A

CopyC#

TokenStream

enumerates the sequence of tokens, either from {@link Field}s of a {@link Document} or from query text.

This is an abstract class. Concrete subclasses are:

• {@link Tokenizer}, a
  CopyC#

  TokenStream

  whose input is a Reader; and
• {@link TokenFilter}, a
  CopyC#

  TokenStream

  whose input is another
  CopyC#

  TokenStream

  .

A new

CopyC#

TokenStream

API has been introduced with Lucene 2.9. This API has moved from being {@link Token} based to {@link Attribute} based. While {@link Token} still exists in 2.9 as a convenience class, the preferred way to store the information of a {@link Token} is to use {@link AttributeImpl}s.

now extends {@link AttributeSource}, which provides access to all of the token {@link Attribute}s for the

CopyC#

TokenStream

. Note that only one instance per {@link AttributeImpl} is created and reused for every token. This approach reduces object creation and allows local caching of references to the {@link AttributeImpl}s. See {@link #IncrementToken()} for further details.

The workflow of the new

API is as follows:

1. Instantiation of
   CopyC#

   TokenStream

   /{@link TokenFilter}s which add/get attributes to/from the {@link AttributeSource}.
2. The consumer calls {@link TokenStream#Reset()}.
3. The consumer retrieves attributes from the stream and stores local references to all attributes it wants to access
4. The consumer calls {@link #IncrementToken()} until it returns false and consumes the attributes after each call.
5. The consumer calls {@link #End()} so that any end-of-stream operations can be performed.
6. The consumer calls {@link #Close()} to release any resource when finished using the
   CopyC#

   TokenStream

To make sure 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 {@link #IncrementToken()}.

You can find some example code for the new API in the analysis package level Javadoc.

Sometimes it is desirable to capture a current state of a

, e. g. for buffering purposes (see {@link CachingTokenFilter}, {@link TeeSinkTokenFilter}). For this usecase {@link AttributeSource#CaptureState} and {@link AttributeSource#RestoreState} can be used.

public abstract class TokenStream : AttributeSource

Public MustInherit Class TokenStream _
	Inherits AttributeSource

public ref class TokenStream abstract : public AttributeSource