Number Format的问题

servlet相关代码： request.getSession().setAttribute("totalPage", totalPage);
在jsp页： String totalPage = (String)session.getAttribute("totalPage");
int total = Integer.parseInt(totalPage);异常信息：--------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: null
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:460)
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:803)
root cause java.lang.NumberFormatException: null
java.lang.Integer.parseInt(Integer.java:415)
java.lang.Integer.parseInt(Integer.java:497)
org.apache.jsp.index_jsp._jspService(index_jsp.java:49)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
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:803)
为什么会有数据转换错误，
--------------------------------------------------------------------------------Apache Tomcat/5.5.25

解决方案 »

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UP?！写J2ee时，jsp里的html用什么写，手工写很烦也容易出錯，或都这样说jsp页代码用什么写
你的代码是没什么问题的  是不是totalPage里面存的数据错了?
把完整的代码贴出来：jsp代码：<%@ page language="java" pageEncoding="gb2312"%>
<%@ page import="java.sql.ResultSet ,java.sql.Statement" %>
<%
ResultSet rs = (ResultSet)session.getAttribute("rs");
  Object totalPage = session.getAttribute("totalPage");
int total = Integer.parseInt(totalPage.toString());

Object currentPage = session.getAttribute("totalPage");
int current = Integer.parseInt(currentPage.toString());
%><html>
<head>
<title>My JSP 'index.jsp' starting page</title> <meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
</head> <body>
<table withd="500"  height="300" align="center" border="1">
<tr withd="500"><th >stor_id</th><th>ord_num</th>
<th>ord_date</th> <th>qty</th>
<th>payments</th> <th>title_id</th>

</tr>
<%
   if(rs!=null){
   while(rs.next()){

%>
     <tr width="500"><td><%=rs.getString("stor_id") %></td><td><%=rs.getString("stor_id") %></td><td> <%=rs.getString("ord_date") %></td><td><%=rs.getString("qty") %></td><td>%=rs.getString("payments") %></td><td><%=rs.getString("title_id") %></td></tr>
     <%} %>
     <tr><td>  <a href="/list/listServer?curretnPage=1"> 首页</a></td><td><a href="/list/listServer">下一页</a></td></tr>
          <tr><td>  <a href="/list/listServer"> 上一页</a></td><td><a href="/list/listServer">尾页</a></td></tr>

          </table>

          <%} else {%>
          <font color="red" size="10">
          <%
             out.println("没有你要找页面！");
           %><%
           }
            %>
            </font>
            <div align="center">
              <a href="/list/listServer?currentPage=1"> 首页</a>共有<%=total %> 当前是第<%=current %>页<a href="/list/listServer">下一页</a>
              <a href="/list/listServer"> 上一页</a>   <a href="/list/listServer">尾页</a>
          </div>
</body>
</html>Server代码：package com.fuyou;import java.io.IOException;
import java.io.PrintWriter;
import java.sql.ResultSet;
import java.sql.SQLException;import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class listServer extends HttpServlet {
private DBConnection dbc = null; private int currentPage = 0; private int eachPage = 5; private int totalPage = 0; public void destroy() {
super.destroy(); } public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { doPost(request, response);
} public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
int total = 0;
String sql = "select stor_id , ord_num,  ord_date ,qty ,payterms,title_id from sales ";
ResultSet rs = dbc.executeQuery(sql);
if (request.getParameter("currentPage") != null) {
this.currentPage = Integer.parseInt(request
.getParameter("currentPage"));
} if (rs != null) {

try {
rs.last();
total = rs.getRow();
totalPage = (total + eachPage - 1) / eachPage;
System.out.println(totalPage);
request.getSession().setAttribute("totalPage", Integer.valueOf(totalPage));
rs.beforeFirst();
while (rs.next()) {

request.getSession().setAttribute("rs", rs);
// System.out.print(rs.getString("stor_id")); System.out.print(rs.getString("ord_num")); // System.out.print(rs.getTimestamp("ord_date"));
// System.out.print(rs.getShort("qty"));
// System.out.print(rs.getString("payterms"));
// System.out.print(rs.getString("title_id"));*/ total = rs.getRow();
System.out.println(total); }
} catch (SQLException e) { e.printStackTrace();
}
} else {
System.out.println("rs==111null");
}
if (this.currentPage < 1 || this.currentPage == 0) {
this.currentPage = 1;
}
request.getSession().setAttribute("currentPage", Integer.valueOf(currentPage));
// System.out.println(totalPage);
System.out.println(this.currentPage);
RequestDispatcher requestDipathcer = request
.getRequestDispatcher("/index.jsp");
requestDipathcer.forward(request, response);
} public void init() throws ServletException {
this.dbc = new DBConnection();
}}上面两运行有下面错误：HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage description The server encountered an internal error () that prevented it from fulfilling this request.exception org.apache.jasper.JasperException: Exception in JSP: /index.jsp:63: <%
4:  ResultSet rs = (ResultSet)session.getAttribute("rs");
5:   Object totalPage = session.getAttribute("totalPage");
6:  int total = Integer.parseInt(totalPage.toString());
7:
8:  Object currentPage = session.getAttribute("totalPage");
9:  int current = Integer.parseInt(currentPage.toString());
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:803)
root cause java.lang.NullPointerException
org.apache.jsp.index_jsp._jspService(index_jsp.java:49)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
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:803)
note The full stack trace of the root cause is available in the Apache Tomcat/5.5.25 logs.
你的Connection、PreparedStatement、ResultSet都关掉了吗？既然用了Servlet，就应该按照MVC的要求来做，不要在页面上操纵ResultSet。private int currentPage = 0;
private int eachPage = 5;
private int totalPage = 0;把这些作为局部变量，没有必要弄成成员变量的。
如果是首次执行index.jsp的话，Session里面肯定是空的了啦。
没关啊，问题关键是数据转换出錯了，我把变里存在session里，在jsp里取出来用!
源码：
String totalPage = (String)session.getAttribute("totalPage");
int total = Integer.parseInt(totalPage);
这样的写法无法排除totalPage=null是字符转换出错。
使用Integer.parseInt这个函数时要保证totalPage是数字。
可以改为如下代码：
String totalPage = (String)session.getAttribute("totalPage");
if(totalPage.equals("")||totalPage==null)
totalPage="0";
int total = Integer.parseInt(totalPage);
保证转换时非null和非空，就不会出现异常了。
LZ,出错信息报的空指针啊！
看看这句int total = Integer.parseInt(totalPage.toString());
totalPage.toString()，如果totalPage是null就出错啦！这种潜在的异常应该要处理一下的啊！
ResultSet rs = dbc.executeQuery(sql);执行后可能查不到数据,rs为空了,所以也没有进到if (rs != null) {
}循环体里,Object totalPage = session.getAttribute("totalPage");
返回的也就是空对象null.