org.apache.lucene.analysis.miscellaneous
Class PrefixAwareTokenFilter

java.lang.Object
  extended by org.apache.lucene.util.AttributeSource
      extended by org.apache.lucene.analysis.TokenStream
          extended by org.apache.lucene.analysis.miscellaneous.PrefixAwareTokenFilter
All Implemented Interfaces:
Closeable

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.


Nested Class Summary
 
Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.AttributeFactory, AttributeSource.State
 
Constructor Summary
PrefixAwareTokenFilter(TokenStream prefix, TokenStream suffix)
           
 
Method Summary
 void close()
          Releases resources associated with this stream.
 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).
 TokenStream getPrefix()
           
 TokenStream getSuffix()
           
 boolean incrementToken()
          Consumers (i.e., IndexWriter) use this method to advance the stream to the next token.
 void reset()
          Resets this stream to the beginning.
 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
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 

Constructor Detail

PrefixAwareTokenFilter

public PrefixAwareTokenFilter(TokenStream prefix,
                              TokenStream suffix)
Method Detail

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 appropriate AttributeImpls 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 AttributeImpls 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 class TokenStream
Returns:
false for end of stream; true otherwise
Throws:
IOException

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 stream
lastPrefixToken - the last token from the prefix stream
Returns:
consumer token

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, after 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.

Overrides:
end in class TokenStream
Throws:
IOException

close

public void close()
           throws IOException
Description copied from class: TokenStream
Releases resources associated with this stream.

Specified by:
close in interface Closeable
Overrides:
close in class TokenStream
Throws:
IOException

reset

public void reset()
           throws IOException
Description copied from class: TokenStream
Resets this stream to the beginning. This is an optional operation, so subclasses may or may not implement this method. TokenStream.reset() is not needed for the standard indexing process. However, if the tokens of a TokenStream are intended to be consumed more than once, it is necessary to implement TokenStream.reset(). Note that if your TokenStream caches tokens and feeds them back again after a reset, it is imperative that you clone the tokens when you store them away (on the first pass) as well as when you return them (on future passes after TokenStream.reset()).

Overrides:
reset in class TokenStream
Throws:
IOException

getPrefix

public TokenStream getPrefix()

setPrefix

public void setPrefix(TokenStream prefix)

getSuffix

public TokenStream getSuffix()

setSuffix

public void setSuffix(TokenStream suffix)


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