Re: Servlet problems - Mailing list pgsql-jdbc
From | Nick Fankhauser |
---|---|
Subject | Re: Servlet problems |
Date | |
Msg-id | NEBBLAAHGLEEPCGOBHDGCEFEEBAA.nickf@ontko.com Whole thread Raw |
In response to | Servlet problems ("Nikola Milutinovic" <Nikola.Milutinovic@ev.co.yu>) |
List | pgsql-jdbc |
Nikola- I have a thought which doesn't match your description precisely, but might still be worth a try if you haven't already thought of it. I'm reminded of it because I had a similar mystery once where my jsp would die mysteriously unless I interrupted it before completion with a debug statement. In my case the problem was that totmcat starts you off with a fairly small chunk of memory to write each page to. I don't remember the exact number, but I'm thinking it was 8K or 16K. The problem was that I overran this buffer, resulting in an error that was misleading every time the page grew to a certain size. A sizable email directory might be big enough to do this. The fix was to insert this line at the top: <%@ page buffer="64kb" %> If this doesn't help, I'd suggest looking in Tomcat's work directory for the java code that gets produced & posting a copy of it to the list. Although many folks on the list don't speak jsp, they'll all be able to grok the java version. -Nick > -----Original Message----- > From: pgsql-jdbc-owner@postgresql.org > [mailto:pgsql-jdbc-owner@postgresql.org]On Behalf Of Nikola Milutinovic > Sent: Monday, December 17, 2001 9:32 AM > To: PostgreSQL JDBC > Subject: [JDBC] Servlet problems > > > 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. > > ---------------------------(end of broadcast)--------------------------- > TIP 3: if posting/reading through Usenet, please send an appropriate > subscribe-nomail command to majordomo@postgresql.org so that your > message can get through to the mailing list cleanly >
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