org.apache.lucene.analysis.miscellaneous
Class PrefixAwareTokenFilter

java.lang.Object
  org.apache.lucene.util.AttributeSource
      org.apache.lucene.analysis.TokenStream
          org.apache.lucene.analysis.miscellaneous.PrefixAwareTokenFilter

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.
TokenStream	getPrefix()
TokenStream	getSuffix()
boolean	incrementToken() Consumers (i.e., IndexWriter) use this method to advance the stream to the next token.
Token	next() Deprecated. Will be removed in Lucene 3.0. This method is final, as it should not be overridden. Delegates to the backwards compatibility layer.
Token	next(Token reusableToken) Deprecated. Will be removed in Lucene 3.0. This method is final, as it should not be overridden. Delegates to the backwards compatibility layer.
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.analysis.TokenStream

end, getOnlyUseNewAPI, setOnlyUseNewAPI

Methods inherited from class org.apache.lucene.util.AttributeSource

addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, 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) or downcasts, 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().

Overrides:

incrementToken in class TokenStream

Returns:

false for end of stream; true otherwise

Note that this method will be defined abstract in Lucene 3.0.

Throws:

IOException

next

public final Token next(Token reusableToken)
                 throws IOException

Deprecated. Will be removed in Lucene 3.0. This method is final, as it should not be overridden. Delegates to the backwards compatibility layer.

Description copied from class: TokenStream

Returns the next token in the stream, or null at EOS. When possible, the input Token should be used as the returned Token (this gives fastest tokenization performance), but this is not required and a new Token may be returned. Callers may re-use a single Token instance for successive calls to this method.

This implicitly defines a "contract" between consumers (callers of this method) and producers (implementations of this method that are the source for tokens):

• A consumer must fully consume the previously returned Token before calling this method again.
• A producer must call Token.clear() before setting the fields in it and returning it

Also, the producer must make no assumptions about a Token after it has been returned: the caller may arbitrarily change it. If the producer needs to hold onto the Token for subsequent calls, it must clone() it before storing it. Note that a TokenFilter is considered a consumer.

Overrides:

next in class TokenStream

Parameters:

reusableToken - a Token that may or may not be used to return; this parameter should never be null (the callee is not required to check for null before using it, but it is a good idea to assert that it is not null.)

Returns:

next Token in the stream or null if end-of-stream was hit

Throws:

IOException

next

public final Token next()
                 throws IOException

Deprecated. Will be removed in Lucene 3.0. This method is final, as it should not be overridden. Delegates to the backwards compatibility layer.

Description copied from class: TokenStream

Returns the next Token in the stream, or null at EOS.

Overrides:

next in class TokenStream

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

close

public void close()
           throws IOException

Description copied from class: TokenStream

Releases resources associated with this stream.

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)