public final class PatternTokenizer extends TokenizerThis tokenizer uses regex pattern matching to construct distinct tokens for the input stream. It takes two arguments: "pattern" and "group".
- "pattern" is the regular expression.
- "group" says which group to extract into tokens.
group=-1 (the default) is equivalent to "split". In this case, the tokens will be equivalent to the output from (without empty tokens):
Using group >= 0 selects the matching group as the token. For example, if you have:
pattern = \'([^\']+)\' group = 0 input = aaa 'bbb' 'ccc'the output will be two tokens: 'bbb' and 'ccc' (including the ' marks). With the same input but using group=1, the output would be: bbb and ccc (no ' marks)
NOTE: This Tokenizer does not output tokens that are of zero length.
- See Also:
Constructors Constructor Description
PatternTokenizer(Reader input, Pattern pattern, int group)creates a new PatternTokenizer returning tokens from group (-1 for split functionality)
PatternTokenizer(AttributeSource.AttributeFactory factory, Reader input, Pattern pattern, int group)creates a new PatternTokenizer returning tokens from group (-1 for split functionality)
All Methods Instance Methods Concrete Methods Modifier and Type Method Description
end()This method is called by the consumer after the last token has been consumed, after
false(using the new
IndexWriter) use this method to advance the stream to the next token.
reset()This method is called by a consumer before it begins consumption using
Methods inherited from class org.apache.lucene.util.AttributeSource
addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState, toString
PatternTokenizercreates a new PatternTokenizer returning tokens from group (-1 for split functionality)
public boolean incrementToken()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.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
public void end() throws IOExceptionThis method is called by the consumer after the last token has been consumed, after
false(using the new
TokenStreamAPI). 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
public void reset() throws IOExceptionThis method is called by a consumer before it begins consumption using
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.