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ContainerProvider.java
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ContainerProvider.java
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/*
* Copyright (c) 2018, 2020 Oracle and/or its affiliates and others.
* All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package jakarta.websocket;
import java.util.Iterator;
import java.util.ServiceConfigurationError;
import java.util.ServiceLoader;
/**
* Provider class that allows the developer to get a reference to the implementation of the WebSocketContainer. The
* provider class uses the
* <a href="http://docs.oracle.com/javase/7/docs/api/java/util/ServiceLoader.html">ServiceLoader</a> to load an
* implementation of ContainerProvider. Specifically, the fully qualified class name of the container implementation of
* ContainerProvider must be listed in the "META-INF/services/jakarta.websocket.ContainerProvider" file in the
* implementation JAR file.
*
* @author dannycoward
*/
public abstract class ContainerProvider {
/**
* Obtain a new instance of a WebSocketContainer. The method looks for the ContainerProvider implementation class in
* the order listed in the "META-INF/services/jakarta.websocket.ContainerProvider" file, returning the first
* WebSocketContainer implementation from the ContainerProvider implementation that is not {@code null}.
*
* @return an implementation provided instance of type WebSocketContainer
*
* @throws ServiceConfigurationError If there is a problem loading one of the discovered ContainerProvider
* implementations. A ServiceConfigurationError is viewed as a serious problem so the exception is allowed
* to propagate rather than swallowing the exception and attempting to load the next provider (if any).
*/
public static WebSocketContainer getWebSocketContainer() {
Iterator<ContainerProvider> providers = ServiceLoader.load(ContainerProvider.class).iterator();
if (providers.hasNext()) {
do {
ContainerProvider impl = providers.next();
WebSocketContainer wsc = impl.getContainer();
if (wsc != null) {
return wsc;
}
} while (providers.hasNext());
throw new RuntimeException("Could not find an implementation class with a non-null WebSocketContainer.");
} else {
throw new RuntimeException("Could not find an implementation class.");
}
}
/**
* Create a new instance of the the WebSocket container implementation.
*
* @return the new instance
*/
protected abstract WebSocketContainer getContainer();
}