分頁查詢關鍵代碼 多條件查詢關鍵代碼 刪除選中商品關鍵代碼 修改要先回顯再修改 修改要先回顯再修改 同一業務集中使用同一servlet的方法

分頁查詢關鍵代碼:

通過servlet轉發回來的各種信息進行分頁的設計(轉發回的信息有 分頁查詢的List集合 查詢的頁碼 查詢的條數 查詢的資料庫總條數 查詢的總頁碼)

從開始時迴圈10次出現十個數字開始逐步細化

註意:jstl(java標磚標簽庫) 的判斷條件 test="" 引號中的變數運算寫在一個${ } EL表達式中,運算完再顯示結果

        <div align="center">
            <c:if test="${pageNumber!=1 }">
                <span style="font-size:x-large;"><a href="${pageContext.request.contextPath }/shangpin?md=findByPage&pageNumber=1">第一頁</a></span>
                <span style="font-size:x-large;"><a href="${pageContext.request.contextPath }/shangpin?md=findByPage&pageNumber=${pageNumber-1 }">上一頁</a></span>
            </c:if>
                <!-- 分頁查詢的核心 -->
                <c:forEach begin="1" end="${totalPages }" step="1" var="n">
                    <!-- n能顯示出來的條件 -->
                    <c:if test="${(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=${pageNumber+1 }">下一頁</a></span>
                <span style="font-size:x-large;"><a href="${pageContext.request.contextPath }/shangpin?md=findByPage&pageNumber=${totalPages }">最後一頁</a></span>
            </c:if>
        </div>

多條件查詢關鍵代碼:

拼串的時候註意如果帶?的不用寫單引號'

如果不帶?的sql串,記得帶單引號'

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;
    }

刪除選中商品關鍵代碼:

    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("確認刪除這些商品嗎?")){
                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}')">刪除</a></td>
                    </tr>
                </c:forEach>
            </form>    
        </c:if>

修改要先回顯再修改

<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", "更新商品失敗了");
            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", "回顯商品失敗了");
            request.getRequestDispatcher("/msg.jsp").forward(request, response);
        }
    }

同一業務集中使用同一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 }">上一頁</a></span>

用?md=findAll的方法

servlet判斷md的值調用相應方法

也可以使用反射的方法代替