Help!! - java.lang.OutOfMemoryError

[Sanjay Anand]

I am trying to generate an XML string from a table with 13160 rows in the result set.
I checked the archives and found this helpful discussion: http://www.javaranch.com/ubb/Forum3/HTML/000465.html
So I tried to implement the same solution, but it's not working.
The code itself is somewhat long. I've posted it at:
http://y42.briefcase.yahoo.com/bc/iamsanjayonly/vwp2?.tok=bc J5XF7AtegBHF8g&.dir=/Code&.dnm=AllDataXML.java&.src=bc
Here are some relevant snippets:

public void readTable (String q)
 {

try
{
Class.forName(driver).newInstance();
}
catch (java.lang.ClassNotFoundException e) 
{
System.out.println("Driver class not found");
}
catch (java.lang.InstantiationException e)
         {
           System.out.println("java.lang.InstantiationException"+e);       
}
catch (java.lang.IllegalAccessException e)
{
System.out.println("java.lang.IllegalAccessException"+e);       
}
    //Reading customer table

   try {
stmt = con.createStatement();
CustResults = stmt.executeQuery(q);
while(CustResults.next())
{
h++;
}
   } catch (Exception ex) {
System.out.println("CustResults - nullcheck: "+ex.toString());
   }
try 
{
if (h==0)
{
flag2="resultsCount set zero while reading customer table";
resultsCount=0;
}
else
{
try {
CustResults = stmt.executeQuery(q);
} catch (Exception ex) {
System.out.println("problem executing query");
}
while(CustResults.next())
{
mainbuf.append("<controlGroup>\n");
mainbuf.append("<instances>\n");
mainbuf.append("<party>\n");
uid = CustResults.getString("uid");
uid = uid.trim();
mainbuf.append("<oid>"+uid+"</oid>\n");
startdate = CustResults.getString("startdate");
mainbuf.append("<creationDate>" + startdate + "</creationDate>\n");
encryptedUID = CustResults.getString("encryptedUID");
mainbuf.append("<properties>\n");
mainbuf.append("<property name=\"uid_\">" + uid + "</property>\n");
mainbuf.append("<property name=\"encryptedUID\">" + encryptedUID + "</property>\n");
 
[ ... AND SO ON. ]

[This message has been edited by Sanjay Anand (edited April 30, 2001).]

[David Freels]

Have you tried boosting the memory used by the VM? Try adding this command line switch -Xmx128m -Xms32m. These are only supported by Sun.
David
Sun Certified Programmer for the Java2 Platform

[Sanjay Anand]

Thanks for your reply. I've tried to do this but where do I do it? I am running this process in a servlet that sits on tomcat on the solaris platform. I've been through the documentation but am still thoroughly confused.
Any help would be appreciated.
Thanks
Sanjay

[balaji iyer]

Change the java startup command in tomcat.bat
------------------
Balaji Iyer,
System Architect,
Net4nuts.com
Ahmedabad
"If you want to make God Laugh, Tell HIM your plans !! "

[Jamie Robertson]

stmt = con.createStatement();
CustResults = stmt.executeQuery(q);
while(CustResults.next())
{
h++;
}
this code snippet looks like you are just counting. why don't you use the count function so you don't have to iterate through so many results? If your query is "select id, name from emp where name like 'something'", you can change it to:
[code]
stmt = con.createStatement();
CustResults = stmt.executeQuery("select count(*) from emp where name like 'something'");
if (CustResults.next())
{
h=CustResults.getInt(1);
}
else
{
....
[\code]
the above may save some time and memory
Jamie

[Sanjay Anand]

stmt = con.createStatement();
CustResults = stmt.executeQuery(q);
while(CustResults.next())
{
  h++;
}

Actually in this snippet I'm checking to see if the resultset is null or not. I've been told that the comparison:
if (CustResults.next())
actually moves the resultset cursor up one count and you therefore lose the first set of data. I have not confirmed this and simply started implementing the suggested solution of moving through the resultset twice.
It seems inelegant but it does work. Any other suggestions?
Thanks for the renewed attention to this topic. I have since cleaned up other parts of my code and actually moved to JRun rather than Tomcat and no longer have this problem
Sanjay

[Jamie Robertson]

Actually in this snippet I'm checking to see if the resultset is null or not. I've been told that the comparison:
if (CustResults.next())
actually moves the resultset cursor up one count and you therefore lose the first set of data. I have not confirmed this and simply started implementing the suggested solution of moving through the resultset twice.
It seems inelegant but it does work. Any other suggestions?
Thanks for the renewed attention to this topic. I have since cleaned up other parts of my code and actually moved to JRun rather than Tomcat and no longer have this problem
Sanjay[/B]

the following will do the same thing:

int h=0;
stmt = con.createStatement();
CustResults = stmt.executeQuery(q);
while(CustResults.next())
{  
mainbuf.append("\n");
mainbuf.append("\n");
mainbuf.append("\n");
uid = CustResults.getString("uid");
uid = uid.trim();
//...and so on
h++;
}
if (h==0)//no results were found
{
flag2="resultsCount set zero while reading customer table";
resultsCount=0;
}

the above works the same as the code that you have posted except it only loops through the resultset once.
Hope that speeds it up a bit,
Jamie

[Sanjay Anand]

Thanks, Jamie for the input. Your solution, however, throws a nullpointer exception when you try to get a null result from the result set and then append it to a StringBuffer. It was precisely this exception that sent me scrambling to check for null through comparison.
Sanjay