Class PatternCaptureGroupTokenFilter
- java.lang.Object
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- org.apache.lucene.util.AttributeSource
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- org.apache.lucene.analysis.TokenStream
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- org.apache.lucene.analysis.TokenFilter
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- org.apache.lucene.analysis.pattern.PatternCaptureGroupTokenFilter
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- All Implemented Interfaces:
java.io.Closeable
,java.lang.AutoCloseable
public final class PatternCaptureGroupTokenFilter extends TokenFilter
CaptureGroup uses Java regexes to emit multiple tokens - one for each capture group in one or more patterns.For example, a pattern like:
"(https?://([a-zA-Z\-_0-9.]+))"
when matched against the string "http://www.foo.com/index" would return the tokens "https://www.foo.com" and "www.foo.com".
If none of the patterns match, or if preserveOriginal is true, the original token will be preserved.
Each pattern is matched as often as it can be, so the pattern
"(...)"
, when matched against"abcdefghi"
would produce["abc","def","ghi"]
A camelCaseFilter could be written as:
"([A-Z]{2,})",
"(?<![A-Z])([A-Z][a-z]+)",
"(?:^|\\b|(?<=[0-9_])|(?<=[A-Z]{2}))([a-z]+)",
"([0-9]+)"plus if
preserveOriginal
is true, it would also return"camelCaseFilter
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Nested Class Summary
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Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.AttributeFactory, AttributeSource.State
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Constructor Summary
Constructors Constructor Description PatternCaptureGroupTokenFilter(TokenStream input, boolean preserveOriginal, java.util.regex.Pattern... patterns)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
incrementToken()
Consumers (i.e.,IndexWriter
) use this method to advance the stream to the next token.void
reset()
This method is called by a consumer before it begins consumption usingTokenStream.incrementToken()
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Methods inherited from class org.apache.lucene.analysis.TokenFilter
close, end
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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
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Constructor Detail
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PatternCaptureGroupTokenFilter
public PatternCaptureGroupTokenFilter(TokenStream input, boolean preserveOriginal, java.util.regex.Pattern... patterns)
- Parameters:
input
- the inputTokenStream
preserveOriginal
- set to true to return the original token even if one of the patterns matchespatterns
- an array ofPattern
objects to match against each token
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Method Detail
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incrementToken
public boolean incrementToken() throws java.io.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 appropriateAttributeImpl
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)
andAttributeSource.getAttribute(Class)
, references to allAttributeImpl
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()
.- Specified by:
incrementToken
in classTokenStream
- Returns:
- false for end of stream; true otherwise
- Throws:
java.io.IOException
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reset
public void reset() throws java.io.IOException
Description copied from class:TokenFilter
This method is called by a consumer before it begins consumption usingTokenStream.incrementToken()
.Resets this stream to a clean state. Stateful implementations must implement this method so that they can be reused, just as if they had been created fresh.
If you override this method, always call
super.reset()
, otherwise some internal state will not be correctly reset (e.g.,Tokenizer
will throwIllegalStateException
on further usage).NOTE: The default implementation chains the call to the input TokenStream, so be sure to call
super.reset()
when overriding this method.- Overrides:
reset
in classTokenFilter
- Throws:
java.io.IOException
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