How can I deploy web app on Tomcat from running app.

Question

I would like to develop updater app. Lets say I've got:
- Running Tomcat
- Running Updater App on the Tomcat
- Running old version of the app on the same Tomcat

I would like to
- Stop old app
- Undeploy old app
- Deploy new version of app (lets assume that I've got new app war file somewere in Updater app resourcess.

Is it possible to do such remote deployment on Tomcat from another app at all?

Answer 1

Yes. There's a set of tools (well, a .jar) released with Tomcat that's usually used by ant but that can be used by anyone willing to call the code. There are tasks for starting and stopping applications, deploying, undeploying, listing applications and so forth; essentially it's an API that wraps the functionality of the manager servlet.

One moment while I try to dig up the name or a link for you...

Here's Apache's information on this stuff: http://tomcat.apache.org/tomcat-5.5-doc/manager-howto.html#Executing Manager Commands With Ant

... and here's a user, elsewhere, describing in detail how he uses these tasks: http://raibledesigns.com/wiki/Wiki.jsp?page=TomcatAntTasks

You may object that you're not ant. That's true, but there's nothing magic about ant, it's just calling code inside the jar. That code can be called from anywhere else that follows the API.

Here's a tutorial on writing ant tasks: http://ant.apache.org/manual/tutorial-writing-tasks.html

Not quite the same, but it should give you an idea of how the API works.

I see no reason why you shouldn't be able to call this API from within a servlet if you want to.

Alternatively, you could run the manager servlet in your Tomcat and simply access the manager application like a Web service: Use your browser or WireShark to snoop on the traffic between your browser and Tomcat when you deploy an app, and then duplicate that to remote control manager. Me, I think using the tools jar is simpler.

Answer 2

If you use a "project lifecycle" tool, this undeploy/deploy can be automatized in the development cycle.

Saying that, I think about Maven2 and his "maven-deploy" plugin :

• mvn compile : java compilation
• mvn package : creation of the war file (for a webbapp project)
• mvn deploy : stop, undeploy the old application, deploy and start the new version !

After, you can couple this automatization with a continous integration server (like Hudson).