Class StandardTokenizer

  • All Implemented Interfaces:
    Closeable, AutoCloseable

    public final class StandardTokenizer
    extends Tokenizer
    A grammar-based tokenizer constructed with JFlex.

    This class implements the Word Break rules from the Unicode Text Segmentation algorithm, as specified in Unicode Standard Annex #29.

    Many applications have specific tokenizer needs. If this tokenizer does not suit your application, please consider copying this source code directory to your project and maintaining your own grammar-based tokenizer.

    • Field Detail


        public static final int SOUTHEAST_ASIAN
        Southeast Asian token type
        See Also:
        Constant Field Values

        public static final int IDEOGRAPHIC
        Ideographic token type
        See Also:
        Constant Field Values

        public static final String[] TOKEN_TYPES
        String token types that correspond to token type int constants

        public static final int MAX_TOKEN_LENGTH_LIMIT
        Absolute maximum sized token
        See Also:
        Constant Field Values
    • Constructor Detail

      • StandardTokenizer

        public StandardTokenizer()
        Creates a new instance of the StandardTokenizer. Attaches the input to the newly created JFlex scanner.


    • Method Detail

      • setMaxTokenLength

        public void setMaxTokenLength​(int length)
        Set the max allowed token length. Tokens larger than this will be chopped up at this token length and emitted as multiple tokens. If you need to skip such large tokens, you could increase this max length, and then use LengthFilter to remove long tokens. The default is StandardAnalyzer.DEFAULT_MAX_TOKEN_LENGTH.
        IllegalArgumentException - if the given length is outside of the range [1, 1048576].
      • getMaxTokenLength

        public int getMaxTokenLength()
        Returns the current maximum token length
        See Also:
      • 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
        false for end of stream; true otherwise
      • 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().

        end in class TokenStream
        IOException - If an I/O error occurs
      • close

        public void close()
                   throws IOException
        Description copied from class: Tokenizer
        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).

        NOTE: The default implementation closes the input Reader, so be sure to call super.close() when overriding this method.

        Specified by:
        close in interface AutoCloseable
        Specified by:
        close in interface Closeable
        close in class Tokenizer
      • 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).

        reset in class Tokenizer