怪了....

[qpg_200505]

request.setCharacterEncoding("gb2312");
String content=request.getParameter("content");
int leaveword=Integer.parseInt(request.getParameter("id"));
String replyuser=(session.getAttribute("username")).toString();
String image=request.getParameter("RadioGroup");
if(content!=null&&content.length()>0)
{
String sql="Insert into reply(leaveword,content,replyuser,image)values('"+leaveword+"','"+content+"','"+replyuser+"','"+image+"')";
int ret=0;
ret=sm.executeUpdate(sql);
if(ret!=0)
{
out.println("<script language='javascript'>alert('回复信息成功！');window.location.href='./back.jsp';</script>");
}
else
{
out.println("<script language='javascript'>alert('回复信息失败！');window.location.href='./back.jsp';</script>");
}
}else
{
response.sendRedirect("./back.jsp");
}
%>
编译以上代码出现以下错误..请问这怎么回事呢?

org.apache.jasper.JasperException: null
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:372)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)


root cause

java.lang.NumberFormatException: null
java.lang.Integer.parseInt(Integer.java:415)
java.lang.Integer.parseInt(Integer.java:497)
org.apache.jsp.actionback_jsp._jspService(actionback_jsp.java:60)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

[lc328]

有可能是这句
int leaveword=Integer.parseInt(request.getParameter("id"));
在把字符串转换成int时产生NumberFormatException异常，，可能取到一个NULL。。

[qpg_200505]

请那要怎么解决呀

[javaboy2006]

可以先判断一下：
if(null!=request.getParameter("id"))
{
int leaveword=Integer.parseInt(request.getParameter("id"));
}

[qpg_200505]

不可能是为空呀!那参数是<a href="writeback.jsp?id=<%=rs.getInt("ID")%>">回复这条留言</a>传过来的...