Fix ClassCastException in hasProtocol method

smack-experimental/src/main/java/org/jivesoftware/smackx/eme/element/ExplicitMessageEncryptionElement.java

@@ -155,11 +155,12 @@ public class ExplicitMessageEncryptionElement implements ExtensionElement {
      * @return true if message has EME element for that namespace, otherwise false
      */
     public static boolean hasProtocol(Message message, String protocolNamespace) {
-        List<ExplicitMessageEncryptionElement> emeElements = message.getExtension(
+        List<ExtensionElement> extensionElements = message.getExtensions(
                 ExplicitMessageEncryptionElement.ELEMENT,
                 ExplicitMessageEncryptionElement.NAMESPACE);
 
-        for (ExplicitMessageEncryptionElement e : emeElements) {
+        for (ExtensionElement extensionElement : extensionElements) {
+            ExplicitMessageEncryptionElement e = (ExplicitMessageEncryptionElement) extensionElement;
             if (e.getEncryptionNamespace().equals(protocolNamespace)) {
                 return true;
             }

smack-experimental/src/test/java/org/jivesoftware/smackx/eme/ExplicitMessageEncryptionElementTest.java

@@ -0,0 +1,77 @@
+/**
+ *
+ * Copyright 2018 Paul Schaub
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.jivesoftware.smackx.eme;
+
+import static junit.framework.TestCase.assertEquals;
+import static junit.framework.TestCase.assertFalse;
+import static junit.framework.TestCase.assertNull;
+import static junit.framework.TestCase.assertTrue;
+
+import java.util.List;
+
+import org.jivesoftware.smack.packet.ExtensionElement;
+import org.jivesoftware.smack.packet.Message;
+import org.jivesoftware.smack.test.util.SmackTestSuite;
+import org.jivesoftware.smackx.eme.element.ExplicitMessageEncryptionElement;
+
+import org.junit.Test;
+
+public class ExplicitMessageEncryptionElementTest extends SmackTestSuite {
+
+    @Test
+    public void addToMessageTest() {
+        Message message = new Message();
+
+        // Check inital state (no elements)
+        assertNull(ExplicitMessageEncryptionElement.from(message));
+        assertFalse(ExplicitMessageEncryptionElement.hasProtocol(message,
+                ExplicitMessageEncryptionElement.ExplicitMessageEncryptionProtocol.omemoVAxolotl));
+
+        List<ExtensionElement> extensions = message.getExtensions();
+        assertEquals(0, extensions.size());
+
+        // Add OMEMO
+        ExplicitMessageEncryptionElement.set(message,
+                ExplicitMessageEncryptionElement.ExplicitMessageEncryptionProtocol.omemoVAxolotl);
+        extensions = message.getExtensions();
+        assertEquals(1, extensions.size());
+        assertTrue(ExplicitMessageEncryptionElement.hasProtocol(message,
+                ExplicitMessageEncryptionElement.ExplicitMessageEncryptionProtocol.omemoVAxolotl));
+        assertTrue(ExplicitMessageEncryptionElement.hasProtocol(message,
+                ExplicitMessageEncryptionElement.ExplicitMessageEncryptionProtocol.omemoVAxolotl.getNamespace()));
+        assertFalse(ExplicitMessageEncryptionElement.hasProtocol(message,
+                ExplicitMessageEncryptionElement.ExplicitMessageEncryptionProtocol.openpgpV0));
+        assertFalse(ExplicitMessageEncryptionElement.hasProtocol(message,
+                ExplicitMessageEncryptionElement.ExplicitMessageEncryptionProtocol.openpgpV0.getNamespace()));
+
+        ExplicitMessageEncryptionElement.set(message,
+                ExplicitMessageEncryptionElement.ExplicitMessageEncryptionProtocol.openpgpV0);
+        extensions = message.getExtensions();
+        assertEquals(2, extensions.size());
+        assertTrue(ExplicitMessageEncryptionElement.hasProtocol(message,
+                ExplicitMessageEncryptionElement.ExplicitMessageEncryptionProtocol.openpgpV0));
+        assertTrue(ExplicitMessageEncryptionElement.hasProtocol(message,
+                ExplicitMessageEncryptionElement.ExplicitMessageEncryptionProtocol.omemoVAxolotl));
+
+        // Check, if adding additional OMEMO wont add another element
+        ExplicitMessageEncryptionElement.set(message,
+                ExplicitMessageEncryptionElement.ExplicitMessageEncryptionProtocol.omemoVAxolotl);
+
+        extensions = message.getExtensions();
+        assertEquals(2, extensions.size());
+    }
+}