LinkedCaseInsensitiveMap properly overrides HashMap.clone()

Issue: SPR-14509
(cherry picked from commit 6459559)

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

@@ -36,7 +36,7 @@ import java.util.Map;
 @SuppressWarnings("serial")
 public class LinkedCaseInsensitiveMap<V> extends LinkedHashMap<String, V> {
 
-	private final Map<String, String> caseInsensitiveKeys;
+	private Map<String, String> caseInsensitiveKeys;
 
 	private final Locale locale;
 
@@ -151,6 +151,14 @@ public class LinkedCaseInsensitiveMap<V> extends LinkedHashMap<String, V> {
 		super.clear();
 	}
 
+	@Override
+	@SuppressWarnings("unchecked")
+	public Object clone() {
+		LinkedCaseInsensitiveMap<V> copy = (LinkedCaseInsensitiveMap<V>) super.clone();
+		copy.caseInsensitiveKeys = new HashMap<String, String>(this.caseInsensitiveKeys);
+		return copy;
+	}
+
 
 	/**
 	 * Convert the given key to a case-insensitive key.

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

@@ -74,4 +74,26 @@ public class LinkedCaseInsensitiveMapTests {
 		assertEquals("N", map.getOrDefault(new Object(), "N"));
 	}
 
+	@Test
+	@SuppressWarnings("unchecked")
+	public void mapClone() {
+		map.put("key", "value1");
+		LinkedCaseInsensitiveMap<String> copy = (LinkedCaseInsensitiveMap<String>) map.clone();
+		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());
+		assertEquals("value1", map.get("key"));
+		assertEquals("value1", map.get("KEY"));
+		assertEquals("value1", map.get("Key"));
+		assertEquals("value2", copy.get("key"));
+		assertEquals("value2", copy.get("KEY"));
+		assertEquals("value2", copy.get("Key"));
+	}
+
 }