500错误~~哪位高手进来给瞅一眼。。？谢谢！
先贴错误，完整如下：

HTTP Status 500 - 

--------------------------------------------

type Exception report

message 

description The server encountered an internal error () that prevented it from fulfilling this request.

exception 

org.apache.jasper.JasperException: java.lang.NullPointerException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:491)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)


root cause 

java.lang.NullPointerException
org.apache.jsp.JSP.list_jsp._jspService(list_jsp.java:87)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)


note The full stack trace of the root cause is available in the Apache Tomcat/6.0.29 logs.


--------------------------------------------

Apache Tomcat/6.0.29


javabean代码也贴上来方便研究：


package book;
import java.sql.*;
public class conn{
String sDBDriver="sun.jdbc.odbc.JdbcOdbcDriver";
String sConnStr="jdbc:odbc:book";
Connection connect=null;
ResultSet rs=null;
public conn(){
try{
Class.forName(sDBDriver);
}
catch(java.lang.ClassNotFoundException e){
System.err.println(e.getMessage());
}
}
public ResultSet executeQuery(String sql){
try{
connect=DriverManager.getConnection(sConnStr);
Statement stmt=connect.createStatement();
rs=stmt.executeQuery(sql);
}
catch(SQLException ex){
System.err.println(ex.getMessage());
}
return rs;
}
}


哪里的问题捏??javabean也已经生成class文件啦，也放到该放的位置啦，怎么还会有错误呢？

------解决方案--------------------
ResultSet RS_result=connDBbean.executeQuery("select * from mybook");
代码不全，无法准确判断。
是否在该处，请经验RS_result的值。
------解决方案--------------------
设置断点，按F6，一步步的往下走
我的异常网推荐解决方案：The server encountered an internal error () that prevented it from fulfilling this request.,http://www.aiyiweb.com/java-web/317.html