org.riotfamily.search.ResultHighlighter.java Source code

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Here is the source code for org.riotfamily.search.ResultHighlighter.java

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/* Licensed 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.
 */
package org.riotfamily.search;

import java.io.IOException;
import java.io.StringReader;

import org.apache.lucene.analysis.SimpleAnalyzer;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.highlight.Encoder;
import org.apache.lucene.search.highlight.Formatter;
import org.apache.lucene.search.highlight.Fragmenter;
import org.apache.lucene.search.highlight.Highlighter;
import org.apache.lucene.search.highlight.InvalidTokenOffsetsException;
import org.apache.lucene.search.highlight.QueryScorer;
import org.apache.lucene.search.highlight.Scorer;
import org.apache.lucene.search.highlight.SimpleFragmenter;
import org.apache.lucene.search.highlight.SimpleHTMLEncoder;
import org.apache.lucene.search.highlight.SimpleHTMLFormatter;

public class ResultHighlighter {

    private int fragmentSize = 75;

    private int maxFragments = 3;

    private String separator = " ... ";

    private String highlightPreTag = "em";

    private String highlightPostTag = "em";

    private Formatter formatter;

    private Encoder encoder = new SimpleHTMLEncoder();

    private Fragmenter fragmenter;

    /**
     * Sets the number of characters per fragment.  Default is <code>75</code>.
     */
    public void setFragmentSize(int fragmentSize) {
        this.fragmentSize = fragmentSize;
    }

    /**
     * Sets the maximum number of fragments. Default is <code>3</code>.
     */
    public void setMaxFragments(int maxFragments) {
        this.maxFragments = maxFragments;
    }

    /**
     * Sets a string that is used to separate the fragments. 
     * Default is <code>" ... "</code>.
     */
    public void setSeparator(String separator) {
        this.separator = separator;
    }

    /**
     * Sets a string that is used as html tag to higlight searched terms in the
     * description snippet. Default is <code>"em"</code> which wraps searched
     * terms within <code>"&lt;em>term&lt;/em>"</code>.
     */
    public void setHighlightTag(String highlightTag) {
        this.highlightPreTag = highlightTag;
        this.highlightPostTag = highlightTag;
    }

    /**
     * Sets a string that is used as html tag to before the searched term in the
     * description snippet. Default is <code>"em"</code>. See {@link #setHighlightTag(String)}.
     */
    public void setHighlightPreTag(String highlightPreTag) {
        this.highlightPreTag = highlightPreTag;
    }

    /**
     * Sets a string that is used as html tag to after the searched term in the
     * description snippet. Default is <code>"em"</code>. See {@link #setHighlightTag(String)}.
     */
    public void setHighlightPostTag(String highlightPostTag) {
        this.highlightPostTag = highlightPostTag;
    }

    public HighlightingContext createContext(IndexSearcher indexSearcher, Query query) throws IOException {

        Scorer scorer = new QueryScorer(indexSearcher.rewrite(query));
        if (formatter == null) {
            formatter = new SimpleHTMLFormatter("<" + highlightPreTag + ">", "</" + highlightPostTag + ">");
        }
        if (fragmenter == null) {
            fragmenter = new SimpleFragmenter(fragmentSize);
        }
        Highlighter highlighter = new Highlighter(formatter, encoder, scorer);
        highlighter.setTextFragmenter(fragmenter);
        return new HighlightingContext(highlighter);
    }

    public class HighlightingContext {

        private Highlighter highlighter;

        private HighlightingContext(Highlighter highlighter) {
            this.highlighter = highlighter;
        }

        public String getFragments(String content) {

            TokenStream ts = new SimpleAnalyzer().tokenStream(null, new StringReader(content));

            String fragments = null;
            try {
                fragments = highlighter.getBestFragments(ts, content, maxFragments, separator);
            } catch (InvalidTokenOffsetsException e) {
            } catch (IOException e) {
            }
            if (fragments != null && fragments.length() > 0) {
                if (separator != null) {
                    fragments = fragments + separator;
                }
                return fragments;
            } else {
                int excerptSize = maxFragments * fragmentSize;
                if (content.length() > excerptSize) {
                    return content.substring(0, excerptSize) + separator;
                }
                return content;
            }
        }
    }
}