Package org.apache.lucene.analysis

Class GraphTokenFilter

java.lang.Object
org.apache.lucene.util.AttributeSource
org.apache.lucene.analysis.TokenStream
org.apache.lucene.analysis.TokenFilter
org.apache.lucene.analysis.GraphTokenFilter
All Implemented Interfaces:
Closeable, AutoCloseable, Unwrappable<TokenStream>
public abstract class GraphTokenFilter extends TokenFilter
An abstract TokenFilter that exposes its input stream as a graph

Call incrementBaseToken() to move the root of the graph to the next position in the TokenStream, incrementGraphToken() to move along the current graph, and incrementGraph() to reset to the next graph based at the current root.

For example, given the stream 'a b/c:2 d e`, then with the base token at 'a', incrementGraphToken() will produce the stream 'a b d e', and then after calling incrementGraph() will produce the stream 'a c e'.

  • Field Details

    • MAX_GRAPH_STACK_SIZE

      public static final int MAX_GRAPH_STACK_SIZE
      The maximum permitted number of routes through a graph
      See Also:

    • MAX_TOKEN_CACHE_SIZE

      public static final int MAX_TOKEN_CACHE_SIZE
      The maximum permitted read-ahead in the token stream
      See Also:

  • Constructor Details

    • GraphTokenFilter

      public GraphTokenFilter(TokenStream input)
      Create a new GraphTokenFilter

  • Method Details

    • incrementBaseToken

      protected final boolean incrementBaseToken() throws IOException
      Move the root of the graph to the next token in the wrapped TokenStream
      Returns:
      false if the underlying stream is exhausted
      Throws:
      IOException

    • incrementGraphToken

      protected final boolean incrementGraphToken() throws IOException
      Move to the next token in the current route through the graph
      Returns:
      false if there are not more tokens in the current graph
      Throws:
      IOException

    • incrementGraph

      protected final boolean incrementGraph() throws IOException
      Reset to the root token again, and move down the next route through the graph
      Returns:
      false if there are no more routes through the graph
      Throws:
      IOException

    • getTrailingPositions

      public int getTrailingPositions()
      Return the number of trailing positions at the end of the graph

      NB this should only be called after incrementGraphToken() has returned false

    • end

      public 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