jbock is a command line parser, which uses the well-known annotation names from JCommander and picocli. Being an annotation processor means it doesn't use 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
- must return something (not
void), - must have no arguments, and
- must be annotated with either
@Option,@Parameteror@VarargsParameter.
The multiplicity of options and parameters is determined by the return type of their declaring method.
The types boolean, List and Optional (including OptionalInt, yada yada) have a special meaning.
See example below.
@Command
abstract class DeleteCommand {
@Option(names = {"-v", "--verbosity"},
description = {"A named option. The return type reflects optionality.",
"Could use Optional<Integer> too, but using int or Integer",
"would make it a 'required option'."})
abstract OptionalInt verbosity();
@Parameter(
index = 0,
description = {"A required positional parameter. Return type is non-optional.",
"Path is a standard type, so no custom converter is needed."})
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.",
"The return type must be List-of-something."})
abstract List<Path> morePaths();
@Option(names = "--dry-run",
description = "A nullary option, a.k.a. mode flag. Return type is boolean.")
abstract boolean dryRun();
@Option(names = "-h",
description = "A repeatable option. Return type is List.")
abstract List<String> headers();
@Option(names = "--charset",
description = "Named option with a custom converter",
converter = CharsetConverter.class)
abstract Optional<Charset> charset();
// sample converter class
static class CharsetConverter extends StringConverter<Charset> {
@Override
protected Charset convert(String token) { return Charset.forName(token); }
}
}The generated class is called DeleteCommandParser. It converts a string array to an instance of DeleteCommand:
public static void main(String[] args) {
DeleteCommand command = new DeleteCommandParser().parseOrExit(args);
// ...
}In addition to parseOrExit, the generated parser has a basic and side-effect free parse method.
This can be used to fine-tune the help and error messages for your users.
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.