activiti的API中，最终要的一个接口就是ProcessEngine,获取到ProcessEngine的实例，就获取了activiti体系中的所有api。重要的接口如下：
ProcessEngine processEngine = ProcessEngines.getDefaultProcessEngine(); RuntimeService runtimeService = processEngine.getRuntimeService(); RepositoryService repositoryService = processEngine.getRepositoryService(); TaskService taskService = processEngine.getTaskService(); ManagementService managementService = processEngine.getManagementService(); IdentityService identityService = processEngine.getIdentityService(); HistoryService historyService = processEngine.getHistoryService(); FormService formService = processEngine.getFormService();
原文：http://www.cnblogs.com/wujinsen/p/4580202.html