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java/javax/websocket/ContainerProvider.java

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 javax.websocket;
+
+import java.lang.reflect.InvocationTargetException;
+import java.util.Iterator;
+import java.util.ServiceLoader;
+
+/**
+ * Use the {@link ServiceLoader} mechanism to provide instances of the WebSocket
+ * client container.
+ */
+public abstract class ContainerProvider {
+
+    private static final String DEFAULT_PROVIDER_CLASS_NAME =
+            "org.apache.tomcat.websocket.WsWebSocketContainer";
+
+    /**
+     * Create a new container used to create outgoing WebSocket connections.
+     *
+     * @return A newly created container.
+     */
+    public static WebSocketContainer getWebSocketContainer() {
+        WebSocketContainer result = null;
+
+        ServiceLoader<ContainerProvider> serviceLoader =
+                ServiceLoader.load(ContainerProvider.class);
+        Iterator<ContainerProvider> iter = serviceLoader.iterator();
+        while (result == null && iter.hasNext()) {
+            result = iter.next().getContainer();
+        }
+
+        // Fall-back. Also used by unit tests
+        if (result == null) {
+            try {
+                @SuppressWarnings("unchecked")
+                Class<WebSocketContainer> clazz =
+                        (Class<WebSocketContainer>) Class.forName(
+                                DEFAULT_PROVIDER_CLASS_NAME);
+                result = clazz.getConstructor().newInstance();
+            } catch (ClassNotFoundException | InstantiationException | IllegalAccessException |
+                    IllegalArgumentException | InvocationTargetException | NoSuchMethodException |
+                    SecurityException e) {
+                // No options left. Just return null.
+            }
+        }
+        return result;
+    }
+
+    protected abstract WebSocketContainer getContainer();
+}