What causes "assigneeLikeIgnoreCase is null" in flowable/flowable-engine?

Apply the criterion only when the value is non-null.

flowable/flowable-engine · error · FlowableIllegalArgumentException

assigneeLikeIgnoreCase is null

Error message

assigneeLikeIgnoreCase is null

What it means

TaskQuery.taskAssigneeLikeIgnoreCase(String) throws FlowableIllegalArgumentException when the argument is null. The method lowercases the value for case-insensitive matching, which requires a non-null string; the null check happens before toLowerCase to avoid an NPE.

Solutions

Apply the criterion only when the value is non-null.
Use Optional.ofNullable(assigneePart).ifPresent(query::taskAssigneeLikeIgnoreCase) style guards.
Normalize the filter DTO so absent values default to a non-null sentinel or are dropped before query building.
Catch FlowableIllegalArgumentException at the API boundary and return 400.

Example fix

// before
query.taskAssigneeLikeIgnoreCase(filter.getAssignee());
// after
if (filter.getAssignee() != null) {
    query.taskAssigneeLikeIgnoreCase(filter.getAssignee());
}

Defensive patterns

Strategy: validation

Validate before calling

if (assigneeLikeIgnoreCase != null) {
    query.taskAssigneeLikeIgnoreCase(assigneeLikeIgnoreCase);
}

Type guard

boolean hasText(String s) { return s != null && !s.trim().isEmpty(); }

Try / catch

try {
    query.taskAssigneeLikeIgnoreCase(value);
} catch (FlowableIllegalArgumentException e) {
    throw new BadRequestException("assigneeLikeIgnoreCase must not be null", e);
}

Prevention

Null-check before all IgnoreIgnoreCase setters — they call toLowerCase() on the input.
Use Optional-based filters so absence is explicit and setters are skipped.
Normalize request payloads so missing JSON fields become 'no filter', not null propagation.
Keep one shared guard utility for all TaskQuery criteria.

When it happens

Trigger: Calling taskAssigneeLikeIgnoreCase(null), commonly from optional case-insensitive assignee search parameters.

Common situations: Search endpoints with optional assignee filters; JSON payloads omitting the field so it deserializes to null; shared filter builders that call every setter unconditionally.

Related errors

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/d03382ea0aa20e50. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-task-service/src/main/java/org/flowable/task/service/impl/TaskQueryImpl.java:456

    }

    @Override
    public TaskQueryImpl taskAssigneeLike(String assigneeLike) {
        if (assigneeLike == null) {
            throw new FlowableIllegalArgumentException("AssigneeLike is null");
        }
        if (orActive) {
            currentOrQueryObject.assigneeLike = assigneeLike;
        } else {
            this.assigneeLike = assigneeLike;
        }
        return this;
    }

    @Override
    public TaskQuery taskAssigneeLikeIgnoreCase(String assigneeLikeIgnoreCase) {
        if (assigneeLikeIgnoreCase == null) {
            throw new FlowableIllegalArgumentException("assigneeLikeIgnoreCase is null");
        }
        if (orActive) {
            currentOrQueryObject.assigneeLikeIgnoreCase = assigneeLikeIgnoreCase.toLowerCase();
        } else {
            this.assigneeLikeIgnoreCase = assigneeLikeIgnoreCase.toLowerCase();
        }
        return this;
    }

    @Override
    public TaskQuery taskAssigneeIds(Collection<String> assigneeIds) {
        if (assigneeIds == null) {
            throw new FlowableIllegalArgumentException("Task assignee list is null");
        }
        if (assigneeIds.isEmpty()) {
            throw new FlowableIllegalArgumentException("Task assignee list is empty");
        }
        for (String assignee : assigneeIds) {

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