#1598问题遗漏的修复

[kajelas]

请参考#1598。
bug fix漏了ValidConnectionChecker的初始化：

private void initValidConnectionChecker() {
     String realDriverClassName = driver.getClass().getName();
        if (realDriverClassName.equals(JdbcConstants.MYSQL_DRIVER) //
            || realDriverClassName.equals(JdbcConstants.MYSQL_DRIVER_6)) {
            this.validConnectionChecker = new MySqlValidConnectionChecker();
        } else if (realDriverClassName.equals(JdbcConstants.ORACLE_DRIVER
                  || realDriverClassName.equals(JdbcConstants.ORACLE_DRIVER2)) { //遗漏了这个地方的初始化
            this.validConnectionChecker = new OracleValidConnectionChecker();
        } else if (realDriverClassName.equals(JdbcConstants.SQL_SERVER_DRIVER)
                   || realDriverClassName.equals(JdbcConstants.SQL_SERVER_DRIVER_SQLJDBC4)
                   || realDriverClassName.equals(JdbcConstants.SQL_SERVER_DRIVER_JTDS)) {
            this.validConnectionChecker = new MSSQLValidConnectionChecker();
        } else if (realDriverClassName.equals(JdbcConstants.POSTGRESQL_DRIVER)) {
            this.validConnectionChecker = new PGValidConnectionChecker();
        }
    }

[lizongbo]

已经修复，请使用最新版验证