org.apache.lucene.analysis

Class Token

java.lang.Object

org.apache.lucene.util.AttributeImpl

org.apache.lucene.analysis.tokenattributes.CharTermAttributeImpl

org.apache.lucene.analysis.Token

All Implemented Interfaces:

Appendable, CharSequence, Cloneable, CharTermAttribute, FlagsAttribute, OffsetAttribute, PayloadAttribute, PositionIncrementAttribute, PositionLengthAttribute, TermToBytesRefAttribute, TypeAttribute, Attribute

public class Token
extends CharTermAttributeImpl
implements TypeAttribute, PositionIncrementAttribute, FlagsAttribute, OffsetAttribute, PayloadAttribute, PositionLengthAttribute

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 DocsAndPositionsEnum.getPayload() 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.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
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

Fields

Modifier and Type	Field and Description
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 interface org.apache.lucene.analysis.tokenattributes.TypeAttribute

DEFAULT_TYPE

Constructor Summary

Constructors

Constructor and Description
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

Methods

Modifier and Type	Method and Description
void	clear() Resets the term text, payload, flags, and positionIncrement, startOffset, endOffset and token type to default.
Token	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.
BytesRef	getPayload() Returns this Token's payload.
int	getPositionIncrement() Returns the position increment of this Token.
int	getPositionLength() Returns the position length 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), setOffset(int, 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), setOffset(int, int), setType(java.lang.String)
Token	reinit(String newTerm, int newStartOffset, int newEndOffset) Shorthand for calling clear(), CharTermAttributeImpl.append(CharSequence), setOffset(int, 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), setOffset(int, 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), setOffset(int, int), setType(java.lang.String)
Token	reinit(String newTerm, int newStartOffset, int newEndOffset, String newType) Shorthand for calling clear(), CharTermAttributeImpl.append(CharSequence), setOffset(int, 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	setFlags(int flags) Set the flags to a new bitset.
void	setOffset(int startOffset, int endOffset) Set the starting and ending offset.
void	setPayload(BytesRef payload) Sets this Token's payload.
void	setPositionIncrement(int positionIncrement) Set the position increment.
void	setPositionLength(int positionLength) Set the position length of this Token.
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, fillBytesRef, getBytesRef, length, resizeBuffer, setEmpty, setLength, subSequence, 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 in the source text

end - end offset in the source text

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 in the source text

end - end offset in the source text

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 - term text

start - start offset in the source text

end - end offset in the source text

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 - buffer containing term text

termBufferOffset - the index in the buffer of the first character

termBufferLength - number of valid characters in the buffer

start - start offset in the source text

end - end offset in the source text

Method Detail

setPositionIncrement

public void setPositionIncrement(int positionIncrement)

Set the position increment. The default value is one.

Specified by:

setPositionIncrement in interface PositionIncrementAttribute

Parameters:

positionIncrement - the distance from the prior term

See Also:

PositionIncrementAttribute

getPositionIncrement

public int getPositionIncrement()

Returns the position increment of this Token.

Specified by:

getPositionIncrement in interface PositionIncrementAttribute

See Also:

PositionIncrementAttribute

setPositionLength

public void setPositionLength(int positionLength)

Set the position length of this Token.

The default value is one.

Specified by:

setPositionLength in interface PositionLengthAttribute

Parameters:

positionLength - how many positions this token spans.

See Also:

PositionLengthAttribute

getPositionLength

public int getPositionLength()

Returns the position length of this Token.

Specified by:

getPositionLength in interface PositionLengthAttribute

See Also:

PositionLengthAttribute

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 OffsetAttribute.endOffset() and startOffset() may not be equal to termText.length(), as the term text may have been altered by a stemmer or some other filter.

Specified by:

startOffset in interface OffsetAttribute

See Also:

OffsetAttribute

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() - OffsetAttribute.startOffset()).

Specified by:

endOffset in interface OffsetAttribute

See Also:

OffsetAttribute

setOffset

public void setOffset(int startOffset,
             int endOffset)

Set the starting and ending offset.

Specified by:

setOffset in interface OffsetAttribute

See Also:

OffsetAttribute

type

public final String type()

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

Specified by:

type in interface TypeAttribute

See Also:

TypeAttribute

setType

public final void setType(String type)

Set the lexical type.

Specified by:

setType in interface TypeAttribute

See Also:

TypeAttribute

getFlags

public int getFlags()

Get the bitset for any bits that have been set.

Specified by:

getFlags in interface FlagsAttribute

Returns:

The bits

See Also:

FlagsAttribute

setFlags

public void setFlags(int flags)

Set the flags to a new bitset.

Specified by:

setFlags in interface FlagsAttribute

See Also:

FlagsAttribute

getPayload

public BytesRef getPayload()

Returns this Token's payload.

Specified by:

getPayload in interface PayloadAttribute

See Also:

PayloadAttribute

setPayload

public void setPayload(BytesRef payload)

Sets this Token's payload.

Specified by:

setPayload in interface PayloadAttribute

See Also:

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 Token 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), setOffset(int, 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), setOffset(int, 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), setOffset(int, 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), setOffset(int, 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), setOffset(int, 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), setOffset(int, 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 - source Token to copy fields from

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 - existing Token

newTerm - new term text

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 - existing Token

newTermBuffer - buffer containing new term text

offset - the index in the buffer of the first character

length - number of valid characters in the buffer

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)