LinkedCaseInsensitiveMap exposes its locale for key conversion

Issue: SPR-15752

Author: jhoeller

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

@@ -49,41 +49,42 @@ public class LinkedCaseInsensitiveMap<V> implements Map<String, V>, Serializable
 
 
 	/**
-	 * Create a new LinkedCaseInsensitiveMap for the default Locale.
-	 * @see java.lang.String#toLowerCase()
+	 * Create a new LinkedCaseInsensitiveMap that stores case-insensitive keys
+	 * according to the default Locale (by default in lower case).
+	 * @see #convertKey(String)
 	 */
 	public LinkedCaseInsensitiveMap() {
 		this((Locale) null);
 	}
 
 	/**
-	 * Create a new LinkedCaseInsensitiveMap that stores lower-case keys
-	 * according to the given Locale.
-	 * @param locale the Locale to use for lower-case conversion
-	 * @see java.lang.String#toLowerCase(java.util.Locale)
+	 * Create a new LinkedCaseInsensitiveMap that stores case-insensitive keys
+	 * according to the given Locale (by default in lower case).
+	 * @param locale the Locale to use for case-insensitive key conversion
+	 * @see #convertKey(String)
 	 */
 	public LinkedCaseInsensitiveMap(@Nullable Locale locale) {
 		this(16, locale);
 	}
 
 	/**
 	 * Create a new LinkedCaseInsensitiveMap that wraps a {@link LinkedHashMap}
-	 * with the given initial capacity and stores lower-case keys according
-	 * to the default Locale.
+	 * with the given initial capacity and stores case-insensitive keys
+	 * according to the default Locale (by default in lower case).
 	 * @param initialCapacity the initial capacity
-	 * @see java.lang.String#toLowerCase()
+	 * @see #convertKey(String)
 	 */
 	public LinkedCaseInsensitiveMap(int initialCapacity) {
 		this(initialCapacity, null);
 	}
 
 	/**
 	 * Create a new LinkedCaseInsensitiveMap that wraps a {@link LinkedHashMap}
-	 * with the given initial capacity and stores lower-case keys according
-	 * to the given Locale.
+	 * with the given initial capacity and stores case-insensitive keys
+	 * according to the given Locale (by default in lower case).
 	 * @param initialCapacity the initial capacity
-	 * @param locale the Locale to use for lower-case conversion
-	 * @see java.lang.String#toLowerCase(java.util.Locale)
+	 * @param locale the Locale to use for case-insensitive key conversion
+	 * @see #convertKey(String)
 	 */
 	public LinkedCaseInsensitiveMap(int initialCapacity, @Nullable Locale locale) {
 		this.targetMap = new LinkedHashMap<String, V>(initialCapacity) {
@@ -115,6 +116,8 @@ private LinkedCaseInsensitiveMap(LinkedCaseInsensitiveMap<V> other) {
 	}
 
 
+	// Implementation of java.util.Map
+
 	@Override
 	public int size() {
 		return this.targetMap.size();
@@ -159,7 +162,7 @@ public V getOrDefault(Object key, V defaultValue) {
 	}
 
 	@Override
-	public V put(String key, V value) {
+	public V put(String key, @Nullable V value) {
 		String oldKey = this.caseInsensitiveKeys.put(convertKey(key), key);
 		if (oldKey != null && !oldKey.equals(key)) {
 			this.targetMap.remove(oldKey);
@@ -229,16 +232,29 @@ public String toString() {
 	}
 
 
+	// Specific to LinkedCaseInsensitiveMap
+
+	/**
+	 * Return the locale used by this {@code LinkedCaseInsensitiveMap}.
+	 * Used for case-insensitive key conversion.
+	 * @since 4.3.10
+	 * @see #LinkedCaseInsensitiveMap(Locale)
+	 * @see #convertKey(String)
+	 */
+	public Locale getLocale() {
+		return this.locale;
+	}
+
 	/**
 	 * Convert the given key to a case-insensitive key.
 	 * <p>The default implementation converts the key
 	 * to lower-case according to this Map's Locale.
 	 * @param key the user-specified key
 	 * @return the key to use for storing
-	 * @see java.lang.String#toLowerCase(java.util.Locale)
+	 * @see String#toLowerCase(Locale)
 	 */
 	protected String convertKey(String key) {
-		return key.toLowerCase(this.locale);
+		return key.toLowerCase(getLocale());
 	}
 
 	/**

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

@@ -108,12 +108,15 @@ public void computeIfAbsentWithComputedValue() {
 	public void mapClone() {
 		map.put("key", "value1");
 		LinkedCaseInsensitiveMap<String> copy = map.clone();
+
+		assertEquals(map.getLocale(), copy.getLocale());
 		assertEquals("value1", map.get("key"));
 		assertEquals("value1", map.get("KEY"));
 		assertEquals("value1", map.get("Key"));
 		assertEquals("value1", copy.get("key"));
 		assertEquals("value1", copy.get("KEY"));
 		assertEquals("value1", copy.get("Key"));
+
 		copy.put("Key", "value2");
 		assertEquals(1, map.size());
 		assertEquals(1, copy.size());