Add PATCH method operation to RestTemplate

This commit adds a HTTP PATCH operation to the RestTemplate:
patchForObject. As with most operations, there are three variants:
varargs, Map, and URI based.

Issue: SPR-14857

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

@@ -1,11 +1,11 @@
 /*
- * 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.
  * You may obtain a copy of the License at
  *
- *     http://www.apache.org/licenses/LICENSE-2.0
+ *      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,
@@ -306,6 +306,56 @@ public interface RestOperations {
 	void put(URI url, Object request) throws RestClientException;
 
 
+	// PATCH
+
+	/**
+	 * Update a resource by PATCHing the given object to the URI template,
+	 * and returns the representation found in the response.
+	 * <p>URI Template variables are expanded using the given URI variables, if any.
+	 * <p>The {@code request} parameter can be a {@link HttpEntity} in order to
+	 * add additional HTTP headers to the request.
+	 * @param url the URL
+	 * @param request the Object to be PATCHed, may be {@code null}
+	 * @param responseType the type of the return value
+	 * @param uriVariables the variables to expand the template
+	 * @return the converted object
+	 * @see HttpEntity
+	 * @since 5.0
+	 */
+	<T> T patchForObject(String url, Object request, Class<T> responseType, Object... uriVariables)
+			throws RestClientException;
+
+	/**
+	 * Update a resource by PATCHing the given object to the URI template,
+	 * and returns the representation found in the response.
+	 * <p>URI Template variables are expanded using the given map.
+	 * <p>The {@code request} parameter can be a {@link HttpEntity} in order to
+	 * add additional HTTP headers to the request.
+	 * @param url the URL
+	 * @param request the Object to be PATCHed, may be {@code null}
+	 * @param responseType the type of the return value
+	 * @param uriVariables the variables to expand the template
+	 * @return the converted object
+	 * @see HttpEntity
+	 */
+	<T> T patchForObject(String url, Object request, Class<T> responseType, Map<String, ?> uriVariables)
+			throws RestClientException;
+
+	/**
+	 * Update a resource by PATCHing the given object to the URL,
+	 * and returns the representation found in the response.
+	 * <p>The {@code request} parameter can be a {@link HttpEntity} in order to
+	 * add additional HTTP headers to the request.
+	 * @param url the URL
+	 * @param request the Object to be POSTed, may be {@code null}
+	 * @param responseType the type of the return value
+	 * @return the converted object
+	 * @see HttpEntity
+	 */
+	<T> T patchForObject(URI url, Object request, Class<T> responseType) throws RestClientException;
+
+
+
 	// DELETE
 
 	/**

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

@@ -458,6 +458,37 @@ public class RestTemplate extends InterceptingHttpAccessor implements RestOperat
 		execute(url, HttpMethod.PUT, requestCallback, null);
 	}
 
+	// PATCH
+
+	@Override
+	public <T> T patchForObject(String url, Object request, Class<T> responseType,
+			Object... uriVariables) throws RestClientException {
+
+		RequestCallback requestCallback = httpEntityCallback(request, responseType);
+		HttpMessageConverterExtractor<T> responseExtractor =
+				new HttpMessageConverterExtractor<>(responseType, getMessageConverters(), logger);
+		return execute(url, HttpMethod.PATCH, requestCallback, responseExtractor, uriVariables);
+	}
+
+	@Override
+	public <T> T patchForObject(String url, Object request, Class<T> responseType,
+			Map<String, ?> uriVariables) throws RestClientException {
+
+		RequestCallback requestCallback = httpEntityCallback(request, responseType);
+		HttpMessageConverterExtractor<T> responseExtractor =
+				new HttpMessageConverterExtractor<>(responseType, getMessageConverters(), logger);
+		return execute(url, HttpMethod.PATCH, requestCallback, responseExtractor, uriVariables);
+	}
+
+	@Override
+	public <T> T patchForObject(URI url, Object request, Class<T> responseType)
+			throws RestClientException {
+
+		RequestCallback requestCallback = httpEntityCallback(request, responseType);
+		HttpMessageConverterExtractor<T> responseExtractor =
+				new HttpMessageConverterExtractor<>(responseType, getMessageConverters());
+		return execute(url, HttpMethod.PATCH, requestCallback, responseExtractor);
+	}
 
 	// DELETE