Java tutorial
/** * 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 com.jcraft.jsch.*; import org.apache.commons.logging.LogFactory; import org.apache.commons.logging.Log; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.Properties; /** * Remote Execution of commands on a remote machine. */ public class SSHRemoteExecution implements RemoteExecution { static final Log LOG = LogFactory.getLog(SSHRemoteExecution.class); static final int SSH_PORT = 22; static final String DEFAULT_IDENTITY = "id_dsa"; static final String DEFAULT_KNOWNHOSTS = "known_hosts"; static final String FS = System.getProperty("file.separator"); static final String LS = System.getProperty("line.separator"); private int exitCode; private StringBuffer output; private String commandString; final StringBuffer errorMessage = new StringBuffer(); public SSHRemoteExecution() throws Exception { } protected String getHomeDir() { String currentUser = System.getProperty("user.name"); String userHome = System.getProperty("user.home"); return userHome.substring(0, userHome.indexOf(currentUser) - 1); } /** * Execute command at remote host under given user * @param remoteHostName remote host name * @param user is the name of the user to be login under; * current user will be used if this is set to <code>null</code> * @param command to be executed remotely * @param identityFile is the name of alternative identity file; default * is ~user/.ssh/id_dsa * @param portNumber remote SSH daemon port number, default is 22 * @throws Exception in case of errors */ public void executeCommand(String remoteHostName, String user, String command, String identityFile, int portNumber) throws Exception { commandString = command; String sessionUser = System.getProperty("user.name"); String userHome = System.getProperty("user.home"); if (user != null) { sessionUser = user; userHome = getHomeDir() + FS + user; } String dotSSHDir = userHome + FS + ".ssh"; String sessionIdentity = dotSSHDir + FS + DEFAULT_IDENTITY; if (identityFile != null) { sessionIdentity = identityFile; } JSch jsch = new JSch(); Session session = jsch.getSession(sessionUser, remoteHostName, portNumber); jsch.setKnownHosts(dotSSHDir + FS + DEFAULT_KNOWNHOSTS); jsch.addIdentity(sessionIdentity); Properties config = new Properties(); config.put("StrictHostKeyChecking", "no"); session.setConfig(config); session.connect(30000); // making a connection with timeout. Channel channel = session.openChannel("exec"); ((ChannelExec) channel).setCommand(command); channel.setInputStream(null); final BufferedReader errReader = new BufferedReader( new InputStreamReader(((ChannelExec) channel).getErrStream())); BufferedReader inReader = new BufferedReader(new InputStreamReader(channel.getInputStream())); channel.connect(); Thread errorThread = new Thread() { @Override public void run() { try { String line = errReader.readLine(); while ((line != null) && !isInterrupted()) { errorMessage.append(line); errorMessage.append(LS); line = errReader.readLine(); } } catch (IOException ioe) { LOG.warn("Error reading the error stream", ioe); } } }; try { errorThread.start(); } catch (IllegalStateException e) { LOG.debug(e); } try { parseExecResult(inReader); String line = inReader.readLine(); while (line != null) { line = inReader.readLine(); } if (channel.isClosed()) { exitCode = channel.getExitStatus(); LOG.debug("exit-status: " + exitCode); } try { // make sure that the error thread exits errorThread.join(); } catch (InterruptedException ie) { LOG.warn("Interrupted while reading the error stream", ie); } } catch (Exception ie) { throw new IOException(ie.toString()); } finally { try { inReader.close(); } catch (IOException ioe) { LOG.warn("Error while closing the input stream", ioe); } try { errReader.close(); } catch (IOException ioe) { LOG.warn("Error while closing the error stream", ioe); } channel.disconnect(); session.disconnect(); } } /** * Execute command at remote host under given username * Default identity is ~/.ssh/id_dsa key will be used * Default known_hosts file is ~/.ssh/known_hosts will be used * @param remoteHostName remote host name * @param user is the name of the user to be login under; * if equals to <code>null</code> then current user name will be used * @param command to be executed remotely */ @Override public void executeCommand(String remoteHostName, String user, String command) throws Exception { executeCommand(remoteHostName, user, command, null, SSH_PORT); } @Override public int getExitCode() { return exitCode; } protected void parseExecResult(BufferedReader lines) throws IOException { output = new StringBuffer(); char[] buf = new char[512]; int nRead; while ((nRead = lines.read(buf, 0, buf.length)) > 0) { output.append(buf, 0, nRead); } } /** Get the output of the ssh command.*/ @Override public String getOutput() { return (output == null) ? "" : output.toString(); } /** Get the String representation of ssh command */ @Override public String getCommandString() { return commandString; } }