public abstract class SegmentingTokenizerBase extends Tokenizer
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.
AttributeSource.State
Modifier and Type | Field and Description |
---|---|
protected char[] |
buffer |
protected static int |
BUFFERMAX |
private java.text.BreakIterator |
iterator |
private int |
length
true length of text in the buffer
|
protected int |
offset
accumulated offset of previous buffers for this reader, for offsetAtt
|
private OffsetAttribute |
offsetAtt |
private int |
usableLength
length in buffer that can be evaluated safely, up to a safe end point
|
private CharArrayIterator |
wrapper |
DEFAULT_TOKEN_ATTRIBUTE_FACTORY
Constructor and Description |
---|
SegmentingTokenizerBase(AttributeFactory factory,
java.text.BreakIterator iterator)
Construct a new SegmenterBase, also supplying the AttributeFactory
|
SegmentingTokenizerBase(java.text.BreakIterator iterator)
Construct a new SegmenterBase, using
the provided BreakIterator for sentence segmentation.
|
Modifier and Type | Method and Description |
---|---|
void |
end()
This method is called by the consumer after the last token has been
consumed, after
TokenStream.incrementToken() returned false
(using the new TokenStream 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 available
|
protected 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 != 0
|
private void |
refill()
Refill the buffer, accumulating the offset and setting usableLength to the
last unambiguous break position
|
void |
reset()
This method is called by a consumer before it begins consumption using
TokenStream.incrementToken() . |
protected abstract void |
setNextSentence(int sentenceStart,
int sentenceEnd)
Provides the next input sentence for analysis
|
close, correctOffset, setReader
addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, endAttributes, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, removeAllAttributes, restoreState, toString
protected static final int BUFFERMAX
protected final char[] buffer
private int length
private int usableLength
protected int offset
private final java.text.BreakIterator iterator
private final CharArrayIterator wrapper
private final OffsetAttribute offsetAtt
public SegmentingTokenizerBase(java.text.BreakIterator iterator)
Note that you should never share BreakIterators across different TokenStreams, instead a newly created or cloned one should always be provided to this constructor.
public SegmentingTokenizerBase(AttributeFactory factory, java.text.BreakIterator iterator)
public final boolean incrementToken() throws java.io.IOException
TokenStream
IndexWriter
) use this method to advance the stream to
the next token. Implementing classes must implement this method and update
the appropriate AttributeImpl
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)
and AttributeSource.getAttribute(Class)
,
references to all AttributeImpl
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()
.
incrementToken
in class TokenStream
java.io.IOException
public void reset() throws java.io.IOException
TokenStream
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).
public final void end() throws java.io.IOException
TokenStream
TokenStream.incrementToken()
returned false
(using the new TokenStream
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()
.
end
in class TokenStream
java.io.IOException
- If an I/O error occursprivate int findSafeEnd()
protected boolean isSafeEnd(char ch)
private void refill() throws java.io.IOException
java.io.IOException
private static int read(java.io.Reader input, char[] buffer, int offset, int length) throws java.io.IOException
java.io.IOException
private boolean incrementSentence() throws java.io.IOException
java.io.IOException
protected abstract void setNextSentence(int sentenceStart, int sentenceEnd)
protected abstract boolean incrementWord()