Token (Lucene 3.6.0 API)

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org.apache.lucene.analysis
Class Token

java.lang.Object
  org.apache.lucene.util.AttributeImpl
      org.apache.lucene.analysis.tokenattributes.CharTermAttributeImpl
          org.apache.lucene.analysis.tokenattributes.TermAttributeImpl
              org.apache.lucene.analysis.Token

All Implemented Interfaces:: Serializable, Appendable, CharSequence, Cloneable, CharTermAttribute, FlagsAttribute, OffsetAttribute, PayloadAttribute, PositionIncrementAttribute, TermAttribute, TypeAttribute, Attribute

public class Token
extends TermAttributeImpl
implements TypeAttribute, PositionIncrementAttribute, FlagsAttribute, OffsetAttribute, PayloadAttribute
extends TermAttributeImpl
implements TypeAttribute, PositionIncrementAttribute, FlagsAttribute, OffsetAttribute, PayloadAttribute

A Token is an occurrence of a term from the text of a field. It consists of a term's text, the start and end offset of the term in the text of the field, and a type string.

The start and end offsets permit applications to re-associate a token with its source text, e.g., to display highlighted query terms in a document browser, or to show matching text fragments in a KWIC display, etc.

The type is a string, assigned by a lexical analyzer (a.k.a. tokenizer), naming the lexical or syntactic class that the token belongs to. For example an end of sentence marker token might be implemented with type "eos". The default token type is "word".

A Token can optionally have metadata (a.k.a. Payload) in the form of a variable length byte array. Use TermPositions.getPayloadLength() and TermPositions.getPayload(byte[], int) to retrieve the payloads from the index.

NOTE: As of 2.9, Token implements all Attribute interfaces that are part of core Lucene and can be found in the tokenattributes subpackage. Even though it is not necessary to use Token anymore, with the new TokenStream API it can be used as convenience class that implements all Attributes, which is especially useful to easily switch from the old to the new TokenStream API.

Tokenizers and TokenFilters should try to re-use a Token instance when possible for best performance, by implementing the TokenStream.incrementToken() API. Failing that, to create a new Token you should first use one of the constructors that starts with null text. To load the token from a char[] use CharTermAttributeImpl.copyBuffer(char[], int, int). To load from a String use CharTermAttributeImpl.setEmpty() followed by CharTermAttributeImpl.append(CharSequence) or CharTermAttributeImpl.append(CharSequence, int, int). Alternatively you can get the Token's termBuffer by calling either CharTermAttributeImpl.buffer(), if you know that your text is shorter than the capacity of the termBuffer or CharTermAttributeImpl.resizeBuffer(int), if there is any possibility that you may need to grow the buffer. Fill in the characters of your term into this buffer, with String.getChars(int, int, char[], int) if loading from a string, or with System.arraycopy(Object, int, Object, int, int), and finally call CharTermAttributeImpl.setLength(int) to set the length of the term text. See LUCENE-969 for details.

Typical Token reuse patterns:

Copying text from a string (type is reset to TypeAttribute.DEFAULT_TYPE if not specified):
```
    return reusableToken.reinit(string, startOffset, endOffset[, type]);
  
```

Copying some text from a string (type is reset to TypeAttribute.DEFAULT_TYPE if not specified):

    return reusableToken.reinit(string, 0, string.length(), startOffset, endOffset[, type]);

Copying text from char[] buffer (type is reset to TypeAttribute.DEFAULT_TYPE if not specified):

    return reusableToken.reinit(buffer, 0, buffer.length, startOffset, endOffset[, type]);

Copying some text from a char[] buffer (type is reset to TypeAttribute.DEFAULT_TYPE if not specified):

    return reusableToken.reinit(buffer, start, end - start, startOffset, endOffset[, type]);

Copying from one one Token to another (type is reset to TypeAttribute.DEFAULT_TYPE if not specified):

    return reusableToken.reinit(source.buffer(), 0, source.length(), source.startOffset(), source.endOffset()[, source.type()]);

A few things to note:

clear() initializes all of the fields to default values. This was changed in contrast to Lucene 2.4, but should affect no one.
Because TokenStreams can be chained, one cannot assume that the Token's current type is correct.
The startOffset and endOffset represent the start and offset in the source text, so be careful in adjusting them.
When caching a reusable token, clone it. When injecting a cached token into a stream that can be reset, clone it again.

