| <!-- |
| |
| Licensed to the Apache Software Foundation (ASF) under one |
| or more contributor license agreements. See the NOTICE file |
| distributed with this work for additional information |
| regarding copyright ownership. The ASF licenses this file |
| to you under the Apache License, Version 2.0 (the |
| "License"); you may not use this file except in compliance |
| with the License. You may obtain a copy of the License at |
| |
| http://www.apache.org/licenses/LICENSE-2.0 |
| |
| Unless required by applicable law or agreed to in writing, |
| software distributed under the License is distributed on an |
| "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| KIND, either express or implied. See the License for the |
| specific language governing permissions and limitations |
| under the License. |
| |
| --> |
| |
| <html> |
| <body> |
| The highlight package contains classes to provide "keyword in context" features |
| typically used to highlight search terms in the text of results pages. The |
| Highlighter class is the central component and can be used to extract the most |
| interesting sections of a piece of text and highlight them, with the help of |
| Fragmenter, FragmentScorer, Formatter classes. |
| <h2>Example Usage</h2> |
| <pre> |
| IndexSearcher searcher = new IndexSearcher(ramDir); |
| Query query = QueryParser.Parse("Kenne*", FIELD_NAME, analyzer); |
| query = query.Rewrite(reader); //required to expand search terms |
| Hits hits = searcher.Search(query); |
| |
| Highlighter highlighter = new Highlighter(this, new QueryScorer(query)); |
| for (int i = 0; i < hits.Length(); i++) |
| { |
| String text = hits.Doc(i).Get(FIELD_NAME); |
| TokenStream tokenStream = analyzer.TokenStream(FIELD_NAME, new StringReader(text)); |
| // Get 3 best fragments and seperate with a "..." |
| String result = highlighter.GetBestFragments(tokenStream, text, 3, "..."); |
| System.Out.Console.WriteLine(result); |
| } |
| </pre> |
| <h2>New features 06/02/2005</h2> |
| This release adds options for encoding (thanks to Nicko Cadell). An "IEncoder" |
| implementation such as the new SimpleHTMLIEncoder class can be passed to the |
| highlighter to encode all those non-xhtml standard characters such as & |
| into legal values. This simple class may not suffice for some languages - |
| Commons Lang has an implementation that could be used: escapeHtml(String) in |
| http://svn.apache.org/viewcvs.cgi/jakarta/commons/proper/lang/trunk/src/java/org/apache/commons/lang/StringEscapeUtils.java?rev=137958&view=markup |
| <h2>New features 22/12/2004</h2> |
| This release adds some new capabilities: |
| <ol> |
| <li> |
| Faster highlighting using Term vector support</li> |
| <li> |
| New formatting options to use color intensity to show informational value</li> |
| <li> |
| Options for better summarization by using term IDF scores to influence fragment |
| selection</li> |
| </ol> |
| <p> |
| The highlighter takes a TokenStream as input. Until now these streams have |
| typically been produced using an Analyzer but the new class TokenSources |
| provides helper methods for obtaining TokenStreams from the new TermVector |
| position support (see latest CVS version).</p> |
| <p>The new class GradientFormatter can use a scale of colors to highlight terms |
| according to their score. A subtle use of color can help emphasise the reasons |
| for matching (useful when doing "MoreLikeThis" queries and you want to see what |
| the basis of the similarities are).</p> |
| <p>The QueryScorer class has a new constructor which can use an IndexReader to |
| derive the IDF (inverse document frequency) for each term in order to |
| influcence the score. This is useful for helping to extracting the most |
| significant sections of a document and in supplying scores used by the new |
| GradientFormatter to color significant words more strongly. The |
| QueryScorer.getMaxWeight method is useful when passed to the GradientFormatter |
| constructor to define the top score which is associated with the top color.</p> |
| </body> |
| </html> |
