org.apache.lucene.analysis
Class FilteringTokenFilter

java.lang.Object
  org.apache.lucene.util.AttributeSource
      org.apache.lucene.analysis.TokenStream
          org.apache.lucene.analysis.TokenFilter
              org.apache.lucene.analysis.FilteringTokenFilter

All Implemented Interfaces:

Closeable

Direct Known Subclasses:

LengthFilter, StopFilter

public abstract class FilteringTokenFilter
extends TokenFilter

Abstract base class for TokenFilters that may remove tokens. You have to implement accept() and return a boolean if the current token should be preserved. incrementToken() uses this method to decide if a token should be passed to the caller.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource

AttributeSource.AttributeFactory, AttributeSource.State

Field Summary

Fields inherited from class org.apache.lucene.analysis.TokenFilter

input

Constructor Summary

FilteringTokenFilter(boolean enablePositionIncrements, TokenStream input)

Method Summary

protected abstract boolean	accept() Override this method and return if the current input token should be returned by incrementToken().
boolean	getEnablePositionIncrements()
boolean	incrementToken() Consumers (i.e., IndexWriter) use this method to advance the stream to the next token.
void	setEnablePositionIncrements(boolean enable) If true, this TokenFilter will preserve positions of the incoming tokens (ie, accumulate and set position increments of the removed tokens).

Methods inherited from class org.apache.lucene.analysis.TokenFilter

close, end, reset

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

FilteringTokenFilter

public FilteringTokenFilter(boolean enablePositionIncrements,
                            TokenStream input)

Method Detail

accept

protected abstract boolean accept()
                           throws IOException

Override this method and return if the current input token should be returned by incrementToken().

Throws:

IOException

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

getEnablePositionIncrements

public boolean getEnablePositionIncrements()

See Also:

setEnablePositionIncrements(boolean)

setEnablePositionIncrements

public void setEnablePositionIncrements(boolean enable)

If true, this TokenFilter will preserve positions of the incoming tokens (ie, accumulate and set position increments of the removed tokens). Generally, true is best as it does not lose information (positions of the original tokens) during indexing.

When set, when a token is stopped (omitted), the position increment of the following token is incremented.

NOTE: be sure to also set QueryParser.setEnablePositionIncrements(boolean) if you use QueryParser to create queries.