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From "Paul" <p...@msci.ca>
Subject Re: Memory leaks?
Date Wed, 03 Sep 2003 19:27:48 GMT
Docs indicate that leaving a stmt or rs object open can cause memory leaks.
Found the following in the tomcat docs somewhere, i think:

Here is an example of properly written code to use a db connection obtained
from a connection pool:

  Connection conn = null;
  Statement stmt = null;  // Or PreparedStatement if needed
  ResultSet rs = null;
  try {
    conn = ... get connection from connection pool ...
    stmt = conn.createStatement("select ...");
    rs = stmt.executeQuery();
    ... iterate through the result set ...
    rs.close();
    rs = null;
    stmt.close();
    stmt = null;
    conn.close(); // Return to connection pool
    conn = null;  // Make sure we don't close it twice
  } catch (SQLException e) {
    ... deal with errors ...
  } finally {
    // Always make sure result sets and statements are closed,
    // and the connection is returned to the pool
    if (rs != null) {
      try { rs.close(); } catch (SQLException e) { ; }
      rs = null;
    }
    if (stmt != null) {
      try { stmt.close(); } catch (SQLException e) { ; }
      stmt = null;
    }
    if (conn != null) {
      try { conn.close(); } catch (SQLException e) { ; }
      conn = null;
    }
  }



----- Original Message ----- 
From: "Jim Lynch" <jwl@sgi.com>
To: "tomcat" <tomcat-user@jakarta.apache.org>
Sent: Wednesday, September 03, 2003 12:56 PM
Subject: Memory leaks?


> I seemed to have read that java/tomcat isn't supposed to have memory
> leaks, but something seems to be running me out of memory and I don't
> know what.
>
> After a number of edit/undeploy/compile/deploy iterations I get the
> following:
>
> javax.servlet.ServletException: Servlet execution threw an exception
> at
>
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Application
FilterChain.java:269)
> at
>
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterCh
ain.java:193)
>
> (Big snip)
>
>
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConne
ction(Http11Protocol.java:392)
> at
> org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:565)
> at
>
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.jav
a:619)
> at java.lang.Thread.run(Thread.java:536)
>
> root cause
>
> java.lang.OutOfMemoryError
>
> I'm running tomcat 4.1.24 on Linux with Apache 1.something.  Java
> 1.4.1_02.
>
> So where do I start looking for the problem?  If I forget to close
> Statements would that cause the problem?
>
> Thanks,
> Jim.
>
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