JavaWeb基础系列（九）商城分页功能

小灰灰 2021-09-27 00:10 305阅读 0赞

# 一、条件查询 #

Jsp页面关键代码：

<form id="Form1" name="Form1" action="${pageContext.request.contextPath}/adminSearchProductList" method="post">
            商品名称：<input type="text" name="pname" value="${condition.pname }">  
            是否热门：<select id="isHot" name="isHot">
                        <option value="">不限</option>
                        <option value="0">否</option>
                        <option value="1">是</option>
            </select>  
                商品类别：<select id="cid" name="cid">
                <option value="">不限</option>
                <c:forEach items="${categoryList }" var="category">
                    <option value="${category.cid }">${category.cname }</option>
                </c:forEach>
            </select>  
            <input type="submit" value="搜索">
            <br/>

Web层：

@WebServlet(name = "adminSearchProductList",
            urlPatterns = {
       "/adminSearchProductList"})
    public class adminSearchProductList extends HttpServlet { 
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            doGet(request,response);
        }
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            request.setCharacterEncoding("UTF-8");
            //1、收集表单数据
            Map<String, String[]> properties = request.getParameterMap();
            //2、将散装的查询数据封装到一个VO实体中
            Condition condition = new Condition();
            try {
                BeanUtils.populate(condition, properties);
            } catch (IllegalAccessException | InvocationTargetException e) {
                e.printStackTrace();
            }
            //3、将实体传递给service层
            AdminProductService service = new AdminProductService();
            List<Product> productList = null;
            try {
                productList = service.findProductListByCondition(condition);
            } catch (SQLException e) {
                e.printStackTrace();
            }
            //准备商品类别
            //获得所有的商品的类别数据
            List<Category> categoryList = null;
            try {
                categoryList = service.findAllCategory();
            } catch (SQLException e) {
                e.printStackTrace();
            }
            request.setAttribute("condition", condition);
            request.setAttribute("categoryList", categoryList);
            request.setAttribute("productList", productList);
            request.getRequestDispatcher("/admin/product/list.jsp").forward(request, response);
        }
    }

Service层：

//根据条件查询商品列表
    public List<Product> findProductListByCondition(Condition condition) throws SQLException {
        AdminProductDao dao = new AdminProductDao();
        return dao.findProductListByCondition(condition);
    }

Dao层：

//条件查询
    public List<Product> findProductListByCondition(Condition condition) throws SQLException {
        QueryRunner runner = new QueryRunner(DataSourceUtils.getDataSource());
        //定义一个存储实际参数的容器
        List<String> list = new ArrayList<String>();
        String sql = "select * from product where 1=1";
        if(condition.getPname()!=null&&!condition.getPname().trim().equals("")){
            sql+=" and pname like ? ";
            list.add("%"+condition.getPname().trim()+"%");
        }
        if(condition.getIsHot()!=null&&!condition.getIsHot().trim().equals("")){
            sql+=" and is_hot=? ";
            list.add(condition.getIsHot().trim());
        }
        if(condition.getCid()!=null&&!condition.getCid().trim().equals("")){
            sql+=" and cid=? ";
            list.add(condition.getCid().trim());
        }
        List<Product> productList = runner.query(sql, new BeanListHandler<Product>(Product.class) , list.toArray());
        return productList;
    }

运行结果：  
![这里写图片描述][70]

# 二、分页的后台代码实现 #

Web层：

@WebServlet(name = "ProductListServlet",
            urlPatterns = {
       "/ProductListServlet"})
    public class ProductListServlet extends HttpServlet { 
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            doGet(request,response);
        }
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            ProductService service = new ProductService();
            //模拟当前是第一页
            String currentPageStr = request.getParameter("currentPage");
            if(currentPageStr==null) currentPageStr="1";
            int currentPage = Integer.parseInt(currentPageStr);
            //认为每页显示12条
            int currentCount = 12;
            PageBean<Product> pageBean = null;
            try {
                pageBean = service.findPageBean(currentPage,currentCount);
            } catch (SQLException e) {
                e.printStackTrace();
            }
            request.setAttribute("pageBean", pageBean);
            request.getRequestDispatcher("/product_list.jsp").forward(request, response);
        }
    }

