NullPointerException when filling in stacktrace?

Question

Hi,
In the app I'm trying to understand, an exception is thrown. I know so, as I use log4j to log what happens. Log4j is set to DEBUG.
This is some of my code
public class CreateCustomerAction extends Action {
  //Logger
  static Logger logger = Logger.getLogger(CreateCustomerAction.class);
  public ActionForward execute(ActionMapping mapping, ActionForm form,
    HttpServletRequest request, HttpServletResponse response) {
     // Some initialisation
    try {
      customerDAO.createCustomer(customerTO);   
      actionMessages.add(ActionMessages.GLOBAL_MESSAGE, new ActionMessage("success.add"));
      saveMessages(request, actionMessages);
      return (mapping.findForward("success"));
    catch (Exception ex) {
      if (ex==null)
          logger.info("exception is null! ============================== ");
      logger.info("an exception occurred! ============================== ",ex.fillInStackTrace()); // LINE 54!The appropriate code in CustomerDAO
    try {
      logger.info("MBE: ++++++ getConnection ++++++++");
      connection = getConnection();
      // Some more code
    catch (SQLException ex) {
      logger.info("MBE: ++++++ SQLException ++++++ ");     
      throw new DAOException();
    }This is what I get in my log file:
11:27:19,506 INFO  app15a.action.CreateCustomerAction - ++++++ getConnection ++++++++
11:27:19,522 INFO  app15a.action.CreateCustomerAction - an exception occurred! ==============================
java.lang.NullPointerException
     at app15a.action.CreateCustomerAction.execute(CreateCustomerAction.java:54)
     at org.apache.struts.action.RequestProcessor.processActionPerform(RequestProcessor.java:421)
     at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:226)
     at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1164)
     at org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:415)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:263)
     at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:852)
     at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:584)
     at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1508)
     at java.lang.Thread.run(Unknown Source)Am I correct in assuming the exception that was thrown in the other class is Null? When not obvious, line 54 is the line containing the following code:
logger.info("an exception occurred! ============================== ",ex.fillInStackTrace());And why did my logfile not show an entry containing ++++++ SQLException ++++++?

Answer 1

Abel wrote:
You lost me. In the line
logger.info("an exception occurred! ============================== ",ex.fillInStackTrace());there are two objects, logger and ex. And IMHO, if I see "an exception occurred! ============================== " and a stack trace, I doubt it is coming from a logger object that is not instantiated. I would not know any other way to check if logger==null.Ok, have it your way. Of course one can never print out 'logger' and 'ex' and one can never use a debugger and one can never look at the code to make sure that 'logger' is initialized to something other than null. What one can do is, without any checks, tell everyone that they are wrong.
Edited by: sabre150 on Jan 2, 2008 1:02 PM