Add native support for Kotlin default values in controllers

Closes spring-projectsgh-33384

spring-web/src/main/java/org/springframework/web/bind/annotation/ControllerMappingReflectiveProcessor.java

@@ -25,11 +25,13 @@
 import org.springframework.aot.hint.ExecutableMode;
 import org.springframework.aot.hint.ReflectionHints;
 import org.springframework.aot.hint.annotation.ReflectiveProcessor;
+import org.springframework.core.KotlinDetector;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.annotation.AnnotatedElementUtils;
 import org.springframework.http.HttpEntity;
 import org.springframework.lang.Nullable;
 import org.springframework.stereotype.Controller;
+import org.springframework.util.ReflectionUtils;
 
 /**
  * {@link ReflectiveProcessor} implementation for {@link Controller} and
@@ -71,6 +73,11 @@ protected void registerTypeHints(ReflectionHints hints, Class<?> type) {
 
  protected void registerMethodHints(ReflectionHints hints, Method method) {
  hints.registerMethod(method, ExecutableMode.INVOKE);
+ Class<?> declaringClass = method.getDeclaringClass();
+ if (KotlinDetector.isKotlinType(declaringClass)) {
+ ReflectionUtils.doWithMethods(declaringClass, m -> hints.registerMethod(m, ExecutableMode.INVOKE),
+ m -> m.getName().equals(method.getName() + "$default"));
+ }
  for (Parameter parameter : method.getParameters()) {
  registerParameterTypeHints(hints, MethodParameter.forParameter(parameter));
  }

spring-web/src/test/kotlin/org/springframework/web/bind/annotation/ControllerMappingReflectiveProcessorKotlinTests.kt

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2002-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web.bind.annotation
+
+import org.assertj.core.api.Assertions
+import org.junit.jupiter.api.Test
+import org.springframework.aot.hint.*
+
+/**
+ * Kotlin tests for {@link ControllerMappingReflectiveProcessor}.
+ *
+ * @author Sebastien Deleuze
+ */
+class ControllerMappingReflectiveProcessorKotlinTests {
+
+ private val processor = ControllerMappingReflectiveProcessor()
+
+ private val hints = ReflectionHints()
+
+ @Test
+ fun registerReflectiveHintsForFunctionWithDefaultArgumentValue() {
+ val method = SampleController::class.java.getDeclaredMethod("defaultValue", Boolean::class.javaObjectType)
+ processor.registerReflectionHints(hints, method)
+ Assertions.assertThat(hints.typeHints()).satisfiesExactlyInAnyOrder(
+ {
+ Assertions.assertThat(it.type).isEqualTo(TypeReference.of(SampleController::class.java))
+ Assertions.assertThat(it.methods()).extracting<String> { executableHint: ExecutableHint -> executableHint.name }
+ .containsExactlyInAnyOrder("defaultValue", "defaultValue\$default")
+ }
+ )
+ }
+
+ class SampleController {
+
+ @GetMapping("/defaultValue")
+ fun defaultValue(@RequestParam(required = false) argument: Boolean? = false) = argument
+ }
+
+}