org.apache.lucene.analysis.cn
Class ChineseTokenizer

java.lang.Object
  org.apache.lucene.util.AttributeSource
      org.apache.lucene.analysis.TokenStream
          org.apache.lucene.analysis.Tokenizer
              org.apache.lucene.analysis.cn.ChineseTokenizer

public final class ChineseTokenizer
extends Tokenizer

Tokenize Chinese text as individual chinese characters.

The difference between ChineseTokenizer and CJKTokenizer is that they have different token parsing logic.

For example, if the Chinese text "C1C2C3C4" is to be indexed:

• The tokens returned from ChineseTokenizer are C1, C2, C3, C4.
• The tokens returned from the CJKTokenizer are C1C2, C2C3, C3C4.

Therefore the index created by CJKTokenizer is much larger.

The problem is that when searching for C1, C1C2, C1C3, C4C2, C1C2C3 ... the ChineseTokenizer works, but the CJKTokenizer will not work.

Version:

1.0

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource

AttributeSource.AttributeFactory, AttributeSource.State

Field Summary

Fields inherited from class org.apache.lucene.analysis.Tokenizer

input

Constructor Summary

ChineseTokenizer(AttributeSource.AttributeFactory factory, Reader in)

ChineseTokenizer(AttributeSource source, Reader in)

ChineseTokenizer(Reader in)

Method Summary

void	end() This method is called by the consumer after the last token has been consumed, after TokenStream.incrementToken() returned false (using the new TokenStream API).
boolean	incrementToken() Consumers (i.e., IndexWriter) use this method to advance the stream to the next token.
void	reset() Resets this stream to the beginning.
void	reset(Reader input) Expert: Reset the tokenizer to a new reader.

Methods inherited from class org.apache.lucene.analysis.Tokenizer

close, correctOffset

Methods inherited from class org.apache.lucene.analysis.TokenStream

getOnlyUseNewAPI, next, next, setOnlyUseNewAPI

Methods inherited from class org.apache.lucene.util.AttributeSource

addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, restoreState, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

ChineseTokenizer

public ChineseTokenizer(Reader in)

ChineseTokenizer

public ChineseTokenizer(AttributeSource source,
                        Reader in)

ChineseTokenizer

public ChineseTokenizer(AttributeSource.AttributeFactory factory,
                        Reader in)

Method Detail

incrementToken

public 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) or downcasts, 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().

Overrides:

incrementToken in class TokenStream

Returns:

false for end of stream; true otherwise

Note that this method will be defined abstract in Lucene 3.0.

Throws:

IOException

end

public final void end()

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.

Overrides:

end in class TokenStream

reset

public void reset()
           throws IOException

Description copied from class: TokenStream

Resets this stream to the beginning. This is an optional operation, so subclasses may or may not implement this method. TokenStream.reset() is not needed for the standard indexing process. However, if the tokens of a TokenStream are intended to be consumed more than once, it is necessary to implement TokenStream.reset(). Note that if your TokenStream caches tokens and feeds them back again after a reset, it is imperative that you clone the tokens when you store them away (on the first pass) as well as when you return them (on future passes after TokenStream.reset()).

Overrides:

reset in class TokenStream

Throws:

IOException

reset

public void reset(Reader input)
           throws IOException

Description copied from class: Tokenizer

Expert: Reset the tokenizer to a new reader. Typically, an analyzer (in its reusableTokenStream method) will use this to re-use a previously created tokenizer.

Overrides:

reset in class Tokenizer

Throws:

IOException