Add MetadataExtractorRegistry.metadataToExtract Kotlin extensions

Closes gh-23705

spring-messaging/src/main/kotlin/org/springframework/messaging/rsocket/MetadataExtractorRegistryExtensions.kt

@@ -0,0 +1,47 @@
+/*
+ * Copyright 2002-2019 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.messaging.rsocket
+
+import org.springframework.util.MimeType
+
+/**
+ * Extension for [MetadataExtractorRegistry.metadataToExtract] providing a `metadataToExtract<Foo>(...)`
+ * variant leveraging Kotlin reified type parameters. This extension is not subject to type
+ * erasure and retains actual generic type arguments.
+ * @param mimeType the mime type of metadata entries to extract
+ * @param name assign a name for the decoded value; if not provided, then
+ * the mime type is used as the key
+ * @param T the target value type to decode to
+ * @author Sebastien Deleuze
+ * @since 5.2
+ */
+inline fun <reified T : Any > MetadataExtractorRegistry.metadataToExtract(mimeType: MimeType, name: String? = null) =
+		metadataToExtract(mimeType, object : org.springframework.core.ParameterizedTypeReference<T>() {}, name)
+
+/**
+ * Extension for [MetadataExtractorRegistry.metadataToExtract] providing a `metadataToExtract<Foo>(...)`
+ * variant leveraging Kotlin reified type parameters. This extension is not subject to type
+ * erasure and retains actual generic type arguments.
+ * @param mimeType the mime type of metadata entries to extract
+ * @param mapper custom logic to add the decoded value to the output map
+ * @param T the target value type to decode to
+ * @author Sebastien Deleuze
+ * @since 5.2
+ */
+inline fun <reified T : Any > MetadataExtractorRegistry.metadataToExtract(mimeType: MimeType, noinline mapper: (T, MutableMap<String, Any>) -> Unit) =
+		metadataToExtract(mimeType, object : org.springframework.core.ParameterizedTypeReference<T>() {}, mapper)
+