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错误如下:
500 Servlet Exception
java.lang.NullPointerException
at _jsp._jsp._main__jsp._jspService(jsp/main.jsp:28)
at com.caucho.jsp.JavaPage.service(JavaPage.java:61)
at com.caucho.jsp.Page.pageservice(Page.java:578)
at com.caucho.server.dispatch.PageFilterChain.doFilter(PageFilterChain.java:192)
at com.caucho.server.webapp.WebAppFilterChain.doFilter(WebAppFilterChain.java:181)
at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:266)
at com.caucho.server.hmux.HmuxRequest.handleRequest(HmuxRequest.java:435)
at com.caucho.server.port.TcpConnection.run(TcpConnection.java:602)
at com.caucho.util.ThreadPool$Item.runTasks(ThreadPool.java:690)
at com.caucho.util.ThreadPool$Item.run(ThreadPool.java:612)
at java.lang.Thread.run(Thread.java:595)在个人计算机上行,可是在这台服务器上不行
配置是jdk1.4.2+tomcat5.0+sqlserver2000
main.jsp代码如下:<%@page contentType="text/html;charset=gb2312" %>
<%@page import="java.sql.*" %>
<%@page import="riso.mybook.jsp.c7.*" %>
<%!
private void showChildRecordes(JspWriter out,int fatherId) {
DBQuery dbQuery = new DBQuery();
try {
ResultSet rs = dbQuery.getChildRecordes(fatherId);
while (rs.next()) {
int fileid = rs.getInt("fileid");
out.print("~回复:<a href=view.jsp>?fileid=");
out.print(fileid);
out.print("target=bottom>");
out.print(rs.getString("title"));
out.print("</a><br>");
showChildRecordes(out,fileid);
}
} catch (java.sql.SQLException e) {
} catch (java.io.IOException e) {
}
}
%>
     <jsp:useBean id="dbQuery" class="riso.mybook.jsp.c7.DBQuery"  scope="page"/>
     <% int pageSize = 5;
       int pageNumber=1;
       int last=0;
        int up,down,count=0,over=0,i;
        ResultSet rs2;
      if (request.getParameter("pageNumber")==null)
        {
       pageNumber=1;
       }
       else if (request.getParameter("pageNumber").equals(""))
        {
       pageNumber=1;
       }
       else

          {
       pageNumber = Integer.parseInt(request.getParameter("pageNumber"));
         }
       rs2=dbQuery.executeQuery( "SELECT * FROM lyb WHERE fatherid=0 ORDER BY addtime DESC");
    while(rs2.next())
  {
   count++;
  }
        over=(int)Math.ceil((double)count/5);
        if(pageNumber==0 || pageNumber>over)
         {
          pageNumber=over;
         }
       if(pageNumber==1)
         {
          up=1;
         }
     else
         {
          up=pageNumber-1;
         }
       if(pageNumber==over)
         {
          down=over;
         }
       else
         {
          down=pageNumber+1;
          }

       if(pageNumber==1)
         {
          rs2=dbQuery.executeQuery("SELECT * FROM lyb WHERE fatherid=0 ORDER BY addtime DESC");
     }
   else
     {
rs2=dbQuery.executeQuery( "SELECT * FROM lyb WHERE fatherid=0 ORDER BY addtime DESC");

     int absoluteLocation=pageSize*(pageNumber-1);

     try{ for(i=1;i<absoluteLocation;i++)
         {
      rs2.next();
     }
        }
     catch(Exception e)
        {e.getMessage();
        }
      }
     %>


      <html>
      <head>
      <title>留言版</title>
      <meta http-equiv="Content-Type" content="text/html;charset=gb2312">

      </head>
      <style type="text/css">
      
      </style>

      <body bgcolor="#FFFFFF" leftmargin="0" topmargin="0" align=center valign=middle>
      <br><blockquote><div align="center" style="font-size: 14pt; color: black;"><h4><font size="6"><strong>南航中德跨文化研究中心留言版</strong></font></h4></div></blockquote>
      <br>


      <table width="760" border="0" align="center" cellpadding="2" cellspacing="2" class="n9pt">

      <tr>

      <td width="500">
      <a href="main.jsp?pageNumber=1">首页</a>
        
      <a href="main.jsp?pageNumber=<%=up%>">前一页</a>
        
      <a href="main.jsp?pageNumber=<%=down%>">后一页</a>
        
      <a href="main.jsp?pageNumber=<%=last %>">最后一页</a>
      </td>
      <td width="130">
           页次:<%=pageNumber%> / <%=over%>
      </td>
       <td width="130" valign=bottom>
     <form action=main.jsp method=post>
      跳至第<input type=text size=3 name=pageNumber>页<input type=submit name=SEND value="go">
     </form>
       </td>
       </tr>


       <tr>

       <td width="500" bgcolor="#CCCCCC">
       <div align="center"><font color="#FFFFFF">标题</font></div>
       </td>
       <td width="130" bgcolor="#CCCCCC">
       <div align="center"><font color="#FFFFFF">作者</font></div>
       </td>
       <td width="130" bgcolor="#CCCCCC">
       <div align="center"><font color="#FFFFFF">发表时间</font></div>
       </td>
       </tr>

     <%
       String title, author, addtime, email;
       int fileid = 1;
       //ResultSet rs2 = dbQuery.getTopicList(pageSize, pageNumber,up,down,over);       if (!(rs2 == null)) {
       int outputRecordCount = 0;
       while (rs2.next()) {
           fileid = rs2.getInt("fileid");
           title = rs2.getString("title");
           author = rs2.getString("author");
           addtime = rs2.getString("addtime");
           java.text.SimpleDateFormat  nowdate=new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
           java.util.Date date=nowdate.parse(addtime);
           String date2 = nowdate.format(date);
           email = rs2.getString("email");


           out.print("<tr><td width=500 height=31 bgcolor=#eeeeee><a href=view.jsp?fileid=");
           out.print(fileid);
           out.print(" target=_blank>");
           out.print(title);
           out.print("</a></td><td width=130 height=31 bgcolor=#eeeeee><div align=center>");

       if ((!(email == null)) && (!(email.equals("")))) {
           out.print("<a href=mailto:");
           out.print(email);
           out.print(">");
           out.print(author);
           out.print("</a>");
          }
      else
          { out.print(author);
          }      out.print("</div></td><td width=130 height=31 bgcolor=#eeeeee><div align=center>");
      out.print(date2);
      out.print("</div></td></tr><tr><td colspan=3>");
      //showChildRecordes(out,fileid);
      out.print("</td></tr>");

        outputRecordCount++;
  if(outputRecordCount>=pageSize)
  { break;
  }
  }
  }
  else
  { out.println("<tr><td colspan=3>您已经在最后一页了</td></tr>");
  }          %>

      </table>
      </body>
      </html>
    谢谢大家!!!

解决方案 »

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java.lang.NullPointerException  main.jsp第28行有空指针一场拒绝看jsp页面中的java代码建议MVC之
楼上的都说了。是空指针异常嘛。
空指针异常就是说调用了一个为空的对象的方法或属性时引发的异常。
一步一步测试吧。
其实我也不太喜欢看JSP里面的代码。头疼。
密密麻麻的、、
java.lang.NullPointerException  main.jsp第28行有空指针一场看看你的28行有什么啊
一个变量一个变量看看哪个为空