What causes "Currently, reactive option doesn't supported by Spring Cloud" in OpenAPITools/openapi-generator?

Remove reactive=true (or set reactive=false) for spring-cloud generation

OpenAPITools/openapi-generator · error · IllegalArgumentException

Currently, reactive option doesn't supported by Spring Cloud

Error message

Currently, reactive option doesn't supported by Spring Cloud

What it means

In the spring generator, the reactive option (reactive=true, which enables WebFlux/Reactor return types) is explicitly incompatible with the spring-cloud library (spring-cloud-openfeign based). processOpts() throws IllegalArgumentException as soon as both are set, because the spring-cloud templates have no reactive variants.

Source

Thrown at modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/SpringCodegen.java:569

        // does not support auto-generated markdown doc at the moment
        // TODO: add doc templates
        modelDocTemplateFiles.remove("model_doc.mustache");
        apiDocTemplateFiles.remove("api_doc.mustache");

        convertPropertyToStringAndWriteBack(TITLE, this::setTitle);
        convertPropertyToStringAndWriteBack(CONFIG_PACKAGE, this::setConfigPackage);
        convertPropertyToStringAndWriteBack(BASE_PACKAGE, this::setBasePackage);
        convertPropertyToBooleanAndWriteBack(VIRTUAL_SERVICE, this::setVirtualService);
        convertPropertyToBooleanAndWriteBack(INTERFACE_ONLY, this::setInterfaceOnly);
        convertPropertyToBooleanAndWriteBack(USE_FEIGN_CLIENT_URL, this::setUseFeignClientUrl);
        convertPropertyToBooleanAndWriteBack(USE_FEIGN_CLIENT_CONTEXT_ID, this::setUseFeignClientContextId);
        convertPropertyToBooleanAndWriteBack(DELEGATE_PATTERN, this::setDelegatePattern);
        convertPropertyToBooleanAndWriteBack(SINGLE_CONTENT_TYPES, this::setSingleContentTypes);
        convertPropertyToBooleanAndWriteBack(SKIP_DEFAULT_INTERFACE, this::setSkipDefaultInterface);
        convertPropertyToBooleanAndWriteBack(ASYNC, this::setAsync);
        if (additionalProperties.containsKey(REACTIVE)) {
            if (SPRING_CLOUD_LIBRARY.equals(library)) {
                throw new IllegalArgumentException("Currently, reactive option doesn't supported by Spring Cloud");
            }
            convertPropertyToBooleanAndWriteBack(REACTIVE, this::setReactive);
            convertPropertyToBooleanAndWriteBack(SSE, this::setSse);
        }
        if (additionalProperties.containsKey(INCLUDE_HTTP_REQUEST_CONTEXT)) {
            convertPropertyToBooleanAndWriteBack(INCLUDE_HTTP_REQUEST_CONTEXT, this::setIncludeHttpRequestContext);
        }
        //set default value for includeHttpRequestContext based on reactive/blocking
        if (includeHttpRequestContext == null) {
            if (this.reactive) {
                //default to true for reactive
                this.setIncludeHttpRequestContext(this.isDefaultIncludeHttpRequestContextForReactive());
                LOGGER.info("Defaulting {} to '{}' for reactive", INCLUDE_HTTP_REQUEST_CONTEXT, this.isDefaultIncludeHttpRequestContextForReactive());
            } else {
                //default to false for blocking
                this.setIncludeHttpRequestContext(this.isDefaultIncludeHttpRequestContextForBlocking());
                LOGGER.info("Defaulting {} to '{}' for blocking", INCLUDE_HTTP_REQUEST_CONTEXT, this.isDefaultIncludeHttpRequestContextForBlocking());
            }

View on GitHub (pinned to fcec517be3)

Solutions

Remove reactive=true (or set reactive=false) for spring-cloud generation
Or switch the library to spring-boot to keep reactive/WebFlux output
Split shared configs so reactive is opt-in per library instead of global
If you need reactive Feign, generate with spring-cloud without reactive and adapt manually

Example fix

# before
openapi-generator-cli generate -i api.yaml -g spring -l spring-cloud -c reactive=true
# after (option A: drop reactive)
openapi-generator-cli generate -i api.yaml -g spring -l spring-cloud
# after (option B: keep reactive, switch library)
openapi-generator-cli generate -i api.yaml -g spring -l spring-boot -c reactive=true

Defensive patterns

Strategy: validation

Validate before calling

# bash: enforce the option-compatibility matrix up front
if [[ "${LIBRARY:-spring-boot}" == spring-cloud && "${REACTIVE:-false}" == true ]]; then
  echo 'reactive=true is not supported with -l spring-cloud'; exit 1
fi

Try / catch

try {
    SpringCodegen codegen = new SpringCodegen();
    codegen.setLibrary("spring-boot");   // not spring-cloud when reactive
    codegen.setReactive(true);
    new DefaultGenerator().opts(new ClientOptInput().opts(codegen)).generate();
} catch (IllegalArgumentException e) {
    // 'Currently, reactive option doesn't supported by Spring Cloud' - drop reactive or switch library
}

Prevention

Keep reactive opt-in per job instead of a global default in shared configs
Document which spring libraries are reactive-capable (spring-boot) vs Feign-based (spring-cloud)
Encode the library x reactive matrix in your generation wrapper so invalid combos fail before the generator runs

When it happens

Trigger: openapi-generator-cli generate -i api.yaml -g spring -l spring-cloud -c reactive=true; or a Maven/Gradle plugin config with <library>spring-cloud</library> and <reactive>true</reactive>. Also hit when reactive=true is set globally (e.g. in a shared config file) while one job selects -l spring-cloud.

Common situations: Organizations with a base config setting reactive=true for all spring services, then adding a Feign/spring-cloud client; upgrading pipelines where reactive was enabled for WebFlux services and later reused unintentionally.

Related errors

AI-assisted analysis of OpenAPITools/openapi-generator@fcec517be3 (2026-08-22). Data as JSON: /api/errors/5a25acbcc21d421f. Report an issue: GitHub.