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package eu.dnetlib.data.collector.plugins.oai;
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import java.io.StringReader;
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import java.io.UnsupportedEncodingException;
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import java.net.URLEncoder;
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import java.util.Iterator;
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import java.util.Queue;
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import java.util.concurrent.PriorityBlockingQueue;
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import org.apache.commons.logging.Log;
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import org.apache.commons.logging.LogFactory;
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import org.dom4j.Document;
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import org.dom4j.DocumentException;
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import org.dom4j.Node;
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import org.dom4j.io.SAXReader;
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import eu.dnetlib.data.collector.plugins.HttpConnector;
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import eu.dnetlib.data.collector.rmi.CollectorServiceException;
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import eu.dnetlib.data.collector.plugins.oai.engine.XmlCleaner;
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public class OaiIterator implements Iterator<String> {
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private static final Log log = LogFactory.getLog(OaiIterator.class); // NOPMD by marko on 11/24/08 5:02 PM
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private Queue<String> queue = new PriorityBlockingQueue<String>();
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private SAXReader reader = new SAXReader();
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private String baseUrl;
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private String set;
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private String mdFormat;
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private String fromDate;
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private String untilDate;
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private String token;
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private boolean started;
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private HttpConnector httpConnector;
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public OaiIterator(final String baseUrl, final String mdFormat, final String set, final String fromDate, final String untilDate, final HttpConnector httpConnector) {
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this.baseUrl = baseUrl;
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this.mdFormat = mdFormat;
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this.set = set;
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this.fromDate = fromDate;
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this.untilDate = untilDate;
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this.started = false;
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this.httpConnector = httpConnector;
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}
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private void verifyStarted() {
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if (!this.started) {
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this.started = true;
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try {
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this.token = firstPage();
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} catch (CollectorServiceException e) {
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throw new RuntimeException(e);
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}
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}
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}
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@Override
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public boolean hasNext() {
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synchronized (queue) {
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verifyStarted();
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return !queue.isEmpty();
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}
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}
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@Override
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public String next() {
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synchronized (queue) {
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verifyStarted();
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final String res = queue.poll();
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while (queue.isEmpty() && (token != null) && !token.isEmpty()) {
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try {
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token = otherPages(token);
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} catch (CollectorServiceException e) {
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throw new RuntimeException(e);
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}
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}
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return res;
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}
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}
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@Override
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public void remove() {}
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private String firstPage() throws CollectorServiceException {
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try {
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String url = baseUrl + "?verb=ListRecords&metadataPrefix=" + URLEncoder.encode(mdFormat,"UTF-8");
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if ((set != null) && !set.isEmpty()) {
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url += "&set=" + URLEncoder.encode(set,"UTF-8");
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}
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if ((fromDate != null) && fromDate.matches("\\d{4}-\\d{2}-\\d{2}")) {
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url += "&from=" + URLEncoder.encode(fromDate,"UTF-8");
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}
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if ((untilDate != null) && untilDate.matches("\\d{4}-\\d{2}-\\d{2}")) {
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url += "&until=" + URLEncoder.encode(untilDate,"UTF-8");
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}
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log.info("Start harvesting using url: " + url);
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return downloadPage(url);
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} catch(UnsupportedEncodingException e) {
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throw new CollectorServiceException(e);
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}
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}
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private String otherPages(final String resumptionToken) throws CollectorServiceException {
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try {
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return downloadPage(baseUrl + "?verb=ListRecords&resumptionToken=" + URLEncoder.encode(resumptionToken,"UTF-8"));
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} catch (UnsupportedEncodingException e) {
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throw new CollectorServiceException(e);
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}
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}
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private String downloadPage(final String url) throws CollectorServiceException {
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final String xml = httpConnector.getInputSource(url);
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Document doc;
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try {
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doc = reader.read(new StringReader(xml));
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} catch (DocumentException e) {
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log.debug("Error parsing xml, I try to clean it: " + xml, e);
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final String cleaned = XmlCleaner.cleanAllEntities(xml);
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try {
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doc = reader.read(new StringReader(cleaned));
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} catch (DocumentException e1) {
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throw new CollectorServiceException("Error parsing cleaned document:" + cleaned, e1);
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}
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}
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final Node errorNode = doc.selectSingleNode("/*[local-name()='OAI-PMH']/*[local-name()='error']");
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if (errorNode != null) {
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final String code = errorNode.valueOf("@code");
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if ("noRecordsMatch".equalsIgnoreCase(code.trim())) {
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log.warn("noRecordsMatch for oai call: " + url);
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return null;
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} else {
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throw new CollectorServiceException(code + " - " + errorNode.getText());
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}
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}
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for (Object o : doc.selectNodes("//*[local-name()='ListRecords']/*[local-name()='record']")) {
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queue.add(((Node) o).asXML());
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}
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return doc.valueOf("//*[local-name()='resumptionToken']");
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}
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}
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