Class SegmentingTokenizerBase
- All Implemented Interfaces:
Closeable
,AutoCloseable
- Direct Known Subclasses:
HMMChineseTokenizer
,ThaiTokenizer
BreakIterator
and allows subclasses to decompose these
sentences into words.
This can be used by subclasses that need sentence context for tokenization purposes, such as CJK segmenters.
Additionally it can be used by subclasses that want to mark sentence boundaries (with a custom attribute, extra token, position increment, etc) for downstream processing.
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Nested Class Summary
Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.State
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Field Summary
FieldsModifier and TypeFieldDescriptionprotected final char[]
protected static final int
private final BreakIterator
private int
true length of text in the bufferprotected int
accumulated offset of previous buffers for this reader, for offsetAttprivate final OffsetAttribute
private int
length in buffer that can be evaluated safely, up to a safe end pointprivate final CharArrayIterator
Fields inherited from class org.apache.lucene.analysis.TokenStream
DEFAULT_TOKEN_ATTRIBUTE_FACTORY
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Constructor Summary
ConstructorsConstructorDescriptionSegmentingTokenizerBase
(BreakIterator iterator) Construct a new SegmenterBase, using the provided BreakIterator for sentence segmentation.SegmentingTokenizerBase
(AttributeFactory factory, BreakIterator iterator) Construct a new SegmenterBase, also supplying the AttributeFactory -
Method Summary
Modifier and TypeMethodDescriptionfinal void
end()
This method is called by the consumer after the last token has been consumed, afterTokenStream.incrementToken()
returnedfalse
(using the newTokenStream
API).private int
Returns the last unambiguous break position in the text.private boolean
return true if there is a token from the buffer, or null if it is exhausted.final boolean
Consumers (i.e.,IndexWriter
) use this method to advance the stream to the next token.protected abstract boolean
Returns true if another word is availableprotected boolean
isSafeEnd
(char ch) For sentence tokenization, these are the unambiguous break positions.private static int
commons-io's readFully, but without bugs if offset != 0private void
refill()
Refill the buffer, accumulating the offset and setting usableLength to the last unambiguous break positionvoid
reset()
This method is called by a consumer before it begins consumption usingTokenStream.incrementToken()
.protected abstract void
setNextSentence
(int sentenceStart, int sentenceEnd) Provides the next input sentence for analysisMethods inherited from class org.apache.lucene.analysis.Tokenizer
close, correctOffset, setReader, setReaderTestPoint
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
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Field Details
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BUFFERMAX
protected static final int BUFFERMAX- See Also:
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buffer
protected final char[] buffer -
length
private int lengthtrue length of text in the buffer -
usableLength
private int usableLengthlength in buffer that can be evaluated safely, up to a safe end point -
offset
protected int offsetaccumulated offset of previous buffers for this reader, for offsetAtt -
iterator
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wrapper
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offsetAtt
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Constructor Details
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SegmentingTokenizerBase
Construct a new SegmenterBase, using the provided BreakIterator for sentence segmentation.Note that you should never share BreakIterators across different TokenStreams, instead a newly created or cloned one should always be provided to this constructor.
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SegmentingTokenizerBase
Construct a new SegmenterBase, also supplying the AttributeFactory
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Method Details
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incrementToken
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:
IOException
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reset
Description copied from class:TokenStream
This method is called by a consumer before it begins consumption usingTokenStream.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 throwIllegalStateException
on further usage).- Overrides:
reset
in classTokenizer
- Throws:
IOException
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end
Description copied from class:TokenStream
This method is called by the consumer after the last token has been consumed, afterTokenStream.incrementToken()
returnedfalse
(using the newTokenStream
API). Streams implementing the old API should upgrade to use this feature.This method can be used to perform any end-of-stream operations, such as setting the final offset of a stream. The final offset of a stream might differ from the offset of the last token eg in case one or more whitespaces followed after the last token, but a WhitespaceTokenizer was used.
Additionally any skipped positions (such as those removed by a stopfilter) can be applied to the position increment, or any adjustment of other attributes where the end-of-stream value may be important.
If you override this method, always call
super.end()
.- Overrides:
end
in classTokenStream
- Throws:
IOException
- If an I/O error occurs
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findSafeEnd
private int findSafeEnd()Returns the last unambiguous break position in the text. -
isSafeEnd
protected boolean isSafeEnd(char ch) For sentence tokenization, these are the unambiguous break positions. -
refill
Refill the buffer, accumulating the offset and setting usableLength to the last unambiguous break position- Throws:
IOException
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read
commons-io's readFully, but without bugs if offset != 0- Throws:
IOException
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incrementSentence
return true if there is a token from the buffer, or null if it is exhausted.- Throws:
IOException
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setNextSentence
protected abstract void setNextSentence(int sentenceStart, int sentenceEnd) Provides the next input sentence for analysis -
incrementWord
protected abstract boolean incrementWord()Returns true if another word is available
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