Class CachingTokenFilter

  • All Implemented Interfaces:
    Closeable, AutoCloseable

    public final class CachingTokenFilter
    extends TokenFilter
    This class can be used if the token attributes of a TokenStream are intended to be consumed more than once. It caches all token attribute states locally in a List.

    CachingTokenFilter implements the optional method TokenStream.reset(), which repositions the stream to the first Token.

    • Constructor Detail

      • CachingTokenFilter

        public CachingTokenFilter​(TokenStream input)
    • Method Detail

      • 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
      • end

        public final void end()
                       throws IOException
        Description copied from class: TokenFilter
        Performs end-of-stream operations, if any, and calls then end() on the input TokenStream.

        NOTE: Be sure to call super.end() first when overriding this method.

        Overrides:
        end in class TokenFilter
        Throws:
        IOException