org.apache.lucene.search.spell
Class SpellChecker

java.lang.Object
  org.apache.lucene.search.spell.SpellChecker

All Implemented Interfaces:

Closeable

public class SpellChecker
extends Object
implements Closeable

Spell Checker class (Main class)
(initially inspired by the David Spencer code).

Example Usage:

  SpellChecker spellchecker = new SpellChecker(spellIndexDirectory);
  // To index a field of a user index:
  spellchecker.indexDictionary(new LuceneDictionary(my_lucene_reader, a_field));
  // To index a file containing words:
  spellchecker.indexDictionary(new PlainTextDictionary(new File("myfile.txt")));
  String[] suggestions = spellchecker.suggestSimilar("misspelt", 5);
 

Field Summary

static float	DEFAULT_ACCURACY The default minimum score to use, if not specified by calling setAccuracy(float) .
static String	F_WORD Field name for each word in the ngram index.

Constructor Summary

SpellChecker(Directory spellIndex)
Use the given directory as a spell checker index with a LevensteinDistance as the default StringDistance.

SpellChecker(Directory spellIndex, StringDistance sd)
Use the given directory as a spell checker index.

SpellChecker(Directory spellIndex, StringDistance sd, Comparator<SuggestWord> comparator)
Use the given directory as a spell checker index with the given StringDistance measure and the given Comparator for sorting the results.

Method Summary

void	clearIndex() Removes all terms from the spell check index.
void	close() Close the IndexSearcher used by this SpellChecker
boolean	exist(String word) Check whether the word exists in the index.
float	getAccuracy() The accuracy (minimum score) to be used, unless overridden in suggestSimilar(String, int, IndexReader, String, SuggestMode, float), to decide whether a suggestion is included or not.
Comparator<SuggestWord>	getComparator() Gets the comparator in use for ranking suggestions.
StringDistance	getStringDistance() Returns the StringDistance instance used by this SpellChecker instance.
void	indexDictionary(Dictionary dict, IndexWriterConfig config, boolean fullMerge) Indexes the data from the given Dictionary.
void	setAccuracy(float acc) Sets the accuracy 0 < minScore < 1; default DEFAULT_ACCURACY
void	setComparator(Comparator<SuggestWord> comparator) Sets the Comparator for the SuggestWordQueue.
void	setSpellIndex(Directory spellIndexDir) Use a different index as the spell checker index or re-open the existing index if spellIndex is the same value as given in the constructor.
void	setStringDistance(StringDistance sd) Sets the StringDistance implementation for this SpellChecker instance.
String[]	suggestSimilar(String word, int numSug) Suggest similar words.
String[]	suggestSimilar(String word, int numSug, float accuracy) Suggest similar words.
String[]	suggestSimilar(String word, int numSug, IndexReader ir, String field, SuggestMode suggestMode) Calls suggestSimilar(word, numSug, ir, suggestMode, field, this.accuracy)
String[]	suggestSimilar(String word, int numSug, IndexReader ir, String field, SuggestMode suggestMode, float accuracy) Suggest similar words (optionally restricted to a field of an index).

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_ACCURACY

public static final float DEFAULT_ACCURACY

The default minimum score to use, if not specified by calling setAccuracy(float) .

See Also:

Constant Field Values

F_WORD

public static final String F_WORD

Field name for each word in the ngram index.

See Also:

Constant Field Values

Constructor Detail

SpellChecker

public SpellChecker(Directory spellIndex,
                    StringDistance sd)
             throws IOException

Use the given directory as a spell checker index. The directory is created if it doesn't exist yet.

Parameters:

spellIndex - the spell index directory

sd - the StringDistance measurement to use

Throws:

IOException - if Spellchecker can not open the directory

SpellChecker

public SpellChecker(Directory spellIndex)
             throws IOException

Use the given directory as a spell checker index with a LevensteinDistance as the default StringDistance. The directory is created if it doesn't exist yet.

Parameters:

spellIndex - the spell index directory

Throws:

IOException - if spellchecker can not open the directory

SpellChecker

public SpellChecker(Directory spellIndex,
                    StringDistance sd,
                    Comparator<SuggestWord> comparator)
             throws IOException

Use the given directory as a spell checker index with the given StringDistance measure and the given Comparator for sorting the results.

Parameters:

spellIndex - The spelling index

sd - The distance

comparator - The comparator

Throws:

IOException - if there is a problem opening the index

Method Detail

setSpellIndex

public void setSpellIndex(Directory spellIndexDir)
                   throws IOException

Use a different index as the spell checker index or re-open the existing index if spellIndex is the same value as given in the constructor.

Parameters:

spellIndexDir - the spell directory to use

Throws:

AlreadyClosedException - if the Spellchecker is already closed

IOException - if spellchecker can not open the directory

setComparator

public void setComparator(Comparator<SuggestWord> comparator)

Sets the Comparator for the SuggestWordQueue.

Parameters:

comparator - the comparator

getComparator

public Comparator<SuggestWord> getComparator()

Gets the comparator in use for ranking suggestions.

