【JAVAWEB学习笔记】21

今天主要学习了数据库的多条件查询、attr和prop的区别和分页的实现

一、实现多条件查询

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;}

 

二、jquery中attr和prop的区别

 

在高版本的jquery引入prop方法后，什么时候该用prop？什么时候用attr？它们两个之间有什么区别？这些问题就出现了。

 

关于它们两个的区别，网上的答案很多。这里谈谈我的心得，我的心得很简单：

 

• 对于HTML元素本身就带有的固有属性，在处理时，使用prop方法。
• 对于HTML元素我们自己自定义的DOM属性，在处理时，使用attr方法。

 

attr和prop的区别我是通过这个了解到的：http://www.cnblogs.com/Showshare/p/different-between-attr-and-prop.html

 

三、分页的实现：

1、创建一个PageBean用于存储分页的数据

public class PageBean<T> {        //当前页    private int currentPage;    //当前页显示的条数    private int currentCount;    //总条数    private int totalCount;    //总页数    private int totalPage;    //每页显示的数据    private List<T> productList = new ArrayList<T>();            public int getCurrentPage() {        return currentPage;    }    public void setCurrentPage(int currentPage) {        this.currentPage = currentPage;    }    public int getCurrentCount() {        return currentCount;    }    public void setCurrentCount(int currentCount) {        this.currentCount = currentCount;    }    public int getTotalCount() {        return totalCount;    }    public void setTotalCount(int totalCount) {        this.totalCount = totalCount;    }    public int getTotalPage() {        return totalPage;    }    public void setTotalPage(int totalPage) {        this.totalPage = totalPage;    }    public List<T> getProductList() {        return productList;    }    public void setProductList(List<T> productList) {        this.productList = productList;    }    }

2、WEB层代码

 

public class ProductListServlet extends HttpServlet {    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);            }    protected void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doGet(request, response);    }}

 

 

 

3、Service层代码

 

public class ProductService {    public List<Product> findAllProduct() throws SQLException {        ProductDao dao = new ProductDao();        return dao.findAllProduct();    }    //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;    }}

 

 

 

4、DAO层代码

 

public class ProductDao {    public List<Product> findAllProduct() throws SQLException {        return new QueryRunner(DataSourceUtils.getDataSource()).query("select * from product", new BeanListHandler<Product>(Product.class));    }    //获得全部的商品条数    public int getTotalCount() throws SQLException {        QueryRunner runner = new QueryRunner(DataSourceUtils.getDataSource());        String sql = "select count(*) from product";        Long query = (Long) runner.query(sql, new ScalarHandler());        return query.intValue();    }    //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);    }}

 

 

 

5、JSP页面代码

 

<div class="row" style="width: 1210px; margin: 0 auto;">        <div class="col-md-12">            <ol class="breadcrumb">                <li><a href="#">首页</a></li>            </ol>        </div>                <c:forEach items="${pageBean.productList }" var="product">            <div class="col-md-2" style="height:250px">                <a href="product_info.htm">                     <img src="${pageContext.request.contextPath }/${product.pimage}" width="170" height="170" style="display: inline-block;">                </a>                <p>                    <a href="product_info.html" style='color: green'>${product.pname }</a>                </p>                <p>                    <font color="#FF0000">商城价：&yen;${product.shop_price }</font>                </p>            </div>        </c:forEach>    </div>    <!--分页 -->    <div style="width: 380px; margin: 0 auto; margin-top: 50px;">        <ul class="pagination" style="text-align: center; margin-top: 10px;">            <!-- 上一页 -->            <!-- 判断当前页是否是第一页 -->            <c:if test="${pageBean.currentPage==1 }">                <li class="disabled">                    <a href="javascript:void(0);" aria-label="Previous">                        <span aria-hidden="true">&laquo;</span>                    </a>                </li>            </c:if>            <c:if test="${pageBean.currentPage!=1 }">                <li>                    <a href="${pageContext.request.contextPath }/productList?currentPage=${pageBean.currentPage-1}" aria-label="Previous">                        <span aria-hidden="true">&laquo;</span>                    </a>                </li>            </c:if>                                                            <c:forEach begin="1" end="${pageBean.totalPage }" var="page">                <!-- 判断当前页 -->                <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>                        <!-- 判断当前页是否是最后一页 -->            <c:if test="${pageBean.currentPage==pageBean.totalPage }">                <li class="disabled">                    <a href="javascript:void(0);" aria-label="Next">                         <span aria-hidden="true">&raquo;</span>                    </a>                </li>            </c:if>            <c:if test="${pageBean.currentPage!=pageBean.totalPage }">                <li>                    <a href="${pageContext.request.contextPath }/productList?currentPage=${pageBean.currentPage+1}" aria-label="Next">                         <span aria-hidden="true">&raquo;</span>                    </a>                </li>            </c:if>                </ul>    </div>    <!-- 分页结束 -->