org.apache.lucene.collation

Class ICUCollationAttributeFactory

java.lang.Object

org.apache.lucene.util.AttributeSource.AttributeFactory

org.apache.lucene.collation.ICUCollationAttributeFactory

public class ICUCollationAttributeFactory
extends AttributeSource.AttributeFactory

Converts each token into its CollationKey, and then encodes bytes as an index term.

WARNING: Make sure you use exactly the same Collator at index and query time -- CollationKeys are only comparable when produced by the same Collator. RuleBasedCollators are independently versioned, so it is safe to search against stored CollationKeys if the following are exactly the same (best practice is to store this information with the index and check that they remain the same at query time):

1. Collator version - see Collator.getVersion()
2. The collation strength used - see Collator.setStrength(int)

CollationKeys generated by ICU Collators are not compatible with those generated by java.text.Collators. Specifically, if you use ICUCollationAttributeFactory to generate index terms, do not use CollationAttributeFactory on the query side, or vice versa.

ICUCollationAttributeFactory is significantly faster and generates significantly shorter keys than CollationAttributeFactory. See http://site.icu-project.org/charts/collation-icu4j-sun for key generation timing and key length comparisons between ICU4J and java.text.Collator over several languages.

Field Summary

Fields inherited from class org.apache.lucene.util.AttributeSource.AttributeFactory

DEFAULT_ATTRIBUTE_FACTORY

Constructor Summary

Constructors

Constructor and Description
ICUCollationAttributeFactory(AttributeSource.AttributeFactory delegate, com.ibm.icu.text.Collator collator) Create an ICUCollationAttributeFactory, using the supplied Attribute Factory as the factory for all other attributes.
ICUCollationAttributeFactory(com.ibm.icu.text.Collator collator) Create an ICUCollationAttributeFactory, using AttributeSource.AttributeFactory.DEFAULT_ATTRIBUTE_FACTORY as the factory for all other attributes.

Method Summary

Methods

Modifier and Type	Method and Description
AttributeImpl	createAttributeInstance(Class<? extends Attribute> attClass)

Methods inherited from class java.lang.Object

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

Constructor Detail

ICUCollationAttributeFactory

public ICUCollationAttributeFactory(com.ibm.icu.text.Collator collator)

Create an ICUCollationAttributeFactory, using AttributeSource.AttributeFactory.DEFAULT_ATTRIBUTE_FACTORY as the factory for all other attributes.

Parameters:

collator - CollationKey generator

ICUCollationAttributeFactory

public ICUCollationAttributeFactory(AttributeSource.AttributeFactory delegate,
                            com.ibm.icu.text.Collator collator)

Create an ICUCollationAttributeFactory, using the supplied Attribute Factory as the factory for all other attributes.

Parameters:

delegate - Attribute Factory

collator - CollationKey generator

Method Detail

createAttributeInstance

public AttributeImpl createAttributeInstance(Class<? extends Attribute> attClass)

Specified by:

createAttributeInstance in class AttributeSource.AttributeFactory