org.apache.hadoop.util.ProgramDriver Maven / Gradle / Ivy
/**
* 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.util;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Map;
import java.util.TreeMap;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
/** A driver that is used to run programs added to it
*/
@InterfaceAudience.LimitedPrivate({"HDFS", "MapReduce"})
@InterfaceStability.Unstable
public class ProgramDriver {
/**
* A description of a program based on its class and a
* human-readable description.
*/
Map programs;
public ProgramDriver(){
programs = new TreeMap();
}
static private class ProgramDescription {
static final Class[] paramTypes = new Class[] {String[].class};
/**
* Create a description of an example program.
* @param mainClass the class with the main for the example program
* @param description a string to display to the user in help messages
* @throws SecurityException if we can't use reflection
* @throws NoSuchMethodException if the class doesn't have a main method
*/
public ProgramDescription(Class mainClass,
String description)
throws SecurityException, NoSuchMethodException {
this.main = mainClass.getMethod("main", paramTypes);
this.description = description;
}
/**
* Invoke the example application with the given arguments
* @param args the arguments for the application
* @throws Throwable The exception thrown by the invoked method
*/
public void invoke(String[] args)
throws Throwable {
try {
main.invoke(null, new Object[]{args});
} catch (InvocationTargetException except) {
throw except.getCause();
}
}
public String getDescription() {
return description;
}
private Method main;
private String description;
}
private static void printUsage(Map programs) {
System.out.println("Valid program names are:");
for(Map.Entry item : programs.entrySet()) {
System.out.println(" " + item.getKey() + ": " +
item.getValue().getDescription());
}
}
/**
* This is the method that adds the classed to the repository
* @param name The name of the string you want the class instance to be called with
* @param mainClass The class that you want to add to the repository
* @param description The description of the class
* @throws NoSuchMethodException
* @throws SecurityException
*/
public void addClass(String name, Class mainClass, String description)
throws Throwable {
programs.put(name , new ProgramDescription(mainClass, description));
}
/**
* This is a driver for the example programs.
* It looks at the first command line argument and tries to find an
* example program with that name.
* If it is found, it calls the main method in that class with the rest
* of the command line arguments.
* @param args The argument from the user. args[0] is the command to run.
* @return -1 on error, 0 on success
* @throws NoSuchMethodException
* @throws SecurityException
* @throws IllegalAccessException
* @throws IllegalArgumentException
* @throws Throwable Anything thrown by the example program's main
*/
public int run(String[] args)
throws Throwable
{
// Make sure they gave us a program name.
if (args.length == 0) {
System.out.println("An example program must be given as the" +
" first argument.");
printUsage(programs);
return -1;
}
// And that it is good.
ProgramDescription pgm = programs.get(args[0]);
if (pgm == null) {
System.out.println("Unknown program '" + args[0] + "' chosen.");
printUsage(programs);
return -1;
}
// Remove the leading argument and call main
String[] new_args = new String[args.length - 1];
for(int i=1; i < args.length; ++i) {
new_args[i-1] = args[i];
}
pgm.invoke(new_args);
return 0;
}
/**
* API compatible with Hadoop 1.x
*/
public void driver(String[] argv) throws Throwable {
if (run(argv) == -1) {
System.exit(-1);
}
}
}