不知道出了什么错误啊 急

Question

java.sql.SQLException: Before start of result set
at com.mysql.jdbc.ResultSet.checkRowPos(ResultSet.java:687)
at com.mysql.jdbc.ResultSet.getInt(ResultSet.java:2367)
at com.song.UserBeanCl.getPageCounter(UserBeanCl.java:95)
at com.servlet.UserServlet.doGet(UserServlet.java:51)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:118)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)
at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:799)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:705)
at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:577)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
at java.lang.Thread.run(Thread.java:619)

Answer 1

忘记写next方法??????
没取到当前记录

Answer 2

先执行结果集的rs.next()方法，再取值！

Answer 3

我是这样做的啊
package com.song;import java.sql.*;
import java.util.*;public class UserBeanCl {

private Connection conn=null;
private Statement st=null;
private ResultSet rs=null;
private int rowCounter=0;//存放总的记录数
    private int pageCounter=0;//存放总的页数
    private int grade=0;

//验证用户是否合法的方法
public boolean checkUser(String name,String pass){
boolean b=false;

try{

DBconn db=new DBconn();
conn=db.getConnection();
st=conn.createStatement();
String sql="select passW,grade from user where name='"+name+"'";
rs=st.executeQuery(sql);
if(rs.next()){
if(pass.equals(rs.getString(1))){
b=true;
grade=rs.getInt(2);
}
}
}catch(SQLException e){
e.printStackTrace();
}finally{
this.close();
}
return b;
}

//分页方法
    public Vector split(int pageSize,int pageNow ){
    Vector v=new Vector();
    
try{

DBconn db=new DBconn();
conn=db.getConnection();

st=conn.createStatement();
String sql2="select id,name,tel from friends limit "+(pageNow-1)*pageSize+","+pageSize;
rs=st.executeQuery(sql2);
while(rs.next()){
UserBean ub=new UserBean();
ub.setId(rs.getInt(1));
ub.setName(rs.getString(2));
ub.setTel(rs.getString(3));
v.add(ub);
}
}catch(SQLException e){
e.printStackTrace();
}finally{
this.close();
}
    
    return v;
    }
    public void close(){
     try{
if(rs!=null){
rs.close();
rs=null;
}
            if(rs!=null){
st.close();
st=null;
}
            if(rs!=null){
conn.close();
conn=null;
}
}catch(SQLException e){
e.printStackTrace();
}
    }
    public int getPageCounter(int pageSize){
     try{
    
     //获取数据库中的记录数
         DBconn db=new DBconn();
     conn=db.getConnection();
     st=conn.createStatement();
     String sql1="select count(*) from friends";
     rs=st.executeQuery(sql1);
     rowCounter=rs.getInt(1);
     }catch(SQLException e){
     e.printStackTrace();
     }finally{
     this.close();
     }
    
     if(rowCounter%pageSize==0){
     pageCounter=rowCounter/pageSize;
     }
     if(rowCounter%pageSize!=0){
     pageCounter=rowCounter/pageSize+1;
     }
     return pageCounter;
    }
    public int getGrade(){
     return grade;
    }
}

Answer 4

prepareStatement(sql,ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
没有设置游标为可以滚动