Re: Servlet problems

Hi!

I'm afraid I don't speak JSP ;-) but I may siggest something.

Can you try to flush every output you send?

For every println(), if you use them, just place a flush() immediately
after it. That WILL NOT solve your problem, and WILL degrade
performance, but MAY help you find the source for your trouble. Once
your problem is solved (I let you do the hard work), you can safely take
them away.

Good luck!

Antonio

Nikola Milutinovic wrote:

>Hi all.
>
>I'm a bit confused here. I'm using Tomcat JSP/Servlet engine. I have a database in PostgreSQL, which holds a table describing an n-tree structure (hierarchy). I would like my JSP page to able to display (if parameter "print" is present) a complete sub-tree of a given node. This is a simple recursion. What I'm trying to do is make our coroporate E-Mail address book, so I have organizational units and users.
>
>Without recursion everything works fine, all the direct subnodes are displayed. When I use recusrion to include all subnodes, I get strange errors.
>
>First, it was killing the response in the middile of a table, in the middle of a row. Now it dies with "NullPointerException: next()". In other words, in one of the "ResultSet.next()" methods, it runs into a non existant ResultSet.
>
>I have tried putting a "breakpoint" (throwing a ServletException) on all lines of my JSP page. When there is a "breakpoint" I do not run into a NullPointerException. When I remove it, I have exception.
>
>My conclusion was that I get the error AFTER my JSP page starts emerging from the recursion (if it was inside recursion, it would have been stopped by the "breakpoint"). So, after a page calls itself once, the "insider" does it's thing and then exits and releases control to it's caller, the the exception occurs.
>
>I must admit that JSP page closes it's JDBC objects, I thought it would be OK, since the page creates them.
>
>This is the flow of events:
>
>OUDisplay.jsp [instance 1]:
>----------------------------
> DriverManager.getConnection()
> Connection.createStatement()
> Statement.executeQuery()
> while( ResultSet.next() ) {
> ...
> <jsp.include page="OUDisplay.jsp" />
>
> OUDisplay.jsp [instance 2]:
> ----------------------------
> DriverManager.getConnection()
> Connection.createStatement()
> Statement.executeQuery()
> while( ResultSet.next() ) {
> ...
> }
> ResultSet.close()
> Statement.close()
> Connection.close()
> --------------[instance 2]-
>
> }
> ResultSet.close()
> Statement.close()
> Connection.close()
>--------------[instance 1]-
>
>The problem occurs inside the outer "next() {...}", which leads me to believe that Some objects in the "instance 1" get screwed up, but I don't know how.
>
>Any insight?
>
>Nix.
>
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