我正试图用嵌入式derby编写一个程序，但当我运行它时，它会显示：

run:
Jul 14, 2017 9:19:54 PM gfdh.Login Doconnect
SEVERE: null
java.sql.SQLException: No suitable driver found for jdbc:derby:gdtu:create=true
...

代码：

public class Login extends javax.swing.JFrame {

Connection con;
Statement stmt;
ResultSet rs;

private static final String DRIVER = "org.apache.derby.jdbc.EmbeddedDriver";
private static final String JDBC_URL = "jdbc:derby:gdtu:create=true";

public Login(){
    initComponents();
    Doconnect();
}

private void Doconnect(){

    try {
        this.con = DriverManager.getConnection(JDBC_URL);
        if(this.con != null){
            System.out.println("Connected to database");
        }
    } catch (SQLException ex) {
        Logger.getLogger(Login.class.getName()).log(Level.SEVERE, null, ex);
    }

}

}
}