@Override
	public void destroy() {
		shutdownServer();
	}
On UNIX operating systems, return the number of open file descriptors. On non UNIX operating systems this returns
-1.

@return number of open file descriptors if this is executing on a UNIX operating system
spring-xd-batch/src/main/java/org/springframework/xd/batch/hsqldb/server/HSQLServerBean.java