This standalone Spring Boot application will relay messages from a Gitter chat room to a Slack webhook. Its purpose is to unify the platforms so that if you have a Slack channel open all day, you can receive notifications of chat messages from a Gitter chat that you use for public support, without having to have the Gitter application or web page open in addition to Slack.
To use it, you must have some CLI parameters set. You need --gitter.token and --gitter.roomId options and a --slack.webhookUrl option. The former should be set to your Gitter token that will be used to set the Authorization: Bearer header as well as the unique room ID of your chat room on Gitter and the latter will be used as the Slack webhook URL to which a formatted message will be POSTed when a Gitter message is received.
The Relay is a plain Spring Boot application. You run it just like any other. To generate the single, executable jar file:
> ./gradlew bootRepackage
Then to run the app:
> java -jar build/libs/gitter-slack-relay-0.0.1-SNAPSHOT.jar --gitter.token=GITTER_TOKEN --gitter.roomId=GITTER_ROOM --slack.webhookUrl=SLACK_WEBHOOK