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java.lang.Object org.apache.lucene.util.AttributeSource org.apache.lucene.analysis.TokenStream org.apache.lucene.analysis.miscellaneous.PrefixAwareTokenFilter
public class PrefixAwareTokenFilter
Joins two token streams and leaves the last token of the first stream available to be used when updating the token values in the second stream based on that token. The default implementation adds last prefix token end offset to the suffix token start and end offsets.
NOTE: This filter might not behave correctly if used with custom Attributes, i.e. Attributes other than the ones located in org.apache.lucene.analysis.tokenattributes.
Nested Class Summary |
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Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource |
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AttributeSource.AttributeFactory, AttributeSource.State |
Constructor Summary | |
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PrefixAwareTokenFilter(TokenStream prefix,
TokenStream suffix)
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Method Summary | |
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void |
close()
Releases resources associated with this stream. |
TokenStream |
getPrefix()
|
TokenStream |
getSuffix()
|
boolean |
incrementToken()
Consumers (i.e., IndexWriter ) use this method to advance the stream to
the next token. |
Token |
next()
Deprecated. Will be removed in Lucene 3.0. This method is final, as it should not be overridden. Delegates to the backwards compatibility layer. |
Token |
next(Token reusableToken)
Deprecated. Will be removed in Lucene 3.0. This method is final, as it should not be overridden. Delegates to the backwards compatibility layer. |
void |
reset()
Resets this stream to the beginning. |
void |
setPrefix(TokenStream prefix)
|
void |
setSuffix(TokenStream suffix)
|
Token |
updateSuffixToken(Token suffixToken,
Token lastPrefixToken)
The default implementation adds last prefix token end offset to the suffix token start and end offsets. |
Methods inherited from class org.apache.lucene.analysis.TokenStream |
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end, getOnlyUseNewAPI, setOnlyUseNewAPI |
Methods inherited from class org.apache.lucene.util.AttributeSource |
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addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, restoreState, toString |
Methods inherited from class java.lang.Object |
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clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Constructor Detail |
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public PrefixAwareTokenFilter(TokenStream prefix, TokenStream suffix)
Method Detail |
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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)
or downcasts,
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
Note that this method will be defined abstract in Lucene 3.0.
IOException
public final Token next(Token reusableToken) throws IOException
TokenStream
This implicitly defines a "contract" between consumers (callers of this method) and producers (implementations of this method that are the source for tokens):
Token
before calling this method again.Token.clear()
before setting the fields in
it and returning itToken
after it
has been returned: the caller may arbitrarily change it. If the producer
needs to hold onto the Token
for subsequent calls, it must clone()
it before storing it. Note that a TokenFilter
is considered a
consumer.
next
in class TokenStream
reusableToken
- a Token
that may or may not be used to return;
this parameter should never be null (the callee is not required to
check for null before using it, but it is a good idea to assert that
it is not null.)
Token
in the stream or null if end-of-stream was hit
IOException
public final Token next() throws IOException
TokenStream
Token
in the stream, or null at EOS.
next
in class TokenStream
IOException
public Token updateSuffixToken(Token suffixToken, Token lastPrefixToken)
suffixToken
- a token from the suffix streamlastPrefixToken
- the last token from the prefix stream
public void close() throws IOException
TokenStream
close
in class TokenStream
IOException
public void reset() throws IOException
TokenStream
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()
).
reset
in class TokenStream
IOException
public TokenStream getPrefix()
public void setPrefix(TokenStream prefix)
public TokenStream getSuffix()
public void setSuffix(TokenStream suffix)
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