CommandLine.Command (picocli 3.9.6 API)
Date: 2019-04-06

picocli

## Annotation Type CommandLine.Command

-     @Retention(value=RUNTIME)
       @Target(value={TYPE,LOCAL_VARIABLE,FIELD,PACKAGE,METHOD})
      public static @interface CommandLine.Command

  Annotate your class with `@Command` when you want more control over the format of the generated help message. From 3.6, methods can also be annotated with `@Command`, where the method parameters define the command options and positional parameters.

       @Command(name      = "Encrypt", mixinStandardHelpOptions = true,
              description = "Encrypt FILE(s), or standard input, to standard output or to the output file.",
              version     = "Encrypt version 1.0",
              footer      = "Copyright (c) 2017")
       public class Encrypt {
           @Parameters(paramLabel = "FILE", description = "Any number of input files")
           private List<File> files = new ArrayList<File>();

           @Option(names = { "-o", "--out" }, description = "Output file (default: print to console)")
           private File outputFile;

           @Option(names = { "-v", "--verbose"}, description = "Verbose mode. Helpful for troubleshooting. Multiple -v options increase the verbosity.")
           private boolean[] verbose;
       }

  The structure of a help message looks like this:

  - [header]
  - [synopsis]: `Usage: <commandName> [OPTIONS] [FILE...]`
  - [description]
  - [parameter list]: `[FILE...] Any number of input files`
  - [option list]: `-h, --help prints this help message and exits`
  - [footer]

- - ### Optional Element Summary

    Optional Elements
    Modifier and Type | Optional Element and Description
    --- | ---
    `boolean` | `abbreviateSynopsis` Specify `true` to generate an abbreviated synopsis like `"<main> [OPTIONS] [PARAMETERS...]"`.
    `boolean` | `addMethodSubcommands` Specify whether methods annotated with `@Command` should be registered as subcommands of their enclosing `@Command` class.
    `java.lang.String[]` | `aliases` Alternative command names by which this subcommand is recognized on the command line.
    `java.lang.String` | `commandListHeading` Set the heading preceding the subcommands list.
    `java.lang.String[]` | `customSynopsis` Specify one or more custom synopsis lines to display instead of an auto-generated synopsis.
    `java.lang.Class<? extends CommandLine.IDefaultValueProvider>` | `defaultValueProvider` Class that can provide default values dynamically at runtime.
    `java.lang.String[]` | `description` Optional text to display between the synopsis line(s) and the list of options.
    `java.lang.String` | `descriptionHeading` Set the heading preceding the description section.
    `java.lang.String[]` | `footer` Optional text to display after the list of options.
    `java.lang.String` | `footerHeading` Set the heading preceding the footer section.
    `java.lang.String[]` | `header` Optional summary description of the command, shown before the synopsis.
    `java.lang.String` | `headerHeading` Set the heading preceding the header section.
    `boolean` | `helpCommand` Set this attribute to `true` if this subcommand is a help command, and required options and positional parameters of the parent command should not be validated.
    `boolean` | `hidden` Set `hidden=true` if this command should not be included in the list of commands in the usage help of the parent command.
    `boolean` | `mixinStandardHelpOptions` Adds the standard `-h` and `--help` usageHelp options and `-V` and `--version` versionHelp options to the options of this command.
    `java.lang.String` | `name` Program name to show in the synopsis.
    `java.lang.String` | `optionListHeading` Set the heading preceding the options list.
    `java.lang.String` | `parameterListHeading` Set the heading preceding the parameters list.
    `char` | `requiredOptionMarker` Prefix required options with this character in the options list.
    `java.lang.String` | `resourceBundle` Set the base name of the ResourceBundle to find option and positional parameters descriptions, as well as usage help message sections and section headings.
    `java.lang.String` | `separator` String that separates options from option parameters.
    `boolean` | `showDefaultValues` Specify `true` to show default values in the description column of the options list (except for boolean options).
    `boolean` | `sortOptions` Specify `false` to show Options in declaration order.
    `java.lang.Class<?>[]` | `subcommands` A list of classes to instantiate and register as subcommands.
    `java.lang.String` | `synopsisHeading` Set the heading preceding the synopsis text.
    `int` | `usageHelpWidth` Set the `usage help message width`.
    `java.lang.String[]` | `version` Version information for this command, to print to the console when the user specifies an option to request version help.
    `java.lang.Class<? extends CommandLine.IVersionProvider>` | `versionProvider` Class that can provide version information dynamically at runtime.

