Class ASCIIFoldingFilter
- All Implemented Interfaces:
Closeable
,AutoCloseable
,Unwrappable<TokenStream>
Characters from the following Unicode blocks are converted; however, only those characters with reasonable ASCII alternatives are converted:
- C1 Controls and Latin-1 Supplement: http://www.unicode.org/charts/PDF/U0080.pdf
- Latin Extended-A: http://www.unicode.org/charts/PDF/U0100.pdf
- Latin Extended-B: http://www.unicode.org/charts/PDF/U0180.pdf
- Latin Extended Additional: http://www.unicode.org/charts/PDF/U1E00.pdf
- Latin Extended-C: http://www.unicode.org/charts/PDF/U2C60.pdf
- Latin Extended-D: http://www.unicode.org/charts/PDF/UA720.pdf
- IPA Extensions: http://www.unicode.org/charts/PDF/U0250.pdf
- Phonetic Extensions: http://www.unicode.org/charts/PDF/U1D00.pdf
- Phonetic Extensions Supplement: http://www.unicode.org/charts/PDF/U1D80.pdf
- General Punctuation: http://www.unicode.org/charts/PDF/U2000.pdf
- Superscripts and Subscripts: http://www.unicode.org/charts/PDF/U2070.pdf
- Enclosed Alphanumerics: http://www.unicode.org/charts/PDF/U2460.pdf
- Dingbats: http://www.unicode.org/charts/PDF/U2700.pdf
- Supplemental Punctuation: http://www.unicode.org/charts/PDF/U2E00.pdf
- Alphabetic Presentation Forms: http://www.unicode.org/charts/PDF/UFB00.pdf
- Halfwidth and Fullwidth Forms: http://www.unicode.org/charts/PDF/UFF00.pdf
For example, 'à' will be replaced by 'a'.
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Nested Class Summary
Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource
AttributeSource.State
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate char[]
private int
private final PositionIncrementAttribute
private final boolean
private AttributeSource.State
private final CharTermAttribute
Fields inherited from class org.apache.lucene.analysis.TokenFilter
input
Fields inherited from class org.apache.lucene.analysis.TokenStream
DEFAULT_TOKEN_ATTRIBUTE_FACTORY
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Constructor Summary
ConstructorsConstructorDescriptionASCIIFoldingFilter
(TokenStream input) ASCIIFoldingFilter
(TokenStream input, boolean preserveOriginal) Create a newASCIIFoldingFilter
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Method Summary
Modifier and TypeMethodDescriptionvoid
foldToASCII
(char[] input, int length) Converts characters above ASCII to their ASCII equivalents.static final int
foldToASCII
(char[] input, int inputPos, char[] output, int outputPos, int length) Converts characters above ASCII to their ASCII equivalents.boolean
Consumers (i.e.,IndexWriter
) use this method to advance the stream to the next token.boolean
Does the filter preserve the original tokens?private boolean
needToPreserve
(char[] input, int inputLength) Check if foldToASCII generated a different token.void
reset()
This method is called by a consumer before it begins consumption usingTokenStream.incrementToken()
.Methods inherited from class org.apache.lucene.analysis.TokenFilter
close, end, unwrap
Methods inherited from class org.apache.lucene.util.AttributeSource
addAttribute, addAttributeImpl, captureState, clearAttributes, cloneAttributes, copyTo, endAttributes, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, removeAllAttributes, restoreState, toString
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Field Details
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termAtt
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posIncAttr
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preserveOriginal
private final boolean preserveOriginal -
output
private char[] output -
outputPos
private int outputPos -
state
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Constructor Details
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ASCIIFoldingFilter
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ASCIIFoldingFilter
Create a newASCIIFoldingFilter
.- Parameters:
input
- TokenStream to filterpreserveOriginal
- should the original tokens be kept on the input stream with a 0 position increment from the folded tokens?
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Method Details
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isPreserveOriginal
public boolean isPreserveOriginal()Does the filter preserve the original tokens? -
incrementToken
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:
IOException
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reset
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:
IOException
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foldToASCII
public void foldToASCII(char[] input, int length) Converts characters above ASCII to their ASCII equivalents. For example, accents are removed from accented characters.- Parameters:
input
- The string to foldlength
- The number of characters in the input string
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needToPreserve
private boolean needToPreserve(char[] input, int inputLength) Check if foldToASCII generated a different token.- Parameters:
input
- original terminputLength
- length of the original term- Returns:
- true if foldToASCII generated a different token
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foldToASCII
public static final int foldToASCII(char[] input, int inputPos, char[] output, int outputPos, int length) Converts characters above ASCII to their ASCII equivalents. For example, accents are removed from accented characters.- Parameters:
input
- The characters to foldinputPos
- Index of the first character to foldoutput
- The result of the folding. Should be of size >=length * 4
.outputPos
- Index of output where to put the result of the foldinglength
- The number of characters to fold- Returns:
- length of output
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