quarkusio/quarkus · error · RuntimeException

Could not find provider class: ${name}

Error message

Could not find provider class: ${name}

What it means

providerClassForName() loads each REST client provider class by name from the thread context ClassLoader and wraps ClassNotFoundException in a RuntimeException when the class is absent. Providers listed in @RegisterProvider, quarkus.rest-client.<key>.providers, or MP RestClient config must be on the runtime classpath.

Source

Thrown at extensions/resteasy-classic/resteasy-client/runtime/src/main/java/io/quarkus/restclient/runtime/RestClientBase.java:266

        }
        if (clientProviders != null) {
            for (Class<?> annotationProvider : clientProviders) {
                builder.register(annotationProvider);
            }
        }
    }

    private void registerProviders(RestClientBuilder builder, String providersAsString) {
        for (String s : providersAsString.split(",")) {
            builder.register(providerClassForName(s.trim()));
        }
    }

    private Class<?> providerClassForName(String name) {
        try {
            return Class.forName(name, true, Thread.currentThread().getContextClassLoader());
        } catch (ClassNotFoundException e) {
            throw new RuntimeException("Could not find provider class: " + name);
        }
    }

    protected void configureTimeouts(RestClientBuilder builder) {
        Long connectTimeout = restClientConfig.connectTimeout().orElse(this.configRoot.connectTimeout());
        if (connectTimeout != null) {
            builder.connectTimeout(connectTimeout, TimeUnit.MILLISECONDS);
        }

        Long readTimeout = restClientConfig.readTimeout().orElse(this.configRoot.readTimeout());
        if (readTimeout != null) {
            builder.readTimeout(readTimeout, TimeUnit.MILLISECONDS);
        }
    }

    protected void configureBaseUrl(RestClientBuilder builder) {
        Optional<String> baseUrlOptional = oneOf(restClientConfig.uriReload(), restClientConfig.urlReload());
        if (((baseUriFromAnnotation == null) || baseUriFromAnnotation.isEmpty()) && baseUrlOptional.isEmpty()) {

View on GitHub (pinned to e1c734241f)

Solutions

1. Correct the fully-qualified class name in the providers config property or annotation
2. Add the module/dependency containing the provider to the runtime classpath
3. Search the codebase for the class to confirm its current package and name
4. If the provider belongs to a library, add the artifact that ships it rather than assuming transitive availability

Example fix

// before (application.properties)
quarkus.rest-client.inventory.providers=com.example.old.AuthFilter
// after
quarkus.rest-client.inventory.providers=com.example.rest.AuthFilter

// verify provider classes exist before startup
String providers = ConfigProvider.getConfig()
    .getValue("quarkus.rest-client.my-client.providers", String.class);
for (String name : providers.split(",")) {
    Class.forName(name.trim(), false, Thread.currentThread().getContextClassLoader()); // throws if absent
}

When it happens

Trigger: A class listed in quarkus.rest-client.<key>.providers=com.example.MyFilter does not exist at runtime — typo, missing Maven dependency, or the class lives in a test/dev-only module.

Common situations: Renaming/refactoring a provider class without updating the config property; provider contributed by a dependency marked <scope>provided</scope> or only in the test classpath; fully-qualified name with wrong package after a package move.

Related errors

• Unable to find class for provider ${providerToRegister}
• Multiple RestClientBuilderFactory implementations found: ${s
• Failed to initialize trust store from classpath resource ${t
• Classpath resource ${path} not found for MicroProfile Rest C
• Class ${className} used in ${annotationName} on ${declaringC

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/4762233508adefc3. Report an issue: GitHub.