io.grpc.ServerProvider Maven / Gradle / Ivy
/*
* 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 io.grpc.ManagedChannelProvider.ProviderNotFoundException;
/**
* Provider of servers 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.ServerProvider} 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 ServerProvider {
/**
* Returns the ClassLoader-wide default server.
*
* @throws ProviderNotFoundException if no provider is available
*/
public static ServerProvider provider() {
ServerProvider provider = ServerRegistry.getDefaultRegistry().provider();
if (provider == null) {
throw new ProviderNotFoundException("No functional server found. "
+ "Try adding a dependency on the 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 port.
*/
protected abstract ServerBuilder builderForPort(int port);
/**
* Creates a new builder with the given port and credentials. Returns an error-string result if
* unable to understand the credentials.
*/
protected NewServerBuilderResult newServerBuilderForPort(int port, ServerCredentials creds) {
return NewServerBuilderResult.error("ServerCredentials are unsupported");
}
public static final class NewServerBuilderResult {
private final ServerBuilder serverBuilder;
private final String error;
private NewServerBuilderResult(ServerBuilder serverBuilder, String error) {
this.serverBuilder = serverBuilder;
this.error = error;
}
public static NewServerBuilderResult serverBuilder(ServerBuilder builder) {
return new NewServerBuilderResult(Preconditions.checkNotNull(builder), null);
}
public static NewServerBuilderResult error(String error) {
return new NewServerBuilderResult(null, Preconditions.checkNotNull(error));
}
public ServerBuilder getServerBuilder() {
return serverBuilder;
}
public String getError() {
return error;
}
}
}