- - ### Element Detail

    - #### name

          public abstract java.lang.String name

      Program name to show in the synopsis. If omitted, `"<main class>"` is used. For declaratively added subcommands, this attribute is also used by the parser to recognize subcommands in the command line arguments.
      Returns:
        the program name to show in the synopsis
      See Also:
        `CommandLine.Model.CommandSpec.name()`, `CommandLine.Help.commandName()`
      Default:
        "<main class>"

  - - #### aliases

          public abstract java.lang.String[] aliases

      Alternative command names by which this subcommand is recognized on the command line.
      Returns:
        one or more alternative command names
      Since:
        3.1
      Default:
        {}

  - - #### subcommands

          public abstract java.lang.Class<?>[] subcommands

      A list of classes to instantiate and register as subcommands. When registering subcommands declaratively like this, you don't need to call the `CommandLine.addSubcommand(String, Object)` method. For example, this:

           @Command(subcommands = {
                   GitStatus.class,
                   GitCommit.class,
                   GitBranch.class })
           public class Git { ... }

           CommandLine commandLine = new CommandLine(new Git());

      is equivalent to this:

           // alternative: programmatically add subcommands.
           // NOTE: in this case there should be no `subcommands` attribute on the @Command annotation.
           @Command public class Git { ... }

           CommandLine commandLine = new CommandLine(new Git())
                   .addSubcommand("status",   new GitStatus())
                   .addSubcommand("commit",   new GitCommit())
                   .addSubcommand("branch",   new GitBranch());

      Returns:
        the declaratively registered subcommands of this command, or an empty array if none
      Since:
        0.9.8
      See Also:
        `CommandLine.addSubcommand(String, Object)`, `CommandLine.HelpCommand`
      Default:
        {}

  - - #### addMethodSubcommands

          public abstract boolean addMethodSubcommands

      Specify whether methods annotated with `@Command` should be registered as subcommands of their enclosing `@Command` class. The default is `true`. For example:

           @Command
           public class Git {
               @Command
               void status() { ... }
           }

           CommandLine git = new CommandLine(new Git());

      is equivalent to this:

           // don't add command methods as subcommands automatically
           @Command(addMethodSubcommands = false)
           public class Git {
               @Command
               void status() { ... }
           }

           // add command methods as subcommands programmatically
           CommandLine git = new CommandLine(new Git());
           CommandLine status = new CommandLine(CommandLine.getCommandMethods(Git.class, "status").get(0));
           git.addSubcommand("status", status);

      Returns:
        whether methods annotated with `@Command` should be registered as subcommands
      Since:
        3.6.0
      See Also:
        `CommandLine.addSubcommand(String, Object)`, `CommandLine.getCommandMethods(Class, String)`, `CommandLine.Model.CommandSpec.addMethodSubcommands()`
      Default:
        true

  - - #### separator

          public abstract java.lang.String separator

      String that separates options from option parameters. Default is `"="`. Spaces are also accepted.
      Returns:
        the string that separates options from option parameters, used both when parsing and when generating usage help
      See Also:
        `CommandLine.setSeparator(String)`
      Default:
        "="

  - - #### version

          public abstract java.lang.String[] version

      Version information for this command, to print to the console when the user specifies an option to request version help. Each element of the array is rendered on a separate line.

      May contain embedded format specifiers like `%n` line separators. Literal percent `'%'` characters must be escaped with another `%`.

      This is not part of the usage help message.

      Returns:
        a string or an array of strings with version information about this command (each string in the array is displayed on a separate line).
      Since:
        0.9.8
      See Also:
        `CommandLine.printVersionHelp(PrintStream)`
      Default:
        {}

  - - #### versionProvider

          public abstract java.lang.Class<? extends CommandLine.IVersionProvider> versionProvider

      Class that can provide version information dynamically at runtime. An implementation may return version information obtained from the JAR manifest, a properties file or some other source.
      Returns:
        a Class that can provide version information dynamically at runtime
      Since:
        2.2
      Default:
        picocli.CommandLine.NoVersionProvider.class

  - - #### mixinStandardHelpOptions

          public abstract boolean mixinStandardHelpOptions

      Adds the standard `-h` and `--help` usageHelp options and `-V` and `--version` versionHelp options to the options of this command.

