| /* |
| * Copyright 2015, Google Inc. All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are |
| * met: |
| * |
| * * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * * Redistributions in binary form must reproduce the above |
| * copyright notice, this list of conditions and the following disclaimer |
| * in the documentation and/or other materials provided with the |
| * distribution. |
| * |
| * * Neither the name of Google Inc. nor the names of its |
| * contributors may be used to endorse or promote products derived from |
| * this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| package io.grpc; |
| |
| import com.google.common.annotations.VisibleForTesting; |
| |
| import io.grpc.ManagedChannelProvider.ProviderNotFoundException; |
| |
| import java.util.ServiceLoader; |
| |
| /** |
| * Provider of servers for transport agnostic consumption. |
| * |
| * <p>Implementations <em>should not</em> throw. If they do, it may interrupt class loading. If |
| * exceptions may reasonably occur for implementation-specific reasons, implementations should |
| * generally handle the exception gracefully and return {@code false} from {@link #isAvailable()}. |
| */ |
| @Internal |
| public abstract class ServerProvider { |
| private static final ServerProvider provider = |
| load(Thread.currentThread().getContextClassLoader()); |
| |
| @VisibleForTesting |
| static final ServerProvider load(ClassLoader cl) { |
| ServiceLoader<ServerProvider> providers = ServiceLoader.load(ServerProvider.class, cl); |
| ServerProvider best = null; |
| |
| for (ServerProvider current : providers) { |
| if (!current.isAvailable()) { |
| continue; |
| } else if (best == null) { |
| best = current; |
| } else if (current.priority() > best.priority()) { |
| best = current; |
| } |
| } |
| return best; |
| } |
| |
| /** |
| * Returns the ClassLoader-wide default server. |
| * |
| * @throws ProviderNotFoundException if no provider is available |
| */ |
| public static ServerProvider provider() { |
| if (provider == null) { |
| throw new ProviderNotFoundException("No functional server found. " |
| + "Try adding a dependency on the grpc-netty artifact"); |
| } |
| return provider; |
| } |
| |
| /** |
| * Whether this provider is available for use, taking the current environment into consideration. |
| * If {@code false}, no other methods are safe to be called. |
| */ |
| protected abstract boolean isAvailable(); |
| |
| /** |
| * A priority, from 0 to 10 that this provider should be used, taking the current environment into |
| * consideration. 5 should be considered the default, and then tweaked based on environment |
| * detection. A priority of 0 does not imply that the provider wouldn't work; just that it should |
| * be last in line. |
| */ |
| protected abstract int priority(); |
| |
| /** |
| * Creates a new builder with the given port. |
| */ |
| protected abstract ServerBuilder<?> builderForPort(int port); |
| } |
| |