Using Mutually Exclusive Options

Ahoy there, mateys! Welcome aboard to another article on Apache Commons CLI. Today, we will be discussing how to specify mutually exclusive options using this library.

When creating a command line interface, sometimes it’s necessary to limit the number of options that can be used together. For example, you might have an option to add or delete a user, but not both at the same time. This is where mutually exclusive options come in handy.

Specifying Mutually Exclusive Options

To specify mutually exclusive options with Apache Commons CLI, we use the OptionGroup class. An OptionGroup is a collection of options, where only one option in the group can be used at a time.

Let’s say we have two options: -a to add a user and -d to delete a user. We want to ensure that the user can only choose one of these options at a time. Here’s how we can do it:

Option addOption = Option.builder("a")
                    .longOpt("add")
                    .desc("Add a user")
                    .build();

Option deleteOption = Option.builder("d")
                    .longOpt("delete")
                    .desc("Delete a user")
                    .build();

OptionGroup optionGroup = new OptionGroup();
optionGroup.addOption(addOption);
optionGroup.addOption(deleteOption);
optionGroup.setRequired(true);

Options options = new Options();
options.addOptionGroup(optionGroup);

In the above code, we first create two options, -a and -d, using the Option.builder() method. We then create an OptionGroup and add both options to it using the addOption() method. We also set the option group as required using the setRequired() method. Finally, we add the OptionGroup to our Options object using the addOptionGroup() method.

With this setup, if the user tries to use both -a and -d options together, Apache Commons CLI will throw a MissingOptionException error.

That’s all for now, me hearties! Next up, we will discuss how to handle conflicts between options when they are used together. Keep sailing!

Handling Conflicts Between Options

In some cases, you might want to allow multiple options to be used together, but not others. For example, you might have options -a and -d to add and delete a user, but also have an option -u to update a user. You might want to ensure that -u cannot be used with either -a or -d.

To handle conflicts between options, we can use the OptionBuilder class. Here’s an example:

Option addOption = Option.builder("a")
                    .longOpt("add")
                    .desc("Add a user")
                    .build();

Option deleteOption = Option.builder("d")
                    .longOpt("delete")
                    .desc("Delete a user")
                    .build();

Option updateOption = Option.builder("u")
                    .longOpt("update")
                    .desc("Update a user")
                    .build();

OptionGroup optionGroup = new OptionGroup();
optionGroup.addOption(addOption);
optionGroup.addOption(deleteOption);

Options options = new Options();
options.addOptionGroup(optionGroup);
options.addOption(updateOption);

options.addOptionGroup(optionGroup);

CommandLineParser parser = new DefaultParser();
try {
    CommandLine cmd = parser.parse(options, args);
    if (cmd.hasOption("a")) {
        // add user code
    } else if (cmd.hasOption("d")) {
        // delete user code
    } else if (cmd.hasOption("u")) {
        if (cmd.hasOption("a") || cmd.hasOption("d")) {
            throw new ParseException("Option -u cannot be used with -a or -d.");
        }
        // update user code
    }
} catch (ParseException e) {
    System.err.println("Error: " + e.getMessage());
}

In the above code, we create three options, -a, -d, and -u. We then create an OptionGroup containing -a and -d, and add it to our Options object. We also add the -u option directly to our Options object.

When parsing the command line arguments, we check if the user has used -a or -d, and handle those options accordingly. If the user has used -u, we then check if -a or -d have also been used. If they have, we throw a ParseException with an error message.

Conclusion

And that’s how you can use Apache Commons CLI to specify mutually exclusive options and handle conflicts between options. With these techniques, you can create flexible and user-friendly command line interfaces that can handle a wide variety of use cases.

As always, me hearties, make sure to test your code thoroughly and write clear and concise usage messages. Happy coding, and until next time, keep sailing the high seas of programming!