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From "Narayanaswamy, Mohan" <Mohan.Narayanasw...@in.standardchartered.com>
Subject RE: Tomcat & JDK upgrade
Date Wed, 17 Jan 2007 14:17:40 GMT

1. Since it is shared environment, we have to allow JDK1.5 features for
future applications - So We have to compile them against JDK1.5_b10 (We
don't like to run multiple Tomcat JVM as of now)

Can you share past experiences in migrating JDK1.4 to JDK1.5 - projects.

2. Yes, We came across few codes are written against specific parser,
trying to package those parsers along with web application.

Regards,
Mohan

-----Original Message-----
From: Peter Crowther [mailto:Peter.Crowther@melandra.com] 
Sent: Wednesday, January 17, 2007 4:40 PM
To: Tomcat Users List
Subject: RE: Tomcat & JDK upgrade

> From: Narayanaswamy, Mohan
> Questions 1) Is there any document or guidelines for migrating of web 
> applications using JDK1.4_2 to JDK1.5. I am searching Java sdn and 
> Java platform migration guide, but they are not really very useful 
> related to web application.
> 
> Couple of things I came across, Old code with enum as variable should 
> be refactored with different name and Comparable Interface in
> JDK1.5 is not
> compatible with JDK1.4_2 because of Generic. Also assumed that we need

> to change to exact type wherever we used java.lang.Object as variable 
> type. (Is Generics causing all the trouble, Generics going to be our 
> nightmare).
> 
> I am expecting some more guidelines like above (if possible migration 
> approach), Some of the open source project should have some 
> guidelines, but I am not able to grep it. Please help me by sending 
> the appropriate links.

Just a quick question: Do you plan to:

- Upgrade Tomcat but continue to run the same compiled webapps (still
compiled under 1.4 or with 1.4 compatibility turned on in a later
compiler), or

- Upgrade Tomcat and compile the webapps with the 1.5 compiler in 1.5
mode?

These are two different options.  If you are concerned about your
webapps not compiling under 1.5, you may wish to go with the first
option - at least while you migrate the Tomcat version!

> Questions 2) Is there anything I should carefully consider to migrate 
> from Tomcat/4.1.29-LE-jdk14 to Tomcat_5.5.20?

Library versions, especially those of the XML parser if you're using
that.  It's very easy to introduce dependencies on a specific XML parser
or parser version without intending to.

> Questions 3) Will I get any performance gain by the above migration?

There's been a lot of optimisation for 5.0 and 5.5.  You should expect
to see performance improvements in terms of memory use and request
overhead.  However, your webapp code is almost always the largest part
of any request's time and space cost, and Tomcat can't optimise that for
you!

		- Peter

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