org.yarnandtail.andhow.valuetype

Class FlagType

java.lang.Object

org.yarnandtail.andhow.valuetype.BaseValueType<Boolean>

org.yarnandtail.andhow.valuetype.BolType

org.yarnandtail.andhow.valuetype.FlagType

All Implemented Interfaces:

FlaggableType<Boolean>, ValueType<Boolean>

public class FlagType
extends BolType
implements FlaggableType<Boolean>

Metadata and parsing for a Boolean type which is never null, similar to a 'nix flag behavior.

This would be used to parse a command line argument that is true by its presence, e.g.:
java MyClass launch
If launch is an AndHow property using the FlagType (i.e. FlagProp), launch will be considered true just by its presence.

This class is threadsafe and uses a singleton pattern to prevent multiple instances since all users can safely use the same instance.

Field Summary

Fields inherited from class org.yarnandtail.andhow.valuetype.BaseValueType

clazzType

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	FlagType()

Method Summary

Modifier and Type	Method and Description
static FlagType	instance() Fetch the single, shared instance of this ValueType
Boolean	parseFlag(String sourceValue) Attempts to parse the passed String into the destination type with flag semantics.

Methods inherited from class org.yarnandtail.andhow.valuetype.BolType

cast, parse

Methods inherited from class org.yarnandtail.andhow.valuetype.BaseValueType

getDestinationType, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.yarnandtail.andhow.api.ValueType

cast, getDestinationType, parse, toString

Constructor Detail

FlagType

protected FlagType()

Method Detail

instance

public static FlagType instance()

Fetch the single, shared instance of this ValueType

Returns:

An instance of the FlagType()

parseFlag

public Boolean parseFlag(String sourceValue)
                  throws ParsingException

Description copied from interface: FlaggableType

Attempts to parse the passed String into the destination type with flag semantics.

This method behaves as ValueType.parse(String), but with these differences:

• Null is interpreted as 'property is present' and thus set to a non-null value The actual value is implementation dependant - see FlagProp for an example.
• Null is never returned, since the intent to give null sourceValue values a non-null destination value.
• It is not reversible with ValueType.toString(Object)

This method should only be called by loaders that support Flags. For instance, loading a non-null value from the properties file entry 'name = ' would be unexpected, so a properties file loader should use the 'parse' method. However, a command line loader would be expected to support flags, so could call this method instead of 'parse'.

This method may still throw a ParsingException, since non-null values may still be parsed. As with ValueType.parse(String), all trimming (removing whitespace from around a value) should be assumed to already have happened for the incoming sourceValue.

Implementations should be careful to ONLY throw a ParsingException - Integers and other types may throw other unchecked exceptions when trying to convert values, which should be handled in this method and rethrown as a ParsingException.

Specified by:

parseFlag in interface FlaggableType<Boolean>

Returns:

A non-null value.

Throws:

ParsingException - for any type of failure.