DRYing to Exception Monad

Attention.md

DRYing to Exception Monad (Java)

Authenticate.java

class Authenticate {
  public static void main(String[] args) throws Exception {
    final URL dashboard = new URL("http://dashboard");
    final URL loginPage = new URL("http://login");
    
    final String userid = "softwareartisan";
    final String pwd  = "1234";
    User user;

    Authenticator authenticator = new Authenticator();
    try {
      user = authenticator.login(userid, pwd);
    } catch (Exception es) {
      try {
        user = authenticator.gmailLogin(userid, pwd);
      } catch(Exception eg) {
        Dispatcher.redirect(loginPage);
        return;
      }
    }
    URL target;
    try {
      long twoFactorPwd = 167840;
      authenticator.twoFactor(user, twoFactorPwd);
      target = dashboard;
    } catch (Exception tfe) {
      target = loginPage;
    }
    Dispatcher.redirect(target);
  }
}

Authenticator.java

class Authenticator {
  public User login(String id, String pwd) throws Exception {
   // throw new Exception("password mismatch");
    return new User(id, "Dhaval");
  }

  public User gmailLogin(String id, String pwd) throws Exception {
   // throw new IOException("some problem");
    return new User(id, "Dhaval");
  }

  public void twoFactor(User user, long pwd) {
   // throw new RuntimeException("twoFactor Incorrect key");
  }
}

Dispatcher.java

class Dispatcher {
  static void redirect(URL target) {
    System.out.println("Going to => " + target);
  }
}

User.java

class User {
  private final String id;
  private final String name;
  
  User(final String id, final String name) {
    this.id = id;
    this.name = name;
  }
  
  public String getName() { 
     return name; 
  }

  public String getId() {
     return id; 
  }
}