Commands

Core annotations and patterns for defining CLI commands, options, and argument handling in Crest.

Crest turns Java methods into CLI commands through a small set of annotations. A method annotated with @Command becomes a command. Its parameters become options and positional arguments. The framework handles parsing, type conversion, validation, and help generation automatically.

This section covers everything you need to define and organize commands:

  • Annotations – @Command, @Option, @Default, and @Required form the foundation of every CLI tool built with Crest.
  • Options Classes – Bundle related options into reusable @Options classes and compose them across commands.
  • Command Groups – Organize commands into groups with sub-commands using class-level @Command.
  • Return Types – Choose from String, StreamingOutput, PrintOutput, Stream, and more to control command output.
  • I/O Streams – Inject stdin, stdout, and stderr into commands with @In, @Out, and @Err.

Annotations

The core annotations for defining commands, options, defaults, and required parameters in Crest.

Options Classes

Bundle related options into reusable classes with @Options, compose them across commands, and use @GlobalOptions.

Command Groups

Organize commands into groups and sub-commands using class-level @Command annotations.

Return Types

Supported return types for Crest commands including String, StreamingOutput, PrintOutput, Stream, and void.

I/O Streams

Inject stdin, stdout, and stderr into Crest commands using @In, @Out, and @Err annotations.