flowable/flowable-engine · error · FlowableObjectNotFoundException

Cannot find task with id

Error message

Cannot find task with id

What it means

CreateAttachmentCmd.verifyTaskParameters looks up the task by taskId via the task service; when no task exists with that id it throws FlowableObjectNotFoundException with the task class. This guards referential integrity of attachments: they must attach to a real task.

Solutions

  1. Fetch the task first (taskService.createTaskQuery().taskId(taskId).singleResult()) and only create the attachment if it is non-null.
  2. Correct the taskId source; ensure the id passed is the persistent task id (String) not a business key.
  3. Catch FlowableObjectNotFoundException and handle as a business 'task no longer exists' case if the task may legitimately disappear.

Example fix

// before
taskService.createAttachment(null, taskId, processInstanceId, name, description, url);
// after
Task task = taskService.createTaskQuery().taskId(taskId).singleResult();
if (task == null) {
    throw new IllegalArgumentException("Unknown taskId: " + taskId);
}
taskService.createAttachment(null, taskId, task.getProcessInstanceId(), name, description, url);
Defensive patterns

Strategy: validation

Validate before calling

Task task = taskService.createTaskQuery().taskId(taskId).singleResult();
if (task == null) {
    throw new IllegalArgumentException("Task does not exist: " + taskId);
}

Try / catch

try {
    taskService.createAttachment(null, taskId, pid, name, desc, url);
} catch (FlowableObjectNotFoundException e) {
    log.warn("Task vanished before attachment: {}", taskId);
}

Prevention

When it happens

Trigger: Calling TaskService.createAttachment(...) with a taskId that does not match any task in the database (typo, already-deleted task, attachment created after the task/completed-and-removed task, wrong data source).

Common situations: Stale task ids held by a client after the task was completed and historic data cleaned; copy-pasted ids between test and prod databases; creating attachments in an async job after the task was deleted.

Understand the failure class

Background: "Not found" and "does not exist" errors: why "Task not found", "No such folder", and "Can't find" fire when a lookup comes back empty — this error's family across 14 libraries.

Related errors

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/9cde2bbcc1c67aa8. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-engine/src/main/java/org/flowable/engine/impl/cmd/CreateAttachmentCmd.java:143

                    processDefinitionId = process.getProcessDefinitionId();
                }
            }

            eventDispatcher.dispatchEvent(FlowableEventBuilder.createEntityEvent(FlowableEngineEventType.ENTITY_CREATED, attachment, 
                    processInstanceId, processInstanceId, processDefinitionId), processEngineConfiguration.getEngineCfgKey());
            eventDispatcher.dispatchEvent(FlowableEventBuilder.createEntityEvent(FlowableEngineEventType.ENTITY_INITIALIZED, attachment, 
                    processInstanceId, processInstanceId, processDefinitionId), processEngineConfiguration.getEngineCfgKey());
        }

        return attachment;
    }

    protected TaskEntity verifyTaskParameters(CommandContext commandContext) {
        ProcessEngineConfigurationImpl processEngineConfiguration = CommandContextUtil.getProcessEngineConfiguration(commandContext);
        TaskEntity task = processEngineConfiguration.getTaskServiceConfiguration().getTaskService().getTask(taskId);

        if (task == null) {
            throw new FlowableObjectNotFoundException("Cannot find task with id " + taskId, Task.class);
        }

        if (task.isSuspended()) {
            throw new FlowableException("It is not allowed to add an attachment to a suspended " + task);
        }

        return task;
    }

    protected ExecutionEntity verifyExecutionParameters(CommandContext commandContext) {
        ExecutionEntity execution = CommandContextUtil.getExecutionEntityManager(commandContext).findById(processInstanceId);

        if (execution == null) {
            throw new FlowableObjectNotFoundException("Process instance " + processInstanceId + " doesn't exist", ProcessInstance.class);
        }

        if (execution.isSuspended()) {
            throw new FlowableException("It is not allowed to add an attachment to a suspended " + execution);

View on GitHub (pinned to d6d39ce1c6)