Class CategoryAttributesStream

  extended by org.apache.lucene.util.AttributeSource
      extended by org.apache.lucene.analysis.TokenStream
          extended by org.apache.lucene.facet.index.streaming.CategoryAttributesStream
All Implemented Interfaces:

public class CategoryAttributesStream
extends TokenStream

An attribute stream built from an Iterable of CategoryAttribute. This stream should then be passed through several filters (see CategoryParentsStream, CategoryListTokenizer and CategoryTokenizer) until a token stream is produced that can be indexed by Lucene.

A CategoryAttributesStream object can be reused for producing more than one stream. To do that, the user should cause the underlying Iterable object to return a new set of categories, and then call reset() to allow this stream to be used again.

WARNING: This API is experimental and might change in incompatible ways in the next release.

Nested Class Summary
Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.AttributeFactory, AttributeSource.State
Field Summary
protected  CategoryAttribute categoryAttribute
Constructor Summary
CategoryAttributesStream(Iterable<CategoryAttribute> iterable)
Method Summary
 boolean incrementToken()
          Consumers (i.e., IndexWriter) use this method to advance the stream to the next token.
 void reset()
          Resets this stream to the beginning.
Methods inherited from class org.apache.lucene.analysis.TokenStream
close, end
Methods inherited from class org.apache.lucene.util.AttributeSource
addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState, toString
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail


protected CategoryAttribute categoryAttribute
Constructor Detail


public CategoryAttributesStream(Iterable<CategoryAttribute> iterable)

iterable - Iterable of CategoryAttribute, from which categories are taken.
Method Detail


public final boolean incrementToken()
                             throws IOException
Description copied from class: TokenStream
Consumers (i.e., IndexWriter) use this method to advance the stream to the next token. Implementing classes must implement this method and update the appropriate AttributeImpls with the attributes of the next token.

The producer must make no assumptions about the attributes after the method has been returned: the caller may arbitrarily change it. If the producer needs to preserve the state for subsequent calls, it can use AttributeSource.captureState() to create a copy of the current attribute state.

This method is called for every token of a document, so an efficient implementation is crucial for good performance. To avoid calls to AttributeSource.addAttribute(Class) and AttributeSource.getAttribute(Class), references to all AttributeImpls that this stream uses should be retrieved during instantiation.

To ensure that filters and consumers know which attributes are available, the attributes must be added during instantiation. Filters and consumers are not required to check for availability of attributes in TokenStream.incrementToken().

Specified by:
incrementToken in class TokenStream
false for end of stream; true otherwise


public void reset()
Description copied from class: TokenStream
Resets this stream to the beginning. This is an optional operation, so subclasses may or may not implement this method. TokenStream.reset() is not needed for the standard indexing process. However, if the tokens of a TokenStream are intended to be consumed more than once, it is necessary to implement TokenStream.reset(). Note that if your TokenStream caches tokens and feeds them back again after a reset, it is imperative that you clone the tokens when you store them away (on the first pass) as well as when you return them (on future passes after TokenStream.reset()).

reset in class TokenStream

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