dear all:
Human task server requires all users and groups to be predefined before trying to assign a task to that user or group.
So you need to make sure you add the necessary users and group to the database using the taskSession.addUser(user) and taskSession.addGroup(group) methods.
In persistence.xml there is "org.jbpm.task.User",is the users stored in table User? why after I run the human task server, there is no table User in database jbpm?