org.apache.lucene.index.memory
Class SynonymTokenFilter

java.lang.Object
  org.apache.lucene.analysis.TokenStream
      org.apache.lucene.analysis.TokenFilter
          org.apache.lucene.index.memory.SynonymTokenFilter

public class SynonymTokenFilter
extends TokenFilter

Injects additional tokens for synonyms of token terms fetched from the underlying child stream; the child stream must deliver lowercase tokens for synonyms to be found.

Author:

whoschek.AT.lbl.DOT.gov

Field Summary

static String

SYNONYM_TOKEN_TYPE The Token.type used to indicate a synonym to higher level filters.

Fields inherited from class org.apache.lucene.analysis.TokenFilter

input

Constructor Summary

SynonymTokenFilter(TokenStream input, SynonymMap synonyms, int maxSynonyms)
Creates an instance for the given underlying stream and synonym table.

Method Summary

protected Token	createToken(String synonym, Token current) Creates and returns a token for the given synonym of the current input token; Override for custom (stateless or stateful) behaviour, if desired.
Token	next() Returns the next token in the stream, or null at EOS.

Methods inherited from class org.apache.lucene.analysis.TokenFilter

close

Methods inherited from class java.lang.Object

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

Field Detail

SYNONYM_TOKEN_TYPE

public static final String SYNONYM_TOKEN_TYPE

The Token.type used to indicate a synonym to higher level filters.

See Also:

Constant Field Values

Constructor Detail

SynonymTokenFilter

public SynonymTokenFilter(TokenStream input,
                          SynonymMap synonyms,
                          int maxSynonyms)

Creates an instance for the given underlying stream and synonym table.

Parameters:

input - the underlying child token stream

synonyms - the map used to extract synonyms for terms

maxSynonyms - the maximum number of synonym tokens to return per underlying token word (a value of Integer.MAX_VALUE indicates unlimited)

Method Detail

next

public Token next()
           throws IOException

Returns the next token in the stream, or null at EOS.

Specified by:

next in class TokenStream

Throws:

IOException

createToken

protected Token createToken(String synonym,
                            Token current)

Creates and returns a token for the given synonym of the current input token; Override for custom (stateless or stateful) behaviour, if desired.

Parameters:

synonym - a synonym for the current token's term

current - the current token from the underlying child stream

Returns:

a new token, or null to indicate that the given synonym should be ignored