picocli

Annotation Type CommandLine.Parameters

@Retention(value=RUNTIME)
 @Target(value={FIELD,METHOD,PARAMETER})
public static @interface CommandLine.Parameters

Fields annotated with @Parameters will be initialized with positional parameters. By specifying the index() attribute you can pick the exact position or a range of positional parameters to apply. If no index is specified, the field will get all positional parameters (and so it should be an array or a collection).

In the case of command methods (annotated with @Command), method parameters may be annotated with @Parameters, but are are considered positional parameters by default, unless they are annotated with @Option.

Command class example:

 import static picocli.CommandLine.*;

 public class MyCalcParameters {
     @Parameters(description = "Any number of input numbers")
     private List<BigDecimal> files = new ArrayList<BigDecimal>();

     @Option(names = { "-h", "--help" }, usageHelp = true, description = "Display this help and exit")
     private boolean help;
 }
 

A field cannot be annotated with both @Parameters and @Option or a ParameterException is thrown.

Field Summary

Fields

Modifier and Type	Fields and Description
static String	NULL_VALUE Special value that can be used in some annotation attributes to designate null.

Optional Element Summary

Optional Elements

Modifier and Type	Optional Element and Description
String	arity Specifies the minimum number of required parameters and the maximum number of accepted parameters.
Class<? extends Iterable<String>>	completionCandidates Use this attribute to specify an Iterable<String> class that generates completion candidates for this positional parameter.
Class<? extends CommandLine.ITypeConverter<?>>[]	converter Optionally specify one or more CommandLine.ITypeConverter classes to use to convert the command line argument into a strongly typed value (or key-value pair for map fields).
String	defaultValue Returns the default value of this positional parameter, before splitting and type conversion.
String[]	description Description of the parameter(s), used when generating the usage documentation.
String	descriptionKey ResourceBundle key for this option.
boolean	echo Use this attribute to control whether user input for an interactive positional parameter is echoed to the console or not.
boolean	hidden Set hidden=true if this parameter should not be included in the usage message.
boolean	hideParamSyntax Returns whether usage syntax decorations around the paramLabel should be suppressed.
String	index Specify an index ("0", or "1", etc.) to pick which of the command line arguments should be assigned to this field.
boolean	interactive Set interactive=true if this positional parameter will prompt the end user for a value (like a password).
String	mapFallbackValue For positional parameters of type Map, setting the mapFallbackValue to any value allows end user to specify key-only parameters for this parameter.
Class<? extends CommandLine.IParameterConsumer>	parameterConsumer Optionally specify a custom IParameterConsumer to temporarily suspend picocli's parsing logic and process one or more command line arguments in a custom manner.
String	paramLabel Specify a paramLabel for the parameter to be used in the usage help message.
Class<? extends CommandLine.IParameterPreprocessor>	preprocessor Returns the preprocessor for this positional parameter.
String	prompt Use this attribute to customize the text displayed to the end user for an interactive positional parameter when asking for user input.
CommandLine.ScopeType	scope Determines on which command(s) this positional parameter exists: on this command only (the default), or whether this is a "global" parameter that is applied to this command and all subcommands, sub-subcommands, etc.
CommandLine.Help.Visibility	showDefaultValue Use this attribute to control for a specific positional parameter whether its default value should be shown in the usage help message.
String	split Specify a regular expression to use to split positional parameter values before applying them to the field.
String	splitSynopsisLabel Specify a string to show the split option parameter values in usage
Class<?>[]	type Optionally specify a type to control exactly what Class the positional parameter should be converted to.

Field Detail

NULL_VALUE

public static final String NULL_VALUE

Special value that can be used in some annotation attributes to designate null.

Since:

4.6

See Also:

defaultValue(), mapFallbackValue()

Element Detail

index

public abstract String index

Specify an index ("0", or "1", etc.) to pick which of the command line arguments should be assigned to this field. For array or Collection fields, you can also specify an index range ("0..3", or "2..*", etc.) to assign a subset of the command line arguments to this field. The default is "*", meaning all command line arguments.

Returns:

an index or range specifying which of the command line arguments should be assigned to this field

Default:

""

description

public abstract String[] description

Description of the parameter(s), used when generating the usage documentation. 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 %.

The description may contain variables that are rendered when help is requested. The string ${DEFAULT-VALUE} is replaced with the default value of the positional parameter. This is regardless of the command's showDefaultValues setting or the positional parameter's showDefaultValue setting. The string ${COMPLETION-CANDIDATES} is replaced with the completion candidates generated by completionCandidates() in the description for this positional parameter. Also, embedded %n newline markers are converted to actual newlines.

