Oracle REST Data Services has a plugin programming model which allows for an incredible degree of extensibility in the product. The Getting Started guide provides a walk through of creating a plugin to add custom functionality. After developing the plugin, the key command to add it to ORDS is:
java -jar ords.war plugin built/plugin-demo.jar
From time to time, it may be necessary to remove the custom jar. There is not a specific command in ORDS to do that but there is an option with ZIP at the command line. In this case, the plugin-demo.jar is packaged in the ords.war at WEB-INF\lib so unplugging it is as simple as this on Windows:
zip -d ords.war WEB-INF\lib\plugin-demo.jar
On Linux or Mac, that would be:
zip -d ords.war WEB-INF/lib/plugin-demo.jar
It really is that easy.