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java.lang.Object org.apache.lucene.util.AttributeSource org.apache.lucene.analysis.TokenStream org.apache.lucene.analysis.TokenFilter org.apache.lucene.analysis.FilteringTokenFilter
public abstract class FilteringTokenFilter
Abstract base class for TokenFilters that may remove tokens.
You have to implement accept()
and return a boolean if the current
token should be preserved. incrementToken()
uses this method
to decide if a token should be passed to the caller.
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 |
Field Summary |
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Fields inherited from class org.apache.lucene.analysis.TokenFilter |
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input |
Constructor Summary | |
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FilteringTokenFilter(boolean enablePositionIncrements,
TokenStream input)
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Method Summary | |
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protected abstract boolean |
accept()
Override this method and return if the current input token should be returned by incrementToken() . |
boolean |
getEnablePositionIncrements()
|
boolean |
incrementToken()
Consumers (i.e., IndexWriter ) use this method to advance the stream to
the next token. |
void |
reset()
Reset the filter as well as the input TokenStream. |
void |
setEnablePositionIncrements(boolean enable)
If true , this TokenFilter will preserve
positions of the incoming tokens (ie, accumulate and
set position increments of the removed tokens). |
Methods inherited from class org.apache.lucene.analysis.TokenFilter |
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close, end |
Methods inherited from class org.apache.lucene.util.AttributeSource |
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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 |
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clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Constructor Detail |
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public FilteringTokenFilter(boolean enablePositionIncrements, TokenStream input)
Method Detail |
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protected abstract boolean accept() throws IOException
incrementToken()
.
IOException
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 void reset() throws IOException
TokenFilter
reset
in class TokenFilter
IOException
public boolean getEnablePositionIncrements()
setEnablePositionIncrements(boolean)
public void setEnablePositionIncrements(boolean enable)
true
, this TokenFilter will preserve
positions of the incoming tokens (ie, accumulate and
set position increments of the removed tokens).
Generally, true
is best as it does not
lose information (positions of the original tokens)
during indexing.
When set, when a token is stopped (omitted), the position increment of the following token is incremented.
NOTE: be sure to also
set QueryParser.setEnablePositionIncrements(boolean)
if
you use QueryParser to create queries.
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