1 版本一

版本只能在首页显示类别，当切换到了其它页面就不会显示

1 web层IndexServlet代码

package www.test.web.servlet;

import java.io.IOException;

import java.sql.SQLException;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import www.test.domain.Category;

import www.test.domain.Product;

import www.test.service.ProductService;

public class IndexServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        ProductService service = new ProductService();

        //获取热门商品-----List<Product>

        List<Product> hotProductList = null;

        try {

            hotProductList = service.findHotProductList();

        } catch (SQLException e) {

            e.printStackTrace();

        }

        //获取最新商品-----List<Product>

        List<Product> newProductList = null;

        try {

            newProductList = service.findNewProductList();

        } catch (SQLException e) {

            e.printStackTrace();

        }

        //准备分类数据

        List<Category> categoryList =null;

        try {

            categoryList = service.findAllCategory();

        } catch (SQLException e) {

            e.printStackTrace();

        }

        request.setAttribute("categoryList", categoryList);

        //将获取的数据存入request域

        request.setAttribute("hotProductList", hotProductList);

        request.setAttribute("newProductList", newProductList);

        //转发

        request.getRequestDispatcher("/index.jsp").forward(request, response);

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        doGet(request, response);

    }

}

2 service层代码

//获取商品分类

public List<Category> findAllCategory() throws SQLException {

    ProductDao dao = new ProductDao();

    List<Category> categoryList = dao.findAllCategory();

    return categoryList;

}

3 dao层代码

//获取商品分类

public List<Category> findAllCategory() throws SQLException {

    QueryRunner qr = new QueryRunner(C3P0Utils.getDataSource());

    String sql = "select * from category";

    List<Category> categoryList = qr.query(sql, new BeanListHandler<Category>(Category.class));

    return categoryList;

}

4 heaher.jsp代码修改

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

<!DOCTYPE html>

<!-- 登录 注册 购物车... -->

<div class="container-fluid">

    <div class="col-md-4">

        <img src="img/logo2.png"/>

    </div>

    <div class="col-md-5">

        <img src="img/header.png" />

    </div>

    <div class="col-md-3" style="padding-top:20px">

        <ol class="list-inline">

            <c:if test="${empty user }">

                <li><a href="login.jsp">登录</a></li>

                <li><a href="register.jsp">注册</a></li>

            </c:if>

            <c:if test="${!empty user }">

                <li>欢迎您,${user.username }</li>

                <li><a href="#">退出</a></li>

            </c:if>

            <li><a href="cart.jsp">购物车</a></li>

            <li><a href="order_list.jsp">我的订单</a></li>

        </ol>

    </div>

</div>

<!-- 导航条 -->

<div class="container-fluid">

    <nav class="navbar navbar-inverse">

        <div class="container-fluid">

            <!-- Brand and toggle get grouped for better mobile display -->

            <div class="navbar-header">

                <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1" aria-expanded="false">

                    <span class="sr-only">Toggle navigation</span>

                    <span class="icon-bar"></span>

                    <span class="icon-bar"></span>

                    <span class="icon-bar"></span>

                </button>

                <a class="navbar-brand" href="#">首页</a>

            </div>

            <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">

                <ul class="nav navbar-nav" id="categoryUl">

                    <c:forEach items="${categoryList }" var="category">

                        <li><a href="#">${category.cname }</a>

                    </c:forEach>

                </ul>

                <form class="navbar-form navbar-right" role="search">

                    <div class="form-group">

                        <input type="text" class="form-control" placeholder="Search">

                    </div>

                    <button type="submit" class="btn btn-default">Submit</button>

                </form>

            </div>

        </div>

    </nav>

</div>

2 版本二使用ajax显示类别菜单

版本二中可以实现所有页面的类别的动态获取.原来IndexServlet里面获取类别数据的代码不在需要了

案例19-页面使用ajax显示类别菜单-LMLPHP

新编写一个CategoryListServlet.

1 web层CategoryListServlet代码

package www.test.web.servlet;

import java.io.IOException;

import java.sql.SQLException;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import com.google.gson.Gson;

import www.test.domain.Category;

import www.test.service.ProductService;

public class CategoryListServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        ProductService service = new ProductService();

        // 准备分类数据

        List<Category> categoryList = null;

        try {

            categoryList = service.findAllCategory();

        } catch (SQLException e) {

            e.printStackTrace();

        }

        //使用转换工具将categoryList转换成json格式

        Gson gson = new Gson();

        String json = gson.toJson(categoryList);

        //将转换后的json格式字符串写出

          //写回前先解决乱码问题

        response.setContentType("text/html;charset=UTF-8");

        response.getWriter().write(json);

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        doGet(request, response);

    }

}

service的代码和dao的代码与版本一一样

2 header.jsp代码修改

<%@ page language="java" contentType="text/html; charset=UTF-8"

    pageEncoding="UTF-8"%>

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

<!DOCTYPE html>

<!-- 登录 注册 购物车... -->

<div class="container-fluid">

    <div class="col-md-4">

        <img src="img/logo2.png"/>

    </div>

    <div class="col-md-5">

        <img src="img/header.png" />

    </div>

    <div class="col-md-3" style="padding-top:20px">

        <ol class="list-inline">

            <c:if test="${empty user }">

                <li><a href="login.jsp">登录</a></li>

                <li><a href="register.jsp">注册</a></li>

            </c:if>

            <c:if test="${!empty user }">

                <li>欢迎您,${user.username }</li>

                <li><a href="#">退出</a></li>

            </c:if>

            <li><a href="cart.jsp">购物车</a></li>

            <li><a href="order_list.jsp">我的订单</a></li>

        </ol>

    </div>

</div>

<!-- 导航条 -->

<div class="container-fluid">

    <nav class="navbar navbar-inverse">

        <div class="container-fluid">

            <!-- Brand and toggle get grouped for better mobile display -->

            <div class="navbar-header">

                <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1" aria-expanded="false">

                    <span class="sr-only">Toggle navigation</span>

                    <span class="icon-bar"></span>

                    <span class="icon-bar"></span>

                    <span class="icon-bar"></span>

                </button>

                <a class="navbar-brand" href="#">首页</a>

            </div>

            <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">

                <ul class="nav navbar-nav" id="categoryUl">

                <%-- 不在需要了使用后面的ajax解决问题 --%>

                <%-- <c:forEach items="${categoryList }" var="category">

                        <li><a href="#">${category.cname }</a>

                    </c:forEach> --%>

                </ul>

                <form class="navbar-form navbar-right" role="search">

                    <div class="form-group">

                        <input type="text" class="form-control" placeholder="Search">

                    </div>

                    <button type="submit" class="btn btn-default">Submit</button>

                </form>

            </div>

        </div>

        <!-- 实现引入header.jsp页面的所有页面都动态获取类别 -->

        <script type="text/javascript">

            //header.jsp加载完毕后 去服务器端获得所有的category数据

            //引入header.jsp的页面本身已经引入的jquery文件，所以不用再次引入

            $(function(){

                var content = "";

                $.post(

                    "${pageContext.request.contextPath}/categoryList",

                    function(data){

                        //[{"cid":"xxx","cname":"xxxx"},{},{}]

                        //动态创建<li><a href="#">${category.cname }</a></li>

                        for(var i=;i<data.length;++i){

                            content += "<li><a href='#'>"+data[i].cname+"</a></li>";

                        }

                        //将拼接好的li放置到ul中

                        $("#categoryUl").html(content);

                    },

                 "json"

                );

            });

        </script>

    </nav>

</div>