Box Kotlin value class parameters in web endpoint

In order to avoid "java.lang.IllegalArgumentException:
object is not an instance of declaring class" errors.

Closes gh-31698

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

@@ -18,11 +18,14 @@ package org.springframework.web.method.support;
 
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
 import java.util.Arrays;
 import java.util.Map;
 import java.util.Objects;
 
 import kotlin.Unit;
+import kotlin.jvm.JvmClassMappingKt;
+import kotlin.reflect.KClass;
 import kotlin.reflect.KFunction;
 import kotlin.reflect.KParameter;
 import kotlin.reflect.jvm.KCallablesJvm;
@@ -35,8 +38,10 @@ import org.springframework.core.KotlinDetector;
 import org.springframework.core.MethodParameter;
 import org.springframework.core.ParameterNameDiscoverer;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.ObjectUtils;
+import org.springframework.util.ReflectionUtils;
 import org.springframework.validation.method.MethodValidator;
 import org.springframework.web.bind.WebDataBinder;
 import org.springframework.web.bind.support.SessionStatus;
@@ -60,6 +65,9 @@ public class InvocableHandlerMethod extends HandlerMethod {
 
 	private static final Class<?>[] EMPTY_GROUPS = new Class<?>[0];
 
+	private static final ReflectionUtils.MethodFilter boxImplFilter =
+			(method -> method.isSynthetic() && Modifier.isStatic(method.getModifiers()) && method.getName().equals("box-impl"));
+
 
 	private HandlerMethodArgumentResolverComposite resolvers = new HandlerMethodArgumentResolverComposite();
 
@@ -310,7 +318,15 @@ public class InvocableHandlerMethod extends HandlerMethod {
 					case INSTANCE -> argMap.put(parameter, target);
 					case VALUE -> {
 						if (!parameter.isOptional() || args[index] != null) {
-							argMap.put(parameter, args[index]);
+							if (parameter.getType().getClassifier() instanceof KClass<?> kClass && kClass.isValue()) {
+								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]));
+							}
+							else {
+								argMap.put(parameter, args[index]);
+							}
 						}
 						index++;
 					}

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

@@ -84,6 +84,20 @@ class InvocableHandlerMethodKotlinTests {
 		Assertions.assertThat(value).isNull()
 	}
 
+	@Test
+	fun valueClass() {
+		composite.addResolver(StubArgumentResolver(Long::class.java, 1L))
+		val value = getInvocable(Long::class.java).invokeForRequest(request, null)
+		Assertions.assertThat(value).isEqualTo(1L)
+	}
+
+	@Test
+	fun valueClassDefaultValue() {
+		composite.addResolver(StubArgumentResolver(Double::class.java))
+		val value = getInvocable(Double::class.java).invokeForRequest(request, null)
+		Assertions.assertThat(value).isEqualTo(3.1)
+	}
+
 	private fun getInvocable(vararg argTypes: Class<*>): InvocableHandlerMethod {
 		val method = ResolvableMethod.on(Handler::class.java).argTypes(*argTypes).resolveMethod()
 		val handlerMethod = InvocableHandlerMethod(Handler(), method)
@@ -116,6 +130,18 @@ class InvocableHandlerMethodKotlinTests {
 		fun nullable(arg: String?): String? {
 			return null
 		}
+
+		fun valueClass(limit: LongValueClass) =
+			limit.value
+
+		fun valueClass(limit: DoubleValueClass = DoubleValueClass(3.1)) =
+			limit.value
 	}
 
+	@JvmInline
+	value class LongValueClass(val value: Long)
+
+	@JvmInline
+	value class DoubleValueClass(val value: Double)
+
 }