Fix complexity for DefaultHttpHeaderMapper (#2881)

* Fix complexity for DefaultHttpHeaderMapper

* Deprecate `DefaultHttpHeaderMapper` constants which are fully
Spring Web `HttpHeaders` constants
* Introduce lowercase constants for `getHttpHeader()` switch
* Reuse `HttpHeaders` API as much as possible
* Simplify logic in some methods to break them to smaller methods

* * Remove Java Streams from critical paths
* Rework `setHttpHeader()` for `switch`

* * Use `ObjectUtils.toObjectArray()` to simplify complexity

* * Fix complexity in `setAccept()`, `setAcceptCharset()`, `setAllow()`
& `setIfNoneMatch()` using newly extracted `valueToCollection()`

spring-integration-http/src/main/java/org/springframework/integration/http/outbound/AbstractHttpRequestExecutingMessageHandler.java

@@ -188,9 +188,7 @@ public abstract class AbstractHttpRequestExecutingMessageHandler extends Abstrac
 	 * be returned as a payload of the reply Message.
 	 * To take advantage of the HttpMessageConverters
 	 * registered on this adapter, provide a different type).
-	 *
 	 * @param expectedResponseType The expected type.
-	 *
 	 * Also see {@link #setExpectedResponseTypeExpression(Expression)}
 	 */
 	public void setExpectedResponseType(Class<?> expectedResponseType) {
@@ -221,7 +219,6 @@ public abstract class AbstractHttpRequestExecutingMessageHandler extends Abstrac
 	/**
 	 * Set the Map of URI variable expressions to evaluate against the outbound message
 	 * when replacing the variable placeholders in a URI template.
-	 *
 	 * @param uriVariableExpressions The URI variable expressions.
 	 */
 	public void setUriVariableExpressions(Map<String, Expression> uriVariableExpressions) {
@@ -235,7 +232,6 @@ public abstract class AbstractHttpRequestExecutingMessageHandler extends Abstrac
 	 * Set the {@link Expression} to evaluate against the outbound message; the expression
 	 * must evaluate to a Map of URI variable expressions to evaluate against the outbound message
 	 * when replacing the variable placeholders in a URI template.
-	 *
 	 * @param uriVariablesExpression The URI variables expression.
 	 */
 	public void setUriVariablesExpression(Expression uriVariablesExpression) {
@@ -246,7 +242,6 @@ public abstract class AbstractHttpRequestExecutingMessageHandler extends Abstrac
 	 * Set to true if you wish 'Set-Cookie' headers in responses to be
 	 * transferred as 'Cookie' headers in subsequent interactions for
 	 * a message.
-	 *
 	 * @param transferCookies the transferCookies to set.
 	 */
 	public void setTransferCookies(boolean transferCookies) {
@@ -343,14 +338,14 @@ public abstract class AbstractHttpRequestExecutingMessageHandler extends Abstrac
 	private void doConvertSetCookie(Map<String, Object> headers) {
 		String keyName = null;
 		for (String key : headers.keySet()) {
-			if (key.equalsIgnoreCase(DefaultHttpHeaderMapper.SET_COOKIE)) {
+			if (key.equalsIgnoreCase(HttpHeaders.SET_COOKIE)) {
 				keyName = key;
 				break;
 			}
 		}
 		if (keyName != null) {
 			Object cookies = headers.remove(keyName);
-			headers.put(DefaultHttpHeaderMapper.COOKIE, cookies);
+			headers.put(HttpHeaders.COOKIE, cookies);
 			if (logger.isDebugEnabled()) {
 				logger.debug("Converted Set-Cookie header to Cookie for: "
 						+ cookies);
@@ -562,7 +557,6 @@ public abstract class AbstractHttpRequestExecutingMessageHandler extends Abstrac
 				.usingEvaluationContext(evaluationContextToUse)
 				.withRoot(requestMessage)
 				.build();
-
 	}
 
 }

spring-integration-http/src/main/java/org/springframework/integration/http/outbound/HttpRequestExecutingMessageHandler.java

@@ -61,11 +61,11 @@ import org.springframework.web.client.RestTemplate;
  * @since 2.0
  */
 public class HttpRequestExecutingMessageHandler extends AbstractHttpRequestExecutingMessageHandler {
+
 	private final RestTemplate restTemplate;
 
 	/**
 	 * Create a handler that will send requests to the provided URI.
-	 *
 	 * @param uri The URI.
 	 */
 	public HttpRequestExecutingMessageHandler(URI uri) {
@@ -74,7 +74,6 @@ public class HttpRequestExecutingMessageHandler extends AbstractHttpRequestExecu
 
 	/**
 	 * Create a handler that will send requests to the provided URI.
-	 *
 	 * @param uri The URI.
 	 */
 	public HttpRequestExecutingMessageHandler(String uri) {
@@ -83,7 +82,6 @@ public class HttpRequestExecutingMessageHandler extends AbstractHttpRequestExecu
 
 	/**
 	 * Create a handler that will send requests to the provided URI Expression.
-	 *
 	 * @param uriExpression The URI expression.
 	 */
 	public HttpRequestExecutingMessageHandler(Expression uriExpression) {
@@ -142,9 +140,7 @@ public class HttpRequestExecutingMessageHandler extends AbstractHttpRequestExecu
 
 	/**
 	 * Set the {@link ClientHttpRequestFactory} for the underlying {@link RestTemplate}.
-	 *
 	 * @param requestFactory The request factory.
-	 *
 	 * @see RestTemplate#setRequestFactory(ClientHttpRequestFactory)
 	 */
 	public void setRequestFactory(ClientHttpRequestFactory requestFactory) {
@@ -154,6 +150,7 @@ public class HttpRequestExecutingMessageHandler extends AbstractHttpRequestExecu
 	@Override
 	protected Object exchange(Supplier<URI> uriSupplier, HttpMethod httpMethod, HttpEntity<?> httpRequest,
 			Object expectedResponseType, Message<?> requestMessage) {
+
 		URI uri = uriSupplier.get();
 		ResponseEntity<?> httpResponse;
 		try {
@@ -162,14 +159,13 @@ public class HttpRequestExecutingMessageHandler extends AbstractHttpRequestExecu
 						(ParameterizedTypeReference<?>) expectedResponseType);
 			}
 			else {
-				httpResponse = this.restTemplate.exchange(uri, httpMethod, httpRequest,
-						(Class<?>) expectedResponseType);
+				httpResponse = this.restTemplate.exchange(uri, httpMethod, httpRequest, (Class<?>) expectedResponseType);
 			}
 			return getReply(httpResponse);
 		}
 		catch (RestClientException e) {
-			throw new MessageHandlingException(requestMessage,
-					"HTTP request execution failed for URI [" + uri + "]", e);
+			throw new MessageHandlingException(requestMessage, "HTTP request execution failed for URI [" + uri + "]", e);
 		}
 	}
+
 }