大家帮忙看一下。jsp问题

Question

String[] grade = request.getParameterValues("grade");
  String[] week = request.getParameterValues("week");
  String[] dor_id = request.getParameterValues("dor_id");
  String[] year = request.getParameterValues("year");
  for(int i=1;i<=grade.length;i++)
  {
  sql = "insert into score (dor_id,grade,week,year) values('"+dor_id[i]+"','"+grade[i]+"','"+week[i]+"','"+year[i]+"')";
  stmt.executeUpdate(sql);
  }

Answer 1

这是出错信息：
org.apache.jasper.JasperException: Exception in JSP: /ping.jsp:1815:    String[] year = request.getParameterValues("year");
16:    for(int i=1;i<=grade.length;i++)
17:    {
18:    sql = "insert into score (dor_id,grade,week,year) values('"+dor_id[i]+"','"+grade[i]+"','"+week[i]+"','"+year[i]+"')";
19:    stmt.executeUpdate(sql);
20:    }
21:    %>
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:451)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:373)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
root cause java.lang.NullPointerException
org.apache.jsp.ping_jsp._jspService(ping_jsp.java:104)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)

Answer 2

这是出错信息：
org.apache.jasper.JasperException: Exception in JSP: /ping.jsp:1815:    String[] year = request.getParameterValues("year");
16:    for(int i=1;i<=grade.length;i++)
17:    {
18:    sql = "insert into score (dor_id,grade,week,year) values('"+dor_id[i]+"','"+grade[i]+"','"+week[i]+"','"+year[i]+"')";
19:    stmt.executeUpdate(sql);
20:    }
21:    %>
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:451)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:373)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
root cause java.lang.NullPointerException
org.apache.jsp.ping_jsp._jspService(ping_jsp.java:104)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)

Answer 3

这是源文件：
<%@ include file = "include/dbconn.jsp" %>
<%
      String[] grade = request.getParameterValues("grade");
  String[] week = request.getParameterValues("week");
  String[] dor_id = request.getParameterValues("dor_id");
  String[] year = request.getParameterValues("year");
  for(int i=1;i<=grade.length;i++)
  {
  sql = "insert into score (dor_id,grade,week,year) values('"+dor_id[i]+"','"+grade[i]+"','"+week[i]+"','"+year[i]+"')";
  stmt.executeUpdate(sql);
  }
  %>
  <script language="javascript">alert("评分成功！！");document.location.href = "score.jsp";
  </script>
  
  <%      
   stmt.close();
   conn.close();
%>

Answer 4

 1、 for(int i=1;i <=grade.length;i++)   数组会越界 ， ===>for(int i=1;i <grade.length;i++) 
 2、 确定 grade 、week 、dor_id 、year  四个数组的长度相等 ？ 

Answer 5

root cause 
java.lang.NullPointerException 
估计是你哪得值没取到出异常了。

Answer 6

for(int i=1;i <=grade.length;i++)改成for(int i=0;i < grade.length;i++)数组下标从0开始

Answer 7

楼上说的对，length反回数组有多少个元素，下标是从0开始。
你用的request.getParameterValues会不会有返回空值的情况，之前你不是不应该判断一下是不是为空null

Answer 8

String[] grade  =  request.getParameterValues 获取的值为null的话
....
for (int i = 1 ; i < grade  .length; i++)就回包NullPointerException 错误也 有可能是connection 对象还没有打开
执行 stmt.executeUpdate(sql); 
也会包NullPointerException 错误