Opinions on migration to Java EE

[patricia.joyces]

Hi there,
I want to get your opinion on this. I have a web application that runs
on Tomcat. This has been running smoothly for a number of years. I
would like to migrate this web application to Java EE platform, to be
hosted on an app server like Oracle App Server or any other products.
If you have done this before, can you please share your migration
experiences, like what to look out for, migraton steps, information
links, etc. Any help would be appreciated. Thanks.

 

[Arne Vajhøj]

I want to get your opinion on this. I have a web application that runs
on Tomcat. This has been running smoothly for a number of years. I
would like to migrate this web application to Java EE platform, to be
hosted on an app server like Oracle App Server or any other products.
If you have done this before, can you please share your migration
experiences, like what to look out for, migraton steps, information
links, etc.

An app running on Tomcat is a Java EE app.

Tomcat only support the web part of Java EE, but Oracle AS
supports everything including EJB's.

But your app should run unchanged on Oracle AS.

If you don't change you app, then your will obviously
not utilize the features Oracle AS has that Tomcat does not.

Arne

 

[Arved Sandstrom]

Hi there,
I want to get your opinion on this. I have a web application that runs
on Tomcat. This has been running smoothly for a number of years. I
would like to migrate this web application to Java EE platform, to be
hosted on an app server like Oracle App Server or any other products.
If you have done this before, can you please share your migration
experiences, like what to look out for, migraton steps, information
links, etc. Any help would be appreciated. Thanks.

From the pure functionality viewpoint, an obvious early step is to make sure
that app server X supports the Java language version and the J2EE API
versions you are using.

Be prepared to play with libraries. If you are using Apache XML libraries in
your Tomcat webapp, you may want to stick with them, for example. I brought
this one up because evidently quite a few people have had problems in this
area with OAS. See
http://www.oracle.com/technology/tech/java/oc4j/1013/how_to/how-to-swapxmlparser/doc/readme.html
for OAS; whether or not this is applicable will depend on OC4J version.

There may be similar issues with any server -> other server migration. In a
perfect world libraries written to certain APIs are cleanly swappable - in
the real world they are not. Part of the reason is partial support or
differing interpretations of the APIs.

Other things to look out for, particularly with an older application. One,
use of server-specific APIs to make up for stuff that J2EE didn't do at the
time, or wasn't standardized. Two, non-portable code (things like embedded
references). Non-portable code may come about because of use of vendor APIs
or how you use J2EE APIs (like JDBC).

Look at what you needed to configure on Tomcat - usernames/passwords/roles
etc, JNDI, JDBC, you name it - and figure out how that'll be done on the
target server.

Last but not least, other people have done it before. Googling will dredge
up posts regarding specific issues you run into, and the odds are also
pretty good that there will be a migration guide or guides (sometimes as
specific as Server A to Server B).

Arne and Lew are quite correct insofar as this may be fairly painless. But I
wouldn't go telling your boss that you'll be done with the migration in a
couple of hours either.

AHS

 

[Robert Klemme]

Hi there,
I want to get your opinion on this. I have a web application that runs
on Tomcat. This has been running smoothly for a number of years. I
would like to migrate this web application to Java EE platform, to be
hosted on an app server like Oracle App Server or any other products.
If you have done this before, can you please share your migration
experiences, like what to look out for, migraton steps, information
links, etc. Any help would be appreciated. Thanks.

Why do you want to do this? Why change a system that apparently works
as expected? You give no indication why you intend to migrate to Java
EE (which, in a way, you are using already as has been pointed out) so
for the time being I'd say, don't do it.

Cheers

robert

 

[Markus Tazl]

Hi there,
I want to get your opinion on this. I have a web application that runs
on Tomcat. This has been running smoothly for a number of years. I
would like to migrate this web application to Java EE platform, to be
hosted on an app server like Oracle App Server or any other products.
If you have done this before, can you please share your migration
experiences, like what to look out for, migraton steps, information
links, etc. Any help would be appreciated. Thanks.

Hi Particia,

i'm curious about why you want to do this ? Any additional
requirements you can't meet using Tomcat ?

Anyway, i use Oracle IAS / OC4J and Tomcat 5.x. in my projects and i
also did some migration work in both directions. As Arved mentioned
there might be some minor pitfalls regarding libraries, JNDI and so
on. Migration from Tomcat to OC4J should be more or less painless.
On technet / Oracle online documentation there are some hints, you can
find "Oracle® Containers for J2EE Servlet Developer's Guide" /
"Migrating an Application from Apache Tomcat to OC4J" here :
http://download.oracle.com/docs/cd/B32110_01/web.1013/b28959/develop.htm#CHDFJJDA

best regards
Markus Tazl

 

[Arne Vajhøj]

Why do you want to do this? Why change a system that apparently works
as expected? You give no indication why you intend to migrate to Java
EE (which, in a way, you are using already as has been pointed out) so
for the time being I'd say, don't do it.

One reason could be server consolidation.

He can run the Tomcat apps at Oracle AS. He can probably not run
the Oracle AS apps on Tomcat.

Arne

 

[Abhijat Vatsyayan]

Hi there,
I want to get your opinion on this. I have a web application that runs
on Tomcat. This has been running smoothly for a number of years. I
would like to migrate this web application to Java EE platform, to be
hosted on an app server like Oracle App Server or any other products.
If you have done this before, can you please share your migration
experiences, like what to look out for, migraton steps, information
links, etc. Any help would be appreciated. Thanks.

In addition to ensuring things like not using app server specific
libraries and ensuring that the server supports the specification
versions you are using,

* developers sometimes make subtle assumptions about where and what kind
of environment the code is running in. For example, (an incorrect?) use
of meta information to figure out system paths, loading property files
and doing funky ("the so called clever") things with the classloading
can create problems so you want to review your code for resource and
class loading code.
* If you are not already running in a clustered environment, you could
have code for accessing file system which may not work in a different
app server. So you want to do a code review for file system access as well.
* Security (specially authentication and authorization) plugins can be
very different although you should be OK if you are using JAAS.
* Using MBeans in tomcat could also be a bit of a problem.

Abhijat