[dwdunwetter] Improve server problem handling

bundles/org.openhab.binding.dwdunwetter/src/main/java/org/openhab/binding/dwdunwetter/internal/dto/DwdWarningDataAccess.java

@@ -51,10 +51,14 @@ public String getDataFromEndpoint(String cellId) {
             stringBuilder.append("&CQL_FILTER=");
             stringBuilder.append(URLEncoder.encode("WARNCELLID LIKE '" + cellId + "'", StandardCharsets.UTF_8));
             logger.debug("Refreshing Data for cell {}", cellId);
-            String rawData = HttpUtil.executeUrl("GET", stringBuilder.toString(), 5000);
+            String rawData = getByURL(stringBuilder.toString());
             logger.trace("Raw request: {}", stringBuilder);
             logger.trace("Raw response: {}", rawData);
 
+            if (rawData == null || !rawData.startsWith("<?xml") || !rawData.contains("FeatureCollection")) {
+                logger.warn("Communication error occurred while getting data, response is not in expected XML-format");
+                return "";
+            }
             return rawData;
         } catch (IOException e) {
             logger.warn("Communication error occurred while getting data: {}", e.getMessage());
@@ -63,4 +67,8 @@ public String getDataFromEndpoint(String cellId) {
 
         return "";
     }
+
+    public String getByURL(String url) throws IOException {
+        return HttpUtil.executeUrl("GET", url, 5000);
+    }
 }

bundles/org.openhab.binding.dwdunwetter/src/main/java/org/openhab/binding/dwdunwetter/internal/dto/DwdWarningsData.java

@@ -306,6 +306,6 @@ public void updateCache() {
      */
     protected void setDataAccess(DwdWarningDataAccess dataAccess) {
         dataAccessCached = new ExpiringCache<>(Duration.ofMinutes(MIN_REFRESH_WAIT_MINUTES),
-                () -> dataAccess.getDataFromEndpoint(""));
+                () -> dataAccess.getDataFromEndpoint("TestCity"));
     }
 }

bundles/org.openhab.binding.dwdunwetter/src/main/resources/OH-INF/addon/addon.xml

@@ -7,5 +7,5 @@
 	<name>DWD Unwetter Binding</name>
 	<description>This is the binding for DWD Unwetter.</description>
 	<connection>cloud</connection>
-
+	<countries>de</countries>
 </addon:addon>

bundles/org.openhab.binding.dwdunwetter/src/test/java/org/openhab/binding/dwdunwetter/internal/dto/DwdWarningsDataAccessTest.java

@@ -0,0 +1,76 @@
+/**
+ * Copyright (c) 2010-2023 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.binding.dwdunwetter.internal.dto;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.StringWriter;
+import java.nio.charset.StandardCharsets;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Tests for {@link org.openhab.binding.dwdunwetter.internal.dto.DwdWarningsDataAccess}
+ *
+ * @author Leo Siepel - Initial contribution
+ */
+public class DwdWarningsDataAccessTest {
+    private TestDataProvider testDataProvider = new TestDataProvider();
+
+    @BeforeEach
+    public void setUp() throws IOException {
+        this.testDataProvider = new TestDataProvider();
+        loadXmlFromFile();
+    }
+
+    @Test
+    public void testNullOrBlank() {
+        assertEquals(testDataProvider.getDataFromEndpoint(null), "");
+        assertEquals(testDataProvider.getDataFromEndpoint(""), "");
+    }
+
+    @Test
+    public void testInvalidResponse() {
+        TestDataProvider testDataProvider = new TestDataProvider();
+        testDataProvider.rawData = "Server is not returning xml";
+        assertEquals(testDataProvider.getDataFromEndpoint("TestCity"), "");
+    }
+
+    private void loadXmlFromFile() throws IOException {
+        InputStream stream = getClass().getResourceAsStream("warnings.xml");
+        BufferedReader reader = new BufferedReader(new InputStreamReader(stream, StandardCharsets.UTF_8));
+        String line = null;
+
+        StringWriter stringWriter = new StringWriter();
+        while ((line = reader.readLine()) != null) {
+            stringWriter.write(line);
+        }
+        reader.close();
+        testDataProvider.rawData = stringWriter.toString();
+    }
+
+    private class TestDataProvider extends DwdWarningDataAccess {
+
+        private String rawData = "";
+
+        @Override
+        public String getByURL(String url) {
+            return rawData;
+        }
+    }
+}

bundles/org.openhab.binding.dwdunwetter/src/test/java/org/openhab/binding/dwdunwetter/internal/dto/DwdWarningsDataTest.java

@@ -169,7 +169,7 @@ private class TestDataProvider extends DwdWarningDataAccess {
         private String rawData = "";
 
         @Override
-        public String getDataFromEndpoint(String cellId) {
+        public String getByURL(String url) {
             return rawData;
         }
     }