See Also:

setComparator(Comparator)

setStringDistance

public void setStringDistance(StringDistance sd)

Sets the StringDistance implementation for this SpellChecker instance.

Parameters:

sd - the StringDistance implementation for this SpellChecker instance

getStringDistance

public StringDistance getStringDistance()

Returns the StringDistance instance used by this SpellChecker instance.

Returns:

the StringDistance instance used by this SpellChecker instance.

setAccuracy

public void setAccuracy(float acc)

Sets the accuracy 0 < minScore < 1; default DEFAULT_ACCURACY

Parameters:

acc - The new accuracy

getAccuracy

public float getAccuracy()

The accuracy (minimum score) to be used, unless overridden in suggestSimilar(String, int, IndexReader, String, SuggestMode, float), to decide whether a suggestion is included or not.

Returns:

The current accuracy setting

suggestSimilar

public String[] suggestSimilar(String word,
                               int numSug)
                        throws IOException

Suggest similar words.

As the Lucene similarity that is used to fetch the most relevant n-grammed terms is not the same as the edit distance strategy used to calculate the best matching spell-checked word from the hits that Lucene found, one usually has to retrieve a couple of numSug's in order to get the true best match.

I.e. if numSug == 1, don't count on that suggestion being the best one. Thus, you should set this value to at least 5 for a good suggestion.

Parameters:

word - the word you want a spell check done on

numSug - the number of suggested words

Returns:

String[]

Throws:

IOException - if the underlying index throws an IOException

AlreadyClosedException - if the Spellchecker is already closed

See Also:

suggestSimilar(String, int, IndexReader, String, SuggestMode, float)

suggestSimilar

public String[] suggestSimilar(String word,
                               int numSug,
                               float accuracy)
                        throws IOException

Suggest similar words.

As the Lucene similarity that is used to fetch the most relevant n-grammed terms is not the same as the edit distance strategy used to calculate the best matching spell-checked word from the hits that Lucene found, one usually has to retrieve a couple of numSug's in order to get the true best match.

I.e. if numSug == 1, don't count on that suggestion being the best one. Thus, you should set this value to at least 5 for a good suggestion.

Parameters:

word - the word you want a spell check done on

numSug - the number of suggested words

accuracy - The minimum score a suggestion must have in order to qualify for inclusion in the results

Returns:

String[]

Throws:

IOException - if the underlying index throws an IOException

AlreadyClosedException - if the Spellchecker is already closed

See Also:

suggestSimilar(String, int, IndexReader, String, SuggestMode, float)

suggestSimilar

public String[] suggestSimilar(String word,
                               int numSug,
                               IndexReader ir,
                               String field,
                               SuggestMode suggestMode)
                        throws IOException

Calls suggestSimilar(word, numSug, ir, suggestMode, field, this.accuracy)

Throws:

IOException

suggestSimilar

public String[] suggestSimilar(String word,
                               int numSug,
                               IndexReader ir,
                               String field,
                               SuggestMode suggestMode,
                               float accuracy)
                        throws IOException

Suggest similar words (optionally restricted to a field of an index).

As the Lucene similarity that is used to fetch the most relevant n-grammed terms is not the same as the edit distance strategy used to calculate the best matching spell-checked word from the hits that Lucene found, one usually has to retrieve a couple of numSug's in order to get the true best match.

I.e. if numSug == 1, don't count on that suggestion being the best one. Thus, you should set this value to at least 5 for a good suggestion.

Parameters:

word - the word you want a spell check done on

numSug - the number of suggested words

ir - the indexReader of the user index (can be null see field param)

field - the field of the user index: if field is not null, the suggested words are restricted to the words present in this field.

suggestMode - (NOTE: if indexReader==null and/or field==null, then this is overridden with SuggestMode.SUGGEST_ALWAYS)

accuracy - The minimum score a suggestion must have in order to qualify for inclusion in the results

Returns:

String[] the sorted list of the suggest words with these 2 criteria: first criteria: the edit distance, second criteria (only if restricted mode): the popularity of the suggest words in the field of the user index

Throws:

IOException - if the underlying index throws an IOException

AlreadyClosedException - if the Spellchecker is already closed

clearIndex

public void clearIndex()
                throws IOException

Removes all terms from the spell check index.

Throws:

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

AlreadyClosedException - if the Spellchecker is already closed

exist

public boolean exist(String word)
              throws IOException

Check whether the word exists in the index.

Parameters:

word - word to check

Returns:

true if the word exists in the index

Throws:

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

AlreadyClosedException - if the Spellchecker is already closed

indexDictionary

public final void indexDictionary(Dictionary dict,
                                  IndexWriterConfig config,
                                  boolean fullMerge)
                           throws IOException

Indexes the data from the given Dictionary.

Parameters:

dict - Dictionary to index

config - IndexWriterConfig to use

fullMerge - whether or not the spellcheck index should be fully merged

Throws:

AlreadyClosedException - if the Spellchecker is already closed

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

close

public void close()
           throws IOException

Close the IndexSearcher used by this SpellChecker

Specified by:

close in interface Closeable

Throws:

IOException - if the close operation causes an IOException

AlreadyClosedException - if the SpellChecker is already closed