flowable/flowable-engine · error · FlowableIllegalArgumentException

Unsupported multipart mode

Error message

Unsupported multipart mode: ${mode}. Supported values are: STRICT, BROWSER_COMPATIBLE

What it means

ApacheHttpComponentsFlowableHttpClient.resolveMultipartMode maps the configured multipartMode string to Apache's HttpMultipartMode enum. Null defaults to STRICT; only 'STRICT' and 'BROWSER_COMPATIBLE' are accepted, and any other value throws FlowableIllegalArgumentException listing the supported values.

Solutions

1. Change the multipartMode value to STRICT or BROWSER_COMPATIBLE
2. Remove the multipartMode setting to get the STRICT default (when value is null)
3. If 'RFC6532' behavior is needed, patch/configure at the Apache client level instead of through this config

Example fix

// before
config.setMultipartMode("RFC6532");
// after
config.setMultipartMode("BROWSER_COMPATIBLE");

String mode = config.getMultipartMode();
if (mode != null && !(mode.equalsIgnoreCase("STRICT") || mode.equalsIgnoreCase("BROWSER_COMPATIBLE"))) {
    throw new IllegalArgumentException("multipartMode must be STRICT or BROWSER_COMPATIBLE");
}

boolean isSupportedMultipartMode(String m) { return m == null || m.equalsIgnoreCase("STRICT") || m.equalsIgnoreCase("BROWSER_COMPATIBLE"); }

When it happens

Trigger: Setting httpClientConfig.setMultipartMode(...) (or the equivalent HTTP task config) to a string like 'RFC6532', 'lenient', or a misspelled value that is not STRICT or BROWSER_COMPATIBLE (case-insensitive).

Common situations: Copying multipart mode names from Apache HttpComponents docs (e.g. RFC6532) that Flowable does not expose; typos like 'browser-compatible'; configuring via properties files with wrong casing that also includes stray whitespace is not the issue here since it is trimmed by uppercase only — the value text itself must match.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• A channel key detection value is required for the channel…
• A datasource is required for initializing the engine
• ackMode in definition
• Builder is missing constructor (can't pass features)
• Cannot migrate process(es), not enough information

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/c448050e381446d3. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-http-common/src/main/java/org/flowable/http/common/impl/apache/ApacheHttpComponentsFlowableHttpClient.java:176

    }

    public ApacheHttpComponentsFlowableHttpClient(HttpClientBuilder clientBuilder, int socketTimeout, int connectTimeout,
            int connectionRequestTimeout) {
        this.clientBuilder = clientBuilder;
        this.multipartMode = HttpMultipartMode.STRICT;
        this.socketTimeout = socketTimeout;
        this.connectTimeout = connectTimeout;
        this.connectionRequestTimeout = connectionRequestTimeout;
    }

    protected static HttpMultipartMode resolveMultipartMode(String mode) {
        if (mode == null) {
            return HttpMultipartMode.STRICT;
        }
        return switch (mode.toUpperCase()) {
            case "BROWSER_COMPATIBLE" -> HttpMultipartMode.BROWSER_COMPATIBLE;
            case "STRICT" -> HttpMultipartMode.STRICT;
            default -> throw new FlowableIllegalArgumentException("Unsupported multipart mode: " + mode
                    + ". Supported values are: STRICT, BROWSER_COMPATIBLE");
        };
    }

    @Override
    public ExecutableHttpRequest prepareRequest(HttpRequest requestInfo) {
        try {
            HttpRequestBase request;
            URI uri = createUri(requestInfo.getUrl());
            switch (requestInfo.getMethod()) {
                case "GET": {
                    request = new HttpGet(uri);
                    break;
                }
                case "POST": {
                    HttpPost post = new HttpPost(uri);
                    setRequestEntity(requestInfo, post);
                    request = post;

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