org.apache.lucene.analysis.ngram

Class EdgeNGramTokenFilter

java.lang.Object

org.apache.lucene.util.AttributeSource

org.apache.lucene.analysis.TokenStream

org.apache.lucene.analysis.TokenFilter

org.apache.lucene.analysis.ngram.EdgeNGramTokenFilter

All Implemented Interfaces:

Closeable, AutoCloseable

public final class EdgeNGramTokenFilter
extends TokenFilter

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

This TokenFilter create n-grams from the beginning edge or ending edge of a input token.

As of Lucene 4.4, this filter does not support EdgeNGramTokenFilter.Side.BACK (you can use ReverseStringFilter up-front and afterward to get the same behavior), handles supplementary characters correctly and does not update offsets anymore.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	EdgeNGramTokenFilter.Side Specifies which side of the input the n-gram should be generated from

Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource

AttributeSource.AttributeFactory, AttributeSource.State

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_MAX_GRAM_SIZE
static int	DEFAULT_MIN_GRAM_SIZE
static EdgeNGramTokenFilter.Side	DEFAULT_SIDE

Constructor Summary

Constructors

Constructor and Description
EdgeNGramTokenFilter(Version version, TokenStream input, EdgeNGramTokenFilter.Side side, int minGram, int maxGram) Deprecated.
EdgeNGramTokenFilter(Version version, TokenStream input, int minGram, int maxGram) Creates EdgeNGramTokenFilter that can generate n-grams in the sizes of the given range
EdgeNGramTokenFilter(Version version, TokenStream input, String sideLabel, int minGram, int maxGram) Deprecated.

Method Summary

Modifier and Type	Method and Description
boolean	incrementToken() Consumers (i.e., IndexWriter) use this method to advance the stream to the next token.
void	reset() This method is called by a consumer before it begins consumption using TokenStream.incrementToken().

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, toString

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Field Detail

DEFAULT_SIDE

public static final EdgeNGramTokenFilter.Side DEFAULT_SIDE

DEFAULT_MAX_GRAM_SIZE

public static final int DEFAULT_MAX_GRAM_SIZE

See Also:

Constant Field Values

DEFAULT_MIN_GRAM_SIZE

public static final int DEFAULT_MIN_GRAM_SIZE

See Also:

Constant Field Values

Constructor Detail

EdgeNGramTokenFilter

@Deprecated
public EdgeNGramTokenFilter(Version version,
                                        TokenStream input,
                                        EdgeNGramTokenFilter.Side side,
                                        int minGram,
                                        int maxGram)

Deprecated.

Creates EdgeNGramTokenFilter that can generate n-grams in the sizes of the given range

Parameters:

version - the Lucene match version

input - TokenStream holding the input to be tokenized

side - the EdgeNGramTokenFilter.Side from which to chop off an n-gram

minGram - the smallest n-gram to generate

maxGram - the largest n-gram to generate

EdgeNGramTokenFilter

@Deprecated
public EdgeNGramTokenFilter(Version version,
                                        TokenStream input,
                                        String sideLabel,
                                        int minGram,
                                        int maxGram)

Deprecated.

Creates EdgeNGramTokenFilter that can generate n-grams in the sizes of the given range

Parameters:

version - the Lucene match version

input - TokenStream holding the input to be tokenized

sideLabel - the name of the EdgeNGramTokenFilter.Side from which to chop off an n-gram

minGram - the smallest n-gram to generate

maxGram - the largest n-gram to generate

EdgeNGramTokenFilter

public EdgeNGramTokenFilter(Version version,
                            TokenStream input,
                            int minGram,
                            int maxGram)

Creates EdgeNGramTokenFilter that can generate n-grams in the sizes of the given range

Parameters:

version - the Lucene match version

input - TokenStream holding the input to be tokenized

minGram - the smallest n-gram to generate

maxGram - the largest n-gram to generate

Method Detail

incrementToken

public final boolean incrementToken()
                             throws IOException

Description copied from class: TokenStream

Consumers (i.e., IndexWriter) use this method to advance the stream to the next token. Implementing classes must implement this method and update the appropriate AttributeImpls with the attributes of the next token.

The producer must make no assumptions about the attributes after the method has been returned: the caller may arbitrarily change it. If the producer needs to preserve the state for subsequent calls, it can use AttributeSource.captureState() to create a copy of the current attribute state.

This method is called for every token of a document, so an efficient implementation is crucial for good performance. To avoid calls to AttributeSource.addAttribute(Class) and AttributeSource.getAttribute(Class), references to all AttributeImpls that this stream uses should be retrieved during instantiation.

To ensure that filters and consumers know which attributes are available, the attributes must be added during instantiation. Filters and consumers are not required to check for availability of attributes in TokenStream.incrementToken().

Specified by:

incrementToken in class TokenStream

Returns:

false for end of stream; true otherwise

Throws:

IOException

reset

public void reset()
           throws IOException

Description copied from class: TokenFilter

This method is called by a consumer before it begins consumption using TokenStream.incrementToken().

Resets this stream to a clean state. Stateful implementations must implement this method so that they can be reused, just as if they had been created fresh.

If you override this method, always call super.reset(), otherwise some internal state will not be correctly reset (e.g., Tokenizer will throw IllegalStateException on further usage).

NOTE: The default implementation chains the call to the input TokenStream, so be sure to call super.reset() when overriding this method.

Overrides:

reset in class TokenFilter

Throws:

IOException