Activiti工作流引擎使用 http://www.open-open.com/lib/view/open1350460225367.html
Activiti初学者教程 http://blog.csdn.net/bluejoe2000/article/details/39521405
基于Snaker的三种流程案例(选择分支，任务并行，会签) http://dead-knight.iteye.com/blog/1978302
http://www.open-open.com/doc/view/8eef73d3517442fcbc6a1508edabbc50
Activiti 官方文档 http://www.activiti.org/userguide/index.html#_getting_started_10_minute_tutorial