servlet." + path.substring(0, index) + "Servlet";
methodName = path.substring(index + 1, path.indexOf(".do"));
} else {
className = "com.coke.cake.servlet.defaultServlet";
methodName = path.substring(0, path.indexOf(".do"));
}
System.out.println(className+"--------"+methodName);
try {
/*
* 通过反射执行这个方法
* */
//通过class的静态方法，传递className
Class c = Class.forName(className);
Object object = c.newInstance();
Method method = c.getMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);
//参数一：调用这个方法的对象是哪一个，参数二，三传递调用方法的参数
method.invoke(object, request, response);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
}CatalogServlet中查询所有分类的方法
/**
* 查询所有分类
* url="/admin/Catalog/list.do"
*
* @param request
* @param response
* @throws ServletException
* @throws IOException
*/
public void list(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//调用业务
Catalog root = catalogService.getRoot();
Integer id = root.getId();
Integer pid = root.getPid();
String info = root.getInfo();
root.getChildren();
System.out.println(id + "----" + pid + "---" + info);
//页面跳转
request.setAttribute("root", root);
request.getRequestDispatcher("/WEB-INF/pages/admin/catalog_list.jsp").forward(request, response);
}CatalogService接口
package com.coke.cake.service;
import com.coke.cake.entity.Catalog;
import java.util.List;
public interface CatalogService {
//添加方法，批量添加
void add(List<Catalog> list);
//删除方法
void delete(int id);
//获取分类
Catalog getRoot();
}CatalogServceImpl
package com.coke.cake.service.CatalogServiceImpl;
import com.coke.cake.dao.CatalogDao;
import com.coke.cake.entity.Catalog;
import com.coke.cake.global.DaoFactory;
import com.coke.cake.service.CatalogService;
import java.util.List;
public class CatalogServiceImpl implements CatalogService {
private CatalogDao catalogDao = DaoFactory.getInstance().getDao(CatalogDao.class);
public void add(List<Catalog> list) {
catalogDao.beachInsert(list);
}
public void delete(int id) {
catalogDao.delete(id);
}
public Catalog getRoot() {
return catalogDao.select(10000);
}
}CatalogDao
package com.coke.cake.dao;
import com.coke.cake.entity.Catalog;
import org.apache.ibatis.annotations.*;
import java.util.List;
public interface CatalogDao {
/**
* 插入数据和批量插入数据
* 直接嵌入脚本
* @param list
*/
@Insert("<script>" +
"insert into catalog (title,pid,info) vales" +
"<foreach collection='list' item='catalog' separator=',' >" +
"(#{catalog.title},#{catalog.pid},#{catalog.info})" +
"</foreach>" +
"</script>")
@Options(useGeneratedKeys = true, keyProperty = "id")
void beachInsert(List<Catalog> list);
/**
* 删除数据
*
* @param id
*/
@Delete("delete from catalog where id=#{id}")
void delete(int id);
/**
* 跟据id查询最高级分类
*
* @param id
* @return
*/
@Select("select * from catalog where id=#{id}")
@Results(id = "all", value = { //all是别名,当多个方法同时用相同的注解时,相当于resultMap
@Result(column = "id", property = "id", id = true), //相当于<resultMap>下面的<result>
@Result(column = "title", property = "title"), //相当于<resultMap>下面的<result>
@Result(column = "pid", property = "pid"),
@Result(column = "info", property = "info"),
@Result(column = "id", property = "children", many = @Many(select = "selectByPid"))
})
Catalog select(int id);
/**
* 根据它父类的id，查询它下面所有的子类
*
* @param pid
* @return
*/
@Select("select * from catalog where pid=#{pid}")
@ResultMap("all")
List<Catalog> selectByPid(int pid);
}web.xml
