XStreamAttributeCopier.java

/**
 * Copyright (c) Codice Foundation
 * <p>
 * This is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser
 * General Public License as published by the Free Software Foundation, either version 3 of the
 * License, or any later version.
 * <p>
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
 * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details. A copy of the GNU Lesser General Public License
 * is distributed along with this program and can be found at
 * <http://www.gnu.org/licenses/lgpl.html>.
 **/
package org.codice.ddf.spatial.ogc.csw.catalog.converter;

import java.io.IOException;
import java.io.InputStreamReader;
import java.io.StringWriter;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

import org.apache.commons.io.IOUtils;
import org.apache.commons.lang.StringUtils;
import org.codice.ddf.spatial.ogc.csw.catalog.common.CswConstants;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.xmlpull.v1.XmlPullParser;
import org.xmlpull.v1.XmlPullParserException;
import org.xmlpull.v1.XmlPullParserFactory;

import com.thoughtworks.xstream.converters.ConversionException;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
import com.thoughtworks.xstream.io.copy.HierarchicalStreamCopier;
import com.thoughtworks.xstream.io.naming.NoNameCoder;
import com.thoughtworks.xstream.io.xml.CompactWriter;
import com.thoughtworks.xstream.io.xml.XppReader;

/**
 * XStream tool to copy the contents of a HierarchicalStreamReader into another container.
 */
public class XStreamAttributeCopier {
    private static final Logger LOGGER = LoggerFactory.getLogger(XStreamAttributeCopier.class);

    private static final HierarchicalStreamCopier COPIER = new HierarchicalStreamCopier();

    private static void copyElementWithAttributes(HierarchicalStreamReader source,
            HierarchicalStreamWriter destination, Map<String, String> namespaceMap) {
        destination.startNode(source.getNodeName());
        int attributeCount = source.getAttributeCount();
        for (int i = 0; i < attributeCount; i++) {
            destination.addAttribute(source.getAttributeName(i), source.getAttribute(i));
        }
        if (namespaceMap != null && !namespaceMap.isEmpty()) {
            for (Entry<String, String> entry : namespaceMap.entrySet()) {
                if (StringUtils.isBlank(source.getAttribute(entry.getKey()))) {
                    destination.addAttribute(entry.getKey(), entry.getValue());
                }
            }
        }
        String value = source.getValue();
        if (value != null && value.length() > 0) {
            destination.setValue(value);
        }
        while (source.hasMoreChildren()) {
            source.moveDown();
            COPIER.copy(source, destination);
            source.moveUp();
        }
        destination.endNode();
    }

    /**
     * Copies the entire XML element {@code reader} is currently at into {@code writer} and returns
     * a new reader ready to read the copied element. After the call, {@code reader} will be at the
     * end of the element that was copied.
     * <p>
     * If {@code attributeMap} is provided, the attributes will be added to the copy.
     *
     * @param reader       the reader currently at the XML element you want to copy
     * @param writer       the writer that the element will be copied into
     * @param attributeMap the map of attribute names to values that will be added as attributes of
     *                     the copy, may be null
     * @return a new reader ready to read the copied element
     * @throws ConversionException if a parser to use for the new reader can't be created
     */
    public static HierarchicalStreamReader copyXml(HierarchicalStreamReader reader,
            StringWriter writer, Map<String, String> attributeMap) {
        copyElementWithAttributes(reader,
                new CompactWriter(writer, new NoNameCoder()),
                attributeMap);

        XmlPullParser parser;
        try {
            parser = XmlPullParserFactory.newInstance()
                    .newPullParser();
        } catch (XmlPullParserException e) {
            throw new ConversionException("Unable to create XmlPullParser, cannot parse XML.", e);
        }

        try {
            // NOTE: must specify encoding here, otherwise the platform default
            // encoding will be used which will not always work
            return new XppReader(new InputStreamReader(IOUtils.toInputStream(writer.toString(),
                    StandardCharsets.UTF_8.name())), parser);
        } catch (IOException e) {
            LOGGER.debug("Unable create reader with UTF-8 encoding, Exception {}", e);
            return new XppReader(new InputStreamReader(IOUtils.toInputStream(writer.toString())),
                    parser);
        }
    }

    /**
     * Copies the namespace declarations on the XML element {@code reader} is currently at into
     * {@code context}. The namespace declarations will be available in {@code context} at the key
     * {@link CswConstants#NAMESPACE_DECLARATIONS}. The new namespace declarations will be added to any
     * existing ones already in {@code context}.
     *
     * @param reader  the reader currently at the XML element with namespace declarations you want
     *                to copy
     * @param context the {@link UnmarshallingContext} that the namespace declarations will be
     *                copied to
     */
    public static void copyXmlNamespaceDeclarationsIntoContext(HierarchicalStreamReader reader,
            UnmarshallingContext context) {
        @SuppressWarnings("unchecked")
        Map<String, String> namespaces =
                (Map<String, String>) context.get(CswConstants.NAMESPACE_DECLARATIONS);

        if (namespaces == null) {
            namespaces = new HashMap<>();
        }

        @SuppressWarnings("unchecked")
        Iterator<String> attributeNames = reader.getAttributeNames();
        while (attributeNames.hasNext()) {
            String name = attributeNames.next();
            if (StringUtils.startsWith(name, CswConstants.XMLNS)) {
                String attributeValue = reader.getAttribute(name);
                namespaces.put(name, attributeValue);
            }
        }
        if (!namespaces.isEmpty()) {
            context.put(CswConstants.NAMESPACE_DECLARATIONS, namespaces);
        }
    }
}