Package org.kohsuke.args4j

## Annotation Type Option

    @Retention(RUNTIME)
    @Target({FIELD,METHOD,PARAMETER})
    public @interface Option

Marks a field/setter that receives a command line switch value.

This annotation can be placed on a field of type T or the method of the form `void `methodName`(T value)`. Its access modified can be anything, but if it's not public, your application needs to run in a security context that allows args4j to access the field/method (see `AccessibleObject.setAccessible(boolean)`.

The behavior of the annotation differs depending on T --- the type of the field or the parameter of the method.

## Boolean Switch

When T is `boolean` , it represents a `boolean` option that takes the form of `-OPT`. When this option is set, the property will be set to `true`.

## String Switch

When T is `String`, it represents an option that takes one operand. The value of the operand is set to the property.

## Enum Switch

When T is derived from `Enum`, it represents an option that takes an operand, which must be one of the enum constant. The comparion between the operand and the enum constant name is done in a case insensitive fashion.

For example, the following definition will represent command line options like `-coin penny` or `-coin DIME`, but things like `-coin` or `-coin abc` are errors.

     enum Coin { PENNY,NICKEL,DIME,QUARTER }

     class Option {
       @Option(name="-coin")
       public Coin coin;
     }

## File Switch

When T is a `File`, it represents an option that takes a file/directory name as an operand.

Author:
  Kohsuke Kawaguchi

### Required Element Summary

Required Elements
`java.lang.String` `name` Name of the option, such as `-foo` or `-bar`.

### Optional Element Summary

Optional Elements
`java.lang.String[]` `aliases` Aliases for the options, such as `--long-option-name`.
`java.lang.String[]` `depends` List of other options that this option depends on.
`java.lang.String[]` `forbids` List of other options that this option is incompatible with..
`java.lang.Class<? extends OptionHandler>` `handler` Specify the `OptionHandler` that processes the command line arguments.
`boolean` `help` Specify that the option is a help option.
`boolean` `hidden` Specify that the option is hidden from the usage, by default.
`java.lang.String` `metaVar` When the option takes an operand, the usage screen will show something like this
`boolean` `required` Specify that the option is mandatory.
`java.lang.String` `usage` Help string used to display the usage screen.

### Element Detail

#### name

    java.lang.String name

Name of the option, such as `-foo` or `-bar`.

#### aliases

    java.lang.String[] aliases

Aliases for the options, such as `--long-option-name`.

Default:
  {}

#### usage

    java.lang.String usage

Help string used to display the usage screen.

This parameter works in two ways. For a simple use, you can just encode the human-readable help string directly, and that will be used as the message. This is easier, but it doesn't support localization.

For more advanced use, this property is set to a key of a `ResourceBundle`. The actual message is obtained by querying a `ResourceBundle` instance supplied to `CmdLineParser` by this key. This allows the usage screen to be properly localized.

If this value is empty, the option will not be displayed in the usage screen.

Default:
  ""

#### metaVar

    java.lang.String metaVar

When the option takes an operand, the usage screen will show something like this

     -x FOO  : blah blah blah

You can replace the `FOO` token by using this parameter.

If left unspecified, this value is infered from the type of the option.

Just like `usage()`, normally, this value is printed as is. But if a `ResourceBundle` is given to the `CmdLineParser`, it will be used to obtain the locale-specific value.

Default:
  ""

#### required

    boolean required

Specify that the option is mandatory.

At the end of `CmdLineParser.parseArgument(String...)`, a `CmdLineException` will be thrown if a required option is not present.

Note that in most of the command line interface design principles, options should be really optional. So use caution when using this flag.

Default:
  false

#### help

    boolean help

Specify that the option is a help option.

When flagging an option being the help option, required arguments or options that are missing in an actual command line don't cause an exception to be thrown.

See Also:
  `required()`

Default:
  false

#### hidden

    boolean hidden

Specify that the option is hidden from the usage, by default.

You can still have `CmdLineParser` show hidden options by using `OptionHandlerFilter.ALL`, which allows you to create an option that shows hidden options.

If you need more complicated filtering logic, define your own annotations and check them in `Setter.asAnnotatedElement()`.

See Also:
  `OptionHandlerFilter.PUBLIC`

Default:
  false

#### handler

    java.lang.Class<? extends OptionHandler> handler

Specify the `OptionHandler` that processes the command line arguments.

The default value `OptionHandler` indicates that the `OptionHandler` will be infered from the type of the field/method where a `Option` annotation is placed.

If this annotation element is used, it overrides the inference and determines the handler to be used. This is convenient for defining a non-standard option parsing semantics.

### Example

     // this is a normal "-r" option
     @Option(name="-r")
     boolean value;

     // this causes arg4j to use MyHandler, not the default
     // handler provided for boolean
     @Option(name="-b",handler=MyHandler.class)
     boolean value;

Default:
  org.kohsuke.args4j.spi.OptionHandler.class

#### depends

    java.lang.String[] depends

List of other options that this option depends on.

### Example

      @Option(name="-a")
      int a;
      //-b is not required but if it's provided, then a becomes required
      @Option(name="-b", depends={"-a"})
      int b;

At the end of `CmdLineParser.parseArgument(String...)`, a `CmdLineException` will be thrown if options required by another one are not present.

Default:
  {}

#### forbids

    java.lang.String[] forbids

List of other options that this option is incompatible with..

### Example

      @Option(name="-a")
      int a;
      // -h and -a cannot be specified together
      @Option(name="-h", forbids={"-a"})
      boolean h;

At the end of `CmdLineParser.parseArgument(String...)`, a `CmdLineException` will be thrown if forbidden option combinations are present.

Default:
  {}