      Note that if no `version()` or `versionProvider()` is specified, the `--version` option will not print anything.

      For internationalization: the help option has `descriptionKey = "mixinStandardHelpOptions.help"`, and the version option has `descriptionKey = "mixinStandardHelpOptions.version"`.

      Returns:
        whether the auto-help mixin should be added to this command
      Since:
        3.0
      Default:
        false

  - - #### helpCommand

          public abstract boolean helpCommand

      Set this attribute to `true` if this subcommand is a help command, and required options and positional parameters of the parent command should not be validated. If a subcommand marked as `helpCommand` is specified on the command line, picocli will not validate the parent arguments (so no "missing required option" errors) and the `CommandLine.printHelpIfRequested(List, PrintStream, PrintStream, Help.Ansi)` method will return `true`.
      Returns:
        `true` if this subcommand is a help command and picocli should not check for missing required options and positional parameters on the parent command
      Since:
        3.0
      Default:
        false

  - - #### headerHeading

          public abstract java.lang.String headerHeading

      Set the heading preceding the header section.

      May contain embedded format specifiers like `%n` line separators. Literal percent `'%'` characters must be escaped with another `%`.

      Returns:
        the heading preceding the header section
      See Also:
        `CommandLine.Model.UsageMessageSpec.headerHeading()`, `CommandLine.Help.headerHeading(Object...)`
      Default:
        ""

  - - #### header

          public abstract java.lang.String[] header

      Optional summary description of the command, shown before the synopsis. Each element of the array is rendered on a separate line.

      May contain embedded format specifiers like `%n` line separators. Literal percent `'%'` characters must be escaped with another `%`.

      Returns:
        summary description of the command
      See Also:
        `CommandLine.Model.UsageMessageSpec.header()`, `CommandLine.Help.header(Object...)`
      Default:
        {}

  - - #### synopsisHeading

          public abstract java.lang.String synopsisHeading

      Set the heading preceding the synopsis text. The default heading is `"Usage: "` (without a line break between the heading and the synopsis text).

      May contain embedded format specifiers like `%n` line separators. Literal percent `'%'` characters must be escaped with another `%`.

      Returns:
        the heading preceding the synopsis text
      See Also:
        `CommandLine.Help.synopsisHeading(Object...)`
      Default:
        "Usage: "

  - - #### abbreviateSynopsis

          public abstract boolean abbreviateSynopsis

      Specify `true` to generate an abbreviated synopsis like `"<main> [OPTIONS] [PARAMETERS...]"`. By default, a detailed synopsis with individual option names and parameters is generated.
      Returns:
        whether the synopsis should be abbreviated
      See Also:
        `CommandLine.Help.abbreviatedSynopsis()`, `CommandLine.Help.detailedSynopsis(Comparator, boolean)`
      Default:
        false

  - - #### customSynopsis

          public abstract java.lang.String[] customSynopsis

      Specify one or more custom synopsis lines to display instead of an auto-generated synopsis. Each element of the array is rendered on a separate line.

      May contain embedded format specifiers like `%n` line separators. Literal percent `'%'` characters must be escaped with another `%`.

      Returns:
        custom synopsis text to replace the auto-generated synopsis
      See Also:
        `CommandLine.Help.customSynopsis(Object...)`
      Default:
        {}

  - - #### descriptionHeading

          public abstract java.lang.String descriptionHeading

      Set the heading preceding the description section.

      May contain embedded format specifiers like `%n` line separators. Literal percent `'%'` characters must be escaped with another `%`.

      Returns:
        the heading preceding the description section
      See Also:
        `CommandLine.Help.descriptionHeading(Object...)`
      Default:
        ""

  - - #### description

          public abstract java.lang.String[] description

      Optional text to display between the synopsis line(s) and the list of options. Each element of the array is rendered on a separate line.

      May contain embedded format specifiers like `%n` line separators. Literal percent `'%'` characters must be escaped with another `%`.

