Class PatternTokenizer

This 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): Replace(string, string)

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 Lucene.Net.Analysis.Tokenizer does not output tokens that are of zero length.

Inheritance

object

AttributeSource

TokenStream

Tokenizer

PatternTokenizer

Implements

IDisposable

Inherited Members

Tokenizer.SetReader(TextReader)

TokenStream.Dispose()

AttributeSource.GetAttributeFactory()

AttributeSource.GetAttributeClassesEnumerator()

AttributeSource.GetAttributeImplsEnumerator()

AttributeSource.AddAttributeImpl(Attribute)

AttributeSource.AddAttribute<T>()

AttributeSource.HasAttributes

AttributeSource.HasAttribute<T>()

AttributeSource.GetAttribute<T>()

AttributeSource.ClearAttributes()

AttributeSource.CaptureState()

AttributeSource.RestoreState(AttributeSource.State)

AttributeSource.GetHashCode()

AttributeSource.Equals(object)

AttributeSource.ReflectAsString(bool)

AttributeSource.ReflectWith(IAttributeReflector)

AttributeSource.CloneAttributes()

AttributeSource.CopyTo(AttributeSource)

AttributeSource.ToString()

object.Equals(object, object)

object.GetType()

object.ReferenceEquals(object, object)

Namespace: Lucene.Net.Analysis.Pattern

Assembly: Lucene.Net.Analysis.Common.dll

Syntax

public sealed class PatternTokenizer : Tokenizer, IDisposable

Constructors

PatternTokenizer(AttributeFactory, TextReader, Regex, int)

creates a new PatternTokenizer returning tokens from group (-1 for split functionality)

Declaration

public PatternTokenizer(AttributeSource.AttributeFactory factory, TextReader input, Regex pattern, int group)

Parameters

Type	Name	Description
AttributeSource.AttributeFactory	factory
TextReader	input
Regex	pattern
int	group

See Also

Regex

PatternTokenizer(TextReader, Regex, int)

creates a new PatternTokenizer returning tokens from group (-1 for split functionality)

Declaration

public PatternTokenizer(TextReader input, Regex pattern, int group)

Parameters

Type	Name	Description
TextReader	input
Regex	pattern
int	group

See Also

Regex

Methods

End()

This method is called by the consumer after the last token has been consumed, after Lucene.Net.Analysis.TokenStream.IncrementToken() returned false (using the new Lucene.Net.Analysis.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 base.End();.

Declaration

public override void End()

Overrides

Lucene.Net.Analysis.TokenStream.End()

Exceptions

Type	Condition
IOException	If an I/O error occurs

See Also

Regex

IncrementToken()

Consumers (i.e., Lucene.Net.Index.IndexWriter) use this method to advance the stream to the next token. Implementing classes must implement this method and update the appropriate Lucene.Net.Util.IAttributes 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 Lucene.Net.Util.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 Lucene.Net.Util.AttributeSource.AddAttribute<T>() and Lucene.Net.Util.AttributeSource.GetAttribute<T>(), references to all Lucene.Net.Util.IAttributes 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 Lucene.Net.Analysis.TokenStream.IncrementToken().

Declaration

public override bool IncrementToken()

Returns

Type	Description
bool	false for end of stream; true otherwise

Overrides

Lucene.Net.Analysis.TokenStream.IncrementToken()

See Also

Regex

Reset()

This method is called by a consumer before it begins consumption using Lucene.Net.Analysis.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 base.Reset(), otherwise some internal state will not be correctly reset (e.g., Lucene.Net.Analysis.Tokenizer will throw InvalidOperationException on further usage).

Declaration

public override void Reset()

Overrides

Lucene.Net.Analysis.Tokenizer.Reset()

See Also

Regex

Implements

IDisposable

See Also

Regex