jbpm 流程实例在从 db 获取 Workflowinstance 变量时抛出 NPE

Question

之前我在这里询问过 jBPM 的 ProcessInstanceInfo 和 WorkItemInfo
Need to know Class of a Byte Array saved in MySQL Database

现在我已将 jBPM 库集成到我的代码中，除了创建新的 ProcessInstance 之外，一切似乎都运行良好。
当我从已经构建的网站创建一个新的 processInstance 时，如果我从我的代码中完成一项任务，则工作流工作正常。但是，当我从我的代码中创建一个新的流程实例时，它在我这边运行良好，但在 Web 上抛出了一个 NullPointer。
我正在使用以下代码来创建新流程实例

    public Long startProject(ProjectDTO projectDto, UserDTO userInfo) {

    ApplicationContext context = new FileSystemXmlApplicationContext(
            ServletContextHolder.getContext().getRealPath("/WEB-INF")
                    + "/dispatcher-servlet.xml");
    SessionFactory sessionFactory = (SessionFactory) context
            .getBean("sessionFactory");

    UserinfoHBM userinfoHBM = new UserinfoHBM(sessionFactory);
    WorkflowHBM workflowHBM = new WorkflowHBM(sessionFactory);

    TemplateHBM templateHBM = new TemplateHBM(sessionFactory);
    Template template = templateHBM.getTemplateById(Integer
            .parseInt(projectDto.getTemplateId()));

    Map<String, Object> processData = new HashMap<String, Object>();

    processData.put("Initiator", userInfo.getUsername());
    UserInfo userInfoReq = userinfoHBM.getUserById(Integer
            .parseInt(userInfo.getRequester()));
    processData.put("Requester", userInfoReq.getFirst_name());
    List<String> requesterEmail = new ArrayList<String>();
    requesterEmail.add(userInfoReq.getEmail());
    processData.put("RequesterEmail", requesterEmail);
    UserInfo userInfoSup = userinfoHBM.getUserById(Integer
            .parseInt(userInfo.getSupplier()));
    processData.put("Supplier", userInfoSup.getFirst_name());
    List<String> supplierEmail = new ArrayList<String>();
    supplierEmail.add(userInfoSup.getEmail());
    processData.put("SupplierEmail", supplierEmail);
    UserInfo userInfoMan = userinfoHBM.getUserById(Integer
            .parseInt(userInfo.getManager()));
    processData.put("Manager", userInfoMan.getFirst_name());
    List<String> managerEmail = new ArrayList<String>();
    managerEmail.add(userInfoMan.getEmail());
    processData.put("ManagerEmail", managerEmail);
    List<String> initiatorEmail = new ArrayList<String>();
    initiatorEmail.add(userInfo.getEmail());

    processData.put("initiatorEmail", initiatorEmail);
    Workflow workflow = workflowHBM.getWorkflow(template.getWorkflow()
            .getWorkflow_id());

    Long processId = startProcess(workflow, processData,
            userInfo.getUsername(), projectDto.getName(),
            projectDto.getUniqueProjectRefId());

    return processId;

}

与

    public Long startProcess(Workflow workflow,
        Map<String, Object> processData, String userName,
        String project_name, String uniqueProRefNo) {
    // TODO Auto-generated method stub
    Long processId = new Long(0);
    try {
        Boolean status = false;
        Map<String, String> taskTypeMap = new HashMap<String, String>();
        Map<String, ProcessTaskData> processTaskDataMap = new HashMap<String, ProcessTaskData>();
        Map<String, WorkflowTask> workflowTaskMap = new HashMap<String, WorkflowTask>();
        for (WorkflowTask workflowTask : workflow.getWorkflow_taskList()) {
            ProcessTaskData processTaskData = new ProcessTaskData();
            processTaskData.setProjectName(project_name);
            processTaskData.setProjectUniNumber(uniqueProRefNo);
            processTaskData.setTaskType(workflowTask.getTask_type());

            processTaskData.setTaskId(workflowTask.getTask_id());

