问Java Servlet和MySQL

EN

public String getBrand(@WebParam(name = "regNr") String regNr) throws SQLException {

    String brand=null;
    Connection con;
    Statement st;
    ResultSet rs;

    String url = "jdbc:mysql://db4free.net:3606/cars";
    String user = "cars";
    String password = "";

    try {
        con = (Connection) DriverManager.getConnection(url, user, password);
        st = (Statement) con.createStatement();
        rs = st.executeQuery("SELECT * FROM Cars WHERE nr= '" + regNr + "'");

        if (rs.next()) {
            brand=rs.getString("brand");
        }


    } catch (SQLException ex) {

    }
    return brand;
}