GoCD recently added support for notification extension point. I've started building slack notification plugin (its a WIP here). As part of that I wrote a Java client for Slack Webhooks. Although I found a java library here, which said it was published but I couldn't find it anywhere on sonatype / maven central. I can't even publish it, so I took that as an inspiration and wrote my own implementation on https://github.com/ashwanthkumar/slack-java-webhook.
Usage
new Slack(webhookUrl) .icon(":smiling_imp:") // Ref - http://www.emoji-cheat-sheet.com/ .sendToUser("slackbot") .displayName("slack-java-client") .push(new SlackMessage("Text from my ").bold("Slack-Java-Client"));
It gets posted in the slack channel like below
Dependencies
For Maven,
<dependency>
<groupId>in.ashwanthkumar</groupId>
<artifactId>slack-java-webhook</artifactId>
<version>0.0.3</version>
</dependency>
For SBT,
libraryDependencies += "in.ashwanthkumar" % "slack-java-webhook" % "0.0.3"