            // processTaskData.setAssign(" User/Group Name");
            processTaskData.setSubassign(workflowTask
                    .getDianamicAssimentGroup());

            taskTypeMap.put(workflowTask.getTask_name(),
                    workflowTask.getTask_type());

            if (workflowTask.getTask_type().equalsIgnoreCase("survey")) {
                List<String> email = new ArrayList<String>();
                email.add(workflowTask.getSendSurveyToemail());
                processTaskData.setSurveyEmail(email);
            }
            processTaskDataMap.put(workflowTask.getTask_name(),
                    processTaskData);

            if ("parallel".equalsIgnoreCase(workflowTask.getTask_Mode())) {

                workflowTaskMap.put(workflowTask.getTask_name(),
                        workflowTask);
            }
            if (workflowTask.getTask_type().equalsIgnoreCase("approve")) {
                status = true;
            }
            if (workflowTask.getTask_type().equalsIgnoreCase("survey")) {
                List<String> email = new ArrayList<String>();
                email.add(workflowTask.getSendSurveyToemail());
                processTaskData.setSurveyId(workflowTask.getSurveyForm()
                        .getSurve_from_Id());
                processTaskData.setSurveyEmail(email);
            }
            if (workflowTask.getTask_type().equalsIgnoreCase("email")) {
                List<String> email = new ArrayList<String>();
                // email.add();
                List<EmailListsItems> items = workflowTask
                        .getEmailListsItems();
                for (EmailListsItems e : items) {
                    email.add(e.getName());
                }
                processTaskData.setEmailList_EmailTask(email);
            }
            // workflowTaskMap

        }

        UserTransaction ut = (UserTransaction) new InitialContext()
                .lookup("java:comp/UserTransaction");
        ut.begin();

        StatefulKnowledgeSession ksession = JbpmAPIUtil.getSession();

        processData.put("workflowTaskMap", workflowTaskMap);
        processData.put("taskTypeMap", taskTypeMap);
        processData.put("formComments", new ArrayList<String>());
        processData.put("processTaskDataMap", processTaskDataMap);
        processData.put("rejectStatus", true);

        ProjectFormData projectFormData = new ProjectFormData();
        projectFormData.setProjectFormDataMap(new HashMap());
        projectFormData.setProjectFormTableMap(new HashMap());
        projectFormData.setProjectSurveyFormMap(new HashMap());

        processData.put("projectFormData", projectFormData);
        CommandBasedWSHumanTaskHandler taskHandler = new CommandBasedWSHumanTaskHandler(
                ksession);
        ksession.getWorkItemManager().registerWorkItemHandler("Human Task",
                taskHandler);

        /*
         * JPAWorkingMemoryDbLogger logger2 = new
         * JPAWorkingMemoryDbLogger(ksession);
         */

        ProcessInstance instance = ksession.startProcess(workflow
                .getWorkflow_name().replaceAll(" ", ""), processData);

        processId = instance.getId();

        /* logger2.dispose(); */

        ut.commit();
        // Thread.sleep(2000);

        while (status) {
            List<TaskSummary> taskSummaryList = JbpmAPIUtil
                    .getAssignedTasks(userName);
            for (TaskSummary taskSummary : taskSummaryList) {
                if (taskSummary.getName() == null) {
                    continue;
                }
                if (taskSummary.getName().equalsIgnoreCase("InitiatorTask")
                        && taskSummary.getProcessInstanceId() == processId) {
                    try {
                        JbpmAPIUtil
                                .completeTask(taskSummary.getId(),
                                        (Map) processData
                                                .get("projectFormDataMap"),
                                        userName);
                        status = false;
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    break;
                }
            }
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {

    }
    return processId;
}

当我执行此代码时，它运行良好，所有数据都插入到表中。 但是，当创建的进程访问 Web 面板时，它会在

处提供 NPE

ProjectFormData projectFormData=(ProjectFormData) process.getVariable("projectFormData");
System.out.println(projectFormData.getProjectFormDataMap()); <- NullPointer

我被困在这个地方好几天了:(
请大家帮帮我。

Answer 1

差异可能与事务划分的差异有关。更具体地说，只要一个流程实例在事务中处于活动状态，它就会“连接”到流程引擎，并且将始终保持最新并包含所有内部信息。事务完成后，流程实例将“断开连接”，并包含事务结束时的信息快照（充当 DTO）。

您从中获取“projectFormData”变量的流程实例似乎现在已断开连接，并且不包含该变量（可能是因为它已过时？）。

解决方案可能是： - 确保在此调用之前某处刷新断开连接的流程实例（使用 ksession.getProcessInstance(..) 以确保您拥有最新版本 - 确保在与您获取流程实例的同一事务中调用 getVariable(..)，因此它仍处于连接状态。

Answer 2

您正在获取此 NPE，因为您尝试获取的某些流程变量在 processinstanceinfo 表中不可用。 process.getVariable("projectFormData"); 现在返回 NULL 是因为它没有保存在流程变量中，可能是因为其他一些方法希望它成为某种填充对象，而不仅仅是新实例化的对象。