org.apache.lucene.analysis.ngram
Class NGramTokenFilter

java.lang.Object
  extended by org.apache.lucene.util.AttributeSource
      extended by org.apache.lucene.analysis.TokenStream
          extended by org.apache.lucene.analysis.TokenFilter
              extended by org.apache.lucene.analysis.ngram.NGramTokenFilter
All Implemented Interfaces:
Closeable

public final class NGramTokenFilter
extends TokenFilter

Tokenizes the input into n-grams of the given size(s).

You must specify the required Version compatibility when creating a NGramTokenFilter. As of Lucene 4.4, this token filters:

You can make this filter use the old behavior by providing a version < Version.LUCENE_44 in the constructor but this is not recommended as it will lead to broken TokenStreams that will cause highlighting bugs.

If you were using this TokenFilter to perform partial highlighting, this won't work anymore since this filter doesn't update offsets. You should modify your analysis chain to use NGramTokenizer, and potentially override NGramTokenizer.isTokenChar(int) to perform pre-tokenization.


Nested Class Summary
 
Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.AttributeFactory, AttributeSource.State
 
Field Summary
static int DEFAULT_MAX_NGRAM_SIZE
           
static int DEFAULT_MIN_NGRAM_SIZE
           
 
Fields inherited from class org.apache.lucene.analysis.TokenFilter
input
 
Constructor Summary
NGramTokenFilter(Version version, TokenStream input)
          Creates NGramTokenFilter with default min and max n-grams.
NGramTokenFilter(Version version, TokenStream input, int minGram, int maxGram)
          Creates NGramTokenFilter with given min and max n-grams.
 
Method Summary
 boolean incrementToken()
          Returns the next token in the stream, or null at EOS.
 void reset()
           
 
Methods inherited from class org.apache.lucene.analysis.TokenFilter
close, end
 
Methods inherited from class org.apache.lucene.util.AttributeSource
addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

DEFAULT_MIN_NGRAM_SIZE

public static final int DEFAULT_MIN_NGRAM_SIZE
See Also:
Constant Field Values

DEFAULT_MAX_NGRAM_SIZE

public static final int DEFAULT_MAX_NGRAM_SIZE
See Also:
Constant Field Values
Constructor Detail

NGramTokenFilter

public NGramTokenFilter(Version version,
                        TokenStream input,
                        int minGram,
                        int maxGram)
Creates NGramTokenFilter with given min and max n-grams.

Parameters:
version - Lucene version to enable correct position increments. See above for details.
input - TokenStream holding the input to be tokenized
minGram - the smallest n-gram to generate
maxGram - the largest n-gram to generate

NGramTokenFilter

public NGramTokenFilter(Version version,
                        TokenStream input)
Creates NGramTokenFilter with default min and max n-grams.

Parameters:
version - Lucene version to enable correct position increments. See above for details.
input - TokenStream holding the input to be tokenized
Method Detail

incrementToken

public final boolean incrementToken()
                             throws IOException
Returns the next token in the stream, or null at EOS.

Specified by:
incrementToken in class TokenStream
Throws:
IOException

reset

public void reset()
           throws IOException
Overrides:
reset in class TokenFilter
Throws:
IOException


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