Docker tomcat edit expanded war files

Question

I am using docker to deploy a tomcat container running a third party war file.

My Dockerfile looks something like this

FROM tomcat:7-jre8

ADD my.war ${CATALINA_HOME}/webapps/my.war 

When I run the container tomcat expands my war at runtime and I can happily access my app at http://my.ip.addr:8080/mywar/.

However my problem is that I want to edit a couple of the config files within the war. I don't really want to unpack and repack the war file as that seems messy and hard to maintain.

I was hoping to be able to tell tomcat to expand the war as part of my RUN steps and then use ADD to put in my custom files but I can't seem to find a way of doing this. The war only gets expanded when the CMD executes and then I can't edit the files after that.

Answer 1

I am not sure exactly how you would achieve it with docker or anything else, as i dont see anyway to ask tomcat to just expand the war before it actually starts. But as per standard practices its not a good idea to explode a war and tweak the contents. It kills the entire purpose of making a war.

Rather you should make changes to the app to read configuration from << TOMCAT_HOME >>/conf.

If you achieve this the only thing you will need to tell Docker is to ADD your configuration file to the containers tomcat conf folder.

Or if it is a must for you to tamper with war file this is what you can do: Explode the war manually (or by script) on your build machine and instead of adding war directly to the docker image, map the folder. Something like this

ADD ./target/app-0.1.0.BUILD-SNAPSHOT /var/lib/jetty/webapps/ROOT.

And then manually add all your files to desired destinations.

ADD login.jsp /var/lib/jetty/webapps/ROOT/Webapps, so on and so forth.

Answer 2

How about unzipping your war manually, before starting tomcat?

ADD my.war /tmp/my.war 
RUN unzip /tmp/my.war -d /usr/local/tomcat/webapps/mywar

# Edit config files

# Now you can start tomcat...
CMD ["catalina.sh", "run"]