org.apache.lucene.analysis.util

Class SegmentingTokenizerBase

  • All Implemented Interfaces:
    Closeable, AutoCloseable
    Direct Known Subclasses:
    HMMChineseTokenizer, ThaiTokenizer


    public abstract class SegmentingTokenizerBase
    extends Tokenizer
    Breaks text into sentences with a BreakIterator and allows subclasses to decompose these sentences into words.

    This can be used by subclasses that need sentence context for tokenization purposes, such as CJK segmenters.

    Additionally it can be used by subclasses that want to mark sentence boundaries (with a custom attribute, extra token, position increment, etc) for downstream processing.

    • Field Detail

      • buffer

        protected final char[] buffer
      • offset

        protected int offset
        accumulated offset of previous buffers for this reader, for offsetAtt
    • Constructor Detail

      • SegmentingTokenizerBase

        public SegmentingTokenizerBase(BreakIterator iterator)
        Construct a new SegmenterBase, using the provided BreakIterator for sentence segmentation.

        Note that you should never share BreakIterators across different TokenStreams, instead a newly created or cloned one should always be provided to this constructor.

    • 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
      • reset

        public void reset()
                   throws 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 Tokenizer
        Throws:
        IOException
      • end

        public final void end()
                       throws 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:
        IOException - If an I/O error occurs
      • isSafeEnd

        protected boolean isSafeEnd(char ch)
        For sentence tokenization, these are the unambiguous break positions.
      • setNextSentence

        protected abstract void setNextSentence(int sentenceStart,
                                                int sentenceEnd)
        Provides the next input sentence for analysis
      • incrementWord

        protected abstract boolean incrementWord()
        Returns true if another word is available