org.apache.lucene.search.suggest.document

Class ContextSuggestField.PrefixTokenFilter

java.lang.Object

org.apache.lucene.util.AttributeSource

org.apache.lucene.analysis.TokenStream

org.apache.lucene.analysis.TokenFilter

org.apache.lucene.search.suggest.document.ContextSuggestField.PrefixTokenFilter

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

Enclosing class:

ContextSuggestField

private static final class ContextSuggestField.PrefixTokenFilter
extends TokenFilter

The ContextSuggestField.PrefixTokenFilter wraps a TokenStream and adds a set prefixes ahead. The position attribute will not be incremented for the prefixes.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.util.AttributeSource

AttributeSource.State

Field Summary

Fields

Modifier and Type	Field and Description
private java.util.Iterator<java.lang.CharSequence>	currentPrefix
private PositionIncrementAttribute	posAttr
private java.lang.Iterable<java.lang.CharSequence>	prefixes
private char	separator
private CharTermAttribute	termAttr

Fields inherited from class org.apache.lucene.analysis.TokenFilter

input

Fields inherited from class org.apache.lucene.analysis.TokenStream

DEFAULT_TOKEN_ATTRIBUTE_FACTORY

Constructor Summary

Constructors

Constructor and Description
PrefixTokenFilter(TokenStream input, char separator, java.lang.Iterable<java.lang.CharSequence> prefixes) Create a new ContextSuggestField.PrefixTokenFilter

Method Summary

Modifier and Type	Method and 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 using TokenStream.incrementToken().

Methods inherited from class org.apache.lucene.analysis.TokenFilter

close, end

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

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

separator

private final char separator

termAttr

private final CharTermAttribute termAttr

posAttr

private final PositionIncrementAttribute posAttr

prefixes

private final java.lang.Iterable<java.lang.CharSequence> prefixes

currentPrefix

private java.util.Iterator<java.lang.CharSequence> currentPrefix

Constructor Detail

PrefixTokenFilter

public PrefixTokenFilter(TokenStream input,
                         char separator,
                         java.lang.Iterable<java.lang.CharSequence> prefixes)

Create a new ContextSuggestField.PrefixTokenFilter

Parameters:

input - TokenStream to wrap

separator - Character used separate prefixes from other tokens

prefixes - Iterable of CharSequence which keeps all prefixes

Method Detail

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 appropriate AttributeImpls 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 AttributeImpls 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 class TokenStream

Returns:

false for end of stream; true otherwise

Throws:

java.io.IOException

reset

public void reset()
           throws java.io.IOException

Description copied from class: TokenFilter

This method is called by a consumer before it begins consumption using TokenStream.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 throw IllegalStateException 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 class TokenFilter

Throws:

java.io.IOException