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+/**
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+ * Copyright 2006 The Apache Software Foundation
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+ *
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+ * Licensed under the Apache License, Version 2.0 (the "License");
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+ * you may not use this file except in compliance with the License.
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+ * You may obtain a copy of the License at
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+ *
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+ * http://www.apache.org/licenses/LICENSE-2.0
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+ *
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+ * Unless required by applicable law or agreed to in writing, software
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+ * distributed under the License is distributed on an "AS IS" BASIS,
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+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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+ * See the License for the specific language governing permissions and
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+ * limitations under the License.
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+ */
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+
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+package org.apache.hadoop.util;
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+
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+import java.lang.reflect.InvocationTargetException;
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+import java.lang.reflect.Method;
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+import java.util.TreeMap;
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+import java.util.Iterator;
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+import java.util.Map;
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+import java.util.Map.Entry;
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+
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+/** A driver that is used to run programs added to it
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+ */
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+
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+public class ProgramDriver {
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+
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+ /**
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+ * A description of a program based on its class and a
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+ * human-readable description.
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+ * @author Owen O'Malley
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+ * @date april 2006
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+ */
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+ Map programs;
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+
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+ public ProgramDriver(){
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+ programs = new TreeMap();
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+ }
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+
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+ static private class ProgramDescription {
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+
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+ static final Class[] paramTypes = new Class[] {String[].class};
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+
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+ /**
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+ * Create a description of an example program.
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+ * @param mainClass the class with the main for the example program
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+ * @param description a string to display to the user in help messages
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+ * @throws SecurityException if we can't use reflection
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+ * @throws NoSuchMethodException if the class doesn't have a main method
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+ */
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+ public ProgramDescription(Class mainClass,
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+ String description)
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+ throws SecurityException, NoSuchMethodException {
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+ this.main = mainClass.getMethod("main", paramTypes);
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+ this.description = description;
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+ }
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+
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+ /**
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+ * Invoke the example application with the given arguments
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+ * @param args the arguments for the application
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+ * @throws Throwable The exception thrown by the invoked method
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+ */
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+ public void invoke(String[] args)
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+ throws Throwable {
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+ try {
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+ main.invoke(null, new Object[]{args});
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+ } catch (InvocationTargetException except) {
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+ throw except.getCause();
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+ }
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+ }
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+
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+ public String getDescription() {
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+ return description;
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+ }
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+
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+ private Method main;
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+ private String description;
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+ }
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+
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+ private static void printUsage(Map programs) {
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+ System.out.println("Valid program names are:");
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+ for(Iterator itr=programs.entrySet().iterator(); itr.hasNext();) {
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+ Map.Entry item = (Entry) itr.next();
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+ System.out.println(" " + (String) item.getKey() + ": " +
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+ ((ProgramDescription) item.getValue()).getDescription());
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+ }
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+ }
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+
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+ /**
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+ * This is the method that adds the classed to the repository
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+ * @param name The name of the string you want the class instance to be called with
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+ * @param mainClass The class that you want to add to the repository
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+ * @param description The description of the class
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+ * @throws NoSuchMethodException
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+ * @throws SecurityException
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+ */
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+ public void addClass (String name, Class mainClass, String description) throws Throwable {
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+ programs.put(name , new ProgramDescription(mainClass, description));
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+ }
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+
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+ /**
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+ * This is a driver for the example programs.
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+ * It looks at the first command line argument and tries to find an
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+ * example program with that name.
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+ * If it is found, it calls the main method in that class with the rest
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+ * of the command line arguments.
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+ * @param args The argument from the user. args[0] is the command to run.
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+ * @throws NoSuchMethodException
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+ * @throws SecurityException
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+ * @throws IllegalAccessException
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+ * @throws IllegalArgumentException
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+ * @throws Throwable Anything thrown by the example program's main
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+ */
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+ public void driver(String[] args)
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+ throws Throwable
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+ {
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+ // Make sure they gave us a program name.
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+ if (args.length == 0) {
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+ System.out.println("An example program must be given as the" +
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+ " first argument.");
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+ printUsage(programs);
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+ return;
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+ }
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+
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+ // And that it is good.
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+ ProgramDescription pgm = (ProgramDescription) programs.get(args[0]);
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+ if (pgm == null) {
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+ System.out.println("Unknown program '" + args[0] + "' chosen.");
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+ printUsage(programs);
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+ return;
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+ }
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+
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+ // Remove the leading argument and call main
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+ String[] new_args = new String[args.length - 1];
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+ for(int i=1; i < args.length; ++i) {
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+ new_args[i-1] = args[i];
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+ }
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+ pgm.invoke(new_args);
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+ }
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+
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+}
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Doug Cutting