      Returns:
        description of this command
      See Also:
        `CommandLine.Help.description(Object...)`
      Default:
        {}

  - - #### parameterListHeading

          public abstract java.lang.String parameterListHeading

      Set the heading preceding the parameters list.

      May contain embedded format specifiers like `%n` line separators. Literal percent `'%'` characters must be escaped with another `%`.

      Returns:
        the heading preceding the parameters list
      See Also:
        `CommandLine.Help.parameterListHeading(Object...)`
      Default:
        ""

  - - #### optionListHeading

          public abstract java.lang.String optionListHeading

      Set the heading preceding the options list.

      May contain embedded format specifiers like `%n` line separators. Literal percent `'%'` characters must be escaped with another `%`.

      Returns:
        the heading preceding the options list
      See Also:
        `CommandLine.Help.optionListHeading(Object...)`
      Default:
        ""

  - - #### sortOptions

          public abstract boolean sortOptions

      Specify `false` to show Options in declaration order. The default is to sort alphabetically.
      Returns:
        whether options should be shown in alphabetic order.
      Default:
        true

  - - #### requiredOptionMarker

          public abstract char requiredOptionMarker

      Prefix required options with this character in the options list. The default is no marker: the synopsis indicates which options and parameters are required.
      Returns:
        the character to show in the options list to mark required options
      Default:
        32

  - - #### defaultValueProvider

          public abstract java.lang.Class<? extends CommandLine.IDefaultValueProvider> defaultValueProvider

      Class that can provide default values dynamically at runtime. An implementation may return default value obtained from a configuration file like a properties file or some other source.
      Returns:
        a Class that can provide default values dynamically at runtime
      Since:
        3.6
      Default:
        picocli.CommandLine.NoDefaultProvider.class

  - - #### showDefaultValues

          public abstract boolean showDefaultValues

      Specify `true` to show default values in the description column of the options list (except for boolean options). False by default.

      Note that picocli 3.2 allows embedding default values anywhere in the option or positional parameter description that ignores this setting.

      Returns:
        whether the default values for options and parameters should be shown in the description column
      Default:
        false

  - - #### commandListHeading

          public abstract java.lang.String commandListHeading

      Set the heading preceding the subcommands list. The default heading is `"Commands:%n"` (with a line break at the end).

      May contain embedded format specifiers like `%n` line separators. Literal percent `'%'` characters must be escaped with another `%`.

      Returns:
        the heading preceding the subcommands list
      See Also:
        `CommandLine.Help.commandListHeading(Object...)`
      Default:
        "Commands:%n"

  - - #### footerHeading

          public abstract java.lang.String footerHeading

      Set the heading preceding the footer section.

      May contain embedded format specifiers like `%n` line separators. Literal percent `'%'` characters must be escaped with another `%`.

      Returns:
        the heading preceding the footer section
      See Also:
        `CommandLine.Help.footerHeading(Object...)`
      Default:
        ""

  - - #### footer

          public abstract java.lang.String[] footer

      Optional text to display after the list of options. Each element of the array is rendered on a separate line.

      May contain embedded format specifiers like `%n` line separators. Literal percent `'%'` characters must be escaped with another `%`.

      Returns:
        text to display after the list of options
      See Also:
        `CommandLine.Help.footer(Object...)`
      Default:
        {}

  - - #### hidden

          public abstract boolean hidden

      Set `hidden=true` if this command should not be included in the list of commands in the usage help of the parent command.
      Returns:
        whether this command should be excluded from the usage message
      Since:
        3.0
      Default:
        false

  - - #### resourceBundle

          public abstract java.lang.String resourceBundle

      Set the base name of the ResourceBundle to find option and positional parameters descriptions, as well as usage help message sections and section headings.

      See `CommandLine.Model.Messages` for more details and an example.

      Returns:
        the base name of the ResourceBundle for usage help strings
      Since:
        3.6
      See Also:
        `CommandLine.Model.ArgSpec.messages()`, `CommandLine.Model.UsageMessageSpec.messages()`, `CommandLine.Model.CommandSpec.resourceBundle()`, `CommandLine.setResourceBundle(ResourceBundle)`
      Default:
        ""

  - - #### usageHelpWidth

          public abstract int usageHelpWidth

      Set the `usage help message width`. The default is 80.
      Since:
        3.7
      Default:
        80