这是个什么错误.非常急1000分!

display.jsp用来从数据库中读取聊天内容.
  display
</title>
<meta http-equiv="refresh" content="10">
<meta http-equiv="Content-Type" content="text/html; charset=gb2312"></head>
<body bgcolor="#d6ebd6"  onload="scroller()">
<%@page language="java" import="java.sql.*"%>
<%@page  import="java.util.*"%>
<%@page  import="java.util.Date"%>
<jsp:useBean id="db" scope="page" class="reg_one.db" />
<%
        String nickname="";
        String color=(String)session.getValue("color_write");

        Date m_date=new Date();
        String now_time=m_date.toLocaleString();
        long nowTime=m_date.getTime();
    //获得用户登录时间
    String nickName=(String)session.getValue("nickName");
        out.print(nickName);
String chatRoom=(String)session.getValue("chatRoom");

String sql="select logonTime from chatUser where nickName like '"+nickName+"'";

ResultSet rs_1=db.executeQuery(sql);
         rs_1.next();


        //toLocateString 格式用于显示和保存到数据库
    long logonTime=rs_1.getLong("logonTime");
        m_date.setTime(logonTime);
        String logon_time=m_date.toLocaleString();
rs_1.close();
        //组合查询
       //int i=0;
       sql="select * from chat where (secret=0 or chat_to='"+nickName+"' or chat_to='all' or chat_from='"+nickName+"') and (chatRoom='"+chatRoom+"') and (chat_time>#"+logon_time+"#) order by id asc";
       ResultSet rs_2=db.executeQuery(sql.);
if(rs_2.next())
   {
            rs_2.afterLast();//这是每次我想显示10条记录
   rs_2.previous();
   int lab_last=rs_2.getRow();
   if(lab_last>10)
       {
      rs_2.absolute(lab_last-10);
}
else
   {
  rs_2.beforeFirst();

}
%><%   while(rs_2.next())
        {

          String chat_from=rs_2.getString("chat_from").trim();
          String chat_to=rs_2.getString("chat_to").trim();
          String chat_time=rs_2.getString("chat_time").trim().substring(11,19);
          String action=rs_2.getString("action").trim();
          String content=rs_2.getString("content").trim();
          int secret=rs_2.getInt("secret");   %>
      <input type="hidden" name="color" value=<%=color%>>
         <tr>
            <td><font color="#669966"><a href="send.jsp?name=<%=chat_from%>" target="mainFrame"><%out.print(chat_from);%></a> </font>
                <font color="#FA85F4"> <%=action%></font>              对<font color="#ff0000">                       <%
                    if(chat_to.compareTo("all")==0)
                        {
                         %>
                          <a href="send.jsp?name=all" target="mainFrame">大家</a>
                        <%
                         }
                          else{
                         %>
                            <a href="send.jsp?name=<%=chat_to%>" target="mainFrame"><%=chat_to%></a></font>                         <%
                          }
                          if(secret==1)
                          {
                             %>悄悄地
                              <%}%>
                              说:<font color=<%=color%>><%=content%></font>(<%=chat_time%>)
                              </td>
                              </tr><br>                           <%
                            }
                           rs_2.close();
           %>
                     <%
                   }
                      else
                       rs_2.close();
  %>

                           </table>                          </body>
                   </html>
   <%
      //刷新用户列表，首先获得在线的所有用户
     sql="select nickName ,chatTime from userlist";
     ResultSet rs_3=db.executeQuery(sql);
     while(rs_3.next())
     {
        //获得这个用户最后的发言的时间和现在的时间
        String checkUser=rs_3.getString("nickName").trim();
        long checkTime=rs_3.getLong("chatTime");
        //如果15分钟没有发言，则认为是发呆，从用户列表中汪除
        if(nowTime-checkTime>15*60*1000)
        {
           sql="delete from userlist where nickName like '"+checkUser+"'";
           db.executeDelete(sql);
           //在聊天室中显示该用户的离开信息
           sql="insert into chat (chatRoom,chat_from,chat_to,chat_time,action,content,secret)values('"+chatRoom+"','"+checkUser+"','all','"+now_time+"','*_*','886','0')";
           db.executeInsert(sql);        }     }
   //  rs_3.close(); %>

这样写代码,实在是太糟糕了。
大体看了一下，以上错误发生的可能是这样
不清楚你的reg_one.db这个类是怎么写的
如果别的页面也用reg_one.db来执行sql,如果共享一个connection
别的页面关闭了这个connection就会导致display.jsp中的结果集不可用。

不好意思,初学者吗?包含一下,reg_one.db里封装了对数据库的几个操作,查询,
删除...代码如下:
   package reg_one;
import java.sql.*;
import java.sql.DriverManager;
public class db{
  String sDBDriver="sun.jdbc.odbc.JdbcOdbcDriver";
  String sConnStr="jdbc:odbc:jsp_db";
  private Statement stmt=null;
  private Connection conn=null;
  ResultSet rs=null;
  public db() {
   try{
     Class.forName(sDBDriver);
   conn=DriverManager.getConnection(sConnStr);
     Statement stmt=conn.createStatement( ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
      }
       catch(java.lang.ClassNotFoundException e)
   {
       System.err.println("db():"+e.getMessage());
    }
   catch(SQLException ex)
   {
         System.err.println("aq.executeQuery:"+ex.getMessage());
    }
     }
   public ResultSet executeQuery(String sql){
      try{
         conn=DriverManager.getConnection(sConnStr);
         stmt=conn.createStatement( ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
         rs=stmt.executeQuery(sql);

