Commons Daemon, formerly known as JSVC, is a Java software library belonging to the Apache Commons Project.

Daemon provides a portable means of starting and stopping a Java Virtual Machine (JVM) that is running server-side applications.

For example, the servlet container Tomcat 4 would need to serialize sessions and shutdown web applications before the JVM process terminates.

Daemon comprises 2 parts: a native library written in C that interfaces with the operating system, and the library that provides the Daemon API, written in Java.

For example, Tomcat-4.1.x uses the daemon interface and Tomcat-5.0.x provides a class whose methods are called by JSVC directly.