org.apache.lucene.analysis

Class Analyzer

java.lang.Object

org.apache.lucene.analysis.Analyzer

Direct Known Subclasses:

KeywordAnalyzer, PerFieldAnalyzerWrapper, SimpleAnalyzer, StandardAnalyzer, StopAnalyzer, WhitespaceAnalyzer

public abstract class Analyzer
extends java.lang.Object

An Analyzer builds TokenStreams, which analyze text. It thus represents a policy for extracting index terms from text.

Typical implementations first build a Tokenizer, which breaks the stream of characters from the Reader into raw Tokens. One or more TokenFilters may then be applied to the output of the Tokenizer.

WARNING: You must override one of the methods defined by this class in your subclass or the Analyzer will enter an infinite loop.

Constructor Summary

Constructors

Constructor and Description
Analyzer()

Method Summary

Modifier and Type	Method and Description
int	getPositionIncrementGap(java.lang.String fieldName) Invoked before indexing a Fieldable instance if terms have already been added to that field.
TokenStream	reusableTokenStream(java.lang.String fieldName, java.io.Reader reader) Creates a TokenStream that is allowed to be re-used from the previous time that the same thread called this method.
abstract TokenStream	tokenStream(java.lang.String fieldName, java.io.Reader reader) Creates a TokenStream which tokenizes all the text in the provided Reader.

Methods inherited from class java.lang.Object

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

Constructor Detail

Analyzer

public Analyzer()

Method Detail

tokenStream

public abstract TokenStream tokenStream(java.lang.String fieldName,
                                        java.io.Reader reader)

Creates a TokenStream which tokenizes all the text in the provided Reader. Default implementation forwards to tokenStream(Reader) for compatibility with older version. Override to allow Analyzer to choose strategy based on document and/or field. Must be able to handle null field name for backward compatibility.

reusableTokenStream

public TokenStream reusableTokenStream(java.lang.String fieldName,
                                       java.io.Reader reader)
                                throws java.io.IOException

Creates a TokenStream that is allowed to be re-used from the previous time that the same thread called this method. Callers that do not need to use more than one TokenStream at the same time from this analyzer should use this method for better performance.

Throws:

java.io.IOException

getPositionIncrementGap

public int getPositionIncrementGap(java.lang.String fieldName)

Invoked before indexing a Fieldable instance if terms have already been added to that field. This allows custom analyzers to place an automatic position increment gap between Fieldable instances using the same field name. The default value position increment gap is 0. With a 0 position increment gap and the typical default token position increment of 1, all terms in a field, including across Fieldable instances, are in successive positions, allowing exact PhraseQuery matches, for instance, across Fieldable instance boundaries.

Parameters:

fieldName - Fieldable name being indexed.

Returns:

position increment gap, added to the next token emitted from tokenStream(String,Reader)