Java support defaults to Tomcat 8
Change effective on 16 July 2015
Heroku’s Java Support has upgraded the default Tomcat container to version 8. This container is used by the heroku-deploy toolbelt plugin and the heroku-maven-plugin.
To acquire the new version, you can deploy with the toolbelt:
$ heroku deploy:war --war <path_to_war_file> --app <app_name>
Or you can revert to Tomcat 7 by adding the --webapp-runner param:
$ heroku deploy:war --war <path_to_war_file> --app <app_name> --webapp-runner 7.0.57.2
For more information on Tomcat 8, see the Apache Tomcat documentation. For more information on Tomcat webapp-runner, the Tomcat container used by Heroku, see the Dev Center article on Deploying Tomcat-based Java Web Applications with Webapp Runner.