Checking if files are present before parsing them

src/main/java/eu/simstadt/regionchooser/fast_xml_parser/CityGmlIterator.java

@@ -2,6 +2,7 @@
 
 import java.io.IOException;
 import java.nio.file.Files;
+import java.nio.file.NoSuchFileException;
 import java.nio.file.Path;
 import java.util.Iterator;
 import java.util.logging.Logger;
@@ -36,10 +37,17 @@ public class CityGmlIterator implements Iterable<CityObjectMember>
 	 * Based on VTD XML, it provides a Building iterator.
 	 *
 	 */
-	public CityGmlIterator(Path citygmlPath) throws XPathParseException {
+	public CityGmlIterator(Path citygmlPath) throws XPathParseException, IOException {
 		this.citygmlPath = citygmlPath;
+		if (!Files.isRegularFile(citygmlPath)) {
+			throw new NoSuchFileException(citygmlPath.toString());
+		}
 		VTDGen parser = new VTDGen();
-		parser.parseFile(citygmlPath.toString(), false);
+		// VTDGen.parseFile() swallows IOExceptions internally and returns false instead of throwing.
+		boolean parsed = parser.parseFile(citygmlPath.toString(), false);
+		if (!parsed) {
+			throw new IOException("Failed to parse " + citygmlPath);
+		}
 		this.navigator = parser.getNav();
 		this.buildingsFinder = new AutoPilot(navigator);
 		buildingsFinder.selectXPath(CityObjectMember.XPATH_PATTERN);

src/main/java/eu/simstadt/regionchooser/fast_xml_parser/ConvexHullCalculator.java

@@ -66,12 +66,12 @@ public static Geometry calculateFromCityGML(Path citygmlPath) throws XPathParseE
 	 * @return area of convex hull, in the same unit as original file. Hopefully m², but possibly ft² or even °².
 	 * @throws XPathParseException
 	 */
-	public static double calculateArea(Path citygmlPath) throws XPathParseException {
+	public static double calculateArea(Path citygmlPath) throws XPathParseException, IOException {
 		Polygon originalConvexHull = getConvexHull(citygmlPath);
 		return originalConvexHull.getArea();
 	}
 
-	private static Polygon getConvexHull(Path citygmlPath) throws XPathParseException {
+	private static Polygon getConvexHull(Path citygmlPath) throws XPathParseException, IOException {
 		GeometryFactory geometryFactory = new GeometryFactory();
 		ArrayList<Coordinate> allPoints = new ArrayList<>();
 		CityGmlIterator citygml = new CityGmlIterator(citygmlPath);

src/test/java/eu/simstadt/regionchooser/fast_xml_parser/CitygmlParserTests.java

@@ -2,7 +2,10 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
+import java.io.IOException;
+import java.nio.file.NoSuchFileException;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import org.junit.jupiter.api.Test;
@@ -15,7 +18,7 @@
 	private static final String COORDINATES_SHOULD_BE_PLAUSIBLE = "Min/Max Coordinates should be plausible";
 	private static final String COORDINATE_SHOULD_BE_A_DOUBLE = "Coordinate should be a double";
 
-	private void testNoNanInCoordinates(Path citygmlPath) throws XPathParseException {
+	private void testNoNanInCoordinates(Path citygmlPath) throws XPathParseException, IOException {
 		CityGmlIterator buildingXmlNodes = new CityGmlIterator(citygmlPath);
 		for (CityObjectMember cityObjectNode : buildingXmlNodes) {
 			assertTrue(cityObjectNode.hasCoordinates(), "Building and vegetations should have coordinates");
@@ -34,7 +37,7 @@ private void testNoNanInCoordinates(Path citygmlPath) throws XPathParseException
 	}
 
 	@Test
-	public void testExtractCoordsFromStuttgart() throws XPathParseException {
+	public void testExtractCoordsFromStuttgart() throws XPathParseException, IOException {
 		Path repo = Paths.get(REGION_CHOOSER_TESTDATA, "Stuttgart.proj");
 		Path citygmlPath = repo.resolve("Stuttgart_LOD0_LOD1_buildings_and_trees.gml");
 		testNoNanInCoordinates(citygmlPath);
@@ -51,28 +54,28 @@ public void testExtractCoordsFromStuttgart() throws XPathParseException {
 	}
 
 	@Test
-	public void testExtractCoordsFromGruenbuehl() throws XPathParseException {
+	public void testExtractCoordsFromGruenbuehl() throws XPathParseException, IOException {
 		Path repo = Paths.get(REGION_CHOOSER_TESTDATA, "Gruenbuehl.proj");
 		Path citygmlPath = repo.resolve("20140218_Gruenbuehl_LOD2_1building.gml");
 		testNoNanInCoordinates(citygmlPath);
 	}
 
 	@Test
-	public void testExtractCoordsFromMunich() throws XPathParseException {
+	public void testExtractCoordsFromMunich() throws XPathParseException, IOException {
 		Path repo = Paths.get(REGION_CHOOSER_TESTDATA, "Muenchen.proj");
 		Path citygmlPath = repo.resolve("Munich_v_1_0_0.gml");
 		testNoNanInCoordinates(citygmlPath);
 	}
 
 	@Test
-	public void testExtractCoordsFromNYC() throws XPathParseException {
+	public void testExtractCoordsFromNYC() throws XPathParseException, IOException {
 		Path repo = Paths.get(REGION_CHOOSER_TESTDATA, "NewYork.proj");
 		Path citygmlPath = repo.resolve("ManhattanSmall.gml");
 		testNoNanInCoordinates(citygmlPath);
 	}
 
 	@Test
-	public void testExtractNoCoordsFromEmptyBuilding() throws XPathParseException {
+	public void testExtractNoCoordsFromEmptyBuilding() throws XPathParseException, IOException {
 		Path repo = Paths.get(REGION_CHOOSER_TESTDATA, "Stuttgart.proj");
 		Path citygmlPath = repo.resolve("Stöckach_empty_buildings.gml");
 		CityGmlIterator buildingXmlNodes = new CityGmlIterator(citygmlPath);
@@ -85,4 +88,11 @@ public void testExtractNoCoordsFromEmptyBuilding() throws XPathParseException {
 		}
 		assertEquals(3, counter, "3 buildings should have been analyzed");
 	}
+
+	@Test
+	public void testCityGmlIteratorThrowsForMissingFile() {
+		Path citygmlPath = Paths.get(REGION_CHOOSER_TESTDATA, "Stuttgart.proj", "does_not_exist.gml");
+		assertThrows(NoSuchFileException.class, () -> new CityGmlIterator(citygmlPath),
+				"A missing CityGML file should raise a clear NoSuchFileException, not an opaque VTD-XML error");
+	}
 }