1. Activiti API and Services

引擎API是我们与Activiti交互的最常用方式。在activiti中，ProcessEngine作为中心起始点，可以从中获取很多囊括工作流/BPM 方法的服务(Services)。ProcessEngine和服务类都是线程安全的，所以建议在整个项目中仅保持它们的一个引用即可：

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();
DynamicBpmnService dynamicBpmnService = processEngine.getDynamicBpmnService();

上图中的服务类是Activiti API的核心，各个类的概要说明如下：