Add @FunctionalInterface on candidate interfaces

Issue: SPR-14432

spring-web/src/main/java/org/springframework/http/StreamingHttpOutputMessage.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -41,6 +41,7 @@ public interface StreamingHttpOutputMessage extends HttpOutputMessage {
 	 * It is useful with HTTP client libraries that provide indirect access to an
 	 * {@link OutputStream} via a callback mechanism.
 	 */
+	@FunctionalInterface
 	interface Body {
 
 		/**

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2011 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -30,6 +30,7 @@ import org.springframework.http.HttpRequest;
  * @see ClientHttpRequestInterceptor
  * @since 3.1
  */
+@FunctionalInterface
 public interface ClientHttpRequestExecution {
 
 	/**

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -28,6 +28,7 @@ import org.springframework.http.HttpMethod;
  * @author Arjen Poutsma
  * @since 3.0
  */
+@FunctionalInterface
 public interface ClientHttpRequestFactory {
 
 	/**

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -31,6 +31,7 @@ import org.springframework.http.HttpRequest;
  * @author Arjen Poutsma
  * @since 3.1
  */
+@FunctionalInterface
 public interface ClientHttpRequestInterceptor {
 
 	/**

spring-web/src/main/java/org/springframework/remoting/httpinvoker/HttpInvokerRequestExecutor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -41,6 +41,7 @@ import org.springframework.remoting.support.RemoteInvocationResult;
  * @since 1.1
  * @see HttpInvokerClientInterceptor#setHttpInvokerRequestExecutor
  */
+@FunctionalInterface
 public interface HttpInvokerRequestExecutor {
 
 	/**

spring-web/src/main/java/org/springframework/web/HttpRequestHandler.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -74,6 +74,7 @@ import javax.servlet.http.HttpServletResponse;
  * @see org.springframework.remoting.caucho.HessianServiceExporter
  * @see org.springframework.remoting.caucho.BurlapServiceExporter
  */
+@FunctionalInterface
 public interface HttpRequestHandler {
 
 	/**

spring-web/src/main/java/org/springframework/web/accept/ContentNegotiationStrategy.java

@@ -28,6 +28,7 @@ import org.springframework.web.context.request.NativeWebRequest;
  * @author Rossen Stoyanchev
  * @since 3.2
  */
+@FunctionalInterface
 public interface ContentNegotiationStrategy {
 
 	/**

spring-web/src/main/java/org/springframework/web/bind/support/WebArgumentResolver.java

@@ -41,6 +41,7 @@ import org.springframework.web.context.request.NativeWebRequest;
  * @since 2.5.2
  * @see org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter#setCustomArgumentResolvers
  */
+@FunctionalInterface
 public interface WebArgumentResolver {
 
 	/**

spring-web/src/main/java/org/springframework/web/client/AsyncRequestCallback.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -30,6 +30,7 @@ import org.springframework.http.client.AsyncClientHttpRequest;
  * @see org.springframework.web.client.AsyncRestTemplate#execute
  * @since 4.0
  */
+@FunctionalInterface
 public interface AsyncRequestCallback {
 
 	/**

spring-web/src/main/java/org/springframework/web/client/RequestCallback.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -30,6 +30,7 @@ import org.springframework.http.client.ClientHttpRequest;
  * @see RestTemplate#execute
  * @since 3.0
  */
+@FunctionalInterface
 public interface RequestCallback {
 
 	/**

spring-web/src/main/java/org/springframework/web/client/ResponseExtractor.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2009 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -32,6 +32,7 @@ import org.springframework.http.client.ClientHttpResponse;
  * @since 3.0
  * @see RestTemplate#execute
  */
+@FunctionalInterface
 public interface ResponseExtractor<T> {
 
 	/**

spring-web/src/main/java/org/springframework/web/context/request/async/DeferredResult.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -243,6 +243,7 @@ public class DeferredResult<T> {
 	/**
 	 * Handles a DeferredResult value when set.
 	 */
+	@FunctionalInterface
 	public interface DeferredResultHandler {
 
 		void handleResult(Object result);