Hi Jing,
That's right.. jbpm5 is flexible enough to provide you that behavior too. Take a look at this tests:
https://github.com/Salaboy/Drools_jBPM5-Training-Examples/blob/master/jbpm5/01-jBPM5-SimpleEmergencyServiceProcess/src/test/java/com/wordpress/salaboy/examples/SimpleEmergencyProcessTest.java
More specifically the test called: reactiveProcessAndRulesTest ()
It uses the engine in reactive mode calling the fireUntilHalt() method.
Hope it helps!
Greetings