Dropwizard + gradle + heroku

Note: all source code is available at https://github.com/nilsmagnus/gradledwheroku

Since the gradle build pack for heroku is still in beta, it is sometimes not straight forward to use gradle with heroku. This is how I did it with gradle, dropwizard and heroku.

• Use gradle wrapper, the built in gradle in heroku is still using version 1.0-beta or something. When you use the wrapper, you decide the gradle version yourself. 
• Use the gradle application plugin
• For some reason, you must have the dropwizard as a submodule in your gradle project.
• When deploying the app to heroku, you must tell the app to use the $PORT specified by heroku to listen to http traffic. You set this configuration by setting the WEBAPP_OPTS variable on heroku. This variable is used by the gradle application plugin when launching your java app. The value might vary, depending on your conf.yaml-file. 

heroku config:set WEBAPP_OPTS-Ddw.server.applicationConnectors[0].port='$PORT'

• The Procfile must point to the shell script generated by the application plugin and the arguments for your application

web: webapp/build/install/webapp/bin/webapp server conf.yaml

• The dropwizard application itself does not need to have any special config to run on heroku. You can even connect to a mongodb hosted at mongolab without any problems. 

If you want a working starting point for your application, have a look at my github project https://github.com/nilsmagnus/gradledwheroku which is "heroku-ready". Clone it, change it, make it your own and deploy to heroku.