Re-introduce the regex pattern for the format pattern check

hibernate-core/src/main/java/org/hibernate/query/sqm/tree/expression/SqmFormat.java

@@ -6,8 +6,7 @@
  */
 package org.hibernate.query.sqm.tree.expression;
 
-import java.time.format.DateTimeFormatter;
-import java.util.Locale;
+import java.util.regex.Pattern;
 
 import org.hibernate.query.SemanticException;
 import org.hibernate.query.sqm.NodeBuilder;
@@ -20,23 +19,35 @@ import org.hibernate.query.sqm.SqmExpressable;
  * @author Gavin King
  */
 public class SqmFormat extends SqmLiteral<String> {
+	// G era
+	// y year in era
+	// Y week year (ISO)
+	// M month in year
+	// w week in year (ISO)
+	// W week in month
+	// E day name in week
+	// e day number in week (*very* inconsistent across DBs)
+	// d day in month
+	// D day in year
+	// a AM/PM
+	// H hour of day (0-23)
+	// h clock hour of am/pm (1-12)
+	// m minute of hour
+	// s second of minute
+	// S fraction of second
+	// z time zone name e.g. PST
+	// x zone offset e.g. +03, +0300, +03:00
+	// Z zone offset e.g. +0300
+	// see https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatter.html
+	private static final Pattern FORMAT = Pattern.compile( "('[^']+'|[:;/,.!@#$^&?~`|()\\[\\]{}<>\\-+*=]|\\s|G{1,2}|[yY]{1,4}|M{1,4}|w{1,2}|W|E{3,4}|e{1,2}|d{1,2}|D{1,3}|a|[Hhms]{1,2}|S{1,6}|[zZx]{1,3})*");
+
 	public SqmFormat(
 			String value,
 			SqmExpressable<String> inherentType,
 			NodeBuilder nodeBuilder) {
 		super(value, inherentType, nodeBuilder);
-		try {
-			DateTimeFormatter.ofPattern( value );
-		}
-		catch (IllegalArgumentException ex) {
-			throw new SemanticException(
-					String.format(
-							Locale.ROOT,
-							"Format [%s] does not conform to the expected format of java.time.DateTimeFormatter!",
-							value
-					),
-					ex
-			);
+		if (!FORMAT.matcher(value).matches()) {
+			throw new SemanticException("illegal format pattern '" + value + "'");
 		}
 	}