BC4J: NullPointerException in Tomcat 4.1.24, but in OC4J it works fine

Question

Dear reader,
I am having a weird exception in tomcat, which does not occur in the OC4J server (shipped with JDeveloper 9.0.3.1).
I have a web-application built with BC4J/struts (struts final release) and this works fine in the OC4J server. In Tomcat it works fine until a certain row does not contain data (it looks like that). The code in the jsp where it goes wrong is the following:
<jbo:RowsetIterate datasource="ConsultantModule.ConsultantGeneralView" changecurrentrow="true" userange="false">
<jbo:Row id="generalRow" datasource="ConsultantModule.ConsultantGeneralView" action="current">
<jbo:Row id="allocatiesRow" datasource="ConsultantModule.AllocatieRegistratiesView" action="current">
The last row it goes wrong if there is no data in it (in OC4J it just works fine there). I've also looked up the generated servlet in tomcat, and the following lines are responsible (for the last jbo:Row tag):
oracle.jbo.Row allocatiesRow = null;
jspxallocatiesRow_1 = allocatiesRow;
oracle.jbo.html.jsp.datatags.RowTag jspxth_jbo_Row_2 = new oracle.jbo.html.jsp.datatags.RowTag();
jspxth_jbo_Row_2.setPageContext(pageContext); jspxth_jbo_Row_2.setParent(_jspx_th_jbo_Row_1); jspxth_jbo_Row_2.setId("allocatiesRow"); jspxth_jbo_Row_2.setDatasource("ConsultantModule.AllocatieRegistratiesView");
jspxth_jbo_Row_2.setAction("current");
int jspxeval_jbo_Row_2 = jspxth_jbo_Row_2.doStartTag(); // This line throws a NullPointerException in Tomcat
Has anyone encountered a similar problem? And is it a bug in the tag libraries, or is it a bug in Tomcat? And most importantly can it be solved, so that I can still deploy to Tomcat.
Thanks a lot for your time!
Regards Martijn

Answer 1

[UPDATE]
I've done some more research to the problem of the NullPointerException in Tomcat.
It seems to happen only when a certain View does not contain rows (no data, it is empty).
Once the <jbo:Row id="anyID" ... > defines a row based on that view, this causes Tomcat to crash on the doStartTag, in the RowTag class. OC4J does not crash. The source tomcat crashes on in the RowTag class is:
   public int doStartTag() throws JspException
      initialize();
      handleAction();
      pageContext.setAttribute(id , row); // NULLPOINTER EXCEPTION
      return Tag.EVAL_BODY_INCLUDE;
   }Apparently row is null, which is the case as I know there is no row, which causes an exception (as per the setAttribute definition of pageContext).
It seems that OC4J does never execute this tag, or it should have crashed as well, wouldn't it? As in the handleAction() method, the action 'current' is defined as follows:
else
if (ACTION_ROW_CURRENT.equalsIgnoreCase(sAction))
         row = rs.getCurrentRow();
         if (row == null)
            row = rs.first();
            if (row == null)
               rs.executeQuery();
               row = rs.first();
      } The row must always be null, as the view doesn't contain any rows (not even after executeQuery()).
Can someone please have a look at this? I really need to know whether this is indeed a Tomcat bug, BC4J tag library bug or an OC4J bug (perhaps the code it generates is too kind to developers, and prevents errors, compared to normal specifications of jsp/servlets?).
Using the <jbo:RowSetIterate ..> tag in front of the <jbo:Row ..> tag (empty one) prevents the crash (also in Tomcat).
If you require the Tomcat and/or OC4J generated java-code to see what happens, please let me know. But it is rather large to paste it here.
Thanks a lot for your time!
Regards Martijn