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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.net.URL;
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import java.util.Iterator;
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import java.util.LinkedList;
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import java.util.Queue;
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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.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.w3c.dom.Node;
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import org.xml.sax.InputSource;
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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 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 Queue<String> queue;
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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 XPathExpression xprResultTotalPath;
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private XPathExpression xprResumptionPath;
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private String queryFormat;
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private String querySize;
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/*
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*
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*/
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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 int resultSizeValue,
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final String queryParams
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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.resultSizeValue = resultSizeValue;
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this.queryParams = queryParams;
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queryFormat = (resultFormatParam!="")? "&" + resultFormatParam + "=" + resultFormatValue : "";
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querySize = (resultSizeParam!="")? "&" + resultSizeParam + "=" + resultSizeValue : "";
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try {
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initXmlTransformation(resultTotalXpath, resumptionXpath);
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}catch(Exception exp) {
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throw new IllegalStateException("xml transformation init failed: " + exp.getMessage());
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}
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initQueue();
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updateQueue();
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}
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private void initXmlTransformation(String resultTotalXpath, String resumptionXpath) throws TransformerConfigurationException, XPathExpressionException{
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String resumpXpath = (resumptionXpath=="") ? "/" : resumptionXpath;
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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(resumpXpath);
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}
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private void initQueue() {
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queue = new LinkedList<String>();
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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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private void updateQueue() {
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String query = baseUrl + "?" + queryParams + querySize + "&" + resumptionParam + "=" + resumptionStr + queryFormat;
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System.out.println("query: " + query);
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queue.add(query);
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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 (queue.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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// TODO Auto-generated method stub
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String nextQuery = queue.remove();
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String resultJson;
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String resultXml = "";
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try {
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resultStream = new URL(nextQuery).openStream();
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if(resultFormatValue == "json"){
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resultJson = IOUtils.toString(resultStream,"UTF-8");
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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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// System.out.println(resultXml);
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resultStream = IOUtils.toInputStream(resultXml,"UTF-8");
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}
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InputSource inSource = new InputSource(resultStream);
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Node resultNode = (Node) xpath.evaluate("/", inSource, XPathConstants.NODE);
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resumptionInt += resultSizeValue;
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if(resumptionType=="scan"){ resumptionStr = xprResumptionPath.evaluate(resultNode);}
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if(resumptionType=="count"){ 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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System.out.println("resultTotal: " + resultTotal);
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}
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System.out.println("resultTotal: " + resultTotal);
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System.out.println("resInt: " + resumptionInt);
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if (resumptionInt < resultTotal) {
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updateQueue();
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}
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return resultXml;
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}catch(Exception exc) {
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exc.printStackTrace(System.err);
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throw new IllegalStateException("collection failed: " + exc.getMessage());
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}
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}
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}
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