Returns:

the description of the parameter(s)

See Also:

Variable Interpolation section of the user manual

Default:

{}

arity

public abstract String arity

Specifies the minimum number of required parameters and the maximum number of accepted parameters. If a positive arity is declared, and the user specifies an insufficient number of parameters on the command line, CommandLine.MissingParameterException is thrown by the CommandLine.parse(String...) method.

The default depends on the type of the parameter: booleans require no parameters, arrays and Collections accept zero to any number of parameters, and any other type accepts one parameter.

For single-value parameters, setting arity = "0..1" makes a positional parameter optional, while setting arity = "1" makes it required.

Required parameters that are part of a group are required within the group, not required within the command: the group's multiplicity determines whether the group itself is required or optional.

Returns:

the range of minimum and maximum parameters accepted by this command

Default:

""

paramLabel

public abstract String paramLabel

Specify a paramLabel for the parameter to be used in the usage help message. If omitted, picocli uses the field name in fish brackets ('<' and '>') by default. Example:

class Example {
     @Parameters(paramLabel="FILE", description="path of the input FILE(s)")
     private File[] inputFiles;
 }

By default, the above gives a usage help message like the following:

 Usage: <main class> [FILE...]
 [FILE...]       path of the input FILE(s)
 

Returns:

name of the positional parameter used in the usage help message

Default:

""

hideParamSyntax

public abstract boolean hideParamSyntax

Returns whether usage syntax decorations around the paramLabel should be suppressed. The default is false: by default, the paramLabel is surrounded with '[' and ']' characters if the value is optional and followed by ellipses ("...") when multiple values can be specified.

Since:

3.6.0

Default:

false

type

public abstract Class<?>[] type

Optionally specify a type to control exactly what Class the positional parameter should be converted to. This may be useful when the field type is an interface or an abstract class. For example, a field can be declared to have type java.lang.Number, and annotating @Parameters(type=Short.class) ensures that the positional parameter value is converted to a Short before setting the field value.

For array fields whose component type is an interface or abstract class, specify the concrete component type. For example, a field with type Number[] may be annotated with @Parameters(type=Short.class) to ensure that positional parameter values are converted to Short before adding an element to the array.

Picocli will use the CommandLine.ITypeConverter that is registered for the specified type to convert the raw String values before modifying the field value.

Prior to 2.0, the type attribute was necessary for Collection and Map fields, but starting from 2.0 picocli will infer the component type from the generic type's type arguments. For example, for a field of type Map<TimeUnit, Long> picocli will know the positional parameter should be split up in key=value pairs, where the key should be converted to a java.util.concurrent.TimeUnit enum value, and the value should be converted to a Long. No @Parameters(type=...) type attribute is required for this. For generic types with wildcards, picocli will take the specified upper or lower bound as the Class to convert to, unless the @Parameters annotation specifies an explicit type attribute.

If the field type is a raw collection or a raw map, and you want it to contain other values than Strings, or if the generic type's type arguments are interfaces or abstract classes, you may specify a type attribute to control the Class that the positional parameter should be converted to.

Returns:

the type(s) to convert the raw String values

Default:

{}

converter

public abstract Class<? extends CommandLine.ITypeConverter<?>>[] converter

Optionally specify one or more CommandLine.ITypeConverter classes to use to convert the command line argument into a strongly typed value (or key-value pair for map fields). This is useful when a particular field should use a custom conversion that is different from the normal conversion for the field's type.

For example, for a specific field you may want to use a converter that maps the constant names defined in java.sql.Types to the int value of these constants, but any other int fields should not be affected by this and should continue to use the standard int converter that parses numeric values.

Returns:

the type converter(s) to use to convert String values to strongly typed values for this field

See Also:

CommandLine.registerConverter(Class, ITypeConverter)

Default:

{}

split

public abstract String split

Specify a regular expression to use to split positional parameter values before applying them to the field. All elements resulting from the split are added to the array or Collection. Previously ignored for single-value fields, from picocli 4.0 a split regex can only be specified on multi-value options and positional parameters.

Returns:

a regular expression to split operand values or "" if the value should not be split

See Also:

String.split(String)

Default:

""

splitSynopsisLabel

public abstract String splitSynopsisLabel

Specify a string to show the split option parameter values in usage

Since:

4.3

Default:

""

hidden

public abstract boolean hidden

Set hidden=true if this parameter should not be included in the usage message.

Returns:

whether this parameter should be excluded from the usage message

Default:

false

defaultValue

public abstract String defaultValue

Returns the default value of this positional parameter, before splitting and type conversion.

To get a null default value, omit specifying a default value or use the special value NULL_VALUE - for positional parameters of type Optional<T> that will result in the Optional.empty() value being assigned when the positional parameters is not specified on the command line.

