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Eclipse Plug-in Developer Guide
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Lucene Analyzer


3.0 (originally added in release 2.0 as

This extension point is used to register text analyzers for use by help when indexing and searching documentation.

Help exploits capabilities of the Lucene search engine, that allows indexing of token streams (streams of words). Analyzers create tokens from the character stream. They examine text content and provide tokens for use with the index. The text stream can be tokenized in many unique ways. A trivial analyzer can tokenize streams at white space, a different one can perform filtering of tokens, based on the application needs. Since the documentation is mostly human-readable text, it is desired that analyzers used by the help system perform language and grammar aware tokenization and normalization of indexed text. For some languages, the quality of search increases significantly if stop word removal and stemming is performed on the indexed text.

The analyzer contributed to this extension point will override the one provided by the Eclipse help system for a given locale.

Configuration Markup:

<!ELEMENT extension ( analyzer*)>

<!ATTLIST extension





<!ELEMENT analyzer EMPTY>

<!ATTLIST analyzer




  • locale - a string identifying locale for which the supplied analyzer is to bue sued. If two letters, language is provided, and the analyzer will be available to all locales of that language.
  • class - a fully qualified name of the Java class extending org.apache.lucene.analysis.Analyzer.

Following is an example of Lucene Analyzer configuration:

 <extension id=
  <analyzer locale=

Supplied Implementation:
The Eclipse help system provides analyzers for all languages. For English and German, the analyzers perform stop word filtering, lowercase filtering, and stemming. For all the other languages the supplied analyzer only performs lowercase filtering.

Copyright (c) 2000, 2005 IBM Corporation and others.
All rights reserved. This program and the accompanying materials are made available under the terms of the Eclipse Public License v1.0 which accompanies this distribution, and is available at

  Published under the terms of the Eclipse Public License Version 1.0 ("EPL") Design by Interspire