Java tutorial
/* * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0 * (the "License"). You may not use this work except in compliance with the License, which is * available at www.apache.org/licenses/LICENSE-2.0 * * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, * either express or implied, as more fully set forth in the License. * * See the NOTICE file distributed with this work for information regarding copyright ownership. */ package alluxio.cli; import alluxio.exception.AlluxioException; import alluxio.exception.status.InvalidArgumentException; import org.apache.commons.cli.CommandLine; import org.apache.commons.cli.CommandLineParser; import org.apache.commons.cli.DefaultParser; import org.apache.commons.cli.Options; import org.apache.commons.cli.ParseException; import java.io.IOException; /** * An interface for all the commands that can be run from a shell. */ public interface Command { /** * Gets the command name as input from the shell. * * @return the command name */ String getCommandName(); /** * @return the supported {@link Options} of the command */ default Options getOptions() { return new Options(); } /** * Parses and validates the arguments. * * @param args the arguments for the command, excluding the command name * @return the parsed command line object * @throws InvalidArgumentException when arguments are not valid */ default CommandLine parseAndValidateArgs(String... args) throws InvalidArgumentException { CommandLine cmdline; Options opts = getOptions(); CommandLineParser parser = new DefaultParser(); try { cmdline = parser.parse(opts, args); } catch (ParseException e) { throw new InvalidArgumentException(String.format("Failed to parse args for %s", getCommandName()), e); } validateArgs(cmdline); return cmdline; } /** * Checks if the arguments are valid or throw InvalidArgumentException. * * @param cl the parsed command line for the arguments * @throws InvalidArgumentException when arguments are not valid */ default void validateArgs(CommandLine cl) throws InvalidArgumentException { } /** * Runs the command. * * @param cl the parsed command line for the arguments * @return the result of running the command */ int run(CommandLine cl) throws AlluxioException, IOException; /** * @return the usage information of the command */ String getUsage(); /** * @return the description information of the command */ String getDescription(); }