XmlDataReader.java

/*******************************************************************************
 * Copyright 2012 André Rouél
 * 
 * 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 net.sf.uadetector.datareader;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.nio.charset.Charset;

import javax.annotation.Nonnull;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import net.sf.qualitycheck.Check;
import net.sf.uadetector.exception.CanNotOpenStreamException;
import net.sf.uadetector.internal.data.Data;
import net.sf.uadetector.internal.data.DataBuilder;
import net.sf.uadetector.internal.data.XmlDataHandler;
import net.sf.uadetector.internal.util.Closeables;
import net.sf.uadetector.internal.util.UrlUtil;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.xml.sax.SAXException;

/**
 * Reader for the XML data for UASparser from <a
 * href="http://user-agent-string.info/">http://user-agent-string.info</a>.<br>
 * <br>
 * This reader is safe when used concurrently by multiple threads.
 * 
 * @author André Rouél
 */
public final class XmlDataReader implements DataReader {

    protected static final class XmlParser {

        private static final String MSG_NOT_PARSED_AS_EXPECTED = "The UAS data has not been parsed as expected.";

        public static void parse(@Nonnull final InputStream stream, @Nonnull final DataBuilder builder)
                throws ParserConfigurationException, SAXException, IOException {
            final SAXParserFactory factory = SAXParserFactory.newInstance();
            factory.setValidating(true);
            final SAXParser parser = factory.newSAXParser();
            final XmlDataHandler handler = new XmlDataHandler(builder);
            parser.parse(stream, handler);
            validate(handler);
        }

        protected static void validate(@Nonnull final XmlDataHandler handler) {
            if (handler.hasError()) {
                throw new IllegalStateException(MSG_NOT_PARSED_AS_EXPECTED);
            }
        }

        private XmlParser() {
            // This class is not intended to create objects from it.
        }

    }

    /**
     * Default character set to read UAS data
     */
    private static final Charset DEFAULT_CHARSET = Charset.forName("UTF-8");

    /**
     * Corresponding default logger for this class
     */
    private static final Logger LOG = LoggerFactory.getLogger(XmlDataReader.class);

    /**
     * Reads the <em>UAS data</em> in XML format based on the given URL.<br>
     * <br>
     * When during the reading errors occur which lead to a termination of the read operation, the information will be
     * written to a log. The termination of the read operation will not lead to a program termination and in this case
     * this method returns {@link Data#EMPTY}.
     * 
     * @param inputStream
     *            an input stream for reading <em>UAS data</em>
     * @param charset
     *            the character set in which the data should be read
     * @return read in <em>UAS data</em> as {@code Data} instance
     * @throws net.sf.qualitycheck.exception.IllegalNullArgumentException
     *             if any of the given arguments is {@code null}
     * @throws net.sf.uadetector.exception.CanNotOpenStreamException
     *             if no stream to the given {@code URL} can be established
     */
    protected static Data readXml(@Nonnull final InputStream inputStream, @Nonnull final Charset charset) {
        Check.notNull(inputStream, "inputStream");
        Check.notNull(charset, "charset");

        final DataBuilder builder = new DataBuilder();
        boolean hasErrors = false;
        try {
            XmlParser.parse(inputStream, builder);
        } catch (final ParserConfigurationException e) {
            hasErrors = true;
            LOG.warn(e.getLocalizedMessage());
        } catch (final SAXException e) {
            hasErrors = true;
            LOG.warn(e.getLocalizedMessage());
        } catch (final IOException e) {
            hasErrors = true;
            LOG.warn(e.getLocalizedMessage());
        } catch (final IllegalStateException e) {
            hasErrors = true;
            LOG.warn(e.getLocalizedMessage());
        } catch (final Exception e) {
            hasErrors = true;
            LOG.warn(e.getLocalizedMessage(), e);
        } finally {
            Closeables.closeAndConvert(inputStream, true);
        }

        return hasErrors ? Data.EMPTY : builder.build();
    }

    /**
     * Reads the <em>UAS data</em> in XML format from the given string.
     * 
     * @param data
     *            <em>UAS data</em> as string
     * @return read in User-Agent data as {@code Data} instance otherwise {@link Data#EMPTY}
     * 
     * @throws net.sf.qualitycheck.exception.IllegalNullArgumentException
     *             if any of the given argument is {@code null}
     */
    @Override
    public Data read(@Nonnull final String data) {
        Check.notNull(data, "data");

        return readXml(new ByteArrayInputStream(data.getBytes(DEFAULT_CHARSET)), DEFAULT_CHARSET);
    }

    /**
     * Reads the <em>UAS data</em> in XML format based on the given URL.
     * 
     * @param url
     *            {@code URL} to User-Agent informations
     * @param charset
     *            the character set in which the data should be read
     * @return read in User-Agent data as {@code Data} instance otherwise {@link Data#EMPTY}
     * 
     * @throws net.sf.qualitycheck.exception.IllegalNullArgumentException
     *             if any of the given arguments is {@code null}
     */
    @Override
    public Data read(@Nonnull final URL url, @Nonnull final Charset charset) {
        Check.notNull(url, "url");
        Check.notNull(charset, "charset");

        Data data = Data.EMPTY;
        try {
            data = readXml(UrlUtil.open(url), charset);
        } catch (final CanNotOpenStreamException e) {
            LOG.warn(e.getLocalizedMessage());
        }

        return data;
    }

}