quarkusio/quarkus · error · IllegalArgumentException

Invalid parameter index '${index}' used when obtaining param

Error message

Invalid parameter index '${index}' used when obtaining parameter values

What it means

This error is thrown by ComputedParamContextImpl.getMethodParameterFromContext when resolving a @PathParam/@QueryParam-style template expression that references a method parameter by index, but the index is out of range of the actual client method parameters. It means the rest client generated a parameter reference that does not exist in the invoked method signature. The library throws it to fail fast instead of returning null for a missing parameter value.

Source

Thrown at extensions/resteasy-reactive/rest-client/runtime/src/main/java/io/quarkus/rest/client/reactive/runtime/ComputedParamContextImpl.java:60

    @Override
    public String name() {
        return name;
    }

    @Override
    public List<MethodParameter> methodParameters() {
        return parameters;
    }

    public static Object getMethodParameterFromContext(ClientRequestContext context, int index) {
        Object property = context.getProperty(INVOKED_METHOD_PARAMETERS_PROP);
        if (property == null) {
            throw new IllegalStateException(
                    "property " + INVOKED_METHOD_PARAMETERS_PROP + " should have been part of the client context");
        }
        List<Object> methodParameterValues = (List<Object>) property;
        if (index > methodParameterValues.size() - 1) {
            throw new IllegalArgumentException("Invalid parameter index '" + index + "' used when obtaining parameter values");
        }
        return methodParameterValues.get(index);
    }

    private static class MethodParameterImpl implements MethodParameter {

        private final Object value;

        private MethodParameterImpl(Object value) {
            this.value = value;
        }

        @Override
        public Object value() {
            return value;
        }
    }
}

View on GitHub (pinned to e1c734241f)

Solutions

1. Fix the template/computed parameter index in the client method annotations to match the actual parameter positions
2. Restore the removed/renamed method parameter that the index refers to
3. Rebuild the project so generated rest-client code is regenerated in sync with the interface

Example fix

// before
@Path("/{id}/items/{0}")
Response get(@PathParam("id") String id);
// after
@Path("/{id}/items/{item}")
Response get(@PathParam("id") String id, @PathParam("item") String item);

int idx = 0; // index you intend to use
java.util.List<?> params = getInvokedMethodParameters(ctx); // or count method params
if (idx < 0 || idx >= params.size()) {
    throw new IllegalStateException("Parameter index " + idx + " out of range (" + params.size() + " params)");
}

boolean isValidParamIndex(int index, int paramCount) {
    return index >= 0 && index < paramCount;
}

try {
    Object v = ctx.getMethodParameter(index);
} catch (IllegalArgumentException e) {
    log.warn("Bad template parameter index: {}", e.getMessage());
    v = null; // or fall back to a default value
}

When it happens

Trigger: Calling a REST client interface method whose @BeanParam or template expression (e.g. {0} or a computed parameter) references parameter index N while the method has fewer than N+1 parameters; typically caused by mismatched generated code or hand-written custom param providers using wrong indices.

Common situations: After refactoring a client interface method signature (removing/adding parameters) without updating annotation/computed-parameter indices; misconfigured ClientRequestFilter or custom ParamConverter provider supplying INVOKED_METHOD_PARAMETERS_PROP incorrectly.

Related errors

• proxyHost must not be null
• Invalid port number
• ExecutorService must not be null
• Name cannot start with '/':${name}
• Predicate already set

AI-assisted analysis of quarkusio/quarkus@e1c734241f (2026-09-05). Data as JSON: /api/errors/d14fdc2c7d6c2b98. Report an issue: GitHub.