Class PrefixAwareTokenFilter
- 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.miscellaneous.PrefixAwareTokenFilter
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- All Implemented Interfaces:
Closeable
,AutoCloseable
public class PrefixAwareTokenFilter extends TokenStream
Joins two token streams and leaves the last token of the first stream available to be used when updating the token values in the second stream based on that token. The default implementation adds last prefix token end offset to the suffix token start and end offsets. NOTE: This filter might not behave correctly if used with custom Attributes, i.e. Attributes other than the ones located in org.apache.lucene.analysis.tokenattributes.
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Nested Class Summary
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Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.AttributeFactory, AttributeSource.State
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Constructor Summary
Constructors Constructor Description PrefixAwareTokenFilter(TokenStream prefix, TokenStream suffix)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
close()
Releases resources associated with this stream.void
end()
This method is called by the consumer after the last token has been consumed, afterTokenStream.incrementToken()
returnedfalse
(using the newTokenStream
API).TokenStream
getPrefix()
TokenStream
getSuffix()
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 usingTokenStream.incrementToken()
.void
setPrefix(TokenStream prefix)
void
setSuffix(TokenStream suffix)
Token
updateSuffixToken(Token suffixToken, Token lastPrefixToken)
The default implementation adds last prefix token end offset to the suffix token start and end offsets.-
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
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Constructor Detail
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PrefixAwareTokenFilter
public PrefixAwareTokenFilter(TokenStream prefix, TokenStream suffix)
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Method Detail
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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 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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updateSuffixToken
public Token updateSuffixToken(Token suffixToken, Token lastPrefixToken)
The default implementation adds last prefix token end offset to the suffix token start and end offsets.- Parameters:
suffixToken
- a token from the suffix streamlastPrefixToken
- the last token from the prefix stream- Returns:
- consumer token
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end
public void end() throws 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:
IOException
- If an I/O error occurs
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close
public void close() throws IOException
Description copied from class:TokenStream
Releases resources associated with this stream.If you override this method, always call
super.close()
, otherwise some internal state will not be correctly reset (e.g.,Tokenizer
will throwIllegalStateException
on reuse).- Specified by:
close
in interfaceAutoCloseable
- Specified by:
close
in interfaceCloseable
- Overrides:
close
in classTokenStream
- Throws:
IOException
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reset
public void reset() throws 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).- Overrides:
reset
in classTokenStream
- Throws:
IOException
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getPrefix
public TokenStream getPrefix()
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setPrefix
public void setPrefix(TokenStream prefix)
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getSuffix
public TokenStream getSuffix()
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setSuffix
public void setSuffix(TokenStream suffix)
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