Download the JAR file from Maven Central.
If you have a WAR file you can use the command line below:
java -jar piranha-micro.jar --war your_webapplication.war
If you have an exploded directory containing the contents of your WAR file you can use the command line below:
java -jar piranha-micro.jar --webapp your_webapp_directory
If you want to use a different HTTP port (e.g to port 8888) you can use --port as illustrated by the command line below:
java -jar piranha-micro.jar --war your_webapplication.war --port 8888
See GitHub at https://github.com/piranhacloud/piranha/tree/master/micro