org.apache.lucene.search.highlight

Class Highlighter

java.lang.Object

org.apache.lucene.search.highlight.Highlighter

public class Highlighter
extends Object

Marks up highlighted terms found in the best sections of text, using configurable Fragmenter, Scorer, Formatter, Encoder and tokenizers. This is Lucene's original Highlighter; there are others.

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_MAX_CHARS_TO_ANALYZE

Constructor Summary

Constructors

Constructor and Description
Highlighter(Formatter formatter, Encoder encoder, Scorer fragmentScorer)
Highlighter(Formatter formatter, Scorer fragmentScorer)
Highlighter(Scorer fragmentScorer)

Method Summary

Modifier and Type	Method and Description
String	getBestFragment(Analyzer analyzer, String fieldName, String text) Highlights chosen terms in a text, extracting the most relevant section.
String	getBestFragment(TokenStream tokenStream, String text) Highlights chosen terms in a text, extracting the most relevant section.
String[]	getBestFragments(Analyzer analyzer, String fieldName, String text, int maxNumFragments) Highlights chosen terms in a text, extracting the most relevant sections.
String[]	getBestFragments(TokenStream tokenStream, String text, int maxNumFragments) Highlights chosen terms in a text, extracting the most relevant sections.
String	getBestFragments(TokenStream tokenStream, String text, int maxNumFragments, String separator) Highlights terms in the text , extracting the most relevant sections and concatenating the chosen fragments with a separator (typically "...").
TextFragment[]	getBestTextFragments(TokenStream tokenStream, String text, boolean mergeContiguousFragments, int maxNumFragments) Low level api to get the most relevant (formatted) sections of the document.
Encoder	getEncoder()
Scorer	getFragmentScorer()
int	getMaxDocCharsToAnalyze()
Fragmenter	getTextFragmenter()
void	setEncoder(Encoder encoder)
void	setFragmentScorer(Scorer scorer)
void	setMaxDocCharsToAnalyze(int maxDocCharsToAnalyze)
void	setTextFragmenter(Fragmenter fragmenter)

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_MAX_CHARS_TO_ANALYZE

public static final int DEFAULT_MAX_CHARS_TO_ANALYZE

See Also:

Constant Field Values

Constructor Detail

Highlighter

public Highlighter(Scorer fragmentScorer)

Highlighter

public Highlighter(Formatter formatter,
                   Scorer fragmentScorer)

Highlighter

public Highlighter(Formatter formatter,
                   Encoder encoder,
                   Scorer fragmentScorer)

Method Detail

getBestFragment

public final String getBestFragment(Analyzer analyzer,
                                    String fieldName,
                                    String text)
                             throws IOException,
                                    InvalidTokenOffsetsException

Highlights chosen terms in a text, extracting the most relevant section. This is a convenience method that calls getBestFragment(TokenStream, String)

Parameters:

analyzer - the analyzer that will be used to split text into chunks

text - text to highlight terms in

fieldName - Name of field used to influence analyzer's tokenization policy

Returns:

highlighted text fragment or null if no terms found

Throws:

InvalidTokenOffsetsException - thrown if any token's endOffset exceeds the provided text's length

IOException

getBestFragment

public final String getBestFragment(TokenStream tokenStream,
                                    String text)
                             throws IOException,
                                    InvalidTokenOffsetsException

Highlights chosen terms in a text, extracting the most relevant section. The document text is analysed in chunks to record hit statistics across the document. After accumulating stats, the fragment with the highest score is returned

Parameters:

tokenStream - a stream of tokens identified in the text parameter, including offset information. This is typically produced by an analyzer re-parsing a document's text. Some work may be done on retrieving TokenStreams more efficiently by adding support for storing original text position data in the Lucene index but this support is not currently available (as of Lucene 1.4 rc2).

text - text to highlight terms in

Returns:

highlighted text fragment or null if no terms found

Throws:

InvalidTokenOffsetsException - thrown if any token's endOffset exceeds the provided text's length

IOException

getBestFragments

public final String[] getBestFragments(Analyzer analyzer,
                                       String fieldName,
                                       String text,
                                       int maxNumFragments)
                                throws IOException,
                                       InvalidTokenOffsetsException

Highlights chosen terms in a text, extracting the most relevant sections. This is a convenience method that calls getBestFragments(TokenStream, String, int)

Parameters:

analyzer - the analyzer that will be used to split text into chunks

fieldName - the name of the field being highlighted (used by analyzer)

text - text to highlight terms in

maxNumFragments - the maximum number of fragments.

Returns:

highlighted text fragments (between 0 and maxNumFragments number of fragments)

Throws:

InvalidTokenOffsetsException - thrown if any token's endOffset exceeds the provided text's length

IOException

getBestFragments

public final String[] getBestFragments(TokenStream tokenStream,
                                       String text,
                                       int maxNumFragments)
                                throws IOException,
                                       InvalidTokenOffsetsException

Highlights chosen terms in a text, extracting the most relevant sections. The document text is analysed in chunks to record hit statistics across the document. After accumulating stats, the fragments with the highest scores are returned as an array of strings in order of score (contiguous fragments are merged into one in their original order to improve readability)

Parameters:

text - text to highlight terms in

maxNumFragments - the maximum number of fragments.

Returns:

highlighted text fragments (between 0 and maxNumFragments number of fragments)

Throws:

InvalidTokenOffsetsException - thrown if any token's endOffset exceeds the provided text's length

IOException

getBestTextFragments

public final TextFragment[] getBestTextFragments(TokenStream tokenStream,
                                                 String text,
                                                 boolean mergeContiguousFragments,
                                                 int maxNumFragments)
                                          throws IOException,
                                                 InvalidTokenOffsetsException

Low level api to get the most relevant (formatted) sections of the document. This method has been made public to allow visibility of score information held in TextFragment objects. Thanks to Jason Calabrese for help in redefining the interface.

Throws:

IOException - If there is a low-level I/O error

InvalidTokenOffsetsException - thrown if any token's endOffset exceeds the provided text's length

getBestFragments

public final String getBestFragments(TokenStream tokenStream,
                                     String text,
                                     int maxNumFragments,
                                     String separator)
                              throws IOException,
                                     InvalidTokenOffsetsException

Highlights terms in the text , extracting the most relevant sections and concatenating the chosen fragments with a separator (typically "..."). The document text is analysed in chunks to record hit statistics across the document. After accumulating stats, the fragments with the highest scores are returned in order as "separator" delimited strings.

Parameters:

text - text to highlight terms in

maxNumFragments - the maximum number of fragments.

separator - the separator used to intersperse the document fragments (typically "...")

Returns:

highlighted text

Throws:

InvalidTokenOffsetsException - thrown if any token's endOffset exceeds the provided text's length

IOException

getMaxDocCharsToAnalyze

public int getMaxDocCharsToAnalyze()

setMaxDocCharsToAnalyze

public void setMaxDocCharsToAnalyze(int maxDocCharsToAnalyze)

getTextFragmenter

public Fragmenter getTextFragmenter()

setTextFragmenter

public void setTextFragmenter(Fragmenter fragmenter)

getFragmentScorer

public Scorer getFragmentScorer()

Returns:

Object used to score each text fragment

setFragmentScorer

public void setFragmentScorer(Scorer scorer)

getEncoder

public Encoder getEncoder()

setEncoder

public void setEncoder(Encoder encoder)