Servlet problems
От | Nikola Milutinovic |
---|---|
Тема | Servlet problems |
Дата | |
Msg-id | 001901c18707$9b9d9080$0a3ea8c0@ev.co.yu обсуждение исходный текст |
Ответы |
Re: Servlet problems
Re: Servlet problems |
Список | pgsql-jdbc |
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 describingan 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-Mailaddress 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 thingand 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 screwedup, but I don't know how. Any insight? Nix.
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