Class SegmentingTokenizerBase
- java.lang.Object
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- org.apache.lucene.util.AttributeSource
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- org.apache.lucene.analysis.TokenStream
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- org.apache.lucene.analysis.Tokenizer
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- org.apache.lucene.analysis.util.SegmentingTokenizerBase
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- All Implemented Interfaces:
java.io.Closeable
,java.lang.AutoCloseable
- Direct Known Subclasses:
HMMChineseTokenizer
,ThaiTokenizer
public abstract class SegmentingTokenizerBase extends Tokenizer
Breaks text into sentences with aBreakIterator
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
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Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.State
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Field Summary
Fields Modifier and Type Field Description protected char[]
buffer
protected static int
BUFFERMAX
private java.text.BreakIterator
iterator
private int
length
true length of text in the bufferprotected int
offset
accumulated offset of previous buffers for this reader, for offsetAttprivate OffsetAttribute
offsetAtt
private int
usableLength
length in buffer that can be evaluated safely, up to a safe end pointprivate CharArrayIterator
wrapper
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Fields inherited from class org.apache.lucene.analysis.TokenStream
DEFAULT_TOKEN_ATTRIBUTE_FACTORY
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Constructor Summary
Constructors Constructor Description SegmentingTokenizerBase(java.text.BreakIterator iterator)
Construct a new SegmenterBase, using the provided BreakIterator for sentence segmentation.SegmentingTokenizerBase(AttributeFactory factory, java.text.BreakIterator iterator)
Construct a new SegmenterBase, also supplying the AttributeFactory
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Method Summary
All Methods Static Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description 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
findSafeEnd()
Returns the last unambiguous break position in the text.private boolean
incrementSentence()
return true if there is a token from the buffer, or null if it is exhausted.boolean
incrementToken()
Consumers (i.e.,IndexWriter
) use this method to advance the stream to the next token.protected abstract boolean
incrementWord()
Returns true if another word is availableprotected boolean
isSafeEnd(char ch)
For sentence tokenization, these are the unambiguous break positions.private static int
read(java.io.Reader input, char[] buffer, int offset, int length)
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 analysis-
Methods inherited from class org.apache.lucene.analysis.Tokenizer
close, correctOffset, setReader, setReaderTestPoint
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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 Detail
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BUFFERMAX
protected static final int BUFFERMAX
- See Also:
- Constant Field Values
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buffer
protected final char[] buffer
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length
private int length
true length of text in the buffer
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usableLength
private int usableLength
length in buffer that can be evaluated safely, up to a safe end point
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offset
protected int offset
accumulated offset of previous buffers for this reader, for offsetAtt
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iterator
private final java.text.BreakIterator iterator
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wrapper
private final CharArrayIterator wrapper
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offsetAtt
private final OffsetAttribute offsetAtt
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Constructor Detail
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SegmentingTokenizerBase
public SegmentingTokenizerBase(java.text.BreakIterator iterator)
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
public SegmentingTokenizerBase(AttributeFactory factory, java.text.BreakIterator iterator)
Construct a new SegmenterBase, also supplying the AttributeFactory
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Method Detail
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incrementToken
public final 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
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reset
public void reset() throws java.io.IOException
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).
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end
public final void end() throws java.io.IOException
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:
java.io.IOException
- If an I/O error occurs
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findSafeEnd
private int findSafeEnd()
Returns the last unambiguous break position in the text.
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isSafeEnd
protected boolean isSafeEnd(char ch)
For sentence tokenization, these are the unambiguous break positions.
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refill
private void refill() throws java.io.IOException
Refill the buffer, accumulating the offset and setting usableLength to the last unambiguous break position- Throws:
java.io.IOException
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read
private static int read(java.io.Reader input, char[] buffer, int offset, int length) throws java.io.IOException
commons-io's readFully, but without bugs if offset != 0- Throws:
java.io.IOException
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incrementSentence
private boolean incrementSentence() throws java.io.IOException
return true if there is a token from the buffer, or null if it is exhausted.- Throws:
java.io.IOException
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setNextSentence
protected abstract void setNextSentence(int sentenceStart, int sentenceEnd)
Provides the next input sentence for analysis
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incrementWord
protected abstract boolean incrementWord()
Returns true if another word is available
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