Recursively box/unbox nested inline value classes

See gh-34592
Signed-off-by: Dmitry Sulman <dmitry.sulman@gmail.com>

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -20,6 +20,7 @@ import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.util.Arrays;
 import java.util.Map;
+import java.util.Objects;
 
 import kotlin.Unit;
 import kotlin.jvm.JvmClassMappingKt;
@@ -322,11 +323,7 @@ public class InvocableHandlerMethod extends HandlerMethod {
 							KType type = parameter.getType();
 							if (!(type.isMarkedNullable() && arg == null) && type.getClassifier() instanceof KClass<?> kClass
 									&& KotlinDetector.isInlineClass(JvmClassMappingKt.getJavaClass(kClass))) {
-								KFunction<?> constructor = KClasses.getPrimaryConstructor(kClass);
-								if (!KCallablesJvm.isAccessible(constructor)) {
-									KCallablesJvm.setAccessible(constructor, true);
-								}
-								arg = constructor.call(arg);
+								arg = box(kClass, arg);
 							}
 							argMap.put(parameter, arg);
 						}
@@ -341,6 +338,19 @@ public class InvocableHandlerMethod extends HandlerMethod {
 			return (result == Unit.INSTANCE ? null : result);
 		}
 
+		private static Object box(KClass<?> kClass, @Nullable Object arg) {
+			KFunction<?> constructor = Objects.requireNonNull(KClasses.getPrimaryConstructor(kClass));
+			KType type = constructor.getParameters().get(0).getType();
+			if (!(type.isMarkedNullable() && arg == null) && type.getClassifier() instanceof KClass<?> parameterClass
+					&& KotlinDetector.isInlineClass(JvmClassMappingKt.getJavaClass(parameterClass))) {
+				arg = box(parameterClass, arg);
+			}
+			if (!KCallablesJvm.isAccessible(constructor)) {
+				KCallablesJvm.setAccessible(constructor, true);
+			}
+			return constructor.call(arg);
+		}
+
 		private static void handleResult(Object result, SynchronousSink<Object> sink) {
 			if (KotlinDetector.isInlineClass(result.getClass())) {
 				try {
@@ -361,7 +371,11 @@ public class InvocableHandlerMethod extends HandlerMethod {
 		}
 
 		private static Object unbox(Object result) throws InvocationTargetException, IllegalAccessException, NoSuchMethodException {
-			return result.getClass().getDeclaredMethod("unbox-impl").invoke(result);
+			Object unboxed = result.getClass().getDeclaredMethod("unbox-impl").invoke(result);
+			if (KotlinDetector.isInlineClass(unboxed.getClass())) {
+				return unbox(unboxed);
+			}
+			return unboxed;
 		}
 	}
 

spring-web/src/test/kotlin/org/springframework/web/method/support/InvocableHandlerMethodKotlinTests.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -109,12 +109,25 @@ class InvocableHandlerMethodKotlinTests {
 		Assertions.assertThat(value).isEqualTo(1L)
 	}
 
+	@Test
+	fun nestedValueClass() {
+		composite.addResolver(StubArgumentResolver(Long::class.java, 1L))
+		val value = getInvocable(ValueClassHandler::nestedValueClass.javaMethod!!).invokeForRequest(request, null)
+		Assertions.assertThat(value).isEqualTo(1L)
+	}
+
 	@Test
 	fun valueClassReturnValue() {
 		val value = getInvocable(ValueClassHandler::valueClassReturnValue.javaMethod!!).invokeForRequest(request, null)
 		Assertions.assertThat(value).isEqualTo("foo")
 	}
 
+	@Test
+	fun nestedValueClassReturnValue() {
+		val value = getInvocable(ValueClassHandler::nestedValueClassReturnValue.javaMethod!!).invokeForRequest(request, null)
+		Assertions.assertThat(value).isEqualTo("foo")
+	}
+
 	@Test
 	fun resultOfUnitReturnValue() {
 		val value = getInvocable(ValueClassHandler::resultOfUnitReturnValue.javaMethod!!).invokeForRequest(request, null)
@@ -273,10 +286,14 @@ class InvocableHandlerMethodKotlinTests {
 
 		fun valueClassReturnValue() = StringValueClass("foo")
 
+		fun nestedValueClassReturnValue() = NestedStringValueClass(StringValueClass("foo"))
+
 		fun resultOfUnitReturnValue() = Result.success(Unit)
 
 		fun longValueClass(limit: LongValueClass) = limit.value
 
+		fun nestedValueClass(limit: ULongValueClass) = limit.value
+
 		fun doubleValueClass(limit: DoubleValueClass = DoubleValueClass(3.1)) = limit.value
 
 		fun valueClassWithInit(valueClass: ValueClassWithInit) = valueClass
@@ -358,9 +375,15 @@ class InvocableHandlerMethodKotlinTests {
 	@JvmInline
 	value class StringValueClass(val value: String)
 
+	@JvmInline
+	value class NestedStringValueClass(val value: StringValueClass)
+
 	@JvmInline
 	value class LongValueClass(val value: Long)
 