Please note: With Lucene 3.1, the toString() method had to be changed to match the CharSequence interface introduced by the interface CharTermAttribute. This method now only prints the term text, no additional information anymore.

See Also:: Payload, Serialized Form

Nested Class Summary
`static class`	`Token.TokenAttributeFactory` Expert: Creates a TokenAttributeFactory returning `Token` as instance for the basic attributes and for all other attributes calls the given delegate factory.

Field Summary
`static AttributeSource.AttributeFactory`	`TOKEN_ATTRIBUTE_FACTORY` Convenience factory that returns `Token` as implementation for the basic attributes and return the default impl (with "Impl" appended) for all other attributes.

Fields inherited from class org.apache.lucene.util.AttributeImpl
`enableBackwards`

Fields inherited from interface org.apache.lucene.analysis.tokenattributes.TypeAttribute
`DEFAULT_TYPE`

Constructor Summary
`Token()` Constructs a Token will null text.
`Token(char[] startTermBuffer, int termBufferOffset, int termBufferLength, int start, int end)` Constructs a Token with the given term buffer (offset & length), start and end offsets
`Token(int start, int end)` Constructs a Token with null text and start & end offsets.
`Token(int start, int end, int flags)` Constructs a Token with null text and start & end offsets plus flags.
`Token(int start, int end, String typ)` Constructs a Token with null text and start & end offsets plus the Token type.
`Token(String text, int start, int end)` Constructs a Token with the given term text, and start & end offsets.
`Token(String text, int start, int end, int flags)` Constructs a Token with the given text, start and end offsets, & type.
`Token(String text, int start, int end, String typ)` Constructs a Token with the given text, start and end offsets, & type.

Method Summary
`void`	`clear()` Resets the term text, payload, flags, and positionIncrement, startOffset, endOffset and token type to default.
`Object`	`clone()` Shallow clone.
`Token`	`clone(char[] newTermBuffer, int newTermOffset, int newTermLength, int newStartOffset, int newEndOffset)` Makes a clone, but replaces the term buffer & start/end offset in the process.
`void`	`copyTo(AttributeImpl target)` Copies the values from this Attribute into the passed-in target attribute.
`int`	`endOffset()` Returns this Token's ending offset, one greater than the position of the last character corresponding to this token in the source text.
`boolean`	`equals(Object obj)`
`int`	`getFlags()` Get the bitset for any bits that have been set.
`Payload`	`getPayload()` Returns this Token's payload.
`int`	`getPositionIncrement()` Returns the position increment of this Token.
`int`	`hashCode()`
`void`	`reflectWith(AttributeReflector reflector)` This method is for introspection of attributes, it should simply add the key/values this attribute holds to the given `AttributeReflector`.
`Token`	`reinit(char[] newTermBuffer, int newTermOffset, int newTermLength, int newStartOffset, int newEndOffset)` Shorthand for calling `clear()`, `CharTermAttributeImpl.copyBuffer(char[], int, int)`, `setStartOffset(int)`, `setEndOffset(int)` `setType(java.lang.String)` on Token.DEFAULT_TYPE
`Token`	`reinit(char[] newTermBuffer, int newTermOffset, int newTermLength, int newStartOffset, int newEndOffset, String newType)` Shorthand for calling `clear()`, `CharTermAttributeImpl.copyBuffer(char[], int, int)`, `setStartOffset(int)`, `setEndOffset(int)`, `setType(java.lang.String)`
`Token`	`reinit(String newTerm, int newStartOffset, int newEndOffset)` Shorthand for calling `clear()`, `CharTermAttributeImpl.append(CharSequence)`, `setStartOffset(int)`, `setEndOffset(int)` `setType(java.lang.String)` on Token.DEFAULT_TYPE
`Token`	`reinit(String newTerm, int newTermOffset, int newTermLength, int newStartOffset, int newEndOffset)` Shorthand for calling `clear()`, `CharTermAttributeImpl.append(CharSequence, int, int)`, `setStartOffset(int)`, `setEndOffset(int)` `setType(java.lang.String)` on Token.DEFAULT_TYPE
`Token`	`reinit(String newTerm, int newTermOffset, int newTermLength, int newStartOffset, int newEndOffset, String newType)` Shorthand for calling `clear()`, `CharTermAttributeImpl.append(CharSequence, int, int)`, `setStartOffset(int)`, `setEndOffset(int)` `setType(java.lang.String)`
`Token`	`reinit(String newTerm, int newStartOffset, int newEndOffset, String newType)` Shorthand for calling `clear()`, `CharTermAttributeImpl.append(CharSequence)`, `setStartOffset(int)`, `setEndOffset(int)` `setType(java.lang.String)`
`void`	`reinit(Token prototype)` Copy the prototype token's fields into this one.
`void`	`reinit(Token prototype, char[] newTermBuffer, int offset, int length)` Copy the prototype token's fields into this one, with a different term.
`void`	`reinit(Token prototype, String newTerm)` Copy the prototype token's fields into this one, with a different term.
`void`	`setEndOffset(int offset)` Set the ending offset.
`void`	`setFlags(int flags)`
`void`	`setOffset(int startOffset, int endOffset)` Set the starting and ending offset.
`void`	`setPayload(Payload payload)` Sets this Token's payload.
`void`	`setPositionIncrement(int positionIncrement)` Set the position increment.
`void`	`setStartOffset(int offset)` Set the starting offset.
`void`	`setType(String type)` Set the lexical type.
`int`	`startOffset()` Returns this Token's starting offset, the position of the first character corresponding to this token in the source text.
`String`	`type()` Returns this Token's lexical type.

