Optimize Kotlin inline class checks

This commit fixes a performance regression caused by spring-projectsgh-31698,
and more specifically by KClass#isValue invocations which are slow since
they load the whole module to find the class to get the descriptor.

After discussing with the Kotlin team, it has been decided that only
checking for the presence of `@JvmInline` annotation is enough for
Spring use case.

As a consequence, this commit introduces a new
KotlinDetector#isInlineClass method that performs such check, and
BeanUtils, CoroutinesUtils and WebMVC/WebFlux InvocableHandlerMethod
have been refined to leverage it.

Closes spring-projectsgh-32334

spring-beans/src/main/java/org/springframework/beans/BeanUtils.java

@@ -32,11 +32,9 @@
 import java.util.Set;
 
 import kotlin.jvm.JvmClassMappingKt;
-import kotlin.jvm.JvmInline;
 import kotlin.reflect.KClass;
 import kotlin.reflect.KFunction;
 import kotlin.reflect.KParameter;
-import kotlin.reflect.full.KAnnotatedElements;
 import kotlin.reflect.full.KClasses;
 import kotlin.reflect.jvm.KCallablesJvm;
 import kotlin.reflect.jvm.ReflectJvmMapping;
@@ -874,8 +872,7 @@ public static <T> Constructor<T> findPrimaryConstructor(Class<T> clazz) {
 				if (primaryCtor == null) {
 					return null;
 				}
-				if (kClass.isValue() && !KAnnotatedElements
-						.findAnnotations(kClass, JvmClassMappingKt.getKotlinClass(JvmInline.class)).isEmpty()) {
+				if (KotlinDetector.isInlineClass(clazz)) {
 					Constructor<?>[] constructors = clazz.getDeclaredConstructors();
 					Assert.state(constructors.length == 1,
 							"Kotlin value classes annotated with @JvmInline are expected to have a single JVM constructor");

spring-core/src/main/java/org/springframework/core/CoroutinesUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * 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.
@@ -120,11 +120,17 @@ public static Publisher<?> invokeSuspendingFunction(CoroutineContext context, Me
 							case INSTANCE -> argMap.put(parameter, target);
 							case VALUE, EXTENSION_RECEIVER -> {
 								if (!parameter.isOptional() || args[index] != null) {
-									if (parameter.getType().getClassifier() instanceof KClass<?> kClass && kClass.isValue()) {
+									if (parameter.getType().getClassifier() instanceof KClass<?> kClass) {
 										Class<?> javaClass = JvmClassMappingKt.getJavaClass(kClass);
-										Method[] methods = ReflectionUtils.getUniqueDeclaredMethods(javaClass, boxImplFilter);
-										Assert.state(methods.length == 1, "Unable to find a single box-impl synthetic static method in " + javaClass.getName());
-										argMap.put(parameter, ReflectionUtils.invokeMethod(methods[0], null, args[index]));
+										if (KotlinDetector.isInlineClass(javaClass)) {
+											Method[] methods = ReflectionUtils.getUniqueDeclaredMethods(javaClass, boxImplFilter);
+											Assert.state(methods.length == 1,
+													"Unable to find a single box-impl synthetic static method in " + javaClass.getName());
+											argMap.put(parameter, ReflectionUtils.invokeMethod(methods[0], null, args[index]));
+										}
+										else {
+											argMap.put(parameter, args[index]);
+										}
 									}
 									else {
 										argMap.put(parameter, args[index]);

spring-core/src/main/java/org/springframework/core/KotlinDetector.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * 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.
@@ -35,24 +35,34 @@ public abstract class KotlinDetector {
 	@Nullable
 	private static final Class<? extends Annotation> kotlinMetadata;
 
+	@Nullable
+	private static final Class<? extends Annotation> kotlinJvmInline;
+
 	// For ConstantFieldFeature compliance, otherwise could be deduced from kotlinMetadata
 	private static final boolean kotlinPresent;
 
 	private static final boolean kotlinReflectPresent;
 
 	static {
-		Class<?> metadata;
 		ClassLoader classLoader = KotlinDetector.class.getClassLoader();
+		Class<?> metadata = null;
+		Class<?> jvmInline = null;
 		try {
 			metadata = ClassUtils.forName("kotlin.Metadata", classLoader);
+			try {
+				jvmInline = ClassUtils.forName("kotlin.jvm.JvmInline", classLoader);
+			}
+			catch (ClassNotFoundException ex) {
+				// JVM inline support not available
+			}
 		}
 		catch (ClassNotFoundException ex) {
 			// Kotlin API not available - no Kotlin support
-			metadata = null;
 		}
 		kotlinMetadata = (Class<? extends Annotation>) metadata;
 		kotlinPresent = (kotlinMetadata != null);
-		kotlinReflectPresent = ClassUtils.isPresent("kotlin.reflect.full.KClasses", classLoader);
+		kotlinReflectPresent = kotlinPresent && ClassUtils.isPresent("kotlin.reflect.full.KClasses", classLoader);
+		kotlinJvmInline = (Class<? extends Annotation>) jvmInline;
 	}
 
