Using Required Options

Ahoy there mateys! Welcome aboard the ship of Apache Commons CLI. In our previous articles, we’ve talked about how to create a parser, add options to it, and parse the command-line arguments. In this article, we’ll be talking about a crucial aspect of command-line parsing, that is, specifying required options.

Now, you might be wondering, “What are required options?” Well, as the name suggests, required options are those options that are mandatory for a command to work correctly. Without these options, the command might not execute or might execute incorrectly, leading to erroneous results.

For example, let’s say we have a command that copies a file from one location to another. Now, for this command to work correctly, we need to specify the source file’s location and the destination location. If we don’t specify these options, the command won’t execute, and we’ll get an error. In this case, the source and destination options are required options.

So, how do we specify required options in Apache Commons CLI? It’s straightforward, mateys! All we need to do is set the option’s required flag to true. Let’s take a look at an example to understand this better:

Option source = Option.builder("s")
                .longOpt("source")
                .hasArg()
                .argName("source")
                .desc("Source file location")
                .required(true) // set required flag to true
                .build();

In the above example, we have defined an option source with a short option -s and a long option --source. We’ve set the required flag to true to indicate that this option is mandatory.

That’s it, mateys! It’s that simple to specify required options in Apache Commons CLI. However, as with all things in life, there’s a catch. What if the user forgets to specify a required option? We’ll be covering that in the next section, so stay tuned!

Using Required Options

Ahoy there mateys! Welcome back. In the previous section, we talked about specifying required options in Apache Commons CLI. We learned that required options are those options that are mandatory for a command to work correctly and how to set the required flag to indicate the same.

However, what happens when a user forgets to specify a required option? We need to handle such scenarios to ensure that our command works correctly. Let’s take a look at how we can do this in Apache Commons CLI.

When we parse the command-line arguments, we can check if all the required options are present. If any required option is missing, we can show an error message and print the usage help to guide the user. Here’s an example:

Options options = new Options();
Option source = Option.builder("s")
                .longOpt("source")
                .hasArg()
                .argName("source")
                .desc("Source file location")
                .required(true) // set required flag to true
                .build();
options.addOption(source);

CommandLineParser parser = new DefaultParser();
try {
    CommandLine cmd = parser.parse(options, args);
    // code to execute the command
} catch (ParseException e) {
    // handle missing required options
    System.out.println("Error: " + e.getMessage());
    HelpFormatter formatter = new HelpFormatter();
    formatter.printHelp("my-command", options);
}

In the above example, we’ve added an option source and set the required flag to true. In the try block, we parse the command-line arguments using the DefaultParser. If any required option is missing, the parse method will throw a ParseException. We catch this exception and show an error message along with the usage help using the HelpFormatter.

So, that’s how we handle missing required options in Apache Commons CLI. By using the required flag and checking for missing options during parsing, we can ensure that our commands work correctly.

That’s all for this article, mateys! We’ve learned how to specify required options and how to handle missing required options in Apache Commons CLI. Keep practicing and incorporating these concepts in your command-line applications, and soon you’ll be a pro at command-line parsing! Until next time, stay salty!