quarkusio/quarkus · error · RuntimeException

Method '${info.name()} of class '${info.declaringClass().nam

Error message

Method '${info.name()} of class '${info.declaringClass().name()}' cannot be private as it is annotated with '@jakarta.ws.rs.ext.Provider'

What it means

checkModifiers in ServerExceptionMapperGenerator rejects exception mapper methods declared private. A method annotated with @jakarta.ws.rs.ext.Provider (or @ServerExceptionMapper) must be non-private because the generated filter/interceptor code invokes it reflectively/via bytecode generated at build time, which requires accessible methods.

Source

Thrown at independent-projects/resteasy-reactive/server/processor/src/main/java/org/jboss/resteasy/reactive/server/processor/generation/exceptionmappers/ServerExceptionMapperGenerator.java:640

            return ReturnType.REST_RESPONSE;
        } else if (targetMethod.returnType().kind() == Type.Kind.PARAMETERIZED_TYPE) {
            ParameterizedType parameterizedType = targetMethod.returnType().asParameterizedType();
            if (parameterizedType.name().equals(UNI) && (parameterizedType.arguments().size() == 1)) {
                if (parameterizedType.arguments().get(0).name().equals(RESPONSE)) {
                    return ReturnType.UNI_RESPONSE;
                }
                if (parameterizedType.arguments().get(0).name().equals(REST_RESPONSE)) {
                    return ReturnType.UNI_REST_RESPONSE;
                }
            }
        }
        throw new RuntimeException("Method '" + targetMethod.name() + " of class '" + targetMethod.declaringClass().name()
                + "' cannot be used as an exception mapper as it does not declare 'Response' or 'Uni<Response>' or as its return type");
    }

    private static void checkModifiers(MethodInfo info) {
        if ((info.flags() & Modifier.PRIVATE) != 0) {
            throw new RuntimeException("Method '" + info.name() + " of class '" + info.declaringClass().name()
                    + "' cannot be private as it is annotated with '@" + SERVER_EXCEPTION_MAPPER
                    + "'");
        }
        if ((info.flags() & Modifier.STATIC) != 0) {
            throw new RuntimeException("Method '" + info.name() + " of class '" + info.declaringClass().name()
                    + "' cannot be static as it is annotated with '@" + SERVER_EXCEPTION_MAPPER
                    + "'");
        }
    }

    private static String getGeneratedClassName(MethodInfo targetMethod, Type handledExceptionType) {
        return targetMethod.declaringClass().name() + "$ExceptionMapper$"
                + HashUtil.sha1(targetMethod.name() + handledExceptionType.name().toString());
    }

    private enum ReturnType {
        RESPONSE,
        REST_RESPONSE,

View on GitHub (pinned to e1c734241f)

Solutions

Change the mapper method from private to at least package-private (recommended: public)
Move the mapper to a dedicated @Provider class if visibility was intentional
Remove the @Provider/@ServerExceptionMapper annotation if the method is not a mapper

Example fix

// before
@ServerExceptionMapper
private Response map(NotFoundException e) { ... }

// after
@ServerExceptionMapper
public Response map(NotFoundException e) { ... }

Defensive patterns

Strategy: validation

Validate before calling

java.lang.reflect.Method m = ...; // annotated mapper
if (java.lang.reflect.Modifier.isPrivate(m.getModifiers())) {
    throw new IllegalStateException("@ServerExceptionMapper methods must not be private: " + m);
}

Type guard

static boolean isAccessibleMapper(java.lang.reflect.Method m) {
    return !java.lang.reflect.Modifier.isPrivate(m.getModifiers());
}

Prevention

Declare exception mapper methods public by default
Avoid IDE 'encapsulate' refactors on annotated methods
Code-review visibility changes in classes containing @ServerExceptionMapper

When it happens

Trigger: A method carrying @ServerExceptionMapper or @Provider whose flags include Modifier.PRIVATE, detected during build-time generation of the exception mapper class.

Common situations: Keeping mapper methods private inside a resource or provider class, IDE auto-generating the method as private, or narrowing visibility during refactoring.

Related errors

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/744aa5e376436e04. Report an issue: GitHub.