flowable/flowable-engine · error · FlowableException

HTTP_TASK_REQUEST_FIELD_INVALID in execution " + execution

Error message

HTTP_TASK_REQUEST_FIELD_INVALID in execution " + execution

What it means

DefaultBpmnHttpActivityDelegate.execute wraps any non-FlowableException raised while building the HTTP request (createRequest) into this FlowableException with code HTTP_TASK_REQUEST_FIELD_INVALID. It signals that a field of the HTTP task's request (URL, method, headers, body expression) could not be resolved or was invalid for the given execution.

Source

Thrown at modules/flowable-engine/src/main/java/org/flowable/engine/impl/bpmn/http/DefaultBpmnHttpActivityDelegate.java:89

    @Override
    protected FlowableHttpClient createHttpClient() {
        HttpClientConfig config = CommandContextUtil.getProcessEngineConfiguration().getHttpClientConfig();
        return config.determineHttpClient();
    }

    @Override
    public CompletableFuture<ExecutionData> execute(DelegateExecution execution, AsyncTaskInvoker taskInvoker) {
        RequestData request;

        HttpServiceTask httpServiceTask = (HttpServiceTask) execution.getCurrentFlowElement();
        try {
            request = createRequest(execution, httpServiceTask.getId());

        } catch (Exception e) {
            if (e instanceof FlowableException) {
                throw (FlowableException) e;
            } else {
                throw new FlowableException(HTTP_TASK_REQUEST_FIELD_INVALID + " in execution " + execution, e);
            }
        }

        ProcessEngineConfigurationImpl processEngineConfiguration = CommandContextUtil.getProcessEngineConfiguration();
        HttpRequestHandler httpRequestHandler = createHttpRequestHandler(httpServiceTask.getHttpRequestHandler(), processEngineConfiguration);

        if (httpRequestHandler != null) {
            httpRequestHandler.handleHttpRequest(execution, request.getHttpRequest(), null);
        }

        // Validate request
        validateRequest(request.getHttpRequest());

        boolean parallelInSameTransaction;
        if (httpServiceTask.getParallelInSameTransaction() != null) {
            parallelInSameTransaction = httpServiceTask.getParallelInSameTransaction();
        } else {
            parallelInSameTransaction = processEngineConfiguration.getHttpClientConfig().isDefaultParallelInSameTransaction();

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Inspect the wrapped cause (getCause()) to see the original expression-evaluation failure.
2. Validate all request fields in the BPMN XML: URL, method, headers, body — ensure referenced variables exist (default them: ${var:defaultValue}).
3. Test expressions in isolation (e.g. via a small unit test with an ExpressionManager) before deploying the process.
4. Guard expressions with null-safe checks: ${var != null ? var : ''} or provide defaults via execution listeners.
5. If your own delegate/field throws, throw FlowableException directly so it isn't double-wrapped.

Example fix

// before
<flowable:field name="requestUrl" expression="${externalUrl}"/> <!-- externalUrl may be null -->

// after
<flowable:field name="requestUrl" expression="${externalUrl != null ? externalUrl : 'https://default.example.com'}"/>

// before the http service task runs
Map<String, Object> vars = runtimeService.getVariables(executionId);
if (vars.get("externalUrl") == null || String.valueOf(vars.get("externalUrl")).isBlank()) {
    throw new IllegalArgumentException("externalUrl must be set before HTTP task");
}

try {
    httpActivityDelegate.execute(delegateExecution);
} catch (FlowableException e) {
    if (e.getMessage().startsWith("HTTP_TASK_REQUEST_FIELD_INVALID")) {
        logger.error("invalid http request fields: {}", e.getCause(), e);
    }
}

When it happens

Trigger: A service task of type 'http' has request field expressions (httpTask URL, headers, body) that throw when evaluated against the execution — missing variables, bad expression syntax, unresolvable Spring beans, null URL — and the underlying exception is not already a FlowableException.

Common situations: URL expression referencing a variable not present in the execution; typo in variable name; expression returning null for the URL; invalid header expressions; missing Spring bean referenced in an expression; wrong field type in the task's <extensionElements>.

Understand the failure class

Background: 'Something went wrong' / 'Request failed (500)' / 'HTTP error! status: 404' — what failed HTTP requests actually mean and how to find the real cause — this error's family across 28 libraries.

Related errors

• scopeContainer cannot be null
• Unable to resolve formFieldValidationExpression to boolean v
• Unable to resolve formFieldValidationExpression without vari
• Expression condition ${condition} did not evaluate to a bool
• Unknown property used in expression:

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/e21f95afec04fda6. Report an issue: GitHub.