From tomcat-user-return-87994-apmail-jakarta-tomcat-user-archive=jakarta.apache.org@jakarta.apache.org Fri Jan 02 20:22:23 2004
Return-Path: <tomcat-user-return-87994-apmail-jakarta-tomcat-user-archive=jakarta.apache.org@jakarta.apache.org>
Delivered-To: apmail-jakarta-tomcat-user-archive@www.apache.org
Received: (qmail 81482 invoked from network); 2 Jan 2004 20:22:23 -0000
Received: from daedalus.apache.org (HELO mail.apache.org) (208.185.179.12)
  by minotaur-2.apache.org with SMTP; 2 Jan 2004 20:22:23 -0000
Received: (qmail 94497 invoked by uid 500); 2 Jan 2004 20:21:53 -0000
Delivered-To: apmail-jakarta-tomcat-user-archive@jakarta.apache.org
Received: (qmail 94477 invoked by uid 500); 2 Jan 2004 20:21:53 -0000
Mailing-List: contact tomcat-user-help@jakarta.apache.org; run by ezmlm
Precedence: bulk
List-Unsubscribe: <mailto:tomcat-user-unsubscribe@jakarta.apache.org>
List-Subscribe: <mailto:tomcat-user-subscribe@jakarta.apache.org>
List-Help: <mailto:tomcat-user-help@jakarta.apache.org>
List-Post: <mailto:tomcat-user@jakarta.apache.org>
List-Id: "Tomcat Users List" <tomcat-user.jakarta.apache.org>
Reply-To: "Tomcat Users List" <tomcat-user@jakarta.apache.org>
Delivered-To: mailing list tomcat-user@jakarta.apache.org
Received: (qmail 94464 invoked from network); 2 Jan 2004 20:21:53 -0000
Received: from unknown (HELO mx.sh-solutions.de) (80.190.247.134)
  by daedalus.apache.org with SMTP; 2 Jan 2004 20:21:53 -0000
Received: from gb143.stw.stud.uni-saarland.de ([134.96.82.158] helo=shs1)
        by mx.sh-solutions.de with asmtp (Exim 4.30)
        id 1AcW4Q-0004dw-E3
        for tomcat-user@jakarta.apache.org; Fri, 02 Jan 2004 21:38:58 +0100
From: "SH Solutions" <info@sh-solutions.de>
To: "'Tomcat Users List'" <tomcat-user@jakarta.apache.org>
Subject: AW: what *really* happens when you reload or stop/start a webapp?
Date: Fri, 2 Jan 2004 21:24:40 +0100
MIME-Version: 1.0
Content-Type: text/plain;
        charset="US-ASCII"
Content-Transfer-Encoding: 7bit
X-Mailer: Microsoft Office Outlook, Build 11.0.5510
In-Reply-To: <bt4huh$asj$1@sea.gmane.org>
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.3790.0
Thread-Index: AcPRa8tb4+5NqzIsTQSYL27a25+7KQAAYdAg
X-Authenticated-Sender:*@sh-solutions.de
X-Spam-Rating: daedalus.apache.org 1.6.2 0/1000/N
X-Spam-Rating: minotaur-2.apache.org 1.6.2 0/1000/N

Hi

> No, this is just an example.  What I'd like to know is if stop/start or
reload has the same effect on a webapp as actually shutting down tomcat and
starting it back up.

When you stop an webapp, its classloader is discarded. Therefor every
information held by you classes is discarded.
Whey you restart an webapp, a new classloader is instantiated for that
webapp and every class is loaded from scratch. Static vars and such are
all-new.

Problems occur, if you pass references of you classes to elements outside
you classloader (in example by using shared libraries).
In that case, the classes referenced from outside your webapp cannot be
discarded due to javas typesafe pointers.
This might result in the existence of the same static variable in two
classloaders. Remember that these are two distinct variables.
Even worse, if you manage to get the reference in the old classloader from
the shared library it won't be even the same type as it was before since
Classes loaded from different classloaders are type-different.

Hence avoid to even try to find a way to make information persistent to
webapp reloads without writing them somewhere outside the VM.

HTH

Steffen


---------------------------------------------------------------------
To unsubscribe, e-mail: tomcat-user-unsubscribe@jakarta.apache.org
For additional commands, e-mail: tomcat-user-help@jakarta.apache.org