REPORT-66916 fix:使用自定义mysql8驱动，连接失败

fine-druid/src/main/java/com/fr/third/alibaba/druid/util/MySqlUtils.java

@@ -386,13 +386,15 @@ public class MySqlUtils {
 
     public static long getLastPacketReceivedTimeMs(Connection conn) throws SQLException {
         if (!class_connectionImpl_Error) {
+            if (conn == null) {
+                return -1;
+            }
             try {
-                class_connectionImpl = Utils.loadClass("com.mysql.jdbc.MySQLConnection");
-                if (class_connectionImpl == null) {
-                    class_connectionImpl = Utils.loadClass("com.mysql.cj.MysqlConnection");
-                    if (class_connectionImpl != null) {
-                        mysqlJdbcVersion6 = true;
-                    }
+                //REPORT-66916 这里之前获取到的是lib下的mysql5实现，而不是自定义mysql8驱动的实现
+                String className = conn.getClass().getName();
+                class_connectionImpl = Utils.loadClass(className);
+                if (className.equals("com.mysql.cj.MysqlConnection")) {
+                    mysqlJdbcVersion6 = true;
                 }
             } catch (Throwable error) {
                 class_connectionImpl_Error = true;
@@ -431,7 +433,7 @@ public class MySqlUtils {
 
                 return System.currentTimeMillis()
                         - ((Long)
-                            getIdleFor.invoke(connImpl))
+                        getIdleFor.invoke(connImpl))
                         .longValue();
             } catch (Exception e) {
                 throw new SQLException("getIdleFor error", e);