Fixes for pagination strategy looping at end of download

dhp-workflows/dhp-aggregation/src/main/java/eu/dnetlib/dhp/collection/plugin/rest/RestIterator.java

@@ -12,6 +12,8 @@ import java.util.Iterator;
 import java.util.Map;
 import java.util.Queue;
 import java.util.concurrent.PriorityBlockingQueue;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 import javax.xml.transform.OutputKeys;
 import javax.xml.transform.Transformer;
@@ -19,16 +21,10 @@ import javax.xml.transform.TransformerConfigurationException;
 import javax.xml.transform.TransformerFactory;
 import javax.xml.transform.dom.DOMSource;
 import javax.xml.transform.stream.StreamResult;
-import javax.xml.xpath.XPath;
+import javax.xml.xpath.*;
-import javax.xml.xpath.XPathConstants;
-import javax.xml.xpath.XPathExpression;
-import javax.xml.xpath.XPathExpressionException;
-import javax.xml.xpath.XPathFactory;
 
 import org.apache.commons.io.IOUtils;
 import org.apache.commons.lang3.StringUtils;
-import org.apache.http.HttpHeaders;
-import org.apache.http.entity.ContentType;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.w3c.dom.Node;
@@ -51,7 +47,6 @@ import eu.dnetlib.dhp.common.collection.HttpClientParams;
  *
  */
 public class RestIterator implements Iterator<String> {
-
 	private static final Logger log = LoggerFactory.getLogger(RestIterator.class);
 	public static final String UTF_8 = "UTF-8";
 	private static final int MAX_ATTEMPTS = 5;
@@ -60,11 +55,15 @@ public class RestIterator implements Iterator<String> {
 
 	private final String AUTHBASIC = "basic";
 
+	private static final String XML_HEADER = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>";
+	private static final String EMPTY_XML = XML_HEADER + "<" + JsonUtils.XML_WRAP_TAG + "></" + JsonUtils.XML_WRAP_TAG
+		+ ">";
+
 	private final String baseUrl;
 	private final String resumptionType;
 	private final String resumptionParam;
 	private final String resultFormatValue;
-	private String queryParams;
+	private String queryParams = "";
 	private final int resultSizeValue;
 	private int resumptionInt = 0; // integer resumption token (first record to harvest)
 	private int resultTotal = -1;
@@ -158,7 +157,12 @@ public class RestIterator implements Iterator<String> {
 	}
 
 	private void initQueue() {
-		this.query = this.baseUrl + "?" + this.queryParams + this.querySize + this.queryFormat;
+		if (queryParams.equals("") && querySize.equals("") && queryFormat.equals("")) {
+			query = baseUrl;
+		} else {
+			query = baseUrl + "?" + queryParams + querySize + queryFormat;
+		}
+
 		log.info("REST calls starting with {}", this.query);
 	}
 
@@ -219,9 +223,8 @@ public class RestIterator implements Iterator<String> {
 
 		try {
 			String resultJson;
-			String resultXml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>";
+			String resultXml = XML_HEADER;
 			String nextQuery = "";
-			final String emptyXml = resultXml + "<" + JsonUtils.XML_WRAP_TAG + "></" + JsonUtils.XML_WRAP_TAG + ">";
 			Node resultNode = null;
 			NodeList nodeList = null;
 			String qUrlArgument = "";
@@ -236,6 +239,21 @@ public class RestIterator implements Iterator<String> {
 				}
 			}
 
+			// find pagination page start number in queryParam and remove before start the first query
+			if ((resumptionType.toLowerCase().equals("pagination") || resumptionType.toLowerCase().equals("page"))
+				&& (query.contains("paginationStart="))) {
+
+				final Matcher m = Pattern.compile("paginationStart=([0-9]+)").matcher(query);
+				m.find(); // guaranteed to be true for this regex
+
+				String[] pageVal = m.group(0).split("=");
+				pagination = Integer.parseInt(pageVal[1]);
+
+				// remove page start number from queryParams
+				query = query.replaceFirst("&?paginationStart=[0-9]+", "");
+
+			}
+
 			try {
 				log.info("requesting URL [{}]", query);
 
@@ -261,7 +279,7 @@ public class RestIterator implements Iterator<String> {
 					this.resultStream = IOUtils.toInputStream(resultXml, UTF_8);
 				}
 
-				if (!(emptyXml).equalsIgnoreCase(resultXml)) {
+				if (!isEmptyXml(resultXml)) {
 					resultNode = (Node) this.xpath
 						.evaluate("/", new InputSource(this.resultStream), XPathConstants.NODE);
 					nodeList = (NodeList) this.xprEntity.evaluate(resultNode, XPathConstants.NODESET);
@@ -270,8 +288,7 @@ public class RestIterator implements Iterator<String> {
 						final StringWriter sw = new StringWriter();
 						this.transformer.transform(new DOMSource(nodeList.item(i)), new StreamResult(sw));
 						final String toEnqueue = sw.toString();
-						if ((toEnqueue == null) || StringUtils.isBlank(toEnqueue)
+						if ((toEnqueue == null) || StringUtils.isBlank(toEnqueue) || isEmptyXml(toEnqueue)) {
-							|| emptyXml.equalsIgnoreCase(toEnqueue)) {
 							log
 								.warn(
 									"The following record resulted in empty item for the feeding queue: {}", resultXml);
@@ -299,6 +316,7 @@ public class RestIterator implements Iterator<String> {
 							throw new CollectorException("Mode: discover, Param 'resultSizeValue' is less than 2");
 						}
 						qUrlArgument = qUrl.getQuery();
+
 						final String[] arrayQUrlArgument = qUrlArgument.split("&");
 						for (final String arrayUrlArgStr : arrayQUrlArgument) {
 							if (arrayUrlArgStr.startsWith(this.resumptionParam)) {
@@ -312,7 +330,7 @@ public class RestIterator implements Iterator<String> {
 							}
 						}
 
-						if (((emptyXml).equalsIgnoreCase(resultXml))
+						if (isEmptyXml(resultXml)
 							|| ((nodeList != null) && (nodeList.getLength() < this.resultSizeValue))) {
 							// resumptionStr = "";
 							if (nodeList != null) {
@@ -331,13 +349,13 @@ public class RestIterator implements Iterator<String> {
 
 					case "pagination":
 					case "page": // pagination, iterate over page numbers
-						this.pagination += 1;
+						if (nodeList != null && nodeList.getLength() > 0) {
-						if (nodeList != null) {
 							this.discoverResultSize += nodeList.getLength();
 						} else {
 							this.resultTotal = this.discoverResultSize;
 							this.pagination = this.discoverResultSize;
 						}
+						this.pagination += 1;
 						this.resumptionInt = this.pagination;
 						this.resumptionStr = Integer.toString(this.resumptionInt);
 						break;
@@ -415,6 +433,10 @@ public class RestIterator implements Iterator<String> {
 
 	}
 
+	private boolean isEmptyXml(String s) {
+		return EMPTY_XML.equalsIgnoreCase(s);
+	}
+
 	private boolean isInteger(final String s) {
 		boolean isValidInteger = false;
 		try {