<!--过滤器配置--> <filter> <filter-name>encoding</filter-name> <filter-class>com.coke.cake.global.EncodingFilter</filter-class> <init-param> <param-name>encoding</param-name> <param-value>UTF-8</param-value> </init-param> </filter> <filter-mapping> <filter-name>encoding</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <servlet> <servlet-name>GlobalServlet</servlet-name> <servlet-class>com.coke.cake.global.GlobalController</servlet-class> </servlet> <servlet-mapping> <servlet-name>GlobalServlet</servlet-name> <url-pattern>*.do</url-pattern> </servlet-mapping>
启动服务器后控制台也没有报错
图中是打印的是CataloServlet中list方法，在上面有代码，发现没后获取到数据库中的信息
写回答
6回答
-
同学你好，在catalog_list.jsp页面中，没有引入jstl的标签库，如：
建议同学添加jstl的标签库再试试，
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
如果我的回答解决了你的疑惑，请采纳。祝：学习愉快~
0h019-07-27 -
Wchisper
提问者
2019-07-27
Catalog_list.jsp <%@ page contentType="text/html;charset=UTF-8" language="java" %> <jsp:include page="top.jsp"/> <section id="content_wrapper"> <section id="content" class="table-layout animated fadeIn"> <div class="tray tray-center"> <div class="content-header"> <h2> 分类管理</h2> <p class="lead"></p> </div> <div class="admin-form theme-primary mw1000 center-block" style="padding-bottom: 175px;"> <div class="panel heading-border"> <div class="panel-menu"> <div class="row"> <div class="hidden-xs hidden-sm col-md-3"> <div class="btn-group"> <button type="button" class="btn btn-default light"> <i class="fa fa-trash"></i> </button> <button type="button" class="btn btn-default light"> <i class="fa fa-plus" onclick="javascript:window.location.href='/admin/Catalog/toAdd.do';"></i> </button> </div> </div> </div> </div> <div class="panel-body pn"> <table id="message-table" class="table admin-form theme-warning tc-checkbox-1"> <thead> <tr class=""> <th class="text-center hidden-xs">Select</th> <th class="hidden-xs">名称</th> <th class="hidden-xs">描述</th> <th>操作</th> </tr> </thead> <tbody> <c:forEach items="${root.children}" var="cat1"> <tr class="message-unread"> <td class="hidden-xs"> <label class="option block mn"> <input type="checkbox" name="mobileos" value="FR"> <span class="checkbox mn"></span> </label> </td> <td>${cat1.title}</td> <td>${cat1.info}</td> <td> <a href="${pageContext.request.contextPath}/admin/Catalog/delete.do?id=${cat1.id}">删除</a> </td> </tr> <c:forEach items="${cat1.children}" var="cat2"> <tr class="message-unread"> <td class="hidden-xs"> <label class="option block mn"> <input type="checkbox" name="mobileos" value="FR"> <span class="checkbox mn"></span> </label> </td> <td style="padding-left: 50px;">${cat2.title}</td> <td>${cat2.info}</td> <td> <a href="${pageContext.request.contextPath}/admin/Catalog/delete.do?id=${cat2.id}">删除</a> </td> </tr> <c:forEach items="${cat2.children}" var="cat3"> <tr class="message-unread"> <td class="hidden-xs"> <label class="option block mn"> <input type="checkbox" name="mobileos" value="FR"> <span class="checkbox mn"></span> </label> </td> <td style="padding-left: 100px;">${cat3.title}</td> <td>${cat3.info}</td> <td> <a href="${pageContext.request.contextPath}/admin/Catalog/delete.do?id=${cat3.id}">删除</a> </td> </tr> </c:forEach> </c:forEach> </c:forEach> </tbody> </table> </div> </div> </div> </div> </section> </section> <jsp:include page="bottom.jsp"/>0 -
Wchisper
提问者
2019-07-27
top.jsp <%@ page contentType="text/html;charset=UTF-8" language="java" %> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>欢迎使用 IMOOC Cake 后台管理系统</title> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <link rel="stylesheet" type="text/css" href="/css/theme.css"> <link rel="stylesheet" type="text/css" href="/css/admin-forms.css"> <!