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/**
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*
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*/
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package eu.dnetlib.data.collector.plugins.rest;
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import java.io.InputStream;
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import java.io.StringWriter;
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import java.net.URL;
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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 javax.xml.transform.OutputKeys;
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import javax.xml.transform.Transformer;
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import javax.xml.transform.TransformerConfigurationException;
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import javax.xml.transform.TransformerFactory;
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import javax.xml.transform.dom.DOMSource;
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import javax.xml.transform.stream.StreamResult;
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import javax.xml.xpath.XPath;
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import javax.xml.xpath.XPathConstants;
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import javax.xml.xpath.XPathExpression;
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import javax.xml.xpath.XPathExpressionException;
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import javax.xml.xpath.XPathFactory;
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import org.apache.commons.io.IOUtils;
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import org.apache.commons.lang3.StringUtils;
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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.w3c.dom.Node;
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import org.w3c.dom.NodeList;
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import org.xml.sax.InputSource;
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import eu.dnetlib.data.collector.plugins.oai.OaiIterator;
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import eu.dnetlib.data.collector.rmi.CollectorServiceException;
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/**
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* @author Jochen Schirrwagen, Aenne Loehden
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*
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*/
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public class RestIterator 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 static final String wrapName = "recordWrap";
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private String baseUrl;
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private String resumptionType;
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private String resumptionParam;
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private String resultFormatValue;
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private String queryParams;
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private int resultSizeValue = 100;
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private int resumptionInt = 0; // integer resumption token (first record to harvest)
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private int resultTotal = -1;
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private String resumptionStr = Integer.toString(resumptionInt); // string resumption token (first record to harvest or token scanned from results)
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private InputStream resultStream;
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private Transformer transformer;
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private XPath xpath;
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private String query;
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private XPathExpression xprResultTotalPath;
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private XPathExpression xprResumptionPath;
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private XPathExpression xprEntity;
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private String queryFormat;
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private String querySize;
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private Queue<String> recordQueue = new PriorityBlockingQueue<String>();
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public RestIterator(
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final String baseUrl,
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final String resumptionType,
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final String resumptionParam,
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final String resumptionXpath,
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final String resultTotalXpath,
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final String resultFormatParam,
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final String resultFormatValue,
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final String resultSizeParam,
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final String queryParams,
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final String entityXpath
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) {
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this.baseUrl = baseUrl;
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this.resumptionType = resumptionType;
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this.resumptionParam = resumptionParam;
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this.resultFormatValue = resultFormatValue;
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this.queryParams = queryParams;
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queryFormat = StringUtils.isNotBlank(resultFormatParam) ? "&" + resultFormatParam + "=" + resultFormatValue : "";
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querySize = StringUtils.isNotBlank(resultSizeParam) ? "&" + resultSizeParam + "=" + resultSizeValue : "";
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try {
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initXmlTransformation(resultTotalXpath, resumptionXpath, entityXpath);
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} catch(Exception e) {
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throw new IllegalStateException("xml transformation init failed: " + e.getMessage());
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}
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initQueue();
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}
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private void initXmlTransformation(String resultTotalXpath, String resumptionXpath, String entityXpath) throws TransformerConfigurationException, XPathExpressionException{
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transformer = TransformerFactory.newInstance().newTransformer();
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transformer.setOutputProperty(OutputKeys.INDENT,"yes");
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transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount","3");
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xpath = XPathFactory.newInstance().newXPath();
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xprResultTotalPath = xpath.compile(resultTotalXpath);
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xprResumptionPath = xpath.compile(StringUtils.isBlank(resumptionXpath) ? "/" : resumptionXpath);
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xprEntity = xpath.compile(entityXpath);
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}
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private void initQueue() {
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query = baseUrl + "?" + queryParams + querySize + "&" + resumptionParam + "=" + resumptionStr + queryFormat;
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}
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private void disconnect() {
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// TODO close inputstream
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}
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/* (non-Javadoc)
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* @see java.util.Iterator#hasNext()
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*/
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@Override
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public boolean hasNext() {
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if (recordQueue.isEmpty() && query.isEmpty()) {
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disconnect();
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return false;
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} else {
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return true;
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}
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}
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/* (non-Javadoc)
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* @see java.util.Iterator#next()
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*/
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@Override
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public String next() {
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synchronized (recordQueue) {
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while (recordQueue.isEmpty() && !query.isEmpty() ) {
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try {
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query = downloadPage(query);
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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 recordQueue.poll();
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}
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}
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/*
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* download page and return nextQuery
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*/
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private String downloadPage(String query) throws CollectorServiceException{
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String resultJson;
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String resultXml = "";
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String nextQuery = "";
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try {
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resultStream = new URL(query).openStream();
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if("json".equals(resultFormatValue)){
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resultJson = IOUtils.toString(resultStream,"UTF-8");
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//TODO move regex definitions as constant fields
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// pre-clean json - rid spaces of element names (misinterpreted as elements with attributes in xml)
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while(resultJson.matches(".*\"([^\"]*)\\s+([^\"]*)\":.*")){
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resultJson = resultJson.replaceAll("\"([^\"]*)\\s+([^\"]*)\":", "\"$1_$2\":");
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}
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org.json.JSONObject jsonObject = new org.json.JSONObject(resultJson);
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resultXml = org.json.XML.toString(jsonObject,wrapName); // wrap xml in single root element
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// log.info(resultXml);
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resultStream = IOUtils.toInputStream(resultXml,"UTF-8");
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}
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Node resultNode = (Node) xpath.evaluate("/", new InputSource(resultStream), XPathConstants.NODE);
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NodeList nodeList = (NodeList) xprEntity.evaluate(resultNode, XPathConstants.NODESET);
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for (int i = 0; i < nodeList.getLength(); i++) {
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StringWriter sw = new StringWriter();
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transformer.transform(new DOMSource(nodeList.item(i)), new StreamResult(sw));
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recordQueue.add(sw.toString());
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}
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resumptionInt += resultSizeValue;
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if("scan".equals(resumptionType)) { resumptionStr = xprResumptionPath.evaluate(resultNode);}
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if("count".equals(resumptionType)){ resumptionStr = Integer.toString(resumptionInt); }
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if (resultTotal == -1) {
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resultTotal = Integer.parseInt(xprResultTotalPath.evaluate(resultNode));
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log.info("resultTotal: " + resultTotal);
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}
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log.info("resultTotal: " + resultTotal);
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log.info("resInt: " + resumptionInt);
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if (resumptionInt < resultTotal) {
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nextQuery = baseUrl + "?" + queryParams + querySize + "&" + resumptionParam + "=" + resumptionStr + queryFormat;
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} else
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nextQuery = "";
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return nextQuery;
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} catch(Exception e) {
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log.error(e);
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throw new IllegalStateException("collection failed: " + e.getMessage());
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}
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}
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}
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