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.

Field Summary

Fields

Modifier and Type	Field and Description
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

Constructors

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

Method Summary

Methods

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

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

close, reset

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

next

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(Token reusableToken)
           throws IOException

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

Overrides:

next in class TokenStream

Throws:

IOException

createToken

protected Token createToken(String synonym,
                Token current,
                Token reusableToken)

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

Parameters:

synonym - a synonym for the current token's term

current - the current token from the underlying child stream

reusableToken - the token to reuse

Returns:

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