better fix

src/main/java/com/zaxxer/hikari/HikariConfig.java

@@ -474,6 +474,7 @@ public class HikariConfig implements HikariConfigMXBean
     * @param metricRegistry the Codahale MetricRegistry to set
     */
    public void setMetricRegistry(Object metricRegistry)
+   {
       if (metricsTrackerFactory != null) {
          throw new IllegalStateException("cannot use setMetricRegistry() and setMetricsTrackerFactory() together");
       }

src/main/java/com/zaxxer/hikari/pool/PoolElf.java

@@ -109,23 +109,24 @@ public final class PoolElf
    {
       if (transactionIsolationName != null) {
          try {
-            int level = Integer.parseInt(transactionIsolationName);
+ 	   		String upperName = transactionIsolationName.toUpperCase();
-            //its number
+ 			if (upperName.startsWith("TRANSACTION_")) {
-            switch (level) {
+ 				Field field = Connection.class.getField(transactionIsolationName);
-               case Connection.TRANSACTION_READ_UNCOMMITTED:
+ 				return field.getInt(null);
-               case Connection.TRANSACTION_READ_COMMITTED:
+ 			}
-               case Connection.TRANSACTION_REPEATABLE_READ:
+ 			else {
-               case Connection.TRANSACTION_SERIALIZABLE:
+ 	            int level = Integer.parseInt(transactionIsolationName);
-                  return level;
+ 	            //its number
-            }
+ 	            switch (level) {
-            throw new IllegalArgumentException("Invalid transaction isolation value: " + transactionIsolationName);
+ 	               case Connection.TRANSACTION_READ_UNCOMMITTED:
-         }
+ 	               case Connection.TRANSACTION_READ_COMMITTED:
-         catch (Exception e) {
+ 	               case Connection.TRANSACTION_REPEATABLE_READ:
-            //its name
+ 	               case Connection.TRANSACTION_SERIALIZABLE:
-         }
+ 	                  return level;
-    	 try {
+ 	            }
-            Field field = Connection.class.getField(transactionIsolationName);
+ 	            //invalid level
-            return field.getInt(null);
+ 	            throw new IllegalArgumentException();
+ 			}
          }
          catch (Exception e) {
             throw new IllegalArgumentException("Invalid transaction isolation value: " + transactionIsolationName);