 
@@ -93,4 +103,14 @@ public static boolean isSuspendingFunction(Method method) {
 		return false;
 	}
 
+	/**
+	 * Determine whether the given {@code Class} is an inline class
+	 * (annotated with {@code @JvmInline}).
+	 * @since 6.1.5
+	 * @see <a href="https://kotlinlang.org/docs/inline-classes.html">Kotlin inline value classes</a>
+	 */
+	public static boolean isInlineClass(Class<?> clazz) {
+		return (kotlinJvmInline != null && clazz.getDeclaredAnnotation(kotlinJvmInline) != null);
+	}
+
 }

spring-core/src/test/kotlin/org/springframework/core/KotlinDetectorTests.kt

@@ -0,0 +1,52 @@
+/*
+ * 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.core
+
+import org.assertj.core.api.Assertions
+import org.junit.jupiter.api.Test
+
+/**
+ * Kotlin tests for [KotlinDetector].
+ *
+ * @author Sebastien Deleuze
+ */
+class KotlinDetectorTests {
+
+	@Test
+	fun isKotlinType() {
+		Assertions.assertThat(KotlinDetector.isKotlinType(KotlinDetectorTests::class.java)).isTrue()
+	}
+
+	@Test
+	fun isNotKotlinType() {
+		Assertions.assertThat(KotlinDetector.isKotlinType(KotlinDetector::class.java)).isFalse()
+	}
+
+	@Test
+	fun isInlineClass() {
+		Assertions.assertThat(KotlinDetector.isInlineClass(ValueClass::class.java)).isTrue()
+	}
+
+	@Test
+	fun isNotInlineClass() {
+		Assertions.assertThat(KotlinDetector.isInlineClass(KotlinDetector::class.java)).isFalse()
+		Assertions.assertThat(KotlinDetector.isInlineClass(KotlinDetectorTests::class.java)).isFalse()
+	}
+
+	@JvmInline
+	value class ValueClass(val value: String)
+
+}

spring-web/src/main/java/org/springframework/web/method/support/InvocableHandlerMethod.java

@@ -319,11 +319,17 @@ public static Object invokeFunction(Method method, Object target, Object[] args)
 					case INSTANCE -> argMap.put(parameter, target);
 					case VALUE, EXTENSION_RECEIVER -> {
 						if (!parameter.isOptional() || args[index] != null) {
-							if (parameter.getType().getClassifier() instanceof KClass<?> kClass && kClass.isValue()) {
+							if (parameter.getType().getClassifier() instanceof KClass<?> kClass) {
 								Class<?> javaClass = JvmClassMappingKt.getJavaClass(kClass);
-								Method[] methods = ReflectionUtils.getUniqueDeclaredMethods(javaClass, boxImplFilter);
-								Assert.state(methods.length == 1, "Unable to find a single box-impl synthetic static method in " + javaClass.getName());
-								argMap.put(parameter, ReflectionUtils.invokeMethod(methods[0], null, args[index]));
+								if (KotlinDetector.isInlineClass(javaClass)) {
+									Method[] methods = ReflectionUtils.getUniqueDeclaredMethods(javaClass, boxImplFilter);
+									Assert.state(methods.length == 1,
+											"Unable to find a single box-impl synthetic static method in " + javaClass.getName());
+									argMap.put(parameter, ReflectionUtils.invokeMethod(methods[0], null, args[index]));
+								}
+								else {
+									argMap.put(parameter, args[index]);
+								}
 							}
 							else {
 								argMap.put(parameter, args[index]);

spring-webflux/src/main/java/org/springframework/web/reactive/result/method/InvocableHandlerMethod.java

@@ -330,11 +330,17 @@ public static Object invokeFunction(Method method, Object target, Object[] args,
 						case INSTANCE -> argMap.put(parameter, target);
 						case VALUE, EXTENSION_RECEIVER -> {
 							if (!parameter.isOptional() || args[index] != null) {
-								if (parameter.getType().getClassifier() instanceof KClass<?> kClass && kClass.isValue()) {
+								if (parameter.getType().getClassifier() instanceof KClass<?> kClass) {
 									Class<?> javaClass = JvmClassMappingKt.getJavaClass(kClass);
-									Method[] methods = ReflectionUtils.getUniqueDeclaredMethods(javaClass, boxImplFilter);
-									Assert.state(methods.length == 1, "Unable to find a single box-impl synthetic static method in " + javaClass.getName());
-									argMap.put(parameter, ReflectionUtils.invokeMethod(methods[0], null, args[index]));
+									if (KotlinDetector.isInlineClass(javaClass)) {
+										Method[] methods = ReflectionUtils.getUniqueDeclaredMethods(javaClass, boxImplFilter);
+										Assert.state(methods.length == 1,
+												"Unable to find a single box-impl synthetic static method in " + javaClass.getName());
+										argMap.put(parameter, ReflectionUtils.invokeMethod(methods[0], null, args[index]));
+									}
+									else {
+										argMap.put(parameter, args[index]);
+									}
 								}
 								else {
 									argMap.put(parameter, args[index]);