Package org.apache.lucene.analysis.miscellaneous

Class LimitTokenCountFilter

java.lang.Object

org.apache.lucene.util.AttributeSource

org.apache.lucene.analysis.TokenStream

org.apache.lucene.analysis.TokenFilter

org.apache.lucene.analysis.miscellaneous.LimitTokenCountFilter

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

public final class LimitTokenCountFilter
extends TokenFilter

This TokenFilter limits the number of tokens while indexing. It is a replacement for the maximum field length setting inside IndexWriter.

By default, this filter ignores any tokens in the wrapped TokenStream once the limit has been reached, which can result in reset() being called prior to incrementToken() returning false. For most TokenStream implementations this should be acceptable, and faster then consuming the full stream. If you are wrapping a TokenStream which requires that the full stream of tokens be exhausted in order to function properly, use the consumeAllTokens option.

Nested Class Summary

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

AttributeSource.AttributeFactory, AttributeSource.State

Constructor Summary

Constructors

Constructor	Description
LimitTokenCountFilter(TokenStream in, int maxTokenCount)	Build a filter that only accepts tokens up to a maximum number.
LimitTokenCountFilter(TokenStream in, int maxTokenCount, boolean consumeAllTokens)	Build an filter that limits the maximum number of tokens per field.

Method Summary

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 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, equals, getAttribute, getAttributeClassesIterator, getAttributeFactory, getAttributeImplsIterator, hasAttribute, hasAttributes, hashCode, reflectAsString, reflectWith, restoreState, toString

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

LimitTokenCountFilter

public LimitTokenCountFilter(TokenStream in,
                             int maxTokenCount)

Build a filter that only accepts tokens up to a maximum number. This filter will not consume any tokens beyond the maxTokenCount limit

See Also:

LimitTokenCountFilter(TokenStream,int,boolean)

LimitTokenCountFilter

public LimitTokenCountFilter(TokenStream in,
                             int maxTokenCount,
                             boolean consumeAllTokens)

Build an filter that limits the maximum number of tokens per field.

Parameters:

in - the stream to wrap

maxTokenCount - max number of tokens to produce

consumeAllTokens - whether all tokens from the input must be consumed even if maxTokenCount is reached.

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