请帮忙看一下这个问题!

hxyuie

package ccbn.conn1;
import java.sql.*;
import java.util.*;
import java.io.*;


public class DBconn
  {
        DBConnectionManager ConnManager=null;
        Connection conn = null;
        ResultSet rs = null;
        ResultSet rs1=null;
        public DBconn()
        {
           ConnManager=new DBConnectionManager();
           conn = ConnManager.getDBConnection();
        }


    public void executeQuery(String sql)
     {
                  try
                        {                  
                          Statement stmt = conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
                          rs = stmt.executeQuery(sql);
                        }
                  catch(SQLException ex)
                        {
                          System.err.println("aq.executeQuery:"+ex.getMessage());
                        }
     }

        public void updateQuery(String sql)
     {
                  try
                        {
                                 Statement stmt = conn.createStatement();
                                 stmt.executeUpdate(sql);
                        }
                  catch(SQLException ex)
                        {
                                System.err.println("aq.executeQuery:"+ex.getMessage());
                        }
     }
       

        public int getColumnCount() throws SQLException
    {
               
                 ResultSetMetaData rsmd=rs.getMetaData();
                 return rsmd.getColumnCount();
                 
          }

        public String getColumnName(int index) throws SQLException
    {
               
                 ResultSetMetaData rsmd=rs.getMetaData();
                 return rsmd.getColumnName(index);
                 
          }

        public boolean next() throws SQLException
          {
                        return rs.next();
                }

        public String getData(int index) throws SQLException
          {
                        return rs.getString(index).trim();
                }

        public String getData(String columnName) throws SQLException
          {
                        return rs.getString(columnName).trim();
                }

        public void close() throws SQLException
          {
                if (rs!=null) rs.close();          
          }
  }

这是一个Bean文件；
----------------------------------------------------------------
<%@ page contentType="text/html; charset=gb2312" %>;
<%@ page import="java.sql.*,java.util.*,ccbn.conn1.*"%>;
<%
        Vector ArrayName;
        int Num=0;
        int i=0;
        String StrTemp=new String();
        String StrSql="Select * From Visitors1";
        DBconn databaseObject=new DBconn();
        databaseObject.executeQuery(StrSql);
        for (i=1;i<databaseObject.getColumnCount();i++)
        {
                out.println(databaseObject.getColumnName(i));
                  **在这里可以正常输出**
        }
        while(databaseObject.next())
        {
                for (i=1;i<databaseObject.getColumnCount();i++)
                {
                        StrTemp=databaseObject.getData(i);
                        out.println(StrTemp);
                          **在这里不能正常输出.不知道为什么呀？**
                }
        }

%>;
--------------------------------------------------------------------
org.apache.jasper.JasperException
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:254)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:295)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
        at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2415)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
        at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
        at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172)
        at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
        at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:223)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:594)
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:392)
        at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:565)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:619)
        at java.lang.Thread.run(Thread.java:536)


root cause

java.lang.NullPointerException
        at ccbn.conn1.DBconn.getData(DBconn.java:83)
        at org.apache.jsp.test_jsp._jspService(test_jsp.java:67)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:137)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:210)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:295)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
        at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2415)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
        at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
        at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172)
        at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
        at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
        at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:223)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:594)
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:392)
        at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:565)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:619)
        at java.lang.Thread.run(Thread.java:536)

这个是报的错误。
请帮忙看一下吧

镖师甲

可能是getData方法中的getString方法返回的是null.就会出现NullPointerException

perryhg

return rs.getString(index).trim();

如果rs.getString(index) 得到的是null的话再trim()就出错了。