Deprecate OkHttp 2.x support

Issue: SPR-14344

spring-web/src/main/java/org/springframework/http/client/OkHttpAsyncClientHttpRequest.java

@@ -39,7 +39,9 @@ import org.springframework.util.concurrent.SettableListenableFuture;
  * @author Arjen Poutsma
  * @since 4.3
  * @see org.springframework.http.client.OkHttp3AsyncClientHttpRequest
+ * @deprecated as of Spring 5.0, in favor of OkHttp 3.x
  */
+@Deprecated
 class OkHttpAsyncClientHttpRequest extends AbstractBufferingAsyncClientHttpRequest {
 
 	private final OkHttpClient client;
@@ -75,6 +77,7 @@ class OkHttpAsyncClientHttpRequest extends AbstractBufferingAsyncClientHttpReque
 	}
 
 
+	@Deprecated
 	private static class OkHttpListenableFuture extends SettableListenableFuture<ClientHttpResponse> {
 
 		private final Call call;

spring-web/src/main/java/org/springframework/http/client/OkHttpClientHttpRequest.java

@@ -34,7 +34,9 @@ import org.springframework.http.HttpMethod;
  * @author Arjen Poutsma
  * @since 4.2
  * @see org.springframework.http.client.OkHttp3ClientHttpRequest
+ * @deprecated as of Spring 5.0, in favor of OkHttp 3.x
  */
+@Deprecated
 class OkHttpClientHttpRequest extends AbstractBufferingClientHttpRequest {
 
 	private final OkHttpClient client;

spring-web/src/main/java/org/springframework/http/client/OkHttpClientHttpRequestFactory.java

@@ -42,7 +42,9 @@ import org.springframework.util.StringUtils;
  * @author Arjen Poutsma
  * @since 4.2
  * @see org.springframework.http.client.OkHttp3ClientHttpRequestFactory
+ * @deprecated as of Spring 5.0, in favor of OkHttp 3.x
  */
+@Deprecated
 public class OkHttpClientHttpRequestFactory
 		implements ClientHttpRequestFactory, AsyncClientHttpRequestFactory, DisposableBean {
 

spring-web/src/main/java/org/springframework/http/client/OkHttpClientHttpResponse.java

@@ -31,7 +31,9 @@ import org.springframework.util.Assert;
  * @author Arjen Poutsma
  * @since 4.2
  * @see org.springframework.http.client.OkHttp3ClientHttpResponse
+ * @deprecated as of Spring 5.0, in favor of OkHttp 3.x
  */
+@Deprecated
 class OkHttpClientHttpResponse extends AbstractClientHttpResponse {
 
 	private final Response response;