Class CachingTokenFilter

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 Reset(), which repositions the stream to the first Token.
Inheritance
object
AttributeSource
TokenStream
TokenFilter
CachingTokenFilter
Implements
Inherited Members
Namespace: Lucene.Net.Analysis
Assembly: Lucene.Net.dll
Syntax
public sealed class CachingTokenFilter : TokenFilter, IDisposable

Constructors

CachingTokenFilter(TokenStream)

Create a new CachingTokenFilter around input, caching its token attributes, which can be replayed again after a call to Reset().

Declaration
public CachingTokenFilter(TokenStream input)
Parameters
Type Name Description
TokenStream input

Methods

Dispose(bool)

Releases resources used by the CachingTokenFilter and if overridden in a derived class, optionally releases unmanaged resources.

Declaration
protected override void Dispose(bool disposing)
Parameters
Type Name Description
bool disposing

true to release both managed and unmanaged resources; false to release only unmanaged resources.
Overrides

End()

This method is called by the consumer after the last token has been consumed, after 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.

NOTE: The default implementation chains the call to the input TokenStream, so be sure to call base.End() first when overriding this method.
Declaration
public override void End()
Overrides
Exceptions
Type Condition
IOException

If an I/O error occurs

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 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 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 AddAttribute<T>() and GetAttribute<T>(), references to all 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 IncrementToken().
Declaration
public override bool IncrementToken()
Returns
Type Description
bool

false for end of stream; true otherwise
Overrides

Reset()

Rewinds the iterator to the beginning of the cached list.

Note that this does not call Reset() on the wrapped tokenstream ever, even the first time. You should Reset() the inner tokenstream before wrapping it with CachingTokenFilter.
Declaration
public override void Reset()
Overrides

Implements