--[if lt IE 9]> <script src="https://oss.maxcdn.com/libs/html5shiv/3.7.0/html5shiv.js"></script> <script src="https://oss.maxcdn.com/libs/respond.js/1.3.0/respond.min.js"></script> <![endif]--> </head> <body class="admin-validation-page" data-spy="scroll" data-target="#nav-spy" data-offset="200"> <div id="main"> <header class="navbar navbar-fixed-top navbar-shadow"> <div class="navbar-branding"> <a class="navbar-brand" href="../index.html"> <H3>IMOOC Cake 后台管理系统</H3> </a> <span id="toggle_sidemenu_l" class="ad ad-lines"></span> </div> </header> <aside id="sidebar_left" class="nano nano-light affix"> <div class="sidebar-left-content nano-content"> <header class="sidebar-header"> <div class="sidebar-widget author-widget"> <div class="media"> <a class="media-left" href="#"> <img src="${pageContext.request.contextPath}/images/head.jpg" class="img-responsive"> </a> <div class="media-body"> <div class="media-author">管理员</div> <div class="media-links"> <a href="login.html">退出</a> </div> </div> </div> </div> <div class="sidebar-widget search-widget hidden"> <div class="input-group"> <span class="input-group-addon"> <i class="fa fa-search"></i> </span> <input type="text" id="sidebar-search" class="form-control" placeholder="Search..."> </div> </div> </header> <ul class="nav sidebar-menu"> <li class="sidebar-label pt20">商品管理</li> <li class="active"> <a href="cake_list.html"> <span class="glyphicon glyphicon-book"></span> <span class="sidebar-title">商品列表</span> </a> </li> <li> <a href="cake_add.html"> <span class="glyphicon glyphicon-home"></span> <span class="sidebar-title">商品上架</span> </a> </li> <li class="sidebar-label pt20">分类管理</li> <li class="active"> <a href="${pageContext.request.contextPath}/admin/Catalog/list.do"> <span class="glyphicon glyphicon-book"></span> <span class="sidebar-title">分类列表</span> </a> </li> <li> <a href="${pageContext.request.contextPath}/admin/Catalog/toAdd.do"> <span class="glyphicon glyphicon-home"></span> <span class="sidebar-title">添加分类</span> </a> </li> </ul> <div class="sidebar-toggle-mini"> <a href="login.html"> <span class="fa fa-sign-out"></span> </a> </div> </div> </aside> butten.jsp <%@ page contentType="text/html;charset=UTF-8" language="java" %> </div> <style> /* demo page styles */ body { min-height: 2300px; } .content-header b, .admin-form .panel.heading-border:before, .admin-form .panel .heading-border:before { transition: all 0.7s ease; } /* responsive demo styles */ @media (max-width: 800px) { .admin-form .panel-body { padding: 18px 12px; } } </style> <style> .ui-datepicker select.ui-datepicker-month, .ui-datepicker select.ui-datepicker-year { width: 48%; margin-top: 0; margin-bottom: 0; line-height: 25px; text-indent: 3px; color: #888; border-color: #DDD; background-color: #FDFDFD; -webkit-appearance: none; /*Optionally disable dropdown arrow*/ } </style> <!-- jQuery --> <script src="${pageContext.request.contextPath}/js/jquery.min.js"></script> <script src="${pageContext.request.contextPath}/js/jquery-ui.min.js"></script> <!-- Theme Javascript --> <script src="${pageContext.request.contextPath}/js/utility.js"></script> <script src="${pageContext.request.contextPath}/js/demo/demo.js"></script> <script src="${pageContext.request.contextPath}/js/main.js"></script> <script src="${pageContext.request.contextPath}/js/pages.js"></script> <!-- END: PAGE SCRIPTS --> </body> </html>0 -
Wchisper
提问者
2019-07-27
浏览器控制台报错了
0 -
好帮手慕阿满
2019-07-27
同学你好，问一下同学打印子分类是否有显示呢？如果有显示，那应该前台页面的显示问题，建议同学看一下浏览器控制台是否报错。如果没有，建议同学将前台的页面显示以及代码贴一下。
祝：学习愉快~
0h019-07-27 -
好帮手慕阿满
2019-07-27
同学你好，打印出10000----0---null是正常的，pid是指该分类的父分类，info是指描述。id为10000是第一级分类，没有父分类，所以pid为0，info在数据库中存储的就是null，查询结果的是null。所以打印10000----0---null是正常的。或者同学可以打印id为10000的子分类，如：
如果我的回答解决了你的疑惑，请采纳。祝：学习愉快~
0h019-07-27
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