Activiti - 任务回退到上一步

package com.studio.util;import java.util.ArrayList;import java.util.List;import java.util.Map;import org.activiti.engine.HistoryService;import org.activiti.engine.IdentityService;import org.activiti.engine.ProcessEngine;import org.activiti.engine.ProcessEngines;import org.activiti.engine.RepositoryService;import org.activiti.engine.RuntimeService;import org.activiti.engine.TaskService;import org.activiti.engine.history.HistoricTaskInstance;import org.activiti.engine.identity.Group;import org.activiti.engine.identity.User;import org.activiti.engine.impl.persistence.entity.ProcessDefinitionEntity;import org.activiti.engine.impl.pvm.PvmActivity;import org.activiti.engine.impl.pvm.PvmTransition;import org.activiti.engine.impl.pvm.process.ActivityImpl;import org.activiti.engine.impl.pvm.process.ProcessDefinitionImpl;import org.activiti.engine.impl.pvm.process.TransitionImpl;import org.activiti.engine.runtime.ProcessInstance;import org.activiti.engine.task.Task;public class ActivitiUtil {private static ProcessEngine processEngine = ProcessEngines.getDefaultProcessEngine();private static  IdentityService  identityService = processEngine.getIdentityService();private static RuntimeService runtimeService = processEngine.getRuntimeService();        private static TaskService taskService = processEngine.getTaskService();        private static RepositoryService repositoryService = processEngine.getRepositoryService();        private static HistoryService historyService = processEngine.getHistoryService();public static void TaskRollBack(String taskId){    try {            Map<String, Object> variables;            // 取得当前任务            HistoricTaskInstance currTask = historyService                    .createHistoricTaskInstanceQuery().taskId(taskId)                    .singleResult();            // 取得流程实例            ProcessInstance instance = runtimeService                    .createProcessInstanceQuery()                    .processInstanceId(currTask.getProcessInstanceId())                    .singleResult();            if (instance == null) {                               //流程结束            }            variables = instance.getProcessVariables();            // 取得流程定义            ProcessDefinitionEntity definition = (ProcessDefinitionEntity) (processEngine.getRepositoryService().getProcessDefinition(currTask                            .getProcessDefinitionId()));                       if (definition == null) {                               //log.error("流程定义未找到");                return ;            }            // 取得上一步活动            ActivityImpl currActivity = ((ProcessDefinitionImpl) definition)                    .findActivity(currTask.getTaskDefinitionKey());            List<PvmTransition> nextTransitionList = currActivity                    .getIncomingTransitions();            // 清除当前活动的出口            List<PvmTransition> oriPvmTransitionList = new ArrayList<PvmTransition>();            List<PvmTransition> pvmTransitionList = currActivity                    .getOutgoingTransitions();            for (PvmTransition pvmTransition : pvmTransitionList) {                oriPvmTransitionList.add(pvmTransition);            }            pvmTransitionList.clear();             // 建立新出口            List<TransitionImpl> newTransitions = new ArrayList<TransitionImpl>();            for (PvmTransition nextTransition : nextTransitionList) {                PvmActivity nextActivity = nextTransition.getSource();                ActivityImpl nextActivityImpl = ((ProcessDefinitionImpl) definition)                        .findActivity(nextActivity.getId());                TransitionImpl newTransition = currActivity                        .createOutgoingTransition();                newTransition.setDestination(nextActivityImpl);                newTransitions.add(newTransition);            }            // 完成任务            List<Task> tasks = taskService.createTaskQuery()                    .processInstanceId(instance.getId())                    .taskDefinitionKey(currTask.getTaskDefinitionKey()).list();            for (Task task : tasks) {                taskService.complete(task.getId(), variables);                historyService.deleteHistoricTaskInstance(task.getId());            }            // 恢复方向            for (TransitionImpl transitionImpl : newTransitions) {                currActivity.getOutgoingTransitions().remove(transitionImpl);            }            for (PvmTransition pvmTransition : oriPvmTransitionList) {                pvmTransitionList.add(pvmTransition);            }                       return ;        } catch (Exception e) {                       return ;        }}}