分页查询关键代码 多条件查询关键代码 删除选中商品关键代码 修改要先回显再修改 修改要先回显再修改 同一业务集中使用同一servlet的方法

分页查询关键代码:

通过servlet转发回来的各种信息进行分页的设计(转发回的信息有 分页查询的List集合 查询的页码 查询的条数 查询的数据库总条数 查询的总页码)

从开始时循环10次出现十个数字开始逐步细化

注意:jstl(java标砖标签库) 的判断条件 test="" 引号中的变量运算写在一个${ } EL表达式中,运算完再显示结果

        <div align="center">
            <c:if test="${pageNumber!=1 }">
                <span style="font-size:x-large;"><a href="${pageContext.request.contextPath }/shangpin?md=findByPage&pageNumber=1">第一页</a></span>
                <span style="font-size:x-large;"><a href="${pageContext.request.contextPath }/shangpin?md=findByPage&pageNumber=${pageNumber-1 }">上一页</a></span>
            </c:if>
                <!-- 分页查询的核心 -->
                <c:forEach begin="1" end="${totalPages }" step="1" var="n">
                    <!-- n能显示出来的条件 -->
                    <c:if test="${(pageNumber-n)<=5&&(n-pageNumber)<=4 }">
                        <c:if test="${n!=pageNumber }">
                            <span style="font-size:x-large;"><a href="${pageContext.request.contextPath }/shangpin?md=findByPage&pageNumber=${n }">${n }</a></span>
                        </c:if>
                        <c:if test="${n==pageNumber }">
                            <span style="font-size:x-large;">${n }</span>
                        </c:if>
                    </c:if>
                </c:forEach>
            <c:if test="${pageNumber!=totalPages }">
                <span style="font-size:x-large;"><a href="${pageContext.request.contextPath }/shangpin?md=findByPage&pageNumber=${pageNumber+1 }">下一页</a></span>
                <span style="font-size:x-large;"><a href="${pageContext.request.contextPath }/shangpin?md=findByPage&pageNumber=${totalPages }">最后一页</a></span>
            </c:if>
        </div>

多条件查询关键代码:

拼串的时候注意如果带?的不用写单引号'

如果不带?的sql串,记得带单引号'

public List<Product> queryMore(String queryName, String queryDesc) throws SQLException {

        String sql="SELECT * FROM product where 1=1 ";
        if(queryName!=null && queryName.trim()!="") {
            sql=sql+"and pname like '%"+queryName+"%'";
        }
        if(queryDesc!=null && queryDesc.trim()!="") {
            sql=sql+" and pdesc like '%"+queryDesc+"%'";
        }
        System.out.println(sql);
        List<Product> pros=qr.query(sql, new BeanListHandler<Product>(Product.class));
        System.out.println(pros);
        return pros;
    }

删除选中商品关键代码:

    public void deleteSelect(String[] checks) throws SQLException {

        String sql="delete from product where pid in(";
        for(String str:checks) {
            sql=sql+"'"+str+"'"+",";
        }
        sql=sql.substring(0, sql.length()-1);
        sql=sql+ ")";
        qr.update(sql);
    }

前端部分

function deleteSelect(){
            if(confirm("确认删除这些商品吗?")){
                var form1=document.getElementById("form1");
                form1.submit();
            }
        }

<c:if test="${not empty shangpins }">
            <form method="post" action="${pageContext.request.contextPath }/shangpin?md=deleteSelect" id="form1">
                <c:forEach items="${shangpins }" var="s">
                    <tr>
                        <td width="6%" align="center"><input name="checks" type="checkbox" value="${s.pid }"></td>
                        <td width="8%"><img width="180px" alt="" src="${s.pimage }"></td>
                        <td width="6%">${s.pname }</td>
                        <td width="8%">${s.shop_price }</td>
                        <td width="8%">${s.market_price }</td>
                        <td>${s.pdesc }</td>
                        <td width="8%"><a href="${pageContext.request.contextPath }/shangpin?md=huixian&pid=${s.pid}">修改</a></td>
                        <td width="8%"><a href="javascript:void(0);" onclick="agree('${s.pid}')">删除</a></td>
                    </tr>
                </c:forEach>
            </form>
        </c:if>

修改要先回显再修改

<td width="8%"><a href="${pageContext.request.contextPath }/shangpin?md=huixian&pid=${s.pid}">修改</a></td>

    private void edit(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        try {
            BeanUtils.populate(p, request.getParameterMap());
            service.edit(p);
            response.sendRedirect(request.getContextPath()+"/shangpin?md=findAll");
        } catch (Exception e) {
            e.printStackTrace();
            request.setAttribute("msg", "更新商品失败了");
            request.getRequestDispatcher("/msg.jsp").forward(request, response);
        } 

    }

    private void huixian(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        try {
            String pid=request.getParameter("pid");
            Product product=service.getProduct(pid);
            request.setAttribute("product", product);
            request.getRequestDispatcher("/xiugaishangpin.jsp").forward(request, response);
        } catch (SQLException e) {
            e.printStackTrace();
            request.setAttribute("msg", "回显商品失败了");
            request.getRequestDispatcher("/msg.jsp").forward(request, response);
        }
    }

同一业务集中使用同一servlet的方法

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

        String md=request.getParameter("md");
        if("findAll".equals(md)) {
            findAll(request,response);
        }else if("add".equals(md)){
            add(request,response);
        }else if("huixian".equals(md)) {
            huixian(request,response);
        }else if("edit".equals(md)) {
            edit(request,response);
        }else if("delete".equals(md)) {
            delete(request,response);
        }else if("deleteSelect".equals(md)) {
            deleteSelect(request,response);
        }else if("queryMore".equals(md)){
            queryMore(request,response);
        }else if("findByPage".equals(md)) {
            findByPage(request,response);
        }
    }

前端

<span style="font-size:x-large;"><a href="${pageContext.request.contextPath }/shangpin?md=findByPage&pageNumber=${pageNumber-1 }">上一页</a></span>

用?md=findAll的方法

servlet判断md的值调用相应方法

也可以使用反射的方法代替