Modify @RequestParam presence handling

Fixes #50321

Author: aureamunoz

extensions/spring-web/resteasy-reactive/runtime/src/main/java/io/quarkus/spring/web/resteasy/reactive/runtime/SpringRequestParamHandler.java

@@ -4,7 +4,9 @@
 import java.util.List;
 import java.util.Map;
 
-import org.jboss.resteasy.reactive.common.jaxrs.ResponseImpl;
+import jakarta.ws.rs.WebApplicationException;
+import jakarta.ws.rs.core.Response;
+
 import org.jboss.resteasy.reactive.common.model.ResourceClass;
 import org.jboss.resteasy.reactive.server.core.ResteasyReactiveRequestContext;
 import org.jboss.resteasy.reactive.server.model.HandlerChainCustomizer;
@@ -21,18 +23,19 @@ public class SpringRequestParamHandler implements HandlerChainCustomizer {
     @Override
     public List<ServerRestHandler> handlers(HandlerChainCustomizer.Phase phase, ResourceClass resourceClass,
             ServerResourceMethod resourceMethod) {
-        if (phase == Phase.AFTER_RESPONSE_CREATED) {
+        if (phase == Phase.RESOLVE_METHOD_PARAMETERS) {
             return Collections.singletonList(new ServerRestHandler() {
                 @Override
                 public void handle(ResteasyReactiveRequestContext requestContext) throws Exception {
                     Map<String, List<String>> parametersMap = requestContext.serverRequest().getQueryParamsMap();
                     if (parametersMap.isEmpty()) {
-                        ResponseImpl response = (ResponseImpl) requestContext.getResponse().get();
-                        response.setStatus(400);
+                        throw new WebApplicationException("Missing required param in method '" + resourceMethod.getName() + "'",
+                                Response.Status.BAD_REQUEST);
                     }
                 }
             });
         }
         return Collections.emptyList();
     }
+
 }