Adding subcommands

A simple subcommand

To add a simple subcommand to our app, we can create a new class and then register it with the main app.

@Command(
  name = "healthtracker",
  description = "A CLI health tracker",
  subcommands = {Welcome.class})
public class App {

  public static void main(String[] args) {
    CommandLine cli = new CommandLine(new App());
    int exitCode = cli.execute(args);
    System.exit(exitCode);
  }

}

@Command(name = "welcome", description = "Shows a nice message")
class Welcome implements Runnable {

  @Parameters(index = "0", description = "The name to greet")
  private String name;

  @Override
  public void run() {
    String msg = String.format("Welcome, %s! Please specify a command.", name);
    System.out.println(msg);
  }

}

Now the user can run the welcome function with healthtracker welcome <name>, and we can add different functions under different subcommands.

> healthtracker welcome Hikaru

Welcome, Hikaru! Please specify a command.

Create a subcommand structure

Often, we will need sub-subcommands.

Let's create a simple Meal class.

class Meal {
  private String mealName;
  private int calories;

  public Meal(String mealName, int calories) {
    this.mealName = mealName;
    this.calories = calories;
  }

  public String getSummary() {
    return String.format("You ate %s and it contained %d calories.", mealName, calories);
  }
}

Now we'll add a controller to work with the meal class. The MealController is mostly empty, but it wraps up the add and list subcommands under the meal subcommand.

@Command(
  name = "meal",
  description = "Save and read your meals",
  subcommands = { AddMeal.class, ListMeals.class })
public class MealController {
}

Now we can create the add and list commands under the meal prefix. For example:

@Command(name = "add", description = "Save a meal")
class AddMeal implements Runnable {

  @Parameters(index = "0", description = "The name of the meal")
  private String mealName;

  @Parameters(index = "1", description = "The number of calories")
  private int calories;

  @Override
  public void run() {
    Meal meal = new Meal(mealName, calories);
    System.out.println(meal.getSummary());
  }

}

Register with App

Once we have created our subcommand controller, we need to register it with the main App.

import com.corndel.controllers.MealController;

@Command(
  name = "healthtracker",
  description = "A CLI health tracker",
  subcommands = {Welcome.class, MealController.class})
public class App {

  public static void main(String[] args) {
    CommandLine cli = new CommandLine(new App());
    int exitCode = cli.execute(args);
    System.exit(exitCode);
  }

}

Now the user can access nested subcommands like this:

> healthtracker meal add Pizza 2000

You ate Pizza and it contained 2000 calories.

> healthtracker meal list

Not implemented.