What causes "invalid url: " + resourceUrl" in flowable/flowable-engine?

Pass a full, valid absolute URL (e.g. file:/path/to/flowable.dmn.cfg.xml or the result of getResource().toString()).

flowable/flowable-engine · error · FlowableException

invalid url: " + resourceUrl

Error message

invalid url: " + resourceUrl

What it means

DmnEngines.retry re-initializes the DMN engine from a stored resource URL string. If that string is not a syntactically valid URL, new URL(resourceUrl) throws MalformedURLException, which is rethrown as a FlowableException. It indicates the persisted engine resource URL is malformed.

Source

Thrown at modules/flowable-dmn-engine/src/main/java/org/flowable/dmn/engine/DmnEngines.java:206

     * @param dmnEngineName
     *            is the name of the dmn engine or null for the default dmn engine.
     */
    public static DmnEngine getDmnEngine(String dmnEngineName) {
        if (!isInitialized()) {
            init();
        }
        return dmnEngines.get(dmnEngineName);
    }

    /**
     * retries to initialize a dmn engine that previously failed.
     */
    public static EngineInfo retry(String resourceUrl) {
        LOGGER.debug("retying initializing of resource {}", resourceUrl);
        try {
            return initDmnEngineFromResource(new URL(resourceUrl));
        } catch (MalformedURLException e) {
            throw new FlowableException("invalid url: " + resourceUrl, e);
        }
    }

    /**
     * provides access to dmn engine to application clients in a managed server environment.
     */
    public static Map<String, DmnEngine> getDmnEngines() {
        return dmnEngines;
    }

    /**
     * closes all dmn engines. This method should be called when the server shuts down.
     */
    public static synchronized void destroy() {
        if (isInitialized()) {
            Map<String, DmnEngine> engines = new HashMap<>(dmnEngines);
            dmnEngines = new HashMap<>();

View on GitHub (pinned to d6d39ce1c6)

Solutions

Pass a full, valid absolute URL (e.g. file:/path/to/flowable.dmn.cfg.xml or the result of getResource().toString()).
If you only have a classpath resource name, convert it: new URL(ClassLoader.getSystemResource(name).toString()) or use initDmnEngineFromSpringResource instead.
URL-encode special characters (spaces, non-ASCII) in file paths before constructing the URL string.
Check where resourceUrl came from (EngineInfo / config) and correct the stored value.

Example fix

// before
EngineInfo info = DmnEngines.retry("flowable.dmn.cfg.xml"); // not a URL

// after
URL url = DmnEngines.class.getClassLoader().getResource("flowable.dmn.cfg.xml");
EngineInfo info = DmnEngines.retry(url.toString());

Defensive patterns

Strategy: validation

Validate before calling

try { new java.net.URL(resourceUrl); } catch (java.net.MalformedURLException e) {
    throw new IllegalArgumentException("Not a valid URL: " + resourceUrl, e);
}

Type guard

null

Try / catch

try {
    return DmnEngines.retry(resourceUrl);
} catch (FlowableException e) {
    LOGGER.error("Invalid resource URL for DMN retry: {}", resourceUrl, e);
    throw new IllegalArgumentException("resourceUrl must be an absolute URL", e);
}

Prevention

Always store resourceUrl from URL.toString(), never a raw classpath name
URL-encode file paths with spaces or special characters
Validate the URL format before persisting it in configuration

When it happens

Trigger: Calling DmnEngines.retry(String resourceUrl) with a string that is not a valid absolute URL, e.g. a bare classpath name like "flowable.dmn.cfg.xml" or a path with illegal characters/spaces.

Common situations: Passing a classpath-relative resource name instead of a full URL; URLs persisted in config with unencoded spaces; corrupted configuration from a previous failed init stored in EngineInfo.getException()/resourceUrl.

Understand the failure class

Background: "Invalid URL" errors: why new URL(), URI.parse, and reqwest::Url reject your string — missing scheme, whitespace, and bad path format — this error's family across 39 libraries.

Related errors

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/d22bef430bd63fc0. Report an issue: GitHub.