Service层：

public class ProductService { 
        public List<Product> findAllProduct() throws SQLException {
            ProductDao dao = new ProductDao();
            List<Product> productList = dao.findAllProduct();
            return productList;
        }
        //分页操作
        public PageBean findPageBean(int currentPage,int currentCount) throws SQLException {
            ProductDao dao = new ProductDao();
            //目的：就是想办法封装一个PageBean 并返回
            PageBean pageBean = new PageBean();
            //1、当前页private int currentPage;
            pageBean.setCurrentPage(currentPage);
            //2、当前页显示的条数private int currentCount;
            pageBean.setCurrentCount(currentCount);
            //3、总条数private int totalCount;
            int totalCount = dao.getTotalCount();
            pageBean.setTotalCount(totalCount);
            //4、总页数private int totalPage;
            /* * 总条数 当前页显示的条数 总页数 * 10 4 3 * 11 4 3 * 12 4 3 * 13 4 4 * * 公式：总页数=Math.ceil(总条数/当前显示的条数) * */
            int totalPage = (int) Math.ceil(1.0 * totalCount / currentCount);
            pageBean.setTotalPage(totalPage);
            //5、每页显示的数据private List<T> productList = new ArrayList<T>();
            /* * 页数与limit起始索引的关系 * 例如 每页显示4条 * 页数 其实索引 每页显示条数 * 1 0 4 * 2 4 4 * 3 8 4 * 4 12 4 * * 索引index = (当前页数-1)*每页显示的条数 * */
            int index = (currentPage - 1) * currentCount;
    
            List<Product> productList = dao.findProductListForPageBean(index, currentCount);
            pageBean.setProductList(productList);
    
            return pageBean;
        }
    }

Dao层：

//获得分页的商品数据
    public List<Product> findProductListForPageBean(int index,int currentCount) throws SQLException {
        QueryRunner runner = new QueryRunner(DataSourceUtils.getDataSource());
        String sql = "select * from product limit ?,?";
        return runner.query(sql, new BeanListHandler<Product>(Product.class), index,currentCount);
    }

# 二、分页的前台代码实现 #

<div style="width: 380px; margin: 0 auto; margin-top: 50px;">
         <ul class="pagination" style="text-align: center; margin-top: 10px;">
             
             
             <c:if test="${pageBean.currentPage==1 }">
                 <li class="disabled">
                     <a href="javascript:void(0);" aria-label="Previous">
                         <span aria-hidden="true">«</span>
                     </a>
                 </li>
             </c:if>
             <c:if test="${pageBean.currentPage!=1 }">
                 <li>
                     <a href="${pageContext.request.contextPath }/productList?currentPage=${pageBean.currentPage-1}" aria-label="Previous">
                         <span aria-hidden="true">«</span>
                     </a>
                 </li>
             </c:if>
             <c:forEach begin="1" end="${pageBean.totalPage }" var="page">
                 
                 <c:if test="${pageBean.currentPage==page }">
                     <li class="active"><a href="javascript:void(0);">${page}</a></li>
                 </c:if>
                 <c:if test="${pageBean.currentPage!=page }">
                     <li><a href="${pageContext.request.contextPath }/productList?currentPage=${page}">${page}</a></li>
                 </c:if>
    
             </c:forEach>
             
             <c:if test="${pageBean.currentPage==pageBean.totalPage }">
                 <li class="disabled">
                     <a href="javascript:void(0);" aria-label="Next">
                         <span aria-hidden="true">»</span>
                     </a>
                 </li>
             </c:if>
             <c:if test="${pageBean.currentPage!=pageBean.totalPage }">
                 <li>
                     <a href="${pageContext.request.contextPath }/productList?currentPage=${pageBean.currentPage+1}" aria-label="Next">
                         <span aria-hidden="true">»</span>
                     </a>
                 </li>
             </c:if>
         </ul>
     </div>

运行结果：  
![这里写图片描述][70 1]

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[70]: /images/20210923/00d8a5e3d9054a93bdba2a1535986a77.png
[70 1]: /images/20210923/c518b47c1dc544719ceea130127da1cb.png
[https_blog.csdn.net_weixin_41835916]: https://blog.csdn.net/weixin_41835916