Activiti/Activiti · error · ActivitiIllegalArgumentException

Process instance id list is empty

Error message

Process instance id list is empty

What it means

HistoricTaskInstanceQueryImpl.processInstanceIdIn() throws ActivitiIllegalArgumentException when the processInstanceIds list is empty. Like the null case, an empty list cannot produce a valid IN clause and would misleadingly return no tasks, so the library treats it as a programming error.

Solutions

1. Ensure the list contains at least one process instance id
2. Return an empty result early when the list is empty instead of executing the query
3. Drop the processInstanceIdIn() filter when no id restriction is intended
4. Validate the upstream id-collection step so it cannot silently produce an empty list

Example fix

// before
query.processInstanceIdIn(collectProcessInstanceIds()); // empty -> throws
// after
List<String> pids = collectProcessInstanceIds();
if (pids.isEmpty()) {
    return Collections.emptyList();
}
query.processInstanceIdIn(pids);

if (processInstanceIds == null || processInstanceIds.isEmpty()) {
    return Collections.emptyList();
}
taskQuery.processInstanceIdIn(processInstanceIds);

boolean isPopulatedList(java.util.List<?> l) { return l != null && !l.isEmpty(); }

try {
    query.processInstanceIdIn(pids);
} catch (org.activiti.engine.ActivitiIllegalArgumentException e) {
    if (!e.getMessage().contains("Process instance id list is empty")) throw e;
    return Collections.emptyList();
}

When it happens

Trigger: Calling processInstanceIdIn(new ArrayList<>()) or passing a list emptied by filtering; piping in ids from a previous query that returned zero rows.

Common situations: Batch correlation flows where the source query matched nothing; dynamic filters from user selection UIs with nothing selected; pagination logic draining the list before the query runs.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• Task assignee list is empty
• Assignee is null
• AssigneeLike is null
• assigneeLikeIgnoreCase is null
• Candidate group list is empty

AI-assisted analysis of Activiti/Activiti@56435b1a97 (2026-09-09). Data as JSON: /api/errors/e304136c704f9ee0. Report an issue: GitHub.

Appendix: source

Thrown at activiti-core/activiti-engine/src/main/java/org/activiti/engine/impl/HistoricTaskInstanceQueryImpl.java:175

        return tasks;
    }

    public HistoricTaskInstanceQueryImpl processInstanceId(String processInstanceId) {
        if (inOrStatement) {
            this.currentOrQueryObject.processInstanceId = processInstanceId;
        } else {
            this.processInstanceId = processInstanceId;
        }
        return this;
    }

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

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

    public HistoricTaskInstanceQueryImpl processInstanceBusinessKey(String processInstanceBusinessKey) {
        if (inOrStatement) {
            this.currentOrQueryObject.processInstanceBusinessKey = processInstanceBusinessKey;

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