flowable/flowable-engine · error · ActivitiIllegalArgumentException

Invalid query usage: cannot set both taskAssigneeIds and…

Error message

Invalid query usage: cannot set both taskAssigneeIds and taskAssignee

What it means

Thrown by TaskQueryImpl.taskAssigneeIds(List<String>) when the query already has an exact assignee filter set via taskAssignee(String). Assignee filters are mutually exclusive — combining the single-assignee filter with the ids IN-clause would produce contradictory WHERE conditions, so the builder rejects the combination with ActivitiIllegalArgumentException.

Solutions

1. Decide on ONE assignee filter: use either taskAssignee or taskAssigneeIds, never both.
2. Normalize the input: wrap a single id in a one-element list and always use taskAssigneeIds.
3. Track which filter was applied and skip the second one (log or warn about the override).
4. Build a fresh TaskQuery per request instead of mutating a shared instance.
5. Catch ActivitiIllegalArgumentException and return a 400 explaining the conflicting filters.

Example fix

// before
query.taskAssignee(assignee);
if (assigneeIds != null) {
    query.taskAssigneeIds(assigneeIds); // throws
}

// after
if (assigneeIds != null && !assigneeIds.isEmpty()) {
    query.taskAssigneeIds(assigneeIds);
} else if (assignee != null) {
    query.taskAssignee(assignee);
}

if (assignee != null && assigneeIds != null) {
    throw new BadRequestException("Use either assignee or assigneeIds, not both");
}

boolean hasConflictingAssigneeFilters(String assignee, List<String> ids) { return assignee != null && ids != null; }

try {
    query.taskAssigneeIds(assigneeIds);
} catch (ActivitiIllegalArgumentException e) {
    throw new BadRequestException("Conflicting assignee filters: " + e.getMessage());
}

When it happens

Trigger: Calling taskAssignee("kermit") earlier on the same TaskQueryImpl and then taskAssigneeIds(list), typically when filters are applied conditionally from multiple code paths or accumulated on a reused query object.

Common situations: A generic search endpoint that applies both a user filter and a users-list filter from request parameters; reusing a shared query object across requests without resetting state; accumulating OR/AND filters in a loop.

Related errors

• Invalid query usage: cannot set both taskAssigneeIds and…
• Assignee is null
• None of the given task assignees can be null
• Task assignee list is empty
• Task assignee list is null

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/fa75c94c294ec322. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable5-engine/src/main/java/org/activiti/engine/impl/TaskQueryImpl.java:390

        return this;
    }

    @Override
    public TaskQuery taskAssigneeIds(List<String> assigneeIds) {
        if (assigneeIds == null) {
            throw new ActivitiIllegalArgumentException("Task assignee list is null");
        }
        if (assigneeIds.isEmpty()) {
            throw new ActivitiIllegalArgumentException("Task assignee list is empty");
        }
        for (String assignee : assigneeIds) {
            if (assignee == null) {
                throw new ActivitiIllegalArgumentException("None of the given task assignees can be null");
            }
        }

        if (assignee != null) {
            throw new ActivitiIllegalArgumentException("Invalid query usage: cannot set both taskAssigneeIds and taskAssignee");
        }
        if (assigneeLike != null) {
            throw new ActivitiIllegalArgumentException("Invalid query usage: cannot set both taskAssigneeIds and taskAssigneeLike");
        }
        if (assigneeLikeIgnoreCase != null) {
            throw new ActivitiIllegalArgumentException("Invalid query usage: cannot set both taskAssigneeIds and taskAssigneeLikeIgnoreCase");
        }

        if (orActive) {
            currentOrQueryObject.assigneeIds = assigneeIds;
        } else {
            this.assigneeIds = assigneeIds;
        }
        return this;
    }

    @Override
    public TaskQueryImpl taskOwner(String owner) {

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