StringUtils.parseLocale consistently handles invalid locale values

Closes gh-22603

Author: jhoeller

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

@@ -774,7 +774,9 @@ public static Locale parseLocale(String localeValue) {
 		if (tokens.length == 1) {
 			validateLocalePart(localeValue);
 			Locale resolved = Locale.forLanguageTag(localeValue);
-			return (resolved.getLanguage().length() > 0 ? resolved : null);
+			if (resolved.getLanguage().length() > 0) {
+				return resolved;
+			}
 		}
 		return parseLocaleTokens(localeValue, tokens);
 	}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -765,4 +765,20 @@ public void testAvailableLocalesWithLanguageTag() {
 		}
 	}
 
+	@Test
+	public void testInvalidLocaleWithLocaleString() {
+		assertEquals(new Locale("invalid"), StringUtils.parseLocaleString("invalid"));
+		assertEquals(new Locale("invalidvalue"), StringUtils.parseLocaleString("invalidvalue"));
+		assertEquals(new Locale("invalidvalue", "foo"), StringUtils.parseLocaleString("invalidvalue_foo"));
+		assertNull(StringUtils.parseLocaleString(""));
+	}
+
+	@Test
+	public void testInvalidLocaleWithLanguageTag() {
+		assertEquals(new Locale("invalid"), StringUtils.parseLocale("invalid"));
+		assertEquals(new Locale("invalidvalue"), StringUtils.parseLocale("invalidvalue"));
+		assertEquals(new Locale("invalidvalue", "foo"), StringUtils.parseLocale("invalidvalue_foo"));
+		assertNull(StringUtils.parseLocale(""));
+	}
+
 }