I hope someone can point me in the right direction on how to resolve the
following issue. Our environment is
Windows NT (Service Pack 5 and 6); have also seen this on Solaris
5.8
Apache 1.3.26
Tomcat 3.3.1
Struts 1.1 Beta 2
Java 2 SDK 1.4.0_01
We have an application that access data from an Oracle 8.1.7 DB based on
various user input. After about 15 or 18 queries, the application appears
to 'hang' - i.e. nothing ever ends up coming back. When I stop Tomcat, I
get the following stack trace (could be due to stopping Tomcat - I'm not
sure):
Error: 500
Location: /aefa/QueryRecordAction.do
Internal Servlet Error:
java.lang.NullPointerException
at
org.apache.struts.action.RequestProcessor.getServletContext(RequestProcessor
.java:1076)
at
org.apache.struts.tiles.TilesRequestProcessor.processTilesDefinition(TilesRe
questProcessor.java:175)
at
org.apache.struts.tiles.TilesRequestProcessor.processForwardConfig(TilesRequ
estProcessor.java:291)
at
org.apache.struts.action.RequestProcessor.processActionForward(RequestProces
sor.java:390)
at
org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:271)
at
org.apache.struts.action.ActionServlet.process(ActionServlet.java:1292)
at
org.apache.struts.action.ActionServlet.doPost(ActionServlet.java:510)
at javax.servlet.http.HttpServlet.service(HttpServlet.java)
at javax.servlet.http.HttpServlet.service(HttpServlet.java)
at
org.apache.tomcat.facade.ServletHandler.doService(ServletHandler.java:574)
at org.apache.tomcat.core.Handler.invoke(Handler.java:322)
at org.apache.tomcat.core.Handler.service(Handler.java:235)
at
org.apache.tomcat.facade.ServletHandler.service(ServletHandler.java:485)
at
org.apache.tomcat.core.ContextManager.internalService(ContextManager.java:91
7)
at
org.apache.tomcat.core.ContextManager.service(ContextManager.java:833)
at
org.apache.tomcat.modules.server.Ajp13Interceptor.processConnection(Ajp13Int
erceptor.java:341)
at
org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:494)
at
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.jav
a:516)
at java.lang.Thread.run(Thread.java:536)
I've monitored the memory usage on WinNT using the task manager; each query
results in an increase in memory usage of between 300 and 400k. I don't
ever see any memory being reclaimed (this is under the 'java' task which is
Tomcat.) QueryRecordAction does a SELECT, then builds a nested bean to hold
the returned 'rows' - the is another bean that holds the actual data. The
code for the two beans is
Results.java
public class Results {
private Vector results;
public Results() {
this.results = new Vector();
}
public Vector getResults() {
return this.results;
}
public void addRow(Row row) {
this.results.add(row);
}
public void clear() {
this.results.clear();
}
}
Row.java
public class Row {
private String name;
private String address; // etc. etc. etc.
public Row() {
this.name = "";
this.address = "";
}
/* normal getters */
public String getName() {
return this.name;
}
public String getAddress() {
return this.address;
}
/* normal setters */
public void setName(String name) {
this.name = name;
}
public void setAddress(String address) {
this.address = address;
}
}
QueryRecordAction cleans up the previous set of beans (if they exist), then
rebuilds the beans and puts the bean back into the session.
QueryRecordAction
public class QueryRecordAction extends Action {
PreparedStatement ps = null;
ResultSet rs = null;
public ActionForward execute(ActionMapping mapping,
ActionForm form, HttpServletRequest request, HttpServletResponse response) {
HttpSession session = request.getSession();
if (session.getAttribute("results") != null)
{
Results results = (Results)
session.getAttribute("results");
results.clear();
session.removeAttribute("results");
}
Results results = new Results();
String queryName = (String)
PropertyUtils.getSimpleProperty(form, "queryName");
try {
DataSource ds = (DataSource)
servlet.getServletContext().getAttribute("AEFA"); // key for datasource in
struts-config
Connection con = ds.getConnection();
ps = con.PrepareStatement("SELECT
name, address from aefa_order where query_name = ?");
ps.setString(1, queryName);
rs = ps.executeQuery();
while(rs.next()) {
Row row = new Row();
row.setName(rs.getString("name"));
row.setAddress(rs.getString("address"));
results.addRow(row);
}
session.setAttribute("results",
results);
rs = null;
ps = null;
con = null;
ds = null;
}
catch(Exception e) {
ActionErrors errors = new
ActionErrors();
errors.add("internal_error", new
ActionError("internal.error", e.getMessage()));
saveErrors(request, errors);
return
(mapping.findForward("error"));
}
return (mapping.findForward("success"));
}
}
The "success" forward displays a table of all the rows that were returned.
Everything works just like I would expect it to, except for Tomcat hanging
after 15 or 18 queries. I've been through the code and can't find where I
would have a memory leak - if anyone can spot one, or has other ideas,
please let me know!
Thanks!
Jerry Jalenak
Web Publishing
LabOne, Inc.
10101 Renner Blvd.
Lenexa, KS 66219
(913) 577-1496
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