ConcurrentModel ignores null value for put (also used by putAll)

Issue: SPR-17141

spring-context/src/main/java/org/springframework/ui/ConcurrentModel.java

@@ -65,6 +65,23 @@ public class ConcurrentModel extends ConcurrentHashMap<String, Object> implement
 	}
 
 
+	@Override
+	public Object put(String key, Object value) {
+		if (value != null) {
+			return super.put(key, value);
+		}
+		else {
+			return remove(key);
+		}
+	}
+
+	@Override
+	public void putAll(Map<? extends String, ?> map) {
+		for (Map.Entry<? extends String, ?> entry : map.entrySet()) {
+			put(entry.getKey(), entry.getValue());
+		}
+	}
+
 	/**
 	 * Add the supplied attribute under the supplied name.
 	 * @param attributeName the name of the model attribute (never {@code null})
@@ -73,12 +90,7 @@ public class ConcurrentModel extends ConcurrentHashMap<String, Object> implement
 	 */
 	public ConcurrentModel addAttribute(String attributeName, @Nullable Object attributeValue) {
 		Assert.notNull(attributeName, "Model attribute name must not be null");
-		if (attributeValue != null) {
+		put(attributeName, attributeValue);
-			put(attributeName, attributeValue);
-		}
-		else {
-			remove(attributeName);
-		}
 		return this;
 	}
 

spring-context/src/main/java/org/springframework/validation/support/BindingAwareConcurrentModel.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -46,12 +46,6 @@ public class BindingAwareConcurrentModel extends ConcurrentModel {
 		return super.put(key, value);
 	}
 
-	@Override
-	public void putAll(Map<? extends String, ?> map) {
-		map.forEach(this::removeBindingResultIfNecessary);
-		super.putAll(map);
-	}
-
 	private void removeBindingResultIfNecessary(String key, Object value) {
 		if (!key.startsWith(BindingResult.MODEL_KEY_PREFIX)) {
 			String resultKey = BindingResult.MODEL_KEY_PREFIX + key;