Package org.apache.lucene.search.uhighlight

Class CustomUnifiedHighlighter

java.lang.Object

org.apache.lucene.search.uhighlight.UnifiedHighlighter

org.apache.lucene.search.uhighlight.CustomUnifiedHighlighter

public class CustomUnifiedHighlighter
extends UnifiedHighlighter

Subclass of the UnifiedHighlighter that works for a single field in a single document. Uses a custom PassageFormatter. Accepts field content as a constructor argument, given that loadings field value can be done reading from _source field. Supports using different BreakIterator to break the text into fragments. Considers every distinct field value as a discrete passage for highlighting (unless the whole content needs to be highlighted). Supports both returning empty snippets and non highlighted snippets when no highlighting can be performed.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.search.uhighlight.UnifiedHighlighter

UnifiedHighlighter.HighlightFlag, UnifiedHighlighter.LimitedStoredFieldVisitor, UnifiedHighlighter.OffsetSource

Field Summary

Fields

Modifier and Type	Field	Description
static char	MULTIVAL_SEP_CHAR

Fields inherited from class org.apache.lucene.search.uhighlight.UnifiedHighlighter

DEFAULT_CACHE_CHARS_THRESHOLD, DEFAULT_MAX_LENGTH, fieldInfos, indexAnalyzer, searcher, ZERO_LEN_AUTOMATA_ARRAY

Constructor Summary

Constructors

Constructor	Description
CustomUnifiedHighlighter(IndexSearcher searcher, Analyzer analyzer, UnifiedHighlighter.OffsetSource offsetSource, PassageFormatter passageFormatter, Locale breakIteratorLocale, BreakIterator breakIterator, String fieldValue, int noMatchSize)	Creates a new instance of CustomUnifiedHighlighter

Method Summary

Modifier and Type	Method	Description
protected BreakIterator	getBreakIterator(String field)	Returns the BreakIterator to use for dividing text into passages.
protected FieldHighlighter	getFieldHighlighter(String field, Query query, Set<Term> allTerms, int maxPassages)
protected PassageFormatter	getFormatter(String field)	Returns the PassageFormatter to use for formatting passages into highlighted snippets.
protected UnifiedHighlighter.OffsetSource	getOffsetSource(String field)	Forces the offset source for this highlighter
Snippet[]	highlightField(String field, Query query, int docId, int maxPassages)	Highlights terms extracted from the provided query within the content of the provided field name
protected List<CharSequence[]>	loadFieldValues(String[] fields, DocIdSetIterator docIter, int cacheCharsThreshold)	Loads the String values for each docId by field to be highlighted.
protected Collection<Query>	preSpanQueryRewrite(Query query)	When highlighting phrases accurately, we may need to handle custom queries that aren't supported in the WeightedSpanTermExtractor as called by the PhraseHelper.

Methods inherited from class org.apache.lucene.search.uhighlight.UnifiedHighlighter

extractTerms, filterExtractedTerms, getAutomata, getCacheFieldValCharsThreshold, getFieldInfo, getFieldMatcher, getFlags, getHighlightComponents, getIndexAnalyzer, getIndexSearcher, getMaxLength, getMaxNoHighlightPassages, getOffsetStrategy, getOptimizedOffsetSource, getPhraseHelper, getScorer, hasUnrecognizedQuery, highlight, highlight, highlightFields, highlightFields, highlightFields, highlightFieldsAsObjects, highlightWithoutSearcher, newLimitedStoredFieldsVisitor, requiresRewrite, setBreakIterator, setCacheFieldValCharsThreshold, setFieldMatcher, setFormatter, setHandleMultiTermQuery, setHighlightPhrasesStrictly, setMaxLength, setMaxNoHighlightPassages, setScorer, shouldHandleMultiTermQuery, shouldHighlightPhrasesStrictly, shouldPreferPassageRelevancyOverSpeed

Methods inherited from class java.lang.Object

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

Field Detail

MULTIVAL_SEP_CHAR

public static final char MULTIVAL_SEP_CHAR

See Also:

