fix: download linked objects in a WFS using "resolvedepth"

Using "resolvedepth" when trying to download data via WFS is now downloading the linked objects.
As the requested hits to a WFS is better to be setup to UNKNOWN_SIZE, so the size comes as well to be always UNKNOWN_SIZE, the code related to hits and size has been removed and the related methods have been changed accordingly.

ING-4128

io/plugins/eu.esdihumboldt.hale.io.gml/src/eu/esdihumboldt/hale/io/gml/reader/internal/wfs/WfsBackedGmlInstanceCollection.java

@@ -42,6 +42,7 @@
 import eu.esdihumboldt.hale.common.instance.model.InstanceCollection;
 import eu.esdihumboldt.hale.common.instance.model.InstanceReference;
 import eu.esdihumboldt.hale.common.instance.model.InstanceResolver;
+import eu.esdihumboldt.hale.common.instance.model.ResourceIterator;
 import eu.esdihumboldt.hale.common.instance.model.ext.InstanceIterator;
 import eu.esdihumboldt.hale.common.instance.model.impl.FilteredInstanceCollection;
 import eu.esdihumboldt.hale.common.instance.model.impl.IndexInstanceReference;
@@ -101,7 +102,8 @@ public class WfsBackedGmlInstanceCollection implements InstanceCollection {
 	// Number of features to retrieve at most with one WFS GetFeature request
 	private final int featuresPerRequest;
 
-	private final int size;
+	private boolean emptyInitialized = false;
+	private boolean empty = false;
 
 	// Parameters needed for instantiation of GmlInstanceCollection
 	private final TypeIndex sourceSchema;
@@ -225,41 +227,6 @@ public WfsBackedGmlInstanceCollection(LocatableInputSupplier<? extends InputStre
 			}
 		}
 
-		// Use primordial URI and issue "hits" request to check if the WFS will
-		// return anything at all
-		int hits;
-		if (ignoreNumberMatched) {
-			hits = UNKNOWN_SIZE;
-		}
-		else {
-			try {
-				hits = requestHits(primordialUri);
-			} catch (WFSException e) {
-				log.debug(MessageFormat.format(
-						"Failed to perform hits query (REQUESTTYPE=hits): {0}", e.getMessage()), e);
-				hits = UNKNOWN_SIZE;
-			}
-		}
-
-		switch (wfsVersion) {
-		case "1.1.0":
-			// The "numberOfFeatures" reported by a 1.1.0 WFS may be smaller
-			// than the actual number of features matches by the query if the
-			// number of features returned per query is limited on the server
-			// side. Therefore do not rely on it as a size information here.
-			this.size = UNKNOWN_SIZE;
-			break;
-		case "2.0.0":
-		case "2.0.2":
-			// The "numberMatched" reported by a 2.0.0/2.0.2 WFS should be
-			// number of features matched by the query. If hits equals
-			// UNKNOWN_SIZE then size is also set to that value
-			this.size = isLimited() ? Math.min(maxNumberOfFeatures, hits) : hits;
-			break;
-		default:
-			this.size = UNKNOWN_SIZE;
-		}
-
 		if (featuresPerRequest != UNLIMITED && featuresPerRequest <= 0) {
 			throw new IllegalArgumentException(MessageFormat.format(
 					"featuresPerRequest must be a positive integer or {0} to disable pagination",
@@ -288,15 +255,15 @@ public void setMaxNumberOfFeatures(int maxNumberOfFeatures) {
 	 */
 	@Override
 	public boolean hasSize() {
-		return size != UNKNOWN_SIZE;
+		return false;
 	}
 
 	/**
 	 * @see InstanceCollection#size()
 	 */
 	@Override
 	public int size() {
-		return size;
+		return UNKNOWN_SIZE;
 	}
 
 	/**
@@ -312,7 +279,18 @@ public WfsBackedGmlInstanceIterator iterator() {
 	 */
 	@Override
 	public boolean isEmpty() {
-		return size == 0;
+		if (!emptyInitialized) {
+			ResourceIterator<Instance> it = iterator();
+			try {
+				empty = !it.hasNext();
+			} finally {
+				it.close();
+			}
+
+			emptyInitialized = true;
+		}
+
+		return empty;
 	}
 
 	/**
@@ -372,21 +350,6 @@ public Instance getInstance(InstanceReference reference) {
 		}
 	}
 
-	private int requestHits(URI requestUri) throws WFSException {
-		URIBuilder builder = new URIBuilder(requestUri);
-		builder.addParameter("RESULTTYPE", "hits");
-
-		InputStream in;
-		try {
-			in = builder.build().toURL().openStream();
-		} catch (IOException | URISyntaxException e) {
-			throw new WFSException(
-					MessageFormat.format("Unable to execute WFS request: {0}", e.getMessage()), e);
-		}
-
-		return FeatureCollectionHelper.getNumberOfFeatures(in);
-	}
-
 	private String getMaxFeaturesParameterName(String version) {
 		// XXX Use WFSVersion
 		switch (version) {
@@ -556,9 +519,8 @@ public boolean hasNext() {
 		 *         number of results reported by the WFS.
 		 */
 		protected boolean isFeatureLimitReached() {
-			return (maxNumberOfFeatures != UNLIMITED
-					&& totalFeaturesProcessed >= maxNumberOfFeatures)
-					|| (size != UNKNOWN_SIZE && totalFeaturesProcessed >= size);
+			return maxNumberOfFeatures != UNLIMITED
+					&& totalFeaturesProcessed >= maxNumberOfFeatures;
 		}
 
 		/**