quarkusio/quarkus · error · IllegalArgumentException

Attempt to pass at least two of form or regular entity as a

Error message

Attempt to pass at least two of form or regular entity as a request body in {restClientInterface}#{jandexMethod.name}

What it means

A REST client method may carry at most one request body. Quarkus detected both a regular entity/body value and form parameters (or two body-ish sources) on the same method, which is ambiguous when building the HTTP request, so generation fails.

Source

Thrown at extensions/resteasy-reactive/rest-client-jaxrs/deployment/src/main/java/io/quarkus/jaxrs/client/reactive/deployment/JaxrsClientReactiveProcessor.java:2710

        if (!exceptions.contains(Exception.class.getName()) && !exceptions.contains(Throwable.class.getName())) {
            exceptions.add(RuntimeException.class.getName());
        }

        CatchBlockCreator catchBlock = tryBlock.addCatch(ProcessingException.class);
        ResultHandle caughtException = catchBlock.getCaughtException();
        ResultHandle cause = catchBlock.invokeVirtualMethod(
                MethodDescriptor.ofMethod(Throwable.class, "getCause", Throwable.class),
                caughtException);
        for (String exception : exceptions) {
            catchBlock.ifTrue(catchBlock.instanceOf(cause, exception))
                    .trueBranch().throwException(cause);
        }

        catchBlock.throwException(caughtException);

        if (bodyValue != null || formParams != null) {
            if (countNonNulls(bodyValue, formParams) > 1) {
                throw new IllegalArgumentException("Attempt to pass at least two of form " +
                        "or regular entity as a request body in " +
                        restClientInterface.name().toString() + "#" + jandexMethod.name());
            }

            if (consumes != null && consumes.length > 0) {

                if (consumes.length > 1) {
                    Set<String> uniqueConsumes = new TreeSet<>(Arrays.asList(consumes));
                    mediaTypeValue = uniqueConsumes.iterator().next();
                    if (uniqueConsumes.size() > 1) {
                        log.debugf("MicroProfile Rest Client `%s`'s method `%s` has multiple `@Consumes` values `%s`,"
                                + " Content-Type will be set to `%s`."
                                + " You can change Content-Type in a custom jakarta.ws.rs.ClientRequestFilter implementation.",
                                restClientInterface.name().toString(), jandexMethod.name(),
                                uniqueConsumes.stream().collect(Collectors.joining(", ")),
                                mediaTypeValue);
                    }
                } else {

View on GitHub (pinned to e1c734241f)

Solutions

Remove one of the two bodies — either send the entity OR the form params, not both
Move form fields into the entity DTO and send a single object
Split into two endpoints/methods: one for the entity, one for the form-encoded request

Example fix

// before
@POST
@Path("submit")
void submit(MyEntity e, @FormParam("tag") String tag);
// after
@POST
@Path("submit")
void submit(SubmitRequest request); // request contains entity fields + tag

Defensive patterns

Strategy: validation

Validate before calling

static void validateSingleBody(Class<?> client) {
    for (var m : client.getDeclaredMethods()) {
        int bodyish = 0;
        for (var p : m.getParameters()) {
            if (p.isAnnotationPresent(jakarta.ws.rs.FormParam.class)
                || p.isAnnotationPresent(org.jboss.resteasy.reactive.PartType.class)
                || p.isAnnotationPresent(org.jboss.resteasy.reactive.RestForm.class)) bodyish++;
        }
        for (var p : m.getParameters()) {
            boolean annotated = p.getAnnotations().length > 0 && java.util.Arrays.stream(p.getAnnotations())
                .anyMatch(a -> a.annotationType().getName().startsWith("jakarta.ws.rs."));
            if (!annotated) bodyish++; // unannotated param = entity body
        }
        if (bodyish > 1) throw new IllegalStateException(
            client.getName() + "#" + m.getName() + " mixes entity body and form params");
    }
}

Prevention

One body per method: either an entity or form params, never both
Fold form fields into a request DTO when both kinds of data are needed
Review client interfaces in code review for mixed @FormParam + entity signatures

When it happens

Trigger: A client method with a @Body-style entity parameter plus @FormParam parameters, or a @MultipartForm combined with an entity argument, on a single interface method.

Common situations: Trying to POST a JSON body along with form fields in one call; mixing @MultipartForm with a payload argument after a refactor.

Related errors

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/69f614daa74af121. Report an issue: GitHub.