Package org.apache.hadoop.util

Class ConfigurationHelper

java.lang.Object

org.apache.hadoop.util.ConfigurationHelper

@Private
public final class ConfigurationHelper
extends Object

Configuration Helper class to provide advanced configuration parsing. Private; external code MUST use Configuration instead

Method Summary

Modifier and Type	Method	Description
static <E extends Enum<E>> Map<String,E>	mapEnumNamesToValues(String prefix, Class<E> enumClass)	Given an enum class, build a map of lower case names to values.
static <E extends Enum<E>> EnumSet<E>	parseEnumSet(String key, String valueString, Class<E> enumClass, boolean ignoreUnknown)	Given a comma separated list of enum values, trim the list, map to enum values in the message (case insensitive) and return the set.
static <E extends Enum<E>> E	resolveEnum(Configuration conf, String name, Class<E> enumClass, Function<String,E> fallback)	Look up an enum from the configuration option and map it to a value in the supplied enum class.

Methods inherited from class java.lang.Object

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

Method Details

parseEnumSet

public static <E extends Enum<E>> EnumSet<E> parseEnumSet(String key,
 String valueString,
 Class<E> enumClass,
 boolean ignoreUnknown)
                                                   throws IllegalArgumentException

Given a comma separated list of enum values, trim the list, map to enum values in the message (case insensitive) and return the set. Special handling of "*" meaning: all values.

Type Parameters:

E - enum type

Parameters:

key - Configuration object key -used in error messages.

valueString - value from Configuration

enumClass - class of enum

ignoreUnknown - should unknown values be ignored?

Returns:

a mutable set of enum values parsed from the valueString, with any unknown matches stripped if ignoreUnknown is true.

Throws:

IllegalArgumentException - if one of the entries was unknown and ignoreUnknown is false, or there are two entries in the enum which differ only by case.

mapEnumNamesToValues

public static <E extends Enum<E>> Map<String,E> mapEnumNamesToValues(String prefix,
 Class<E> enumClass)

Given an enum class, build a map of lower case names to values.

Type Parameters:

E - enum type

Parameters:

prefix - prefix (with trailing ".") for path capabilities probe

enumClass - class of enum

Returns:

a mutable map of lower case names to enum values

Throws:

IllegalArgumentException - if there are two entries which differ only by case.

resolveEnum

public static <E extends Enum<E>> E resolveEnum(Configuration conf,
 String name,
 Class<E> enumClass,
 Function<String,E> fallback)

Look up an enum from the configuration option and map it to a value in the supplied enum class. If no value is supplied or there is no match for the supplied value, the fallback function is invoked, passing in the trimmed and possibly empty string of the value. Extends {link Configuration.getEnum(String, Enum)} by adding case independence and a lambda expression for fallback, rather than a default value.

Type Parameters:

E - enumeration type.

Parameters:

conf - configuration

name - property name

enumClass - classname to resolve

fallback - fallback supplier

Returns:

an enum value

Throws:

IllegalArgumentException - If mapping is illegal for the type provided