|
|||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | ||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |
java.lang.Object org.apache.lucene.util.AttributeSource org.apache.lucene.analysis.TokenStream org.apache.lucene.analysis.TokenFilter org.apache.lucene.analysis.CachingTokenFilter
public final 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
TokenStream.reset()
, which repositions the
stream to the first Token.
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.TokenFilter |
---|
input |
Constructor Summary | |
---|---|
CachingTokenFilter(TokenStream input)
Create a new CachingTokenFilter around input ,
caching its token attributes, which can be replayed again
after a call to reset() . |
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()
Rewinds the iterator to the beginning of the cached list. |
Methods inherited from class org.apache.lucene.analysis.TokenFilter |
---|
close |
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 |
Methods inherited from class java.lang.Object |
---|
clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Constructor Detail |
---|
public CachingTokenFilter(TokenStream input)
input
,
caching its token attributes, which can be replayed again
after a call to reset()
.
Method Detail |
---|
public final boolean incrementToken() throws IOException
TokenStream
IndexWriter
) use this method to advance the stream to
the next token. Implementing classes must implement this method and update
the appropriate AttributeImpl
s 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)
,
references to all AttributeImpl
s 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()
.
incrementToken
in class TokenStream
IOException
public final void end()
TokenFilter
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.
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 super.end()
.
NOTE:
The default implementation chains the call to the input TokenStream, so
be sure to call super.end()
first when overriding this method.
end
in class TokenFilter
public void reset()
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.
reset
in class TokenFilter
|
|||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | ||||||||
SUMMARY: NESTED | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |