Actually, the best way might be to "touch" the war file, or the web.xml file if you are using exploded deployment.
If I recall correctly, the mbean that controls the deployment of the war, if you call the stop() operation then the app gets undeployed, meaning the war is removed form the deploy directory. So you have to copy the war back into that directory. (It has been a while since I tried this so my memory of the exact series of event might not be accurate.) But if you want to try it, run the jmx console and look for mbeans that contain the war file name (but not any of the servlet or jsp names). One of those mbeans will have the lifecycle methods (start/stop/etc).