flowable/flowable-engine · warning · FlowableObjectNotFoundException

The variable does not have a binary data stream.

Error message

The variable does not have a binary data stream.

What it means

FlowableObjectNotFoundException thrown when fetching raw variable data for a historic task whose variable is neither a byte-array (binary) nor a serializable value — i.e. it has no binary stream to return. The endpoint /cmmn-history/historic-task-instances/{taskId}/variables/{variableName}/data only serves byte[] and Serializable variables; plain string/number/boolean variables hit this error.

Source

Thrown at modules/flowable-cmmn-rest/src/main/java/org/flowable/cmmn/rest/service/api/history/task/HistoricTaskInstanceVariableDataResource.java:85

            HttpServletResponse response) {

        try {
            byte[] result = null;
            RestVariable variable = getVariableFromRequest(true, taskId, variableName, scope);
            if (CmmnRestResponseFactory.BYTE_ARRAY_VARIABLE_TYPE.equals(variable.getType())) {
                result = (byte[]) variable.getValue();
                response.setContentType("application/octet-stream");

            } else if (CmmnRestResponseFactory.SERIALIZABLE_VARIABLE_TYPE.equals(variable.getType())) {
                ByteArrayOutputStream buffer = new ByteArrayOutputStream();
                ObjectOutputStream outputStream = new ObjectOutputStream(buffer);
                outputStream.writeObject(variable.getValue());
                outputStream.close();
                result = buffer.toByteArray();
                response.setContentType("application/x-java-serialized-object");

            } else {
                throw new FlowableObjectNotFoundException("The variable does not have a binary data stream.", null);
            }
            return result;

        } catch (IOException ioe) {
            // Re-throw IOException
            throw new FlowableException("Unexpected exception getting variable data", ioe);
        }
    }

    public RestVariable getVariableFromRequest(boolean includeBinary, String taskId, String variableName, String scope) {
        RestVariableScope variableScope = RestVariable.getScopeFromString(scope);
        HistoricTaskInstanceQuery taskQuery = historyService.createHistoricTaskInstanceQuery().taskId(taskId);

        if (variableScope != null) {
            if (variableScope == RestVariableScope.GLOBAL) {
                taskQuery.includeProcessVariables();
            } else {
                taskQuery.includeTaskLocalVariables();

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Use the plain variable endpoint GET .../variables/{variableName} instead of .../variables/{variableName}/data for non-binary variables
2. Check the variable's type in the variable list response; only byte-array/serializable/binary types have raw data
3. If you need the value of a string/number variable, read it from the normal REST variable representation (JSON)
4. If the variable was expected to be binary, verify the process/case actually stored it as byte[] or Serializable

Example fix

// before
byte[] data = get("/cmmn-history/historic-task-instances/" + taskId + "/variables/" + name + "/data");
// after
RestVariable v = getVariable(taskId, name);
byte[] data = v.getType().isBinary() ? getRawData(taskId, name) : String.valueOf(v.getValue()).getBytes();

const vars = await fetch(`/cmmn-history/historic-task-instances/${taskId}/variables`).then(r => r.json());
const v = vars.find(v => v.name === variableName);
if (!['byteArray','binary','serializable'].includes(v.type)) return v.value; // read via plain endpoint

function hasBinaryStream(variable) {
  return variable != null && ['byteArray','binary','serializable'].includes(variable.type);
}

try {
  return await fetchVariableData(taskId, name);
} catch (e) {
  if (String(e.message).includes('binary data stream')) return fetchPlainVariable(taskId, name);
  throw e;
}

When it happens

Trigger: GET /cmmn-history/historic-task-instances/{taskId}/variables/{variableName}/data where the variable is a primitive type (String, Integer, Boolean, Date, etc.) with no byte-array or serializable payload.

Common situations: Trying to download a variable that is a JSON string or number as if it were a file upload; scripts that download all variables via the /data endpoint assuming all are binary; confusion between the plain variable endpoint and the raw-data endpoint.

Understand the failure class

Background: "is not a compatible type" / "cannot merge" errors: when a value's type doesn't match what the library requires — this error's family across 65 libraries.

Related errors

• Unexpected exception getting variable data
• Historic task instance '' couldn't be found.
• The variable does not have a binary data stream.
• Variable '${restVariable.getName()}' has unsupported type: '
• Invalid variable scope: '${scope}'

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/d1e756a9b7e57d8f. Report an issue: GitHub.