org.opencastproject.oaipmh.harvester.ListRecordsResponse.java Source code

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Here is the source code for org.opencastproject.oaipmh.harvester.ListRecordsResponse.java

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/**
 *  Copyright 2009, 2010 The Regents of the University of California
 *  Licensed under the Educational Community 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.osedu.org/licenses/ECL-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.opencastproject.oaipmh.harvester;

import org.opencastproject.util.data.Option;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import java.util.Iterator;
import java.util.NoSuchElementException;

import static org.apache.commons.lang.StringUtils.trimToNull;
import static org.opencastproject.util.data.Option.option;

/**
 * The "ListRecords" response.
 * See <a href="http://www.openarchives.org/OAI/openarchivesprotocol.html#ListRecords">4.5 ListRecords</a> for further
 * information.
 * <p/>
 * todo implement missing element accessors
 */
public class ListRecordsResponse extends OaiPmhResponse {

    public ListRecordsResponse(Document doc) {
        super(doc);
    }

    /**
     * Get the content of all metadata elements in the current response.
     */
    public NodeList getMetadataElems() {
        return xpathNodeList("/oai20:OAI-PMH/oai20:ListRecords/oai20:record/oai20:metadata/*[1]");
    }

    /**
     * Get all records in the current response.
     * <pre>
     *  &lt;record&gt;
     *    &lt;header&gt;...
     *    &lt;/header&gt;
     *    &lt;metadata&gt;...
     *    &lt;/metadata&gt;
     *  &lt;/record&gt;
     * </pre>
     */
    public NodeList getRecords() {
        return xpathNodeList("/oai20:OAI-PMH/oai20:ListRecords/oai20:record");
    }

    /**
     * Extract the content, i.e. the first child node, of the metadata node of a record.
     * <pre>
     *  &lt;record&gt;
     *    &lt;header&gt;...
     *    &lt;/header&gt;
     *    &lt;metadata&gt;
     *      &lt;myMd&gt;
     *      &lt;/myMd&gt;
     *    &lt;/metadata&gt;
     *  &lt;/record&gt;
     *
     *  =&gt;
     *
     *  &lt;myMd&gt;
     *  &lt;/myMd&gt;
     * </pre>
     */
    public static Node metadataOfRecord(Node recordNode) {
        return xpathNode(createXPath(), recordNode, "oai20:metadata/*[1]");
    }

    /**
     * Get all records performing a complete request resuming any partial responses.
     */
    public static Iterable<Node> getAllRecords(final ListRecordsResponse first,
            final OaiPmhRepositoryClient client) {
        return new Iterable<Node>() {
            @Override
            public Iterator<Node> iterator() {
                return new ResponseIterator(first) {
                    @Override
                    protected OaiPmhRepositoryClient getClient() {
                        return client;
                    }

                    @Override
                    protected NodeList extractNodes(ListRecordsResponse response) {
                        return response.getRecords();
                    }
                };
            }
        };
    }

    /**
     * Get all metadata performing a complete request resuming any partial responses.
     */
    public static Iterable<Node> getAllMetadataElems(final ListRecordsResponse first,
            final OaiPmhRepositoryClient client) {
        return new Iterable<Node>() {
            @Override
            public Iterator<Node> iterator() {
                return new ResponseIterator(first) {
                    @Override
                    protected OaiPmhRepositoryClient getClient() {
                        return client;
                    }

                    @Override
                    protected NodeList extractNodes(ListRecordsResponse response) {
                        return response.getMetadataElems();
                    }
                };
            }
        };
    }

    public String getMetadataPrefix() {
        return xpathString("/oai20:OAI-PMH/oai20:request/@metadataPrefix");
    }

    public Option<String> getResumptionToken() {
        return option(trimToNull(xpathString("/oai20:OAI-PMH/oai20:ListRecords/oai20:resumptionToken/text()")));
    }

    //

    private abstract static class ResponseIterator implements Iterator<Node> {

        private NodeList elems;
        private Option<String> token;
        private String metadataPrefix;
        private int i;

        ResponseIterator(ListRecordsResponse response) {
            initIteration(response);
        }

        private void initIteration(ListRecordsResponse response) {
            elems = extractNodes(response);
            token = response.getResumptionToken();
            metadataPrefix = response.getMetadataPrefix();
            i = 0;
        }

        protected abstract OaiPmhRepositoryClient getClient();

        /**
         * Extract the relevant part of the response.
         */
        protected abstract NodeList extractNodes(ListRecordsResponse response);

        @Override
        public boolean hasNext() {
            return hasNextInCurrent() || token.isSome();
        }

        @Override
        public Node next() {
            if (!hasNext())
                throw new NoSuchElementException();
            if (!hasNextInCurrent()) {
                // get next document
                initIteration(getClient().resumeListRecords(metadataPrefix, token.get()));
            }
            return elems.item(i++);
        }

        @Override
        public void remove() {
            throw new UnsupportedOperationException();
        }

        private boolean hasNextInCurrent() {
            return i < elems.getLength();
        }
    }
}