flowable/flowable-engine · error · FlowableException

The channel xml key detection value was not found for the…

Error message

The channel xml key detection value was not found for the channel model with key ${channelModel.key}. One of fixedValue, xmlPathExpression, delegateExpression should be set.

What it means

Thrown when an XML inbound channel has a ChannelEventKeyDetection but none of fixedValue, xmlXPathExpression, or delegateExpression is populated. The block exists yet defines no key detection mechanism, so no InboundEventKeyDetector<Document> can be created.

Solutions

1. Populate one of keyDetection.fixedValue, keyDetection.xmlXPathExpression, or keyDetection.delegateExpression.
2. Use setXmlXPathExpression with an XPath that selects the event key from the document.
3. Use setDelegateExpression for a custom InboundEventKeyDetector<Document> bean.
4. If the detection was meant for JSON, move the channel to the JSON pipeline or convert the detection to an XPath expression.

Example fix

// before
ChannelEventKeyDetection keyDetection = new ChannelEventKeyDetection();
keyDetection.setJsonField("type"); // ignored on XML channels

// after
ChannelEventKeyDetection keyDetection = new ChannelEventKeyDetection();
keyDetection.setXmlXPathExpression("/event/@type");

ChannelEventKeyDetection kd = channelModel.getChannelEventKeyDetection();
if (kd != null && isBlank(kd.getFixedValue()) && isBlank(kd.getXmlXPathExpression())
        && isBlank(kd.getDelegateExpression())) {
    throw new IllegalArgumentException("Empty keyDetection on XML channel " + channelModel.getKey());
}

null

try {
    eventRegistry.registerChannelModel(channelModel);
} catch (FlowableException e) {
    if (e.getMessage().contains("xml key detection value was not found")) {
        logger.error("Set fixedValue/xmlXPathExpression/delegateExpression on channel {}", channelModel.getKey());
    }
    throw e;
}

When it happens

Trigger: Registering an XML inbound channel with a non-null keyDetection where getFixedValue, getXmlXPathExpression and getDelegateExpression are all empty.

Common situations: Empty <keyDetection/> element in the channel model XML; using jsonField/jsonPointer (JSON-only options) on an XML channel — they are ignored here; attribute name typos during hand-editing.

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

• A channel key detection value is required for inbound…
• The channel deserializer expression for the channel model…
• The channel json key detection value was not found for the…
• The channel json tenant detection value was not found for…
• The channel payload extractor expression for the channel…

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/b18aa23511299cdd. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-event-registry/src/main/java/org/flowable/eventregistry/impl/pipeline/InboundChannelModelProcessor.java:232

            eventTransformer = resolveExpression(channelModel.getEventTransformerDelegateExpression(), InboundEventTransformer.class);
        }

        InboundEventKeyDetector<Document> eventKeyDetector;

        ChannelEventKeyDetection keyDetection = channelModel.getChannelEventKeyDetection();
        if (keyDetection == null) {
            throw new FlowableException("A channel key detection value is required for inbound channel " + channelModel.getKey());
        }

        if (StringUtils.isNotEmpty(keyDetection.getFixedValue())) {
            eventKeyDetector = new InboundEventStaticKeyDetector<>(keyDetection.getFixedValue());
        } else if (StringUtils.isNotEmpty(keyDetection.getXmlXPathExpression())) {
            eventKeyDetector = new XpathBasedInboundEventKeyDetector(keyDetection.getXmlXPathExpression());
        } else if (StringUtils.isNotEmpty(keyDetection.getDelegateExpression())) {
            //noinspection unchecked
            eventKeyDetector = resolveExpression(keyDetection.getDelegateExpression(), InboundEventKeyDetector.class);
        } else {
            throw new FlowableException(
                "The channel xml key detection value was not found for the channel model with key " + channelModel.getKey()
                    + ". One of fixedValue, xmlPathExpression, delegateExpression should be set.");
        }

        ChannelEventTenantIdDetection channelEventTenantIdDetection = channelModel.getChannelEventTenantIdDetection();
        if (channelEventTenantIdDetection != null) {
            if (StringUtils.isNotEmpty(channelEventTenantIdDetection.getFixedValue())) {
                eventTenantDetector = new InboundEventStaticTenantDetector<>(channelEventTenantIdDetection.getFixedValue());
            } else if (StringUtils.isNotEmpty(channelEventTenantIdDetection.getXmlXPathExpression())) {
                eventTenantDetector = new XpathBasedInboundEventTenantDetector(channelEventTenantIdDetection.getXmlXPathExpression());
            } else if (StringUtils.isNotEmpty(channelEventTenantIdDetection.getxPathExpression())) {
                eventTenantDetector = new XpathBasedInboundEventTenantDetector(channelEventTenantIdDetection.getxPathExpression());
            } else if (StringUtils.isNotEmpty(channelEventTenantIdDetection.getDelegateExpression())) {
                //noinspection unchecked
                eventTenantDetector = resolveExpression(channelEventTenantIdDetection.getDelegateExpression(), InboundEventTenantDetector.class);
            } else {
                throw new FlowableException(
                    "The channel xml tenant detection value was not found for the channel model with key " + channelModel.getKey()

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