Package picocli

Class CommandLine.Model.PositionalParamSpec

  • Enclosing class:
    CommandLine.Model
    public static class CommandLine.Model.PositionalParamSpec
extends CommandLine.Model.ArgSpec
    The PositionalParamSpec class models aspects of a positional parameter of a command, including whether it is required or optional, and attributes for the usage help message describing the positional parameter.

    Positional parameters have an index (or a range of indices). A positional parameter is matched when the parser encounters a command line argument at that index. Named options and their parameters do not change the index counter, so the command line can contain a mixture of positional parameters and named options.

    Depending on the positional parameter's arity, the parser may consume multiple command line arguments starting from the current index. The parser will call setValue on the PositionalParamSpec for each of the parameters encountered. For multi-value positional parameters, the type may be an array, a Collection or a Map. In this case the parser will get the data structure by calling getValue and modify the contents of this data structure. (In the case of arrays, the array is replaced with a new instance with additional elements.)

    Before calling the setter, picocli converts the positional parameter value from a String to the parameter's type.

    • If a positional parameter-specific converter is configured, this will be used for type conversion. If the positional parameter's type is a Map, the map may have different types for its keys and its values, so converters should provide two converters: one for the map keys and one for the map values.
    • Otherwise, the positional parameter's type is used to look up a converter in the list of registered converters. For multi-value positional parameters, the type may be an array, or a Collection or a Map. In that case the elements are converted based on the positional parameter's auxiliaryTypes. The auxiliaryType is used to look up the converter(s) to use to convert the individual parameter values. Maps may have different types for its keys and its values, so auxiliaryTypes should provide two types: one for the map keys and one for the map values.

    PositionalParamSpec objects are used by the picocli command line interpreter and help message generator. Picocli can construct a PositionalParamSpec automatically from fields and methods with @Parameters annotations. Alternatively a PositionalParamSpec can be constructed programmatically.

    When a PositionalParamSpec is created from a @Parameters -annotated field or method, it is "bound" to that field or method: this field is set (or the method is invoked) when the position is matched and setValue is called. Programmatically constructed PositionalParamSpec instances will remember the value passed to the setValue method so it can be retrieved with the getValue method. This behaviour can be customized by installing a custom CommandLine.Model.IGetter and CommandLine.Model.ISetter on the PositionalParamSpec.

    Since:
    3.0