请高手指点一下关于Servlet重定向问题

我的一个留言板程序，查看留言是由servlet处理逻辑再重定向到JSP页面显示！
一般情况下能正常显示，但为什么我在JSP显示页面里加了一段代码之后，访问Servlet就显示成空白页了？
我只是在JSP页面里加了一个方法：
    public String format(String s)
{
try
{
    s1=s;
    String s2="";
    int rowno=5;
    int allno=s1.length();
    int row=allno/rowno;
    if(allno<rowno)
   {
  s2=s1;
   }
   else
      {
    for(int i=0;i<row;i++)
        {
   s2=s2+s1.substring(i*rowno,(i*rowno+rowno))+"<br/>";
    }

    s2=s2+s1.substring(row*rowno);
  }
  return s2;
}
catch(Exception e)
{
return s;
}
}
%>

然后在后面某个位置调用：<%=format(message.getContent())%>

message.getContent()是从JAVABEAN里取得数据；

如果不调用这个方法，直接在某处显示该数据值：<%=message.getContent()%>
就能正常显示页面，否则就是空白页！

谁能告诉我这是什么原因啊？？？？

有什么方法可以查看出现了什么异常问题

7 个解决方案

#1

把两个JSP页面和servlet类代码都帖出来
我帮你看看..

#2

Servlet代码如下：

package com.iven.mes;

import java.sql.Connection;
import java.sql.Date;
import java.sql.Statement;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.RequestDispatcher;
import java.io.IOException;
import javax.servlet.ServletException;
import java.io.PrintWriter;

public class ViewMessageServlet extends HttpServlet
{
    Connection con;

    public ViewMessageServlet()
    {
        String s="com.microsoft.jdbc.sqlserver.SQLServerDriver";
        String s1="jdbc:microsoft:sqlserver://127.0.0.1:1433;DatabaseName=sczy";
        String s2="iven";
        String s3="ivenhuang";

        try
        {
            Class.forName(s);
            con=DriverManager.getConnection(s1,s2,s3);
        }
        catch(Exception e)
        {
            e.printStackTrace();
        }

    }

    public void doGet(HttpServletRequest request,HttpServletResponse response)throws IOException,ServletException
    {
        response.setContentType("text/html;charset=gb2312"); //±ØÐëÔÚ·½·¨ÀïµÄµÚÒ»ÐÐ´úÂë£¬Ê¹ºóÃæ×ªÏòµÄÒ³ÃæÒ²ÄÜÍ¬²½±àÂë¸ñÊ½£¬Èç¹û²»¼ÓÕâ¾ä£¬
         //×ªÏòµÄjspÒ³ÃæÖÐµÄºº×Ö½«±ä³ÉÂÒÂë£¡
        request.setCharacterEncoding("gb2312"); //±àÂë´æÈëÊý¾Ý¿âÖÐµÄÊý¾Ý£¬Ê¹ºº×Ö²»»á´æÔÚÂÒÂë£¡
        PrintWriter out=response.getWriter();
        ArrayList arraylist=new ArrayList();

         try
         {
             Statement stm=con.createStatement();
             ResultSet resultset=stm.executeQuery("select count(*) from sczy_messageboard");
             int i=0;
             if(resultset.next())
             {
                 i=resultset.getInt(1);//È¡µÃµÚÒ»Ìõ¼ÍÂ¼ÖÐµÄµÚÒ»ÁÐ£¨Êý¾Ý¿âÖÐ×Ö¶ÎÎªnumµÄ×ÔÔö×Ö¶Î£©µÄÖµ£»
                 resultset.close();
             }

             if(i>0)
             {
                 ResultSet resultset1;
                 MessageBean messagebean;

                 for(resultset1=stm.executeQuery("select * from sczy_messageboard order by thedate desc");resultset1.next();arraylist.add(messagebean))
                 {
                     int num=resultset1.getInt(1);
                     String users=resultset1.getString(2);
                     String phone=resultset1.getString(3);
                     String fax=resultset1.getString(4);
                     String email=resultset1.getString(5);
                     String company=resultset1.getString(6);
                     String heading=resultset1.getString(7);
                     String content=resultset1.getString(8);
                     java.util.Date thedate=resultset1.getDate(9);

                     messagebean=new MessageBean();
                     messagebean.setNum(num);
                     messagebean.setUsers(users);
                     messagebean.setPhone(phone);
                     messagebean.setFax(fax);
                     messagebean.setEmail(email);
                     messagebean.setCompany(company);
                     messagebean.setHeading(heading);
                     messagebean.setContent(content);
                     messagebean.setDate(thedate);
                 }
                 resultset1.close();
                 stm.close();
                 //con.close();
             }
             request.setAttribute("messages",arraylist);
             RequestDispatcher requestdispatcher=request.getRequestDispatcher("/WEB-INF/backcontrol/viewmessage.jsp");
             requestdispatcher.forward(request,response);
         }
         catch(Exception e1)
         {
             e1.printStackTrace();
         }

