Leverage kotlin-reflect to determine parameter names

This is especially useful to determine interface parameter names
without requiring Java 8 -parameters compiler flag.

Issue: SPR-15541

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

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2002-2013 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
+ *
+ *      http://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.junit.Test
+
+import org.hamcrest.CoreMatchers.`is`
+import org.hamcrest.MatcherAssert.assertThat
+import org.springframework.util.ReflectionUtils
+
+/**
+ * Tests for KotlinReflectionParameterNameDiscoverer
+ */
+class KotlinReflectionParameterNameDiscovererTests {
+
+	private val parameterNameDiscoverer = KotlinReflectionParameterNameDiscoverer()
+
+	@Test
+	fun getParameterNamesOnInterface() {
+		val method = ReflectionUtils.findMethod(MessageService::class.java,"sendMessage", String::class.java)!!
+		val actualParams = parameterNameDiscoverer.getParameterNames(method)
+		assertThat(actualParams, `is`(arrayOf("message")))
+	}
+
+	@Test
+	fun getParameterNamesOnClass() {
+		val method = ReflectionUtils.findMethod(MessageServiceImpl::class.java,"sendMessage", String::class.java)!!
+		val actualParams = parameterNameDiscoverer.getParameterNames(method)
+		assertThat(actualParams, `is`(arrayOf("message")))
+	}
+
+	interface MessageService {
+		fun sendMessage(message: String)
+	}
+
+	class MessageServiceImpl {
+		fun sendMessage(message: String) = message
+	}
+}