       }
       catch(SQLException ex){
          System.err.println("aq.executeQuery:"+ex.getMessage());
       }
       return rs;
   }   public void executeInsert(String sql){
     try{
       conn=DriverManager.getConnection(sConnStr);
       Statement stmt=conn.createStatement( ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
       stmt.executeUpdate(sql);
       stmt.close();
       conn.close();
     }
     catch(SQLException ex)
     {
       System.err.println("sql_data.executerInset:"+ex.getMessage());
     }
      finally
        {
         if(stmt!=null)
           stmt=null;
         if(conn!=null)
           conn=null;
        }
   }   public void executeUpate(String sql){
       try{
         conn=DriverManager.getConnection(sConnStr);
         Statement stmt=conn.createStatement( ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
         stmt.executeUpdate(sql);
         stmt.close();
         conn.close();
       }
       catch(SQLException ex)
       {
         System.err.println("sql_data.executerUpdate:"+ex.getMessage());
       }
       finally
          {
                   if(stmt!=null)
                     stmt=null;
           if(conn!=null)
             conn=null;
             }
   }   public void executeDelete(String sql){
    try{
      conn=DriverManager.getConnection(sConnStr);
      Statement stmt=conn.createStatement( ResultSet.TYPE_SCROLL_SENSITIVE,   ResultSet.CONCUR_UPDATABLE);
      stmt.executeUpdate(sql);
      stmt.close();
      conn.close();
    }
    catch(SQLException ex)
    {
      System.err.println("sql_data.executerDelete:"+ex.getMessage());
    }
    finally
      {
       if(stmt!=null)
         stmt=null;
       if(conn!=null)
         conn=null;
         }
   }
   public void closeStmt(){
    try{
       stmt.close();
       }
    catch (SQLException e){
    e.printStackTrace();
    }
     }
   public void colseConn(){
    try{
    conn.close();
    }
    catch (SQLException e){
    e.printStackTrace();
    }
   }
}  这回整理了一下.谢谢你.

呵呵。最好的解决方法是重写你的数据库连接这个类。
或者用别人的成熟的产品，比如连接池，比较稳定的如：JPool如果要在现在的基础上解决的话。应该是在调用结果集关闭的地方，就应该关闭这个连接
colseConn()这个方法。如果别的jsp也会调用这个连接类的话。我也预测不到会发生什么
事情了，逻辑比较混乱。colseConn()方法只是保证得到连接，关闭连接，跟结果集关闭保持
一致性，我想应该可以。

那么,如果我偷机,COPY此类,换个名,然后,两个页面分别调用,是不互不景响呢>

我想也会出问题
你先在调用结果集close的地方，就调用db的colseConn()方法试试

org.apache.jasper.JasperException: Unable to compile class for JSPAn error occurred at line: -1 in the jsp file: nullGenerated servlet error:
    [javac] Since fork is true, ignoring compiler setting.
    [javac] Compiling 1 source file
    [javac] Since fork is true, ignoring compiler setting.
    [javac] C:\Tomcat 5.0\work\Standalone\localhost\regapp\chat\display_jsp.java:98: cannot resolve symbol
    [javac] symbol  : method closeConn ()
    [javac] location: class reg_one.db
    [javac]         db.closeConn();
    [javac]           ^
    [javac] C:\Tomcat 5.0\work\Standalone\localhost\regapp\chat\display_jsp.java:189: cannot resolve symbol
    [javac] symbol  : method closeConn ()
    [javac] location: class reg_one.db
    [javac] db.closeConn();
    [javac]                                                           ^
    [javac] C:\Tomcat 5.0\work\Standalone\localhost\regapp\chat\display_jsp.java:198: cannot resolve symbol
    [javac] symbol  : method closeConn ()
    [javac] location: class reg_one.db
    [javac]   db.closeConn();
    [javac]     ^
    [javac] C:\Tomcat 5.0\work\Standalone\localhost\regapp\chat\display_jsp.java:227: cannot resolve symbol
    [javac] symbol  : method closeConn ()
    [javac] location: class reg_one.db
    [javac]      db.closeConn();
    [javac]        ^
    [javac] Note: C:\Tomcat 5.0\work\Standalone\localhost\regapp\chat\display_jsp.java uses or overrides a deprecated API.
    [javac] Note: Recompile with -deprecation for details.
    [javac] 4 errors这是为何???

org.apache.jasper.JasperException
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:370)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:293)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:240)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)root cause java.lang.NullPointerException
at reg_one.db.closeStmt(db.java:102)
at org.apache.jsp.display_jsp._jspService(display_jsp.java:222)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:136)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)什么原因.

下载那个jpool 扩展名是那一个.怎么用,可不可以在线教我.

你在关闭数据库连接是出错了
NullPoint错误

调试易

这是个什么错误.非常急1000分!

解决方案 »