1 /* 2 * Copyright 2015 The gRPC Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package io.grpc; 18 19 import io.grpc.ManagedChannelProvider.ProviderNotFoundException; 20 import io.grpc.ServiceProviders.PriorityAccessor; 21 import java.util.Collections; 22 23 /** 24 * Provider of servers for transport agnostic consumption. 25 * 26 * <p>Implementations <em>should not</em> throw. If they do, it may interrupt class loading. If 27 * exceptions may reasonably occur for implementation-specific reasons, implementations should 28 * generally handle the exception gracefully and return {@code false} from {@link #isAvailable()}. 29 */ 30 @Internal 31 public abstract class ServerProvider { 32 private static final ServerProvider provider = ServiceProviders.load( 33 ServerProvider.class, 34 Collections.<Class<?>>emptyList(), 35 ServerProvider.class.getClassLoader(), 36 new PriorityAccessor<ServerProvider>() { 37 @Override 38 public boolean isAvailable(ServerProvider provider) { 39 return provider.isAvailable(); 40 } 41 42 @Override 43 public int getPriority(ServerProvider provider) { 44 return provider.priority(); 45 } 46 }); 47 48 /** 49 * Returns the ClassLoader-wide default server. 50 * 51 * @throws ProviderNotFoundException if no provider is available 52 */ provider()53 public static ServerProvider provider() { 54 if (provider == null) { 55 throw new ProviderNotFoundException("No functional server found. " 56 + "Try adding a dependency on the grpc-netty or grpc-netty-shaded artifact"); 57 } 58 return provider; 59 } 60 61 /** 62 * Whether this provider is available for use, taking the current environment into consideration. 63 * If {@code false}, no other methods are safe to be called. 64 */ isAvailable()65 protected abstract boolean isAvailable(); 66 67 /** 68 * A priority, from 0 to 10 that this provider should be used, taking the current environment into 69 * consideration. 5 should be considered the default, and then tweaked based on environment 70 * detection. A priority of 0 does not imply that the provider wouldn't work; just that it should 71 * be last in line. 72 */ priority()73 protected abstract int priority(); 74 75 /** 76 * Creates a new builder with the given port. 77 */ builderForPort(int port)78 protected abstract ServerBuilder<?> builderForPort(int port); 79 } 80