org.apache.lucene.search.highlight
Class QueryTermScorer

java.lang.Object
  org.apache.lucene.search.highlight.QueryTermScorer

All Implemented Interfaces:

Scorer

public class QueryTermScorer
extends Object
implements Scorer

Scorer implementation which scores text fragments by the number of unique query terms found. This class uses the QueryTermExtractor class to process determine the query terms and their boosts to be used.

Constructor Summary

QueryTermScorer(Query query)

QueryTermScorer(Query query, IndexReader reader, String fieldName)

QueryTermScorer(Query query, String fieldName)

QueryTermScorer(WeightedTerm[] weightedTerms)

Method Summary

void	allFragmentsProcessed()
float	getFragmentScore() Called when the Highlighter has no more tokens for the current fragment - the Scorer returns the weighting it has derived for the most recent fragment, typically based on the results of Scorer.getTokenScore().
float	getMaxTermWeight()
float	getTokenScore() Called for each token in the current fragment.
TokenStream	init(TokenStream tokenStream) Called to init the Scorer with a TokenStream.
void	startFragment(TextFragment newFragment) Called when a new fragment is started for consideration.

Methods inherited from class java.lang.Object

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

Constructor Detail

QueryTermScorer

public QueryTermScorer(Query query)

Parameters:

query - a Lucene query (ideally rewritten using query.rewrite before being passed to this class and the searcher)

QueryTermScorer

public QueryTermScorer(Query query,
                       String fieldName)

Parameters:

query - a Lucene query (ideally rewritten using query.rewrite before being passed to this class and the searcher)

fieldName - the Field name which is used to match Query terms

QueryTermScorer

public QueryTermScorer(Query query,
                       IndexReader reader,
                       String fieldName)

Parameters:

query - a Lucene query (ideally rewritten using query.rewrite before being passed to this class and the searcher)

reader - used to compute IDF which can be used to a) score selected fragments better b) use graded highlights eg set font color intensity

fieldName - the field on which Inverse Document Frequency (IDF) calculations are based

QueryTermScorer

public QueryTermScorer(WeightedTerm[] weightedTerms)

Method Detail

init

public TokenStream init(TokenStream tokenStream)

Description copied from interface: Scorer

Called to init the Scorer with a TokenStream. You can grab references to the attributes you are interested in here and access them from Scorer.getTokenScore().

Specified by:

init in interface Scorer

Parameters:

tokenStream - the TokenStream that will be scored.

Returns:

either a TokenStream that the Highlighter should continue using (eg if you read the tokenSream in this method) or null to continue using the same TokenStream that was passed in.

startFragment

public void startFragment(TextFragment newFragment)

Description copied from interface: Scorer

Called when a new fragment is started for consideration.

Specified by:

startFragment in interface Scorer

Parameters:

newFragment - the fragment that will be scored next

getTokenScore

public float getTokenScore()

Description copied from interface: Scorer

Called for each token in the current fragment. The Highlighter will increment the TokenStream passed to init on every call.

Specified by:

getTokenScore in interface Scorer

Returns:

a score which is passed to the Highlighter class to influence the mark-up of the text (this return value is NOT used to score the fragment)

getFragmentScore

public float getFragmentScore()

Description copied from interface: Scorer

Called when the Highlighter has no more tokens for the current fragment - the Scorer returns the weighting it has derived for the most recent fragment, typically based on the results of Scorer.getTokenScore().

Specified by:

getFragmentScore in interface Scorer

allFragmentsProcessed

public void allFragmentsProcessed()

getMaxTermWeight

public float getMaxTermWeight()

Returns:

The highest weighted term (useful for passing to GradientFormatter to set top end of coloring scale.