aib aib - 2 months ago 10
Java Question

Apache Commons CLI - option type and default value

How can I give a CLI Option a type - such as

int
or
Integer
? (Later, how can I get the parsed value with a single function call?)

How can I give a CLI Option a default value? Such that
CommandLine.getOptionValue()
or the function call mentioned above return that value unless one is specified on the command line?

Answer

EDIT: Default values are now supported. See answer http://stackoverflow.com/a/14309108/1082541 below.

As Brent Worden already mentioned, default values are not supported.

I had issues with using Option.setType too. I always got a null pointer exception when calling getParsedOptionValue on an option with type Integer.class. Because the documentation was not really helpful I looked into the source code.

Looking at the TypeHandler class and the PatternOptionBuilder class you can see that Number.class must be used for int or Integer.

And here is a simple example:

CommandLineParser cmdLineParser = new PosixParser();

Options options = new Options();
options.addOption(OptionBuilder.withLongOpt("integer-option")
                      .withDescription("description")
                      .withType(Number.class)
                      .hasArg()
                      .withArgName("argname")
                      .create());

try {
    CommandLine cmdLine = cmdLineParser.parse(options, args);

    int value = 0; // initialize to some meaningful default value
    if (cmdLine.hasOption("integer-option")) {
        value = ((Number)cmdLine.getParsedOptionValue("integer-option")).intValue();
    }

    System.out.println(value);
} catch (ParseException e) {
    e.printStackTrace();
}

Keep in mind that value can overflow if a number is provided which does not fit into an int.