Activiti获取某个流程实例的FormKey

通过任务id获得formkey

ProcessDefinitionEntity -->TaskDefinition -->DefaultFormHandler -->Expression.getExpressionText() 

用处是用户点击办理任务时可以跳出业务信息的页面，而页面的位置则存放在对应节点的form key中。

HistoricTaskInstance -->ProcessDefinitionEntity -->TaskDefinition-->DefaultFormHandler -->Expression -->Expression.getExpressionText() ;

当前任务是同时存在 ACT_RU_TASK 和 ACT_HI_TASKINST

/**
	 * 
	 *  @CreateUser:xxxx
	 *  @ReturnType:String
	 *  @param taskId
	 *  @param businessEventId
	 *  @return
	 *  @CreateDate:2014-6-10下午7:49:32
	 *  @UseFor    :根据任务id获得form key值
	 */
	public String getBusinessInfoUrl(String taskId, String businessEventId) {
		String url = "";
		String businessKey = "";
		// 获得任务对象
		HistoricTaskInstance taskInstance = (HistoricTaskInstance) historyService
				.createHistoricTaskInstanceQuery().taskId(taskId)
				.singleResult();
		// 判断当前任务Task是否为空
		if (taskInstance != null) {
			url = getTaskFormData(taskId);
			if (url == null || "".equals(url)) {
				String processDefinitionId = taskInstance.getProcessDefinitionId();
				url = getProcessDefinitionFormData(processDefinitionId);
			}
			// 业务id 即eventid
			businessKey = ((HistoricProcessInstance) historyService
					.createHistoricProcessInstanceQuery()
					.processInstanceId(task.getProcessInstanceId())
					.singleResult()).getBusinessKey();
		} else {
			HistoricProcessInstance historicProcessInstance = (HistoricProcessInstance) historyService
					.createHistoricProcessInstanceQuery()
					.processInstanceBusinessKey(businessEventId).singleResult();
			if (historicProcessInstance != null) {
				url = getProcessDefinitionFormData(historicProcessInstance
						.getProcessDefinitionId());
				businessKey = businessEventId;
			}
		}
		// 拼接URL 把eventid接到url上面 url的格式是 xx.htm?eventid=
		return (new StringBuilder(String.valueOf(url))).append(businessKey)
				.toString();
	}
 /**
	 * 
	 *  @CreateUser:xxxx
	 *  @ReturnType:String
	 *  @param taskId
	 *  @return
	 *  @CreateDate:2014-6-10下午5:21:27
	 *  @UseFor    :根据任务iD获得form Key 值
	 */
	private String getTaskFormData(String taskId) {
		//表单key值
		String formkey = "";
		//获取需查询的任务实例
		HistoricTaskInstance task = (HistoricTaskInstance) historyService
				.createHistoricTaskInstanceQuery().taskId(taskId)
				.singleResult();
		//获取流程定义对象
		ProcessDefinitionEntity processDefinition = getProcessDefinitionEntityByProcessDefinitionId(task
				.getProcessDefinitionId());
		
		TaskDefinition taskDefinition = (TaskDefinition) processDefinition
				.getTaskDefinitions().get(task.getTaskDefinitionKey());
		DefaultFormHandler defaultFormHandler = (DefaultFormHandler) taskDefinition
				.getTaskFormHandler();
		Expression expression = defaultFormHandler.getFormKey();
		if (expression != null)
			formkey = expression.getExpressionText();
		return formkey;
	}

	/**
	 * 
	 *  @CreateUser:xxxx
	 *  @ReturnType:ProcessDefinitionEntity
	 *  @param processDefinitionId
	 *  @return
	 *  @CreateDate:2014-12-10下午7:39:01
	 *  @UseFor    :获得 ProcessDefinitionEntity
	 */
	private ProcessDefinitionEntity getProcessDefinitionEntityByProcessDefinitionId(
			String processDefinitionId) {
		ProcessDefinitionEntity processDefinitionEntity = (ProcessDefinitionEntity) ((RepositoryServiceImpl) repositoryService)
				.getDeployedProcessDefinition(processDefinitionId);
		return processDefinitionEntity;
	}

	/**
	 * 
	 *  @CreateUser:xxxx
	 *  @ReturnType:String
	 *  @param processDefinitionId
	 *  @return
	 *  @CreateDate:2014-12-10下午7:38:46
	 *  @UseFor    :获得第一个节点的Form key
	 */
	private String getProcessDefinitionFormData(String processDefinitionId) {
		StartFormData startFormData = formService
				.getStartFormData(processDefinitionId);
		return startFormData.getFormKey();
	}