Package picocli

Interface CommandLine.ITypeConverter<K>

  • Type Parameters:
    K - the type of the object that is the result of the conversion
    Enclosing class:
    CommandLine
    public static interface CommandLine.ITypeConverter<K>

    When parsing command line arguments and initializing fields annotated with @Option or @Parameters, String values can be converted to any type for which a ITypeConverter is registered.

    This interface defines the contract for classes that know how to convert a String into some domain object. Custom converters can be registered with the CommandLine.registerConverter(Class, ITypeConverter) method.

    Java 8 lambdas make it easy to register custom type converters: 

     commandLine.registerConverter(java.nio.file.Path.class, s -> java.nio.file.Paths.get(s));
 commandLine.registerConverter(java.time.Duration.class, s -> java.time.Duration.parse(s));

    Built-in type converters are pre-registered for the following java 1.5 types:

    • all primitive types
    • all primitive wrapper types: Boolean, Byte, Character, Double, Float, Integer, Long, Short
    • any enum
    • java.io.File
    • java.math.BigDecimal
    • java.math.BigInteger
    • java.net.InetAddress
    • java.net.URI
    • java.net.URL
    • java.nio.charset.Charset
    • java.sql.Time
    • java.util.Date
    • java.util.UUID
    • java.util.regex.Pattern
    • StringBuilder
    • CharSequence
    • String

    • Method Detail

      • convert

        K convert​(String value)
   throws Exception
        Converts the specified command line argument value to some domain object.
        Parameters:
        value - the command line argument String value
        Returns:
        the resulting domain object
        Throws:
        Exception - an exception detailing what went wrong during the conversion. Any exception thrown from this method will be caught and shown to the end user. An example error message shown to the end user could look something like this: Invalid value for option '--some-option': cannot convert 'xxxinvalidinput' to SomeType (java.lang.IllegalArgumentException: Invalid format: must be 'x:y:z' but was 'xxxinvalidinput')
        CommandLine.TypeConversionException - throw this exception to have more control over the error message that is shown to the end user when type conversion fails. An example message shown to the user could look like this: Invalid value for option '--some-option': Invalid format: must be 'x:y:z' but was 'xxxinvalidinput'