flowable/flowable-engine · error · FlowableIllegalArgumentException

None of the given process instance ids can be null

Error message

None of the given process instance ids can be null

What it means

TaskQueryImpl.processInstanceIdIn() iterates the collection and rejects any null element, since a null id in the IN list would produce an invalid or always-false SQL predicate. The library throws FlowableIllegalArgumentException naming the offending condition.

Solutions

1. Filter nulls before the call: ids.removeIf(Objects::isNull) or ids.stream().filter(Objects::nonNull).collect(toList())
2. Fix the producer to never emit null ids
3. If filtering empties the list, also handle the empty-collection case first

Example fix

// before
query.processInstanceIdIn(ids); // may contain nulls
// after
List<String> clean = ids.stream().filter(Objects::nonNull).collect(Collectors.toList());
if (clean.isEmpty()) { return Collections.emptyList(); }
query.processInstanceIdIn(clean);

List<String> clean = processInstanceIds == null
    ? Collections.emptyList()
    : processInstanceIds.stream().filter(Objects::nonNull).collect(Collectors.toList());
if (clean.isEmpty()) { return Collections.emptyList(); }
query.processInstanceIdIn(clean);

boolean hasNoNullIds(Collection<String> c) { return c != null && c.stream().allMatch(Objects::nonNull); }

try {
    tasks = taskService.createTaskQuery().processInstanceIdIn(ids).list();
} catch (org.flowable.common.engine.api.FlowableIllegalArgumentException e) {
    log.warn("Null element in id list: {}", e.getMessage());
    tasks = Collections.emptyList();
}

When it happens

Trigger: Calling .processInstanceIdIn(list) where the list contains null entries, e.g. from Arrays.asList(a, b) with a null, or from a Map lookup keyed by absent ids.

Common situations: Collecting ids into a size-padded array; streaming results where some rows lack a process instance id.

Related errors

• None of the given task categories can be null
• Process instance id list is null
• Task category list is null
• Assignee is null
• Assignee is null

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/3b4c6a8fe6bfe4f2. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-task-service/src/main/java/org/flowable/task/service/impl/TaskQueryImpl.java:745

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

    @Override
    public TaskQuery processInstanceIdIn(Collection<String> processInstanceIds) {
        if (processInstanceIds == null) {
            throw new FlowableIllegalArgumentException("Process instance id list is null");
        }
        if (processInstanceIds.isEmpty()) {
            throw new FlowableIllegalArgumentException("Process instance id list is empty");
        }
        for (String processInstanceId : processInstanceIds) {
            if (processInstanceId == null) {
                throw new FlowableIllegalArgumentException("None of the given process instance ids can be null");
            }
        }

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

    @Override
    public TaskQueryImpl withoutProcessInstanceId() {
        if (orActive) {
            currentOrQueryObject.withoutProcessInstanceId = true;
        } else {
            this.withoutProcessInstanceId = true;
        }

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