Constant Field Values

Constructor Detail

CustomUnifiedHighlighter

public CustomUnifiedHighlighter(IndexSearcher searcher,
                                Analyzer analyzer,
                                UnifiedHighlighter.OffsetSource offsetSource,
                                PassageFormatter passageFormatter,
                                @Nullable
                                Locale breakIteratorLocale,
                                @Nullable
                                BreakIterator breakIterator,
                                String fieldValue,
                                int noMatchSize)

Creates a new instance of CustomUnifiedHighlighter

Parameters:

analyzer - the analyzer used for the field at index time, used for multi term queries internally.

passageFormatter - our own CustomPassageFormatter which generates snippets in forms of Snippet objects.

offsetSource - the UnifiedHighlighter.OffsetSource to used for offsets retrieval.

breakIteratorLocale - the Locale to use for dividing text into passages. If null Locale.ROOT is used.

breakIterator - the BreakIterator to use for dividing text into passages. If null BreakIterator.getSentenceInstance(Locale) is used.

fieldValue - the original field values delimited by MULTIVAL_SEP_CHAR.

noMatchSize - The size of the text that should be returned when no highlighting can be performed.

Method Detail

highlightField

public Snippet[] highlightField(String field,
                                Query query,
                                int docId,
                                int maxPassages)
                         throws IOException

Highlights terms extracted from the provided query within the content of the provided field name

Throws:

IOException

loadFieldValues

protected List<CharSequence[]> loadFieldValues(String[] fields,
                                               DocIdSetIterator docIter,
                                               int cacheCharsThreshold)
                                        throws IOException

Description copied from class: UnifiedHighlighter

Loads the String values for each docId by field to be highlighted. By default this loads from stored fields by the same name as given, but a subclass can change the source. The returned Strings must be identical to what was indexed (at least for postings or term-vectors offset sources). This method must load fields for at least one document from the given DocIdSetIterator but need not return all of them; by default the character lengths are summed and this method will return early when cacheCharsThreshold is exceeded. Specifically if that number is 0, then only one document is fetched no matter what. Values in the array of CharSequence will be null if no value was found.

Overrides:

loadFieldValues in class UnifiedHighlighter

Throws:

IOException

getBreakIterator

protected BreakIterator getBreakIterator(String field)

Description copied from class: UnifiedHighlighter

Returns the BreakIterator to use for dividing text into passages. This returns BreakIterator.getSentenceInstance(Locale) by default; subclasses can override to customize.

Note: this highlighter will call BreakIterator.preceding(int) and BreakIterator.next() many times on it. The default generic JDK implementation of preceding performs poorly.

Overrides:

getBreakIterator in class UnifiedHighlighter

getFormatter

protected PassageFormatter getFormatter(String field)

Description copied from class: UnifiedHighlighter

Returns the PassageFormatter to use for formatting passages into highlighted snippets. This returns a new PassageFormatter by default; subclasses can override to customize.

Overrides:

getFormatter in class UnifiedHighlighter

getFieldHighlighter

protected FieldHighlighter getFieldHighlighter(String field,
                                               Query query,
                                               Set<Term> allTerms,
                                               int maxPassages)

Overrides:

getFieldHighlighter in class UnifiedHighlighter

preSpanQueryRewrite

protected Collection<Query> preSpanQueryRewrite(Query query)

Description copied from class: UnifiedHighlighter

When highlighting phrases accurately, we may need to handle custom queries that aren't supported in the WeightedSpanTermExtractor as called by the PhraseHelper. Should custom query types be needed, this method should be overriden to return a collection of queries if appropriate, or null if nothing to do. If the query is not custom, simply returning null will allow the default rules to apply.

Overrides:

preSpanQueryRewrite in class UnifiedHighlighter

Parameters:

query - Query to be highlighted

Returns:

A Collection of Query object(s) if needs to be rewritten, otherwise null.

getOffsetSource

protected UnifiedHighlighter.OffsetSource getOffsetSource(String field)

Forces the offset source for this highlighter

Overrides:

getOffsetSource in class UnifiedHighlighter