Apache Commons Exec is a library to reliably execute external processes from within the JVM.
Spring Roo Runtime Process Manager
A lightweight library to execute external processes from Java.
An API for creating custom processes/operations plus a collection of pre-written processes including vector/raster conversion.
JBPM Console NG Process Runtime API
A embedded process starter ...
JBPM Workbench Process Runtime API
Processes for handling of features and feature collections.