All Implemented Interfaces:
Closeable, AutoCloseable, Unwrappable<TokenStream>

public class FingerprintFilter extends TokenFilter
Filter outputs a single token which is a concatenation of the sorted and de-duplicated set of input tokens. This can be useful for clustering/linking use cases.
  • Field Details

  • Constructor Details

    • FingerprintFilter

      public FingerprintFilter(TokenStream input)
      Create a new FingerprintFilter with default settings
    • FingerprintFilter

      public FingerprintFilter(TokenStream input, int maxOutputTokenSize, char separator)
      Create a new FingerprintFilter with control over all settings
      Parameters:
      input - the source of tokens to be summarized into a single token
      maxOutputTokenSize - the maximum length of the summarized output token. If exceeded, no output token is emitted
      separator - the character used to separate tokens combined into the single output token
  • Method Details

    • 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
    • buildSingleOutputToken

      private final boolean buildSingleOutputToken() throws IOException
      Gathers all tokens from input, de-duplicates, sorts then concatenates.
      Returns:
      false for end of stream; true otherwise
      Throws:
      IOException
    • end

      public final void end() throws IOException
      Description copied from class: TokenFilter
      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 TokenFilter
      Throws:
      IOException - If an I/O error occurs
    • reset

      public void reset() throws IOException
      Description copied from class: TokenFilter
      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 TokenFilter
      Throws:
      IOException