Add Kotlin extension for RestTemplate

Issue: SPR-15056

Author: sdeleuze

build.gradle

@@ -791,6 +791,7 @@ project("spring-web") {
 		optional("javax.xml.bind:jaxb-api:${jaxbVersion}")
 		optional("javax.xml.ws:jaxws-api:${jaxwsVersion}")
 		optional("javax.mail:javax.mail-api:${javamailVersion}")
+		optional("org.jetbrains.kotlin:kotlin-stdlib:${kotlinVersion}")
 		testCompile(project(":spring-context-support"))  // for JafMediaTypeFactory
 		testCompile("io.projectreactor.addons:reactor-test:${reactorCoreVersion}")
 		testCompile("org.apache.taglibs:taglibs-standard-jstlel:1.2.1") {
@@ -807,7 +808,6 @@ project("spring-web") {
 		testCompile("org.xmlunit:xmlunit-matchers:${xmlunitVersion}")
 		testCompile("org.slf4j:slf4j-jcl:${slf4jVersion}")
 		testCompile("org.jetbrains.kotlin:kotlin-reflect:${kotlinVersion}")
-		testCompile("org.jetbrains.kotlin:kotlin-stdlib:${kotlinVersion}")
 		testRuntime("com.sun.mail:javax.mail:${javamailVersion}")
 		testRuntime("com.sun.xml.bind:jaxb-core:${jaxbVersion}")
 		testRuntime("com.sun.xml.bind:jaxb-impl:${jaxbVersion}")

spring-web/src/main/kotlin/org/springframework/web/client/RestOperationsExtension.kt

@@ -0,0 +1,116 @@
+package org.springframework.web.client
+
+import org.springframework.http.HttpEntity
+import org.springframework.http.HttpMethod
+import org.springframework.http.RequestEntity
+import java.net.URI
+
+/**
+ * Extension for [RestOperations] providing [KClass] based API and avoiding specifying
+ * a class parameter when possible thanks to Kotlin reified type parameters.
+ *
+ * @author Jon Schneider
+ * @author Sebastien Deleuze
+ * @since 5.0
+ */
+object RestOperationsExtension {
+
+	/**
+	 * @see RestOperations.getForObject
+	 */
+	@Throws(RestClientException::class)
+	inline fun <reified T: Any> RestOperations.getForObject(url: String, vararg uriVariables: Any) =
+			getForObject(url, T::class.java, *uriVariables)
+
+	/**
+	 * @see RestOperations.getForObject
+	 */
+	@Throws(RestClientException::class)
+	inline fun <reified T: Any> RestOperations.getForObject(url: String, uriVariables: Map<String, Any?>) =
+			getForObject(url, T::class.java, uriVariables)
+
+	/**
+	 * @see RestOperations.getForObject
+	 */
+	@Throws(RestClientException::class)
+	inline fun <reified T: Any> RestOperations.getForObject(url: URI) =
+			getForObject(url, T::class.java)
+
+	/**
+	 * @see RestOperations.getForEntity
+	 */
+	@Throws(RestClientException::class)
+	inline fun <reified T: Any> RestOperations.getForEntity(url: String, vararg uriVariables: Any) =
+			getForEntity(url, T::class.java, *uriVariables)
+
+	/**
+	 * @see RestOperations.postForObject
+	 */
+	@Throws(RestClientException::class)
+	inline fun <reified T: Any> RestOperations.postForObject(url: String, request: Any, vararg uriVariables: Any) =
+			postForObject(url, request, T::class.java, *uriVariables)
+
+	/**
+	 * @see RestOperations.postForObject
+	 */
+	@Throws(RestClientException::class)
+	inline fun <reified T: Any> RestOperations.postForObject(url: String, request: Any, uriVariables: Map<String, *>) =
+			postForObject(url, request, T::class.java, uriVariables)
+
+	/**
+	 * @see RestOperations.postForObject
+	 */
+	@Throws(RestClientException::class)
+	inline fun <reified T: Any> RestOperations.postForObject(url: URI, request: Any) =
+			postForObject(url, request, T::class.java)
+
+	/**
+	 * @see RestOperations.postForEntity
+	 */
+	@Throws(RestClientException::class)
+	inline fun <reified T: Any> RestOperations.postForEntity(url: String, request: Any, vararg uriVariables: Any) =
+			postForEntity(url, request, T::class.java, *uriVariables)
+
+	/**
+	 * @see RestOperations.postForEntity
+	 */
+	@Throws(RestClientException::class)
+	inline fun <reified T: Any> RestOperations.postForEntity(url: String, request: Any, uriVariables: Map<String, *>) =
+			postForEntity(url, request, T::class.java, uriVariables)
+
+	/**
+	 * @see RestOperations.postForEntity
+	 */
+	@Throws(RestClientException::class)
+	inline fun <reified T: Any> RestOperations.postForEntity(url: URI, request: Any) =
+			postForEntity(url, request, T::class.java)
+
+	/**
+	 * @see RestOperations.exchange
+	 */
+	@Throws(RestClientException::class)
+	inline fun <reified T: Any> RestOperations.exchange(url: String, method: HttpMethod, requestEntity: HttpEntity<*>, vararg uriVariables: Any) =
+			exchange(url, method, requestEntity, T::class.java, *uriVariables)
+
+	/**
+	 * @see RestOperations.exchange
+	 */
+	@Throws(RestClientException::class)
+	inline fun <reified T: Any> RestOperations.exchange(url: String, method: HttpMethod, requestEntity: HttpEntity<*>, uriVariables: Map<String, *>) =
+			exchange(url, method, requestEntity, T::class.java, uriVariables)
+
+	/**
+	 * @see RestOperations.exchange
+	 */
+	@Throws(RestClientException::class)
+	inline fun <reified T: Any> RestOperations.exchange(url: URI, method: HttpMethod, requestEntity: HttpEntity<*>) =
+			exchange(url, method, requestEntity, T::class.java)
+
+	/**
+	 * @see RestOperations.exchange
+	 */
+	@Throws(RestClientException::class)
+	inline fun <reified T: Any> RestOperations.exchange(requestEntity: RequestEntity<*>) =
+			exchange(requestEntity, T::class.java)
+
+}