contrib/textfilters/src/java/org/apache/jackrabbit/core/query/HTMLTextFilter.java

/*
 * Copyright 2004-2005 The Apache Software Foundation or its licensors,
 *                     as applicable.
 *
 * 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.apache.jackrabbit.core.query;

import java.io.StringReader;
import java.util.HashMap;
import java.util.Map;

import javax.jcr.RepositoryException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.TransformerFactoryConfigurationError;
import javax.xml.transform.sax.SAXResult;
import javax.xml.transform.sax.SAXSource;

import org.apache.jackrabbit.core.query.lucene.FieldNames;
import org.apache.jackrabbit.core.state.PropertyState;
import org.apache.jackrabbit.core.value.BLOBFileValue;
import org.apache.jackrabbit.core.value.InternalValue;
import org.xml.sax.InputSource;
import org.xml.sax.helpers.DefaultHandler;

/**
 * Extracts texts from HTML documents. It uses nekohtml library.
 */
public class HTMLTextFilter implements TextFilter {

    private HTMLParser parser;
    private SAXResult result;
    private Transformer transformer;

    /**
     * @return <code>true</code> for <code>text/xml</code>, <code>false</code>
     *         otherwise.
     */
    public boolean canFilter(String mimeType) {
        return "text/html".equalsIgnoreCase(mimeType);
    }

    /**
     * Returns a map with a single entry for field {@link FieldNames#FULLTEXT}.
     *
     * @param data     object containing RTF document data
     * @param encoding text encoding is not used, since it is specified in the
     *                 data.
     * @return a map with a single Reader value for field {@link
     *         FieldNames#FULLTEXT}.
     * @throws RepositoryException if data is a multi-value property or if the
     *                             content can't be extracted
     */
    public Map doFilter(PropertyState data, String encoding)
            throws RepositoryException {

        if (parser == null) {
            initParser();
        }

        InternalValue[] values = data.getValues();
        if (values.length > 0) {
            try {
                try {
                    BLOBFileValue blob =
                            (BLOBFileValue) values[0].internalValue();

                    SAXSource source =
                            new SAXSource(parser,
                                    new InputSource(blob.getStream()));
                    transformer.transform(source, result);

                    String text = parser.getContents();

                    Map result = new HashMap();
                    result.put(FieldNames.FULLTEXT, new StringReader(text));
                    return result;
                } catch (TransformerException te) {
                    throw new RepositoryException(te);
                }

            } catch (IllegalStateException e) {
                throw new RepositoryException(e);
            }
        } else {
            // multi value not supported
            throw new RepositoryException("Multi-valued binary properties not supported.");
        }
    }

    /**
     * Inits the parser engine
     *
     * @throws javax.jcr.RepositoryException If some error happens
     */
    private void initParser() throws javax.jcr.RepositoryException {


        try {
            TransformerFactory factory = TransformerFactory.newInstance();
            transformer = factory.newTransformer();
            parser = new HTMLParser();
            result = new SAXResult(new DefaultHandler());
        } catch (TransformerConfigurationException e) {
            throw new RepositoryException(e);
        } catch (TransformerFactoryConfigurationError e) {
            throw new RepositoryException(e);
        }
    }
}