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/*
 * Copyright 2015 The gRPC Authors
 *
 * 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 io.grpc;

import com.google.common.base.Preconditions;
import java.net.SocketAddress;
import java.util.Collection;

/**
 * Provider of managed channels for transport agnostic consumption.
 *
 * 

Implementations can be automatically discovered by gRPC via Java's SPI mechanism. For * automatic discovery, the implementation must have a zero-argument constructor and include * a resource named {@code META-INF/services/io.grpc.ManagedChannelProvider} in their JAR. The * file's contents should be the implementation's class name. * *

Implementations should not 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 ManagedChannelProvider { /** * Returns the ClassLoader-wide default channel. * * @throws ProviderNotFoundException if no provider is available */ public static ManagedChannelProvider provider() { ManagedChannelProvider provider = ManagedChannelRegistry.getDefaultRegistry().provider(); if (provider == null) { throw new ProviderNotFoundException("No functional channel service provider found. " + "Try adding a dependency on the grpc-okhttp, grpc-netty, or grpc-netty-shaded " + "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 host and port. */ protected abstract ManagedChannelBuilder builderForAddress(String name, int port); /** * Creates a new builder with the given target URI. */ protected abstract ManagedChannelBuilder builderForTarget(String target); /** * Creates a new builder with the given target URI and credentials. Returns an error-string result * if unable to understand the credentials. */ protected NewChannelBuilderResult newChannelBuilder(String target, ChannelCredentials creds) { return NewChannelBuilderResult.error("ChannelCredentials are unsupported"); } /** * Returns the {@link SocketAddress} types this ManagedChannelProvider supports. */ protected abstract Collection> getSupportedSocketAddressTypes(); public static final class NewChannelBuilderResult { private final ManagedChannelBuilder channelBuilder; private final String error; private NewChannelBuilderResult(ManagedChannelBuilder channelBuilder, String error) { this.channelBuilder = channelBuilder; this.error = error; } public static NewChannelBuilderResult channelBuilder(ManagedChannelBuilder builder) { return new NewChannelBuilderResult(Preconditions.checkNotNull(builder), null); } public static NewChannelBuilderResult error(String error) { return new NewChannelBuilderResult(null, Preconditions.checkNotNull(error)); } public ManagedChannelBuilder getChannelBuilder() { return channelBuilder; } public String getError() { return error; } } /** * Thrown when no suitable {@link ManagedChannelProvider} objects can be found. */ public static final class ProviderNotFoundException extends RuntimeException { private static final long serialVersionUID = 1; public ProviderNotFoundException(String msg) { super(msg); } } }





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