Package org.apache.lucene.analysis

Class TokenFilter

java.lang.Object
org.apache.lucene.util.AttributeSource
org.apache.lucene.analysis.TokenStream
org.apache.lucene.analysis.TokenFilter
All Implemented Interfaces:
Closeable, AutoCloseable, Unwrappable<TokenStream>
Direct Known Subclasses:
CachingTokenFilter, FilteringTokenFilter, GraphTokenFilter, LowerCaseFilter
public abstract class TokenFilter extends TokenStream implements Unwrappable<TokenStream>
A TokenFilter is a TokenStream whose input is another TokenStream.

This is an abstract class; subclasses must override TokenStream.incrementToken().

See Also:

  • Field Details

    • input

      protected final TokenStream input
      The source of tokens for this filter.

  • Constructor Details

    • TokenFilter

      protected TokenFilter(TokenStream input)
      Construct a token stream filtering the given input.

  • Method Details

    • end

      public void end() throws IOException
      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.

      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().

      NOTE: The default implementation chains the call to the input TokenStream, so be sure to call super.end() first when overriding this method.

      Overrides:
      end in class TokenStream
      Throws:
      IOException - If an I/O error occurs

    • close

      public void close() throws IOException
      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 throw IllegalStateException on reuse).

      NOTE: The default implementation chains the call to the input TokenStream, so be sure to call super.close() when overriding this method.

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

    • reset

      public void reset() throws IOException
      This method is called by a consumer before it begins consumption using 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).

      NOTE: The default implementation chains the call to the input TokenStream, so be sure to call super.reset() when overriding this method.

      Overrides:
      reset in class TokenStream
      Throws:
      IOException

    • unwrap

      public TokenStream unwrap()
      Description copied from interface: Unwrappable
      Unwraps this instance
      Specified by:
      unwrap in interface Unwrappable<TokenStream>