connection 无法连接数据库

public void getConnection() {
try {
String url = "jdbc:mysql://localhost:3306/olLearn?useUnicode=true&characterEncoding=gbk";
String user = "root";
String pwd = "";
this.conn = DriverManager.getConnection(url, user, pwd); // 创建Connection对象con,olLearn为SQLServer数据库名称
} catch (Exception e) {
e.printStackTrace();
}
}