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

Pass a non-null callbackType string.

flowable/flowable-engine · error · FlowableIllegalArgumentException

callbackType is null

Error message

callbackType is null

What it means

FlowableIllegalArgumentException thrown by CaseInstanceQueryImpl.caseInstanceCallbackType(String) when callbackType is null. The query API treats callback type as a required value when filtering; null is not a valid filter. Supply a non-null callback type string.

Solutions

Pass a non-null callbackType string.
Skip the filter call when the value is absent.
Default to a known callback type constant if one applies.
Verify where the value originates (config/DTO) and why it is null.

Example fix

// before
query.caseInstanceCallbackType(dto.getCallbackType()); // null
// after
if (dto.getCallbackType() != null) {
    query.caseInstanceCallbackType(dto.getCallbackType());
}

Defensive patterns

Strategy: validation

Validate before calling

if (callbackType != null) { query.caseInstanceCallbackType(callbackType); }

Type guard

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

Try / catch

try { query.caseInstanceCallbackType(type); } catch (FlowableIllegalArgumentException e) { log.warn("callbackType filter rejected: {}", e.getMessage()); }

Prevention

Never pass nullable DTO fields directly into required filter setters.
Wrap optional filters in if-present checks.
Define constants for valid callback types.

When it happens

Trigger: Calling caseInstanceCallbackType(null) on a CaseInstanceQuery, directly or via an or() statement where a variable resolved to null.

Common situations: Mapping an optional DTO field straight into the query; null callback type in a case instance model; typos in getter chains returning null.

Related errors

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/afc3efc394552a6c. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-cmmn-engine/src/main/java/org/flowable/cmmn/engine/impl/runtime/CaseInstanceQueryImpl.java:661

    }

    @Override
    public CaseInstanceQuery caseInstanceCallbackIds(Set<String> callbackIds) {
        if (callbackIds == null || callbackIds.isEmpty()) {
            throw new FlowableIllegalArgumentException("callbackIds is null or empty");
        }
        if (inOrStatement) {
            this.currentOrQueryObject.callbackIds = callbackIds;
        } else {
            this.callbackIds = callbackIds;
        }
        return this;
    }

    @Override
    public CaseInstanceQuery caseInstanceCallbackType(String callbackType) {
        if (callbackType == null) {
            throw new FlowableIllegalArgumentException("callbackType is null");
        }
        if (inOrStatement) {
            this.currentOrQueryObject.callbackType = callbackType;
        } else {
            this.callbackType = callbackType;
        }
        return this;
    }
    
    @Override
    public CaseInstanceQuery parentCaseInstanceId(String parentCaseInstanceId) {
        if (parentCaseInstanceId == null) {
            throw new FlowableIllegalArgumentException("parentCaseInstanceId is null");
        }
        if (inOrStatement) {
            this.currentOrQueryObject.parentCaseInstanceId = parentCaseInstanceId;
        } else {
            this.parentCaseInstanceId = parentCaseInstanceId;

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