Java tutorial
// Copyright 2014 The Bazel Authors. All rights reserved. // // 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 com.google.devtools.build.lib.server; import com.google.common.collect.Iterables; import com.google.devtools.build.lib.runtime.BlazeCommandDispatcher.LockingMode; import com.google.devtools.build.lib.runtime.BlazeCommandDispatcher.ShutdownMethod; import com.google.devtools.build.lib.util.Preconditions; import com.google.devtools.build.lib.util.io.OutErr; import java.util.List; import java.util.logging.Logger; /** * An RPCService is a Java object that can process RPC requests. Requests may * be of the form: * <pre> * blaze <blaze-arguments> * </pre> * Requests are delegated to the ServerCommand instance provided * to the constructor. */ public final class RPCService { private static final Logger LOG = Logger.getLogger(RPCService.class.getName()); private final ServerCommand appCommand; private ShutdownMethod shutdown = ShutdownMethod.NONE; public RPCService(ServerCommand appCommand) { this.appCommand = appCommand; } /** * The {@link #executeRequest(List, OutErr, long)} method may * throw this exception if a command is unknown to the RPC service. */ public static class UnknownCommandException extends Exception { private static final long serialVersionUID = 1L; UnknownCommandException(String command) { super("Unknown command: " + command); } } /** * Executes the request; returns Unix like return codes (0 means success). May * also throw arbitrary exceptions. */ public int executeRequest(List<String> request, OutErr outErr, long firstContactTime) throws Exception { if (shutdown != ShutdownMethod.NONE) { throw new IllegalStateException("Received request after shutdown."); } String command = Iterables.getFirst(request, ""); if (appCommand != null && command.equals("blaze")) { // an application request // Blocking is done in the client for AF_UNIX communications, so if blockForLock would block, // something went wrong int result = appCommand.exec(request.subList(1, request.size()), outErr, LockingMode.ERROR_OUT, "AF_UNIX client", firstContactTime); ShutdownMethod commandShutdown = appCommand.shutdown(); if (commandShutdown != ShutdownMethod.NONE) { // an application shutdown request shutdown(commandShutdown); } return result; } else { throw new UnknownCommandException(command); } } /** * After executing this function, further requests will fail, and * {@link #getShutdown()} will the shutdown method passed in. */ public void shutdown(ShutdownMethod method) { Preconditions.checkState(method != ShutdownMethod.NONE); if (shutdown != ShutdownMethod.NONE) { return; } LOG.info("RPC Service: shutting down ..."); shutdown = method; } /** * Has this service been shutdown. If so, any call to * {@link #executeRequest(List, OutErr, long)} will result in an * {@link IllegalStateException} */ public ShutdownMethod getShutdown() { return shutdown; } }