I have a simple webapplication deployed (using WAR) on tomcat and running on my machine.
Now I want to replace some existing java (.class) files with updated ones.
Can anybody please tell me how to do this as I don't want to deploy an updated WAR again.
Actually I don't want to replace/update the WAR file but want to update the running application by replacing some of the .class files in the standard extracted folder structure. Just like deploying a patch.
Are you asking how to do this without restarting the web app? That's quite tricky to pull off; you'd need to pay close attention to classloading details. If this was my problem, I'd look into using OSGi for this.
1. Cut and paste the existing WAR file from webapps to some other location.
2. Stop the tomcat.
3. Replace the existing class files with the updated ones in application folder structure in webapps.
4. Restart the tomcat.
Now running application will reflect the updated functionality.
If you are going to stop and restart the server, why not just build and redeploy the whole war? That's the reason for war files in the first place. Picking and choosing files to update by hand sounds like a recipe for disaster to me.
Your point is very genuine but what you will do if due to some reason you are not able to make a WAR and there is time constraint to update the running application.
Actually I was looking for a solution, for this scenario.
Unless the war file is huge my guess would be that the Tomcat startup time likely dwarfs the time it takes to unpack the war file.
But if time is of the essence -for some reason that you haven't told us about-, then you should look into the solution I mentioned before; use OSGI to bundle the classes you may wish to update, and then stop that bundle and start the new one at runtime. No need to restart Tomcat, or even the web app itself!
