Handle locale tags in date validator

Author: aabashkin

src/main/java/org/owasp/esapi/reference/validation/annotations/ValidDateValidator.java

@@ -30,7 +30,7 @@ public boolean isValid(String input, ConstraintValidatorContext constraintValida
         if (input == null) {
             return true;
         }
-        Locale locale = new Locale(localeString);
+        Locale locale = toLocale(localeString);
         DateFormat dateFormat = DateFormat.getDateInstance(dateStyle, locale);
 
         ValidationErrorList errorList = new ValidationErrorList();
@@ -42,4 +42,16 @@ public boolean isValid(String input, ConstraintValidatorContext constraintValida
 
         return valid;
     }
+
+    private static Locale toLocale(String localeValue) {
+        if (localeValue == null) {
+            return Locale.getDefault();
+        }
+        String normalized = localeValue.trim();
+        if (normalized.isEmpty()) {
+            return Locale.getDefault();
+        }
+        Locale locale = Locale.forLanguageTag(normalized.replace('_', '-'));
+        return Locale.ROOT.equals(locale) ? Locale.getDefault() : locale;
+    }
 }