Class JapaneseKatakanaStemFilter
- java.lang.Object
-
- org.apache.lucene.util.AttributeSource
-
- org.apache.lucene.analysis.TokenStream
-
- org.apache.lucene.analysis.TokenFilter
-
- org.apache.lucene.analysis.ja.JapaneseKatakanaStemFilter
-
- All Implemented Interfaces:
java.io.Closeable
,java.lang.AutoCloseable
,Unwrappable<TokenStream>
public final class JapaneseKatakanaStemFilter extends TokenFilter
ATokenFilter
that normalizes common katakana spelling variations ending in a long sound character by removing this character (U+30FC). Only katakana words longer than a minimum length are stemmed (default is four).Note that only full-width katakana characters are supported. Please use a
CJKWidthFilter
to convert half-width katakana to full-width before using this filter.In order to prevent terms from being stemmed, use an instance of
SetKeywordMarkerFilter
or a customTokenFilter
that sets theKeywordAttribute
before thisTokenStream
.
-
-
Nested Class Summary
-
Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.State
-
-
Field Summary
Fields Modifier and Type Field Description static int
DEFAULT_MINIMUM_LENGTH
private static char
HIRAGANA_KATAKANA_PROLONGED_SOUND_MARK
private KeywordAttribute
keywordAttr
private int
minimumKatakanaLength
private CharTermAttribute
termAttr
-
Fields inherited from class org.apache.lucene.analysis.TokenFilter
input
-
Fields inherited from class org.apache.lucene.analysis.TokenStream
DEFAULT_TOKEN_ATTRIBUTE_FACTORY
-
-
Constructor Summary
Constructors Constructor Description JapaneseKatakanaStemFilter(TokenStream input)
JapaneseKatakanaStemFilter(TokenStream input, int minimumLength)
-
Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
incrementToken()
Consumers (i.e.,IndexWriter
) use this method to advance the stream to the next token.private boolean
isKatakana(char[] term, int length)
private int
stem(char[] term, int length)
-
Methods inherited from class org.apache.lucene.analysis.TokenFilter
close, end, reset, unwrap
-
Methods inherited from class org.apache.lucene.util.AttributeSource
addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, endAttributes, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, removeAllAttributes, restoreState, toString
-
-
-
-
Field Detail
-
DEFAULT_MINIMUM_LENGTH
public static final int DEFAULT_MINIMUM_LENGTH
- See Also:
- Constant Field Values
-
HIRAGANA_KATAKANA_PROLONGED_SOUND_MARK
private static final char HIRAGANA_KATAKANA_PROLONGED_SOUND_MARK
- See Also:
- Constant Field Values
-
termAttr
private final CharTermAttribute termAttr
-
keywordAttr
private final KeywordAttribute keywordAttr
-
minimumKatakanaLength
private final int minimumKatakanaLength
-
-
Constructor Detail
-
JapaneseKatakanaStemFilter
public JapaneseKatakanaStemFilter(TokenStream input, int minimumLength)
-
JapaneseKatakanaStemFilter
public JapaneseKatakanaStemFilter(TokenStream input)
-
-
Method Detail
-
incrementToken
public boolean incrementToken() throws java.io.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 appropriateAttributeImpl
s 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)
andAttributeSource.getAttribute(Class)
, references to allAttributeImpl
s 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 classTokenStream
- Returns:
- false for end of stream; true otherwise
- Throws:
java.io.IOException
-
stem
private int stem(char[] term, int length)
-
isKatakana
private boolean isKatakana(char[] term, int length)
-
-