flowable/flowable-engine · error · DmnXMLException

Error writing DMN XML

Error message

Error writing DMN XML

What it means

DmnXMLConverter.convertToXML wraps any Exception thrown while serializing a DmnDefinition back to DMN XML bytes into DmnXMLException("Error writing DMN XML"). This indicates the model could not be written out to the output stream (writer failure, null/invalid model content, or XMLStreamWriter error).

Source

Thrown at modules/flowable-dmn-xml-converter/src/main/java/org/flowable/dmn/xml/converter/DmnXMLConverter.java:714

            }

            DMNDIExport.writeDMNDI(model, xtw);

            // end definitions root element
            xtw.writeEndElement();
            xtw.writeEndDocument();

            xtw.flush();

            outputStream.close();

            xtw.close();

            return outputStream.toByteArray();

        } catch (Exception e) {
            LOGGER.error("Error writing DMN XML", e);
            throw new DmnXMLException("Error writing DMN XML", e);
        }
    }

    protected void writeItemDefinition(List<ItemDefinition> itemDefinitions, DmnDefinition model, XMLStreamWriter xtw) throws Exception {
        writeItemDefinition(itemDefinitions, false, model, xtw);
    }

    protected void writeItemDefinition(List<ItemDefinition> itemDefinitions, boolean isItemComponent, DmnDefinition model, XMLStreamWriter xtw) throws Exception {
        if (itemDefinitions == null) {
            return;
        }

        for (ItemDefinition itemDefinition : itemDefinitions) {
            if (isItemComponent) {
                xtw.writeStartElement(ELEMENT_ITEM_COMPONENT);
            } else {
                xtw.writeStartElement(ELEMENT_ITEM_DEFINITION);
            }

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Inspect the logged stack trace to see which write* call failed
2. Validate the DmnDefinition: ensure required elements (decisions, rules, expressions) are non-null and populated
3. Sanitize string values in the model to remove illegal XML control characters
4. Serialize the model through the Flowable DMN model API (DmnJsonConverter/model builders) instead of hand-building it

Example fix

// before
DmnDefinition model = new DmnDefinition(); // partially populated
byte[] xml = converter.convertToXML(model);
// after
DmnDefinition model = builder.withDecisions(populatedDecisions).build();
Objects.requireNonNull(model.getDecisions(), "decisions required");
byte[] xml = converter.convertToXML(model);

// validate model before serializing
if (model == null || model.getDecisions() == null || model.getDecisions().isEmpty()) {
    throw new IllegalStateException("DmnDefinition has no decisions; cannot serialize");
}

try {
    byte[] xml = converter.convertToXML(model);
} catch (DmnXMLException e) {
    LOGGER.error("DMN serialization failed: {}", e.getCause(), e);
    throw e;
}

When it happens

Trigger: Calling convertToXML(DmnDefinition) when the XMLStreamWriter (e.g. writeStartElement, writeAttribute) throws — typically due to an incomplete or null DmnDefinition, illegal XML characters in values, or an underlying output-stream failure.

Common situations: Programmatically constructed DmnDefinition objects missing required fields, strings containing characters illegal in XML, or ByteArrayOutputStream/transformer failures when converting a model between DMN and XML representations in tests or deployments.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• Error writing BPMN XML
• Error writing CMMN XML
• The bpmn 2.0 xml is not properly encoded
• Error while reading the BPMN 2.0 XML
• e.getMessage()

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/09f5acc1dd529323. Report an issue: GitHub.