    }

    public void doPost(HttpServletRequest request,HttpServletResponse response)throws IOException,ServletException
    {
        doGet(request,response);
    }
}

#3

jsp代码如下：

<%@ page contentType="text/html; charset=gb2312" language="java" errorPage="" %>
<%@ page  import="java.lang.*,com.iven.mes.MessageBean,java.sql.*,java.util.*"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>²é¿´ÁôÑÔ</title>
<style type="text/css">


</style>
</head>

<body>
<center>
<p class="style1">ËùÓÐ·Ã¿ÍÁôÑÔ</p>
<hr>
<%
  int count=1;
  int pagesize=5;
  int rowcount=0;
  int pagecount=0;

  Collection messagearray=(Collection)request.getAttribute("messages");
  Iterator it=messagearray.iterator();
  if(!it.hasNext())
  {
      out.print("没有记录!");
  }
  else
  {

  rowcount=messagearray.size();
  int showpage=1;
  pagecount=((rowcount%pagesize)==0?(rowcount/pagesize):(rowcount/pagesize)+1);
  String topage=request.getParameter("topage");
  if(topage!=null)
  {
  showpage=Integer.parseInt(topage);

      if(showpage>pagecount)
     {
      showpage=pagecount;
     }
      if(showpage<=0)
     {
      showpage=1;
     }
  }
  int skip=1;
      while(skip<((showpage-1)*pagesize+1))
  {
  it.next();
  ++skip;
  }
  for(int i=1;i<=pagesize;i++)
  {
     MessageBean message=(MessageBean)it.next();
%>
<table width="527" height="175" border="1" cellpadding="0" cellspacing="0">
  
  <tr>
    <td width="51" height="25" valign="top"><table width="100%" border="0" cellpadding="0" cellspacing="0">
      
      <tr>
        <td width="50" height="23" bgcolor="#66CC00"><div align="right">±àºÅ£º</div></td>
      </tr>
    </table></td>
    <td width="58" height="25"><div align="right"><%=(count+pagesize*(showpage-1))%></div></td>
    <td colspan="3" bgcolor="#66CC00"> </td>
    </tr>
  <tr>
    <td height="25" colspan="2"><div align="right">用户名</div></td>
    <td width="211"><%=message.getUsers()%></td>
    <td width="90"><div align="right">联系电话</div></td>
    <td width="105"><%=message.getPhone()%></td>
  </tr>
  <tr>
    <td height="25" colspan="2"><div align="right">E-mail:</div></td>
    <td><%=message.getEmail()%></td>
    <td><div align="right">传真</div></td>
    <td><%=message.getFax()%></td>
  </tr>
  <tr>
    <td height="25" colspan="2"><div align="right">公司名称</div></td>
    <td colspan="3"><%=message.getCompany()%></td>
    </tr>
  <tr>
    <td height="25" colspan="2"><div align="right">留言时间</div></td>
    <td colspan="2"><%=message.getDate()%></td>
    <td><div align="center">删除留言</div></td>
  </tr>
  <tr>
    <td height="25" colspan="2"><div align="right">留言主题</div></td>
    <td colspan="3"><%=message.getHeading()%></td>
  </tr>
  <tr>
    <td height="25" colspan="2"><div align="right">留言内容</div></td>
    <td colspan="3"><div>
<%    out.print(message.getContent());
  %>
     </div></td>
  </tr>
</table>
<%
  count++;
  out.print("<br/><br/>");

  if(!it.hasNext())
{break;}

     }
%>
<table width="810">
<tr>
<td width="535" height="25" colspan="8" align="right">
       <a href="/sczy/ViewMessageServlet?topage=<%=1%>">首页</a>
   <a href="/sczy/ViewMessageServlet?topage=<%=showpage-1%>上一页  </a>
   <a href="/sczy/ViewMessageServlet?topage=<%=showpage+1%>"> 下一页</a>
   <a href="/sczy/ViewMessageServlet?topage=<%=pagecount%>"> 末页</a>
   <span>这是第<%=showpage%>页 共<%=pagecount%>页</span>
</td>
</tr>
</table>
<%
  }
%>
</center>
</body>
</html>

#4

public String format(String s)
{
try
{
s1=s;
________________________________
s1变量没有定义???

#5

关注

#6

1,在int row=allno/rowno;下面加一句Out.println(s1);
2,把catch语句ramark掉;

然后再测试

#7

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#1