RequestHeaderMapMethodArgumentResolver defensively checks for non-existing header values

Issue: SPR-14091
(cherry picked from commit 8f6ede5)

spring-web/src/main/java/org/springframework/web/method/annotation/RequestHeaderMapMethodArgumentResolver.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.
@@ -46,8 +46,8 @@ import org.springframework.web.method.support.ModelAndViewContainer;
 public class RequestHeaderMapMethodArgumentResolver implements HandlerMethodArgumentResolver {
 
 	public boolean supportsParameter(MethodParameter parameter) {
-		return parameter.hasParameterAnnotation(RequestHeader.class)
-				&& Map.class.isAssignableFrom(parameter.getParameterType());
+		return (parameter.hasParameterAnnotation(RequestHeader.class) &&
+				Map.class.isAssignableFrom(parameter.getParameterType()));
 	}
 
 	public Object resolveArgument(
@@ -56,7 +56,6 @@ public class RequestHeaderMapMethodArgumentResolver implements HandlerMethodArgu
 			throws Exception {
 
 		Class<?> paramType = parameter.getParameterType();
-
 		if (MultiValueMap.class.isAssignableFrom(paramType)) {
 			MultiValueMap<String, String> result;
 			if (HttpHeaders.class.isAssignableFrom(paramType)) {
@@ -67,8 +66,11 @@ public class RequestHeaderMapMethodArgumentResolver implements HandlerMethodArgu
 			}
 			for (Iterator<String> iterator = webRequest.getHeaderNames(); iterator.hasNext();) {
 				String headerName = iterator.next();
-				for (String headerValue : webRequest.getHeaderValues(headerName)) {
-					result.add(headerName, headerValue);
+				String[] headerValues = webRequest.getHeaderValues(headerName);
+				if (headerValues != null) {
+					for (String headerValue : headerValues) {
+						result.add(headerName, headerValue);
+					}
 				}
 			}
 			return result;
@@ -78,9 +80,12 @@ public class RequestHeaderMapMethodArgumentResolver implements HandlerMethodArgu
 			for (Iterator<String> iterator = webRequest.getHeaderNames(); iterator.hasNext();) {
 				String headerName = iterator.next();
 				String headerValue = webRequest.getHeader(headerName);
-				result.put(headerName, headerValue);
+				if (headerValue != null) {
+					result.put(headerName, headerValue);
+				}
 			}
 			return result;
 		}
 	}
+
 }