Package org.apache.lucene.analysis.miscellaneous

Class PrefixAwareTokenFilter

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable
    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.

    • Method Detail

      • incrementToken

        public final boolean incrementToken()
                             throws java.io.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:
        java.io.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

      • end

        public void end()
         throws java.io.IOException
        Description copied from class: TokenStream
        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().

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

      • close

        public void close()
           throws java.io.IOException
        Description copied from class: TokenStream
        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).

        Specified by:
        close in interface java.lang.AutoCloseable
        Specified by:
        close in interface java.io.Closeable
        Overrides:
        close in class TokenStream
        Throws:
        java.io.IOException

      • reset

        public void reset()
           throws java.io.IOException
        Description copied from class: TokenStream
        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).

        Overrides:
        reset in class TokenStream
        Throws:
        java.io.IOException

      • setPrefix

        public void setPrefix​(TokenStream prefix)

      • setSuffix

        public void setSuffix​(TokenStream suffix)