Methods inherited from class org.apache.lucene.analysis.tokenattributes.CharTermAttributeImpl
`append, append, append, append, append, append, buffer, charAt, copyBuffer, length, resizeBuffer, resizeTermBuffer, setEmpty, setLength, setTermBuffer, setTermBuffer, setTermBuffer, setTermLength, subSequence, term, termBuffer, termLength, toString`

Methods inherited from class org.apache.lucene.util.AttributeImpl
`reflectAsString`

Methods inherited from class java.lang.Object
`finalize, getClass, notify, notifyAll, wait, wait, wait`

Field Detail

TOKEN_ATTRIBUTE_FACTORY

public static final AttributeSource.AttributeFactory TOKEN_ATTRIBUTE_FACTORY

Convenience factory that returns Token as implementation for the basic attributes and return the default impl (with "Impl" appended) for all other attributes.

Since:: 3.0

Constructor Detail

Token

public Token()

Constructs a Token will null text.

Token

public Token(int start,
             int end)

Constructs a Token with null text and start & end offsets.

Parameters:: start - start offset in the source text; end - end offset in the source text

Token

public Token(int start,
             int end,
             String typ)

Constructs a Token with null text and start & end offsets plus the Token type.

Parameters:: start - start offset in the source text; end - end offset in the source text; typ - the lexical type of this Token

Token

public Token(int start,
             int end,
             int flags)

Constructs a Token with null text and start & end offsets plus flags. NOTE: flags is EXPERIMENTAL.

Parameters:: start - start offset in the source text; end - end offset in the source text; flags - The bits to set for this token

Token

public Token(String text,
             int start,
             int end)

Constructs a Token with the given term text, and start & end offsets. The type defaults to "word." NOTE: for better indexing speed you should instead use the char[] termBuffer methods to set the term text.

Parameters:: text - term text; start - start offset; end - end offset

Token

public Token(String text,
             int start,
             int end,
             String typ)

Constructs a Token with the given text, start and end offsets, & type. NOTE: for better indexing speed you should instead use the char[] termBuffer methods to set the term text.

Parameters:: text - term text; start - start offset; end - end offset; typ - token type

Token

public Token(String text,
             int start,
             int end,
             int flags)

Constructs a Token with the given text, start and end offsets, & type. NOTE: for better indexing speed you should instead use the char[] termBuffer methods to set the term text.

Parameters:: text -; start -; end -; flags - token type bits

Token

public Token(char[] startTermBuffer,
             int termBufferOffset,
             int termBufferLength,
             int start,
             int end)

Constructs a Token with the given term buffer (offset & length), start and end offsets

Parameters:: startTermBuffer -; termBufferOffset -; termBufferLength -; start -; end -

Method Detail

setPositionIncrement

public void setPositionIncrement(int positionIncrement)

Set the position increment. This determines the position of this token relative to the previous Token in a TokenStream, used in phrase searching.

