org.apache.lucene.collation
Class CollationAttributeFactory

java.lang.Object
  org.apache.lucene.util.AttributeSource.AttributeFactory
      org.apache.lucene.collation.CollationAttributeFactory

public class CollationAttributeFactory
extends AttributeSource.AttributeFactory

Converts each token into its CollationKey, and then encodes the 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. Since RuleBasedCollators are not independently versioned, it is unsafe to search against stored CollationKeys unless 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. JVM vendor
2. JVM version, including patch version
3. The language (and country and variant, if specified) of the Locale used when constructing the collator via Collator.getInstance(java.util.Locale).
4. The collation strength used - see Collator.setStrength(int)

The ICUCollationAttributeFactory in the analysis-icu package uses ICU4J's Collator, which makes its version available, thus allowing collation to be versioned independently from the JVM. ICUCollationAttributeFactory is also 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.

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

Field Summary

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

DEFAULT_ATTRIBUTE_FACTORY

Constructor Summary

CollationAttributeFactory(AttributeSource.AttributeFactory delegate, Collator collator)
Create a CollationAttributeFactory, using the supplied Attribute Factory as the factory for all other attributes.

CollationAttributeFactory(Collator collator)
Create a CollationAttributeFactory, using AttributeSource.AttributeFactory.DEFAULT_ATTRIBUTE_FACTORY as the factory for all other attributes.

Method Summary

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

CollationAttributeFactory

public CollationAttributeFactory(Collator collator)

Create a CollationAttributeFactory, using AttributeSource.AttributeFactory.DEFAULT_ATTRIBUTE_FACTORY as the factory for all other attributes.

Parameters:

collator - CollationKey generator

CollationAttributeFactory

public CollationAttributeFactory(AttributeSource.AttributeFactory delegate,
                                 Collator collator)

Create a CollationAttributeFactory, 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