+	@JvmInline
+	value class ULongValueClass(val value: ULong)
+
 	@JvmInline
 	value class DoubleValueClass(val value: Double)
 

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

@@ -23,6 +23,7 @@ import java.lang.reflect.Type;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.stream.Stream;
 
 import kotlin.Unit;
@@ -361,11 +362,7 @@ public class InvocableHandlerMethod extends HandlerMethod {
 								KType type = parameter.getType();
 								if (!(type.isMarkedNullable() && arg == null) && type.getClassifier() instanceof KClass<?> kClass
 										&& KotlinDetector.isInlineClass(JvmClassMappingKt.getJavaClass(kClass))) {
-									KFunction<?> constructor = KClasses.getPrimaryConstructor(kClass);
-									if (!KCallablesJvm.isAccessible(constructor)) {
-										KCallablesJvm.setAccessible(constructor, true);
-									}
-									arg = constructor.call(arg);
+									arg = box(kClass, arg);
 								}
 								argMap.put(parameter, arg);
 							}
@@ -381,6 +378,19 @@ public class InvocableHandlerMethod extends HandlerMethod {
 			}
 		}
 
+		private static Object box(KClass<?> kClass, Object arg) {
+			KFunction<?> constructor = Objects.requireNonNull(KClasses.getPrimaryConstructor(kClass));
+			KType type = constructor.getParameters().get(0).getType();
+			if (!(type.isMarkedNullable() && arg == null) && type.getClassifier() instanceof KClass<?> parameterClass
+					&& KotlinDetector.isInlineClass(JvmClassMappingKt.getJavaClass(parameterClass))) {
+				arg = box(parameterClass, arg);
+			}
+			if (!KCallablesJvm.isAccessible(constructor)) {
+				KCallablesJvm.setAccessible(constructor, true);
+			}
+			return constructor.call(arg);
+		}
+
 		private static void handleResult(Object result, SynchronousSink<Object> sink) {
 			if (KotlinDetector.isInlineClass(result.getClass())) {
 				try {
@@ -401,7 +411,11 @@ public class InvocableHandlerMethod extends HandlerMethod {
 		}
 
 		private static Object unbox(Object result) throws InvocationTargetException, IllegalAccessException, NoSuchMethodException {
-			return result.getClass().getDeclaredMethod("unbox-impl").invoke(result);
+			Object unboxed = result.getClass().getDeclaredMethod("unbox-impl").invoke(result);
+			if (KotlinDetector.isInlineClass(unboxed.getClass())) {
+				return unbox(unboxed);
+			}
+			return unboxed;
 		}
 
 	}

spring-webflux/src/test/kotlin/org/springframework/web/reactive/result/InvocableHandlerMethodKotlinTests.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2024 the original author or authors.
+ * Copyright 2002-2025 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.
@@ -205,6 +205,14 @@ class InvocableHandlerMethodKotlinTests {
 		assertHandlerResultValue(result, "1")
 	}
 
+	@Test
+	fun nestedValueClass() {
+		this.resolvers.add(stubResolver(1L, Long::class.java))
+		val method = ValueClassController::nestedValueClass.javaMethod!!
+		val result = invoke(ValueClassController(), method,1L)
+		assertHandlerResultValue(result, "1")
+	}
+
 	@Test
 	fun valueClassReturnValue() {
 		val method = ValueClassController::valueClassReturnValue.javaMethod!!
@@ -212,6 +220,13 @@ class InvocableHandlerMethodKotlinTests {
 		assertHandlerResultValue(result, "foo")
 	}
 
+	@Test
+	fun nestedValueClassReturnValue() {
+		val method = ValueClassController::nestedValueClassReturnValue.javaMethod!!
+		val result = invoke(ValueClassController(), method)
+		assertHandlerResultValue(result, "foo")
+	}
+
 	@Test
 	fun resultOfUnitReturnValue() {
 		val method = ValueClassController::resultOfUnitReturnValue.javaMethod!!
@@ -448,8 +463,12 @@ class InvocableHandlerMethodKotlinTests {
 
 		fun valueClass(limit: LongValueClass) = "${limit.value}"
 
+		fun nestedValueClass(limit: ULongValueClass) = "${limit.value}"
+
 		fun valueClassReturnValue() = StringValueClass("foo")
 
+		fun nestedValueClassReturnValue() = NestedStringValueClass(StringValueClass("foo"))
+
 		fun resultOfUnitReturnValue() = Result.success(Unit)
 
 		fun valueClassWithDefault(limit: DoubleValueClass = DoubleValueClass(3.1)) = "${limit.value}"
@@ -533,9 +552,15 @@ class InvocableHandlerMethodKotlinTests {
 	@JvmInline
 	value class StringValueClass(val value: String)
 
+	@JvmInline
+	value class NestedStringValueClass(val value: StringValueClass)
+
 	@JvmInline
 	value class LongValueClass(val value: Long)
 
+	@JvmInline
+	value class ULongValueClass(val value: ULong)
+
 	@JvmInline
 	value class DoubleValueClass(val value: Double)