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Arity

Arity defines how many parameters option parsing takes.

There are limitations in a legacy annotation compared to annotation and programmatic use of arity settings. These are mentioned in notes in below samples.

  • Programmatic

  • Annotation

  • Legacy Annotation

CommandRegistration zeroOrOne() {
	return CommandRegistration.builder()
		.command("example")
		.withOption()
			.longNames("arg")
			.arity(OptionArity.ZERO_OR_ONE)
			.and()
		.build();
}
@Command(command = "example")
String zeroOrOne(
	@Option(arity = OptionArity.ZERO_OR_ONE) String arg)
{
	return String.format("Hi '%s'", arg);
}
@ShellMethod(key = "example")
String zeroOrOne(
	@ShellOption(arity = 1) String arg)
{
	return String.format("Hi '%s'", arg);
}
Table 1. OptionArity
Value min/max

ZERO

0 / 0

ZERO_OR_ONE

0 / 1

EXACTLY_ONE

1 / 1

ZERO_OR_MORE

0 / Integer MAX

ONE_OR_MORE

1 / Integer MAX
legacy annotation doesn’t support defining minimum arity.

  • Programmatic

  • Annotation

  • Legacy Annotation

CommandRegistration zeroOrOneWithMinMax() {
	return CommandRegistration.builder()
		.command("example")
		.withOption()
			.longNames("arg")
			.arity(0, 1)
			.and()
		.build();
}
@Command(command = "example")
String zeroOrOneWithMinMax(
	@Option(arityMin = 0, arityMax = 1) String arg)
{
	return String.format("Hi '%s'", arg);
}
@ShellMethod(key = "example")
String zeroOrOneWithMinMax(
	@ShellOption(arity = 1) String arg)
{
	return String.format("Hi '%s'", arg);
}

In below example we have option arg1 and it’s defined as type String[]. Arity defines that it needs at least 1 parameter and not more that 2. As seen in below spesific exceptions TooManyArgumentsOptionException and NotEnoughArgumentsOptionException are thrown to indicate arity mismatch.

shell:>e2e reg arity-errors --arg1
Not enough arguments --arg1 requires at least 1.

shell:>e2e reg arity-errors --arg1 one
Hello [one]

shell:>e2e reg arity-errors --arg1 one two
Hello [one, two]

shell:>e2e reg arity-errors --arg1 one two three
Too many arguments --arg1 requires at most 2.