Add headers in InterceptingClientHttpRequest

This commit *adds* the "intercepted" headers to the ClientHttpRequest,
as opposed to replacing them, which is what happened before this commit.

Issue: SPR-15166

spring-core/src/main/java/org/springframework/util/CollectionUtils.java

 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -406,14 +406,16 @@ public abstract class CollectionUtils {
 
 		@Override
 		public void add(K key, V value) {
-			List<V> values = this.map.get(key);
-			if (values == null) {
-				values = new LinkedList<>();
-				this.map.put(key, values);
-			}
+			List<V> values = this.map.computeIfAbsent(key, k -> new LinkedList<>());
 			values.add(value);
 		}
 
+		@Override
+		public void addAll(K key, List<V> values) {
+			List<V> currentValues = this.map.computeIfAbsent(key, k -> new LinkedList<>());
+			currentValues.addAll(values);
+		}
+
 		@Override
 		public V getFirst(K key) {
 			List<V> values = this.map.get(key);

spring-core/src/main/java/org/springframework/util/LinkedMultiValueMap.java

 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -75,14 +75,16 @@ public class LinkedMultiValueMap<K, V> implements MultiValueMap<K, V>, Serializa
 
 	@Override
 	public void add(K key, V value) {
-		List<V> values = this.targetMap.get(key);
-		if (values == null) {
-			values = new LinkedList<>();
-			this.targetMap.put(key, values);
-		}
+		List<V> values = this.targetMap.computeIfAbsent(key, k -> new LinkedList<>());
 		values.add(value);
 	}
 
+	@Override
+	public void addAll(K key, List<V> values) {
+		List<V> currentValues = this.targetMap.computeIfAbsent(key, k -> new LinkedList<>());
+		currentValues.addAll(values);
+	}
+
 	@Override
 	public V getFirst(K key) {
 		List<V> values = this.targetMap.get(key);

spring-core/src/main/java/org/springframework/util/MultiValueMap.java

 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2017 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 +41,13 @@ public interface MultiValueMap<K, V> extends Map<K, List<V>> {
 	 */
 	void add(K key, V value);
 
+	/**
+	 * Add all the values of the given list to the current list of values for the given key.
+	 * @param key they key
+	 * @param values the values to be added
+	 */
+	void addAll(K key, List<V> values);
+
 	/**
 	 * Set the given single value under the given key.
 	 * @param key the key

spring-core/src/test/java/org/springframework/util/LinkedMultiValueMapTests.java

 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -17,6 +17,7 @@
 package org.springframework.util;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
@@ -25,7 +26,8 @@ import java.util.Map;
 import org.junit.Before;
 import org.junit.Test;
 
-import static org.junit.Assert.*;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
 
 /**
  * @author Arjen Poutsma
@@ -50,6 +52,18 @@ public class LinkedMultiValueMapTests {
 		assertEquals(expected, map.get("key"));
 	}
 
+	@Test
+	public void addAll() throws Exception {
+		map.add("key", "value1");
+		map.addAll("key", Arrays.asList("value2", "value3"));
+		assertEquals(1, map.size());
+		List<String> expected = new ArrayList<>(2);
+		expected.add("value1");
+		expected.add("value2");
+		expected.add("value3");
+		assertEquals(expected, map.get("key"));
+	}
+
 	@Test
 	public void getFirst() {
 		List<String> values = new ArrayList<>(2);

spring-messaging/src/main/java/org/springframework/messaging/simp/stomp/StompHeaders.java

 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -397,14 +397,16 @@ public class StompHeaders implements MultiValueMap<String, String>, Serializable
 	 */
 	@Override
 	public void add(String headerName, String headerValue) {
-		List<String> headerValues = headers.get(headerName);
-		if (headerValues == null) {
-			headerValues = new LinkedList<>();
-			this.headers.put(headerName, headerValues);
-		}
+		List<String> headerValues = headers.computeIfAbsent(headerName, k -> new LinkedList<>());
 		headerValues.add(headerValue);
 	}
 
+	@Override
+	public void addAll(String headerName, List<String> headerValues) {
+		List<String> currentValues = headers.computeIfAbsent(headerName, k -> new LinkedList<>());
+		currentValues.addAll(headerValues);
+	}
+
 	/**
 	 * Set the given, single header value under the given name.
 	 * @param headerName the header name

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

 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -1333,14 +1333,17 @@ public class HttpHeaders implements MultiValueMap<String, String>, Serializable
 	 */
 	@Override
 	public void add(String headerName, String headerValue) {
-		List<String> headerValues = this.headers.get(headerName);
-		if (headerValues == null) {
-			headerValues = new LinkedList<>();
-			this.headers.put(headerName, headerValues);
-		}
+		List<String> headerValues =
+				this.headers.computeIfAbsent(headerName, k -> new LinkedList<>());
 		headerValues.add(headerValue);
 	}
 
+	@Override
+	public void addAll(String key, List<String> values) {
+		List<String> currentValues = this.headers.computeIfAbsent(key, k -> new LinkedList<>());
+		currentValues.addAll(values);
+	}
+
 	/**
 	 * Set the given, single header value under the given name.
 	 * @param headerName the header name

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

 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -20,6 +20,7 @@ import java.io.IOException;
 import java.net.URI;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Map;
 
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
@@ -86,7 +87,9 @@ class InterceptingClientHttpRequest extends AbstractBufferingClientHttpRequest {
 			}
 			else {
 				ClientHttpRequest delegate = requestFactory.createRequest(request.getURI(), request.getMethod());
-				delegate.getHeaders().putAll(request.getHeaders());
+				for (Map.Entry<String, List<String>> entry : request.getHeaders().entrySet()) {
+					delegate.getHeaders().addAll(entry.getKey(), entry.getValue());
+				}
 				if (body.length > 0) {
 					StreamUtils.copy(body, delegate.getBody());
 				}