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首页 > 解决方案 > 为什么随机复选框选择给出错误，而不是在 JSP 页面中以串行方式？

java - 为什么随机复选框选择给出错误，而不是在 JSP 页面中以串行方式？

问题描述

我正在尝试制作一个基本的商店计费 JSP 项目。现在，当我用复选框输入随机产品数量时，它会给出如下图所示的错误。但是当我用串行方式检查值时，它没有给出错误，它给了我想要的结果。我也检查它是否为空。但无法摆脱这个错误。我怎样才能摆脱它？在此处输入图像描述

在此处输入图像描述

代码：

<%-- 
    Document   : order
    Created on : Jun 15, 2019, 3:11:06 PM
    Author     : Riddhi
--%>

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@page import="java.sql.*"  %>
<!DOCTYPE html>
<html lang="en">
<%@ include file="header.jsp" %>
<h2 class="text-center"> ShopBilling </h2>

<p><br/></p>
        <%
        String Host = "jdbc:mysql://localhost:3306/shopbilling";
        Connection connection = null;
        Statement statement = null;
        ResultSet rs = null;
        PreparedStatement ps=null;
        Class.forName("com.mysql.jdbc.Driver").newInstance();
        connection = DriverManager.getConnection(Host, "root", "");
        StringBuilder sb = new StringBuilder();
        %>
        <div class="row justify-content-center">

            <div class="col-md-6">
                <div class="row">
                    <div class="col-md-6"><h3>Product Details</h3></div>
                    <div class="col-md-6 text-right">
                        <a href="products.jsp" class="btn btn-info">Back to Home</a>
                    </div>
                </div>
                <p></p>

             <form action="" method="post">

 <%
    String products[] = request.getParameterValues("products"); 
    String items[] = request.getParameterValues("item_no"); 

   int sum=0; 
    if (products!= null && items!= null && products.length != 0 && items.length != 0) {
        for (int i = 0; i < products.length; i++) {

%>             <%
                    statement = connection.createStatement();
                    String u=request.getParameter("u");
                    int num=Integer.parseInt(products[i]);                                        
                    String Data = "select * from products_tbl where id='"+num+"'";
                    rs = statement.executeQuery(Data);
                    while (rs.next()) {
                    %>   
                    <input type="hidden" name="id" value='<%=rs.getString("id")%>'/>
                    <div class="form-group">
                        <label for="product_name">Product Name: <%=rs.getString("product_name")%></label>
                        <input type="hidden" class="form-control" id="product_name" name="product_name" value='<%=rs.getString("product_name")%>'>
                    </div>
                    <div class="form-group">
                        <label for="product_price">Product Single Price: <%=rs.getString("product_price")%></label>
                        <input type="hidden" class="form-control" id="product_price" name="product_price" value='<%=rs.getString("product_price")%>'>
                    </div>
                    <div class="form-group">
                        <label for="product_name">Item Quantity: <% out.println(items[i]);   %></label>
                        <input type="hidden" class="form-control" id="item_no" name="item_no" value='items[j]'>
                    </div>

                   <div class="form-group">
                        <label for="product_name">Product Total Price: <% 

                            int num1=Integer.parseInt(items[i]);
                            int propri=Integer.parseInt(rs.getString("product_price"));
                           out.println(num1 * propri); int gtotal= num1 * propri;   %></label>
                        <input type="hidden" class="form-control" id="item_no" name="item_no" value='items[j]'>
                    </div>

                    <hr>


                 <%  sum= sum + gtotal;   %>


                    <% 

                }
               }
}
                    %>

          <div class="form-group">
                        <label for="product_name">Grand Total: <% 
                            out.println(sum);   %></label>
                        <input type="hidden" class="form-control" id="item_no" name="item_no" value='items[j]'>
                    </div>          

            <button type="print" onclick="window.print();" class="btn btn-warning">Print</button>


                </form>
            </div>
        </div>
<%@ include file="footer.jsp" %>    
</html>

标签： javajspservlets

解决方案

我认为您的代码中的问题在于，<input type="text" name="item_no" />因为上面代码中的每一行都有checkbox，当您提交表单时，只有选定checkbox的被传递，但<input type="text" name="item_no" />即使null您没有给出任何值，所有的也会传递，所以当您迭代时，您得到null value了那也是。现在，要解决这个问题，请执行以下操作：

//give value to your check-box i.e id of that row
 <input type="checkbox" name="products" value ='<%=rs.getString("id")%>' />
//pass that id with your input type i.e item_no_1 ..etc
<input type="text" name='item_no_<%=rs.getString("id")%>' />

然后只获得Product Quantity您选择的地方的特定值，Checkbox如下所示：

 String products[] = request.getParameterValues("products"); 
     if (products!= null && items!= null && products.length != 0 && items.length != 0) {
            for (int i = 0; i < products.length; i++) {
     //your code
   <div class="form-group">
    <label for="product_name">Product Total Price: <%
    //getting item value of that selected checkbox 
  int item_no=Integer.parseInt(request.getParameter("item_no_" + products[i]));
  int propri=Integer.parseInt(rs.getString("product_price"));
  out.println(num1 * propri); int gtotal= num1 * propri;   %></label>
      <input type="hidden" class="form-control" id="item_no" name="item_no" value='items[j]'>
</div>

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