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/**
* 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.tools;
import java.io.PrintStream;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.util.Tool;
/**
* This program is a CLI utility base class utilizing hadoop Tool class.
*/
public abstract class CommandShell extends Configured implements Tool {
private PrintStream out = System.out;
private PrintStream err = System.err;
/** The subcommand instance for this shell command, if any. */
private SubCommand subcommand = null;
/**
* Return usage string for the command including any summary of subcommands.
*/
public abstract String getCommandUsage();
public void setSubCommand(SubCommand cmd) {
subcommand = cmd;
}
public void setOut(PrintStream p) {
out = p;
}
public PrintStream getOut() {
return out;
}
public void setErr(PrintStream p) {
err = p;
}
public PrintStream getErr() {
return err;
}
@Override
public int run(String[] args) throws Exception {
int exitCode = 0;
try {
exitCode = init(args);
if (exitCode != 0 || subcommand == null) {
printShellUsage();
return exitCode;
}
if (subcommand.validate()) {
subcommand.execute();
} else {
printShellUsage();
exitCode = 1;
}
} catch (Exception e) {
printShellUsage();
printException(e);
return 1;
}
return exitCode;
}
/**
* Parse the command line arguments and initialize subcommand instance.
* @param args
* @return 0 if the argument(s) were recognized, 1 otherwise
*/
protected abstract int init(String[] args) throws Exception;
protected final void printShellUsage() {
if (subcommand != null) {
out.println(subcommand.getUsage());
} else {
out.println(getCommandUsage());
}
out.flush();
}
protected void printException(Exception ex){
ex.printStackTrace(err);
}
/**
* Base class for any subcommands of this shell command.
*/
protected abstract class SubCommand {
public boolean validate() {
return true;
}
public abstract void execute() throws Exception;
public abstract String getUsage();
}
}