The default value is one.

Some common uses for this are:

Set it to zero to put multiple terms in the same position. This is useful if, e.g., a word has multiple stems. Searches for phrases including either stem will match. In this case, all but the first stem's increment should be set to zero: the increment of the first instance should be one. Repeating a token with an increment of zero can also be used to boost the scores of matches on that token.
Set it to values greater than one to inhibit exact phrase matches. If, for example, one does not want phrases to match across removed stop words, then one could build a stop word filter that removes stop words and also sets the increment to the number of stop words removed before each non-stop word. Then exact phrase queries will only match when the terms occur with no intervening stop words.

Specified by:: setPositionIncrement in interface PositionIncrementAttribute

Parameters:: positionIncrement - the distance from the prior term
See Also:: TermPositions

getPositionIncrement

public int getPositionIncrement()

Returns the position increment of this Token.

Specified by:: getPositionIncrement in interface PositionIncrementAttribute

See Also:: setPositionIncrement(int)

startOffset

public final int startOffset()

Returns this Token's starting offset, the position of the first character corresponding to this token in the source text. Note that the difference between endOffset() and startOffset() may not be equal to CharTermAttributeImpl.length(), as the term text may have been altered by a stemmer or some other filter.

Specified by:: startOffset in interface OffsetAttribute

setStartOffset

public void setStartOffset(int offset)

Set the starting offset.

See Also:: startOffset()

endOffset

public final int endOffset()

Returns this Token's ending offset, one greater than the position of the last character corresponding to this token in the source text. The length of the token in the source text is (endOffset - startOffset).

Specified by:: endOffset in interface OffsetAttribute

setEndOffset

public void setEndOffset(int offset)

Set the ending offset.

See Also:: endOffset()

setOffset

public void setOffset(int startOffset,
                      int endOffset)

Set the starting and ending offset.

Specified by:: setOffset in interface OffsetAttribute

See Also:: and #endOffset()

type

public final String type()

Returns this Token's lexical type. Defaults to "word".

Specified by:: type in interface TypeAttribute

setType

public final void setType(String type)

Set the lexical type.

Specified by:: setType in interface TypeAttribute

See Also:: type()

getFlags

public int getFlags()

Get the bitset for any bits that have been set. This is completely distinct from type(), although they do share similar purposes. The flags can be used to encode information about the token for use by other TokenFilters.

Specified by:: getFlags in interface FlagsAttribute

Returns:: The bits
WARNING: This API is experimental and might change in incompatible ways in the next release.: While we think this is here to stay, we may want to change it to be a long.

setFlags

public void setFlags(int flags)

Specified by:: setFlags in interface FlagsAttribute

See Also:: getFlags()

getPayload

public Payload getPayload()

Returns this Token's payload.

Specified by:: getPayload in interface PayloadAttribute

setPayload

public void setPayload(Payload payload)

Sets this Token's payload.

Specified by:: setPayload in interface PayloadAttribute

clear

public void clear()

Resets the term text, payload, flags, and positionIncrement, startOffset, endOffset and token type to default.

Overrides:: clear in class CharTermAttributeImpl

clone

public Object clone()

Description copied from class: AttributeImpl

Shallow clone. Subclasses must override this if they need to clone any members deeply,

Overrides:: clone in class CharTermAttributeImpl

clone

public Token clone(char[] newTermBuffer,
                   int newTermOffset,
                   int newTermLength,
                   int newStartOffset,
                   int newEndOffset)

Makes a clone, but replaces the term buffer & start/end offset in the process. This is more efficient than doing a full clone (and then calling CharTermAttributeImpl.copyBuffer(char[], int, int)) because it saves a wasted copy of the old termBuffer.

equals

public boolean equals(Object obj)

Overrides:: equals in class CharTermAttributeImpl

hashCode

public int hashCode()

Overrides:: hashCode in class CharTermAttributeImpl

reinit

public Token reinit(char[] newTermBuffer,
                    int newTermOffset,
                    int newTermLength,
                    int newStartOffset,
                    int newEndOffset,
                    String newType)

Shorthand for calling clear(), CharTermAttributeImpl.copyBuffer(char[], int, int), setStartOffset(int), setEndOffset(int), setType(java.lang.String)

