我的代码中出现以下异常：
我经常收到这个错误。
java.lang.NullPointerException
at com.mysql.jdbc.ResultSet.buildIndexMapping(ResultSet.java:616)
at com.mysql.jdbc.ResultSet.findColumn(ResultSet.java:946)
at com.mysql.jdbc.ResultSet.getString(ResultSet.java:5613)
at com.sfmfm.database.DB_DashBoard.doGet(DB_DashBoard.java:275)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
对于这个jsp数据没有正确加载。浏览器：火狐最新
如果我在 Eclipse 中运行它，它工作正常。
import java.util.Calendar;
import java.util.Date;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.sfmfm.properties.efmfm;
@WebServlet("/DB_DashBoard")
public class DB_DashBoard extends DB_Conn {
/**
*
*/
private static final long serialVersionUID = -5639866791158510975L;
static Statement st,st1;
public DB_DashBoard() throws Exception {
super();
st=con.createStatement();
st1=con.createStatement();
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
out=response.getWriter();
String query=request.getParameter("query");
// create a java calendar instance
//Calendar calendar = Calendar.getInstance();
// get a java.util.Date from the calendar instance.
// this date will represent the current instant, or "now".
Date now = new Date();
if(query != null && query.contains("~"))
{
System.out.println("Web Browser Request--"+query);
/*System.out.println("Today Date" +now); */
String browser_req[]=query.split("~");
if(browser_req[0].equals("Fetch_Pending_Fee"))
{
StringBuffer AllList = new StringBuffer();
try {
ResultSet rs=st1.executeQuery("SELECT sm.first_name, sm.last_name, " +
"cs.section_name, cs.class_name, sp.balance_amount, tm.first_name as tfname,tm.last_name as tlname, " +
"sm.contact_no, ft.due_date FROM teacher_master tm,student_master sm," +
" student_payment sp, class_section cs, fee_type ft, student_class sc WHERE" +
" sp.balance_amount!=0 AND sp.student_id = sm.student_id AND" +
" sm.student_id = sc.student_id AND sc.class_id = cs.class_id AND " +
"cs.class_name = ft.class_name AND tm.teacher_id = cs.teacher_id AND ft.fee_type_id=sp.payment_id AND " +
"TO_DAYS(ft.due_date) < TO_DAYS(NOW())");
if (rs != null)
{
while(rs.next())
{
AllList.append("<PENDING>");
AllList.append("<FIRSTNAME>" + rs.getString("first_name") + "</FIRSTNAME>");
AllList.append("<LASTNAME>" + rs.getString("last_name") + "</LASTNAME>");
AllList.append("<CONTACT>" + rs.getString("contact_no") + "</CONTACT>");
AllList.append("<BALANCE>" + rs.getString("balance_amount") + "</BALANCE>");
AllList.append("<DUE>" + rs.getString("due_date") + "</DUE>");
AllList.append("<SECTION>" + rs.getString("section_name") + "</SECTION>");
AllList.append("<CLASS>" + rs.getString("class_name") + "</CLASS>");
AllList.append("<TFNAME>" + rs.getString("tfname") + "</TFNAME>");
AllList.append("<TLNAME>" + rs.getString("tlname") + "</TLNAME>");
AllList.append("<SECTION>" + rs.getString("section_name") + "</SECTION>");
AllList.append("</PENDING>");
}
response.setContentType("text/xml");
response.setHeader("Cache-Control", "no-cache");
response.setHeader("Access-Control-Allow-Origin", "*");
response.getWriter().println("<CATALOG>" + AllList.toString() +"</CATALOG>");
System.out.println("Response sent="+"<CATALOG>" + AllList.toString()+ "</CATALOG>");
}
}
catch (Exception e)
{
System.out.println("S: Errorhai2");
e.printStackTrace();
}
}
else if(browser_req[0].equals("alert_past_info"))
{
StringBuffer AllList = new StringBuffer();
try {
ResultSet rs=st.executeQuery("SELECT DAY(date_time) AS aday, MONTHNAME(date_time) AS amonth,TIME(date_time) AS atime,title,category,sub_category,details FROM post_alert ");
if (rs != null)
{
while(rs.next())
{
AllList.append("<PASTALERT>");
AllList.append("<ADAY>" + rs.getInt("aday") + "</ADAY>");
AllList.append("<AMONTH>" + rs.getString("amonth") + "</AMONTH>");
AllList.append("<ATIME>" + rs.getInt("atime") + "</ATIME>");
AllList.append("<ATITLE>" + rs.getString("title") + "</ATITLE>");
AllList.append("<ACATA>" + rs.getString("category") + "</ACATA>");
AllList.append("<ASUB>" + rs.getString("sub_category") + "</ASUB>");
AllList.append("<ADESC>" + rs.getString("details") + "</ADESC>");
AllList.append("</PASTALERT>");
}
response.setContentType("text/xml");
response.setHeader("Cache-Control", "no-cache");
response.setHeader("Access-Control-Allow-Origin", "*");
response.getWriter().println("<CATALOG>" + AllList.toString() +"</CATALOG>");
System.out.println("Response sent="+"<CATALOG>" + AllList.toString()+ "</CATALOG>");
}
}
catch (Exception e)
{
System.out.println("Error On Past Alert Viewing");
e.printStackTrace();
}
}
}
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}
请提供清除此错误的建议。