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.

Quick rundown

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, @Parameter or @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));
}

Standard types

Some types don't need a custom converter. See StandardConverters.java.

Subcommands

The @SuperCommand annotation can be used to define a git-like subcommand structure. See javadoc.

Sample projects

• jbock-maven-example
• jbock-gradle-example

Alternatives

• Tim's list