Activiti7 獲取當前任務節點出口連線（動態生成處理節點）
Activiti7 中 PVM，ActivitiImpl，PvmTransition ，ExecutionImpl, TransitionImpl 替代方法
通過閱讀官方文檔：
PVM classes
All classes from the org.activiti.engine.impl.pvm package (and subpackages) have been removed. This is because the PVM (Process Virtual Machine) model has been removed and replaced by a simpler and more lightweight model.
This means that usages of ActivitiImpl, ProcessDefinitionImpl, ExecutionImpl, TransitionImpl are invalid.
Generally, most of the usage of these classes in version 5 came down to getting information that was contained in the process definition. In version 6, all the process definition information can be found through the BpmnModel, which is a Java representation of the BPMN 2.0 XML for the process definition (enhanced to make certain operations and searches easier).
The quickest way to get the BpmnModel for a process definition is to use the org.activiti.engine.impl.util.ProcessDefinitionUtil class:
// The whole model
ProcessDefinitionUtil.getBpmnModel(String processDefinitionId);
// Only the specific process definition
ProcessDefinitionUtil.getProcess(String processDefinitionId);
大致是說：官方爲了輕量化，所以就把原來的PVM 流程引擎給優化了、
刪了後推薦我們獲取bpmnModel或者process來獲取模型的參數。
BpmnModel獲取方式可以使用官方推薦的，我這邊交互剛好只有taskId,就用這個做個demo；
// 獲取當前任務
Task task = taskService.createTaskQuery().taskId(taskId).singleResult();
//獲取當前模型
BpmnModel bpmnModel = repositoryService.getBpmnModel(task.getProcessDefinitionId());
// 獲取當前節點
FlowElement flowElement = bpmnModel.getFlowElement(task.getTaskDefinitionKey());
// 這裏不轉也有方法拿到，我這是爲了後人閱讀方便
UserTask userTask = (UserTask)flowElement;
//獲取節點出口線段
List<SequenceFlow> outgoingFlows = userTask.getOutgoingFlows();
// 我這邊暫時是解析expression 獲取條件和約定的值返回到前端構造button