Returns:

a String that (after type conversion) will be used as the value for this positional parameter if no value was specified on the command line

Since:

3.2

Default:

"__no_default_value__"

showDefaultValue

public abstract CommandLine.Help.Visibility showDefaultValue

Use this attribute to control for a specific positional parameter whether its default value should be shown in the usage help message. If not specified, the default value is only shown when the CommandLine.Command.showDefaultValues() is set true on the command. Use this attribute to specify whether the default value for this specific positional parameter should always be shown or never be shown, regardless of the command setting.

Note that picocli 3.2 allows embedding default values by specifying the variable ${DEFAULT-VALUE} anywhere in the description that ignores this setting.

Returns:

whether this positional parameter's default value should be shown in the usage help message

Default:

picocli.CommandLine.Help.Visibility.ON_DEMAND

completionCandidates

public abstract Class<? extends Iterable<String>> completionCandidates

Use this attribute to specify an Iterable<String> class that generates completion candidates for this positional parameter. For map fields, completion candidates should be in key=value form.

Completion candidates are used in bash completion scripts generated by the picocli.AutoComplete class. Unfortunately, picocli.AutoComplete is not very good yet at generating completions for positional parameters.

Returns:

a class whose instances can iterate over the completion candidates for this positional parameter

Since:

3.2

See Also:

CommandLine.IFactory

Default:

picocli.CommandLine.NoCompletionCandidates.class

interactive

public abstract boolean interactive

Set interactive=true if this positional parameter will prompt the end user for a value (like a password). Only supported for single-value positional parameters (not arrays, collections or maps). When running on Java 6 or greater and echo = false (the default), this will use the Console.readPassword() API to get a value without echoing input to the console, otherwise it will simply read a value from System.in.

Returns:

whether this positional parameter prompts the end user for a value to be entered on the command line

Since:

3.5

Default:

false

echo

public abstract boolean echo

Use this attribute to control whether user input for an interactive positional parameter is echoed to the console or not. If echo = true, the user input is echoed to the console. This attribute is ignored when interactive = false (the default).

Returns:

whether the user input for an interactive positional parameter should be echoed to the console or not

Since:

4.6

See Also:

CommandLine.Model.ArgSpec.echo()

Default:

false

prompt

public abstract String prompt

Use this attribute to customize the text displayed to the end user for an interactive positional parameter when asking for user input. When omitted, the displayed text is derived from the positional parameter's position (index) and the first description line. This attribute is ignored when interactive = false (the default).

Returns:

the text to display to the end user for an interactive positional parameter when asking for user input

Since:

4.6

See Also:

CommandLine.Model.ArgSpec.prompt()

Default:

""

descriptionKey

public abstract String descriptionKey

ResourceBundle key for this option. If not specified, (and a ResourceBundle exists for this command) an attempt is made to find the positional parameter description using paramLabel() + "[" + index() + "]" as key.

Since:

3.6

See Also:

CommandLine.Model.ArgSpec.description()

Default:

""

scope

public abstract CommandLine.ScopeType scope

Determines on which command(s) this positional parameter exists: on this command only (the default), or whether this is a "global" parameter that is applied to this command and all subcommands, sub-subcommands, etc.

Since:

4.3

Default:

picocli.CommandLine.ScopeType.LOCAL

parameterConsumer

public abstract Class<? extends CommandLine.IParameterConsumer> parameterConsumer

Optionally specify a custom IParameterConsumer to temporarily suspend picocli's parsing logic and process one or more command line arguments in a custom manner.

Since:

4.0

Default:

picocli.CommandLine.NullParameterConsumer.class

mapFallbackValue

public abstract String mapFallbackValue

For positional parameters of type Map, setting the mapFallbackValue to any value allows end user to specify key-only parameters for this parameter. For example, key instead of key=value.

The value specified in this annotation is the value that is put into the Map for the user-specified key. Use the special value NULL_VALUE to specify null - for maps of type Map<K, Optional<V>> that will result in Optional.empty() values in the map when only the key is specified.

If no mapFallbackValue is set, key-only Map parameters like -Dkey are considered invalid user input and cause a CommandLine.ParameterException to be thrown.

Since:

4.6

See Also:

CommandLine.Model.ArgSpec.mapFallbackValue()

Default:

"__unspecified__"

preprocessor

public abstract Class<? extends CommandLine.IParameterPreprocessor> preprocessor

Returns the preprocessor for this positional parameter.

Since:

4.6

See Also:

CommandLine.IParameterPreprocessor

Default:

picocli.CommandLine.NoOpParameterPreprocessor.class