| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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 org.apache.hadoop.fs.shell; |
| |
| import java.util.Arrays; |
| import java.util.HashMap; |
| import java.util.Map; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| import org.apache.hadoop.conf.Configuration; |
| import org.apache.hadoop.conf.Configured; |
| import org.apache.hadoop.util.ReflectionUtils; |
| import org.apache.hadoop.util.StringUtils; |
| |
| /** class to search for and register commands */ |
| |
| @InterfaceAudience.Private |
| @InterfaceStability.Unstable |
| |
| public class CommandFactory extends Configured { |
| private Map<String, Class<? extends Command>> classMap = |
| new HashMap<String, Class<? extends Command>>(); |
| |
| private Map<String, Command> objectMap = |
| new HashMap<String, Command>(); |
| |
| /** Factory constructor for commands */ |
| public CommandFactory() { |
| this(null); |
| } |
| |
| /** |
| * Factory constructor for commands |
| * @param conf the hadoop configuration |
| */ |
| public CommandFactory(Configuration conf) { |
| super(conf); |
| } |
| |
| /** |
| * Invokes "static void registerCommands(CommandFactory)" on the given class. |
| * This method abstracts the contract between the factory and the command |
| * class. Do not assume that directly invoking registerCommands on the |
| * given class will have the same effect. |
| * @param registrarClass class to allow an opportunity to register |
| */ |
| public void registerCommands(Class<?> registrarClass) { |
| try { |
| registrarClass.getMethod( |
| "registerCommands", CommandFactory.class |
| ).invoke(null, this); |
| } catch (Exception e) { |
| throw new RuntimeException(StringUtils.stringifyException(e)); |
| } |
| } |
| |
| /** |
| * Register the given class as handling the given list of command |
| * names. |
| * @param cmdClass the class implementing the command names |
| * @param names one or more command names that will invoke this class |
| */ |
| public void addClass(Class<? extends Command> cmdClass, String ... names) { |
| for (String name : names) classMap.put(name, cmdClass); |
| } |
| |
| /** |
| * Register the given object as handling the given list of command |
| * names. Avoid calling this method and use |
| * {@link #addClass(Class, String...)} whenever possible to avoid |
| * startup overhead from excessive command object instantiations. This |
| * method is intended only for handling nested non-static classes that |
| * are re-usable. Namely -help/-usage. |
| * @param cmdObject the object implementing the command names |
| * @param names one or more command names that will invoke this class |
| */ |
| public void addObject(Command cmdObject, String ... names) { |
| for (String name : names) { |
| objectMap.put(name, cmdObject); |
| classMap.put(name, null); // just so it shows up in the list of commands |
| } |
| } |
| |
| /** |
| * Returns an instance of the class implementing the given command. The |
| * class must have been registered via |
| * {@link #addClass(Class, String...)} |
| * @param cmd name of the command |
| * @return instance of the requested command |
| */ |
| public Command getInstance(String cmd) { |
| return getInstance(cmd, getConf()); |
| } |
| |
| /** |
| * Get an instance of the requested command |
| * @param cmdName name of the command to lookup |
| * @param conf the hadoop configuration |
| * @return the {@link Command} or null if the command is unknown |
| */ |
| public Command getInstance(String cmdName, Configuration conf) { |
| if (conf == null) throw new NullPointerException("configuration is null"); |
| |
| Command instance = objectMap.get(cmdName); |
| if (instance == null) { |
| Class<? extends Command> cmdClass = classMap.get(cmdName); |
| if (cmdClass != null) { |
| instance = ReflectionUtils.newInstance(cmdClass, conf); |
| instance.setName(cmdName); |
| instance.setCommandFactory(this); |
| } |
| } |
| return instance; |
| } |
| |
| /** |
| * Gets all of the registered commands |
| * @return a sorted list of command names |
| */ |
| public String[] getNames() { |
| String[] names = classMap.keySet().toArray(new String[0]); |
| Arrays.sort(names); |
| return names; |
| } |
| } |