Check for asterisk range in CronExpression

This commit makes sure that in CronExpression, the asterisk is only used
in a range field, and is not surrounded by unexpected characters.

Closes gh-19500

Author: poutsma

spring-context/src/main/java/org/springframework/scheduling/support/BitsCronField.java

@@ -150,7 +150,7 @@ private static BitsCronField parseField(String value, Type type) {
 	}
 
 	private static ValueRange parseRange(String value, Type type) {
-		if (value.indexOf('*') != -1) {
+		if (value.equals("*")) {
 			return type.range();
 		}
 		else {

spring-context/src/test/java/org/springframework/scheduling/support/BitsCronFieldTests.java

@@ -48,6 +48,9 @@ void invalidRange() {
 		assertThatIllegalArgumentException().isThrownBy(() -> BitsCronField.parseMonth("13"));
 		assertThatIllegalArgumentException().isThrownBy(() -> BitsCronField.parseDaysOfWeek("8"));
 		assertThatIllegalArgumentException().isThrownBy(() -> BitsCronField.parseSeconds("20-10"));
+		assertThatIllegalArgumentException().isThrownBy(() -> BitsCronField.parseDaysOfWeek("*SUN"));
+		assertThatIllegalArgumentException().isThrownBy(() -> BitsCronField.parseDaysOfWeek("SUN*"));
+		assertThatIllegalArgumentException().isThrownBy(() -> BitsCronField.parseHours("*ANYTHING_HERE"));
 	}
 
 	@Test