Returns:: this Token instance

reinit

public Token reinit(char[] newTermBuffer,
                    int newTermOffset,
                    int newTermLength,
                    int newStartOffset,
                    int newEndOffset)

Shorthand for calling clear(), CharTermAttributeImpl.copyBuffer(char[], int, int), setStartOffset(int), setEndOffset(int) setType(java.lang.String) on Token.DEFAULT_TYPE

Returns:: this Token instance

reinit

public Token reinit(String newTerm,
                    int newStartOffset,
                    int newEndOffset,
                    String newType)

Shorthand for calling clear(), CharTermAttributeImpl.append(CharSequence), setStartOffset(int), setEndOffset(int) setType(java.lang.String)

Returns:: this Token instance

reinit

public Token reinit(String newTerm,
                    int newTermOffset,
                    int newTermLength,
                    int newStartOffset,
                    int newEndOffset,
                    String newType)

Shorthand for calling clear(), CharTermAttributeImpl.append(CharSequence, int, int), setStartOffset(int), setEndOffset(int) setType(java.lang.String)

Returns:: this Token instance

reinit

public Token reinit(String newTerm,
                    int newStartOffset,
                    int newEndOffset)

Shorthand for calling clear(), CharTermAttributeImpl.append(CharSequence), setStartOffset(int), setEndOffset(int) setType(java.lang.String) on Token.DEFAULT_TYPE

Returns:: this Token instance

reinit

public Token reinit(String newTerm,
                    int newTermOffset,
                    int newTermLength,
                    int newStartOffset,
                    int newEndOffset)

Shorthand for calling clear(), CharTermAttributeImpl.append(CharSequence, int, int), setStartOffset(int), setEndOffset(int) setType(java.lang.String) on Token.DEFAULT_TYPE

Returns:: this Token instance

reinit

public void reinit(Token prototype)

Copy the prototype token's fields into this one. Note: Payloads are shared.

Parameters:: prototype -

reinit

public void reinit(Token prototype,
                   String newTerm)

Copy the prototype token's fields into this one, with a different term. Note: Payloads are shared.

Parameters:: prototype -; newTerm -

reinit

public void reinit(Token prototype,
                   char[] newTermBuffer,
                   int offset,
                   int length)

Copy the prototype token's fields into this one, with a different term. Note: Payloads are shared.

Parameters:: prototype -; newTermBuffer -; offset -; length -

copyTo

public void copyTo(AttributeImpl target)

Description copied from class: AttributeImpl

Copies the values from this Attribute into the passed-in target attribute. The target implementation must support all the Attributes this implementation supports.

Overrides:: copyTo in class CharTermAttributeImpl

reflectWith

public void reflectWith(AttributeReflector reflector)

Description copied from class: AttributeImpl

This method is for introspection of attributes, it should simply add the key/values this attribute holds to the given AttributeReflector.

The default implementation calls AttributeReflector.reflect(java.lang.Class, java.lang.String, java.lang.Object) for all non-static fields from the implementing class, using the field name as key and the field value as value. The Attribute class is also determined by reflection. Please note that the default implementation can only handle single-Attribute implementations.

Custom implementations look like this (e.g. for a combined attribute implementation):

   public void reflectWith(AttributeReflector reflector) {
     reflector.reflect(CharTermAttribute.class, "term", term());
     reflector.reflect(PositionIncrementAttribute.class, "positionIncrement", getPositionIncrement());
   }

If you implement this method, make sure that for each invocation, the same set of Attribute interfaces and keys are passed to AttributeReflector.reflect(java.lang.Class, java.lang.String, java.lang.Object) in the same order, but possibly different values. So don't automatically exclude e.g. null properties!

Overrides:: reflectWith in class CharTermAttributeImpl

See Also:: AttributeImpl.reflectAsString(boolean)

Overview

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org.apache.lucene.analysis Class Token

TOKEN_ATTRIBUTE_FACTORY

Token

Token

Token

Token

Token

Token

Token

Token

setPositionIncrement

getPositionIncrement

startOffset

setStartOffset

endOffset

setEndOffset

setOffset

type

setType

getFlags

setFlags

getPayload

setPayload

clear

clone

clone

equals

hashCode

reinit

reinit

reinit

reinit

reinit

reinit

reinit

reinit

reinit

copyTo

reflectWith

org.apache.lucene.analysis
Class Token