flowable/flowable-engine · error · ActivitiObjectNotFoundException

Cannot find task with id " + taskId

Error message

Cannot find task with id " + taskId

What it means

Thrown when the taskId is non-null but no task entity with that id exists; ActivitiObjectNotFoundException is raised with the expected Task.class. The task may have been completed or deleted, or the id belongs to a different engine/database.

Solutions

1. Check existence first via taskService.createTaskQuery().taskId(id).singleResult() and handle the not-found case gracefully in the UI.
2. Treat the task as already processed on ObjectNotFoundException (idempotent handling) rather than retrying blindly.
3. Verify engine/datasource configuration so the call hits the database that actually owns the task.
4. Refresh the task list instead of reusing cached ids from an old page render.

Example fix

// before
taskService.complete(taskId);

// after
Task task = taskService.createTaskQuery().taskId(taskId).singleResult();
if (task != null) {
    taskService.complete(taskId);
} else {
    logger.info("Task {} already completed or deleted", taskId);
}

Task task = taskService.createTaskQuery().taskId(taskId).singleResult();
if (task == null) throw new IllegalStateException("task not found: " + taskId);

try {
    taskService.complete(taskId);
} catch (ActivitiObjectNotFoundException e) {
    // idempotent: task already completed or deleted
}

When it happens

Trigger: Calling taskService.complete/claim/setAssignee/etc. with an id of a task that was already completed, deleted by another user, never existed in this database, or comes from a stale form/UI payload.

Common situations: Double-submit: two users or retries complete the same task and the second call fails; long-lived UI sessions holding task ids after a DB cleanup; connecting to the wrong datasource or cluster.

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

• execution " + executionId + " doesn't exist
• Candidate group is null
• Candidate group list is empty
• Candidate group list is empty
• Candidate group list is null

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/92c1252d35c0f3b6. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable5-engine/src/main/java/org/activiti/engine/impl/cmd/NeedsActiveTaskCmd.java:52

    protected String taskId;

    public NeedsActiveTaskCmd(String taskId) {
        this.taskId = taskId;
    }

    @Override
    public T execute(CommandContext commandContext) {

        if (taskId == null) {
            throw new ActivitiIllegalArgumentException("taskId is null");
        }

        TaskEntity task = commandContext
                .getTaskEntityManager()
                .findTaskById(taskId);

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

        if (task.isSuspended()) {
            throw new ActivitiException(getSuspendedTaskException());
        }

        return execute(commandContext, task);
    }

    /**
     * Subclasses must implement in this method their normal command logic. The provided task is ensured to be active.
     */
    protected abstract T execute(CommandContext commandContext, TaskEntity task);

    /**
     * Subclasses can override this method to provide a customized exception message that will be thrown when the task is suspended.
     */
    protected String getSuspendedTaskException() {

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