jbock is a command line parser, which uses the same well-known annotation names as JCommander and picocli. It is an annotation processor which does not use runtime reflection, but generates a custom parser at compile time instead.
Create an abstract class, or alternatively a Java interface,
and add the @Command annotation.
In this so-called command class, each abstract method represents a command line option or argument.
Every such method must have
- getter signature (doesn't return
void, takes no arguments) and - annotation (either
@Option,@Parameteror@VarargsParameter).
The types boolean, List and Optional (including OptionalInt) have special meaning.
See example below.
@Command
abstract class DeleteCommand {
@Option(names = {"-v", "--verbosity"},
description = {"A non-required, named option. The return type is optionalish.",
"Using int or Integer would make it required."})
abstract OptionalInt verbosity();
@Parameter(
index = 0,
description = {"A required positional parameter. Return type is not optionalish.",
"Built-in converter is available for type Path."})
abstract Path path();
@Parameter(
index = 1,
description = "An optional positional parameter.")
abstract Optional<Path> anotherPath();
@VarargsParameter(
description = {"A varargs parameter. There can only be one of these.",
"Must return List."})
abstract List<Path> morePaths();
@Option(names = "--dry-run",
description = "A nullary option, a.k.a. mode flag. Must return boolean.")
abstract boolean dryRun();
@Option(names = "-h",
description = "A repeatable option. Must return List.")
abstract List<String> headers();
@Option(names = "--charset",
description = "Named option with a custom converter",
converter = CharsetConverter.class)
abstract Optional<Charset> charset();
static class CharsetConverter extends StringConverter<Charset> {
@Override
protected Charset convert(String token) { return Charset.forName(token); }
}
}The generated class is called *Parser.
public static void main(String[] args) {
DeleteCommand command = DeleteCommandParser.parseOrExit(args);
// alternatively:
// Either<ParsingFailed, DeleteCommand> either = DeleteCommandParser.parse(List.of(args));
}Some types don't need a custom converter. See StandardConverters.java.
The @SuperCommand annotation can be used to define a git-like subcommand structure. See javadoc.