Hi HuiSheng,
It seems that there has been a workaround developed for this exact issue. Perhaps you have seen it before. It is located here: http://diversit.eu/2010/01/10/jbpm-4-3-with-spring/
Why this was never incorporated as a patch instead of creating some side project is beside me. But I would love to see something like this make it into jBPM 4.4 so that we could upgrade our production environment.