Ant example source code file (SSHExec.java)

This example Ant source code file (SSHExec.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Ant tags/keywords

buildexception, buildexception, bytearrayoutputstream, bytearrayoutputstream, caught, channelexec, file, io, sshexec, string, string, stringreader, stringreader, teeoutputstream, thread

The SSHExec.java source code

/*
 *  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.tools.ant.taskdefs.optional.ssh;

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.Project;
import org.apache.tools.ant.util.TeeOutputStream;
import org.apache.tools.ant.util.KeepAliveOutputStream;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.StringReader;

import com.jcraft.jsch.ChannelExec;
import com.jcraft.jsch.JSchException;
import com.jcraft.jsch.Session;

/**
 * Executes a command on a remote machine via ssh.
 * @since     Ant 1.6 (created February 2, 2003)
 */
public class SSHExec extends SSHBase {

    /** the command to execute via ssh */
    private String command = null;

    /** units are milliseconds, default is 0=infinite */
    private long maxwait = 0;

    /** for waiting for the command to finish */
    private Thread thread = null;

    private String outputProperty = null;   // like <exec>
    private File outputFile = null;   // like <exec>
    private boolean append = false;   // like <exec>

    private static final String TIMEOUT_MESSAGE =
        "Timeout period exceeded, connection dropped.";

    /**
     * Constructor for SSHExecTask.
     */
    public SSHExec() {
        super();
    }

    /**
     * Sets the command to execute on the remote host.
     *
     * @param command  The new command value
     */
    public void setCommand(String command) {
        this.command = command;
    }

    /**
     * The connection can be dropped after a specified number of
     * milliseconds. This is sometimes useful when a connection may be
     * flaky. Default is 0, which means "wait forever".
     *
     * @param timeout  The new timeout value in seconds
     */
    public void setTimeout(long timeout) {
        maxwait = timeout;
    }

    /**
     * If used, stores the output of the command to the given file.
     *
     * @param output  The file to write to.
     */
    public void setOutput(File output) {
        outputFile = output;
    }

    /**
     * Determines if the output is appended to the file given in
     * <code>setOutput. Default is false, that is, overwrite
     * the file.
     *
     * @param append  True to append to an existing file, false to overwrite.
     */
    public void setAppend(boolean append) {
        this.append = append;
    }

    /**
     * If set, the output of the command will be stored in the given property.
     *
     * @param property  The name of the property in which the command output
     *      will be stored.
     */
    public void setOutputproperty(String property) {
        outputProperty = property;
    }

    /**
     * Execute the command on the remote host.
     *
     * @exception BuildException  Most likely a network error or bad parameter.
     */
    public void execute() throws BuildException {
        if (getHost() == null) {
            throw new BuildException("Host is required.");
        }
        if (getUserInfo().getName() == null) {
            throw new BuildException("Username is required.");
        }
        if (getUserInfo().getKeyfile() == null
            && getUserInfo().getPassword() == null) {
            throw new BuildException("Password or Keyfile is required.");
        }
        if (command == null) {
            throw new BuildException("Command is required.");
        }

        ByteArrayOutputStream out = new ByteArrayOutputStream();
        TeeOutputStream tee = new TeeOutputStream(out, new KeepAliveOutputStream(System.out));

        Session session = null;
        try {
            // execute the command
            session = openSession();
            session.setTimeout((int) maxwait);
            final ChannelExec channel = (ChannelExec) session.openChannel("exec");
            channel.setCommand(command);
            channel.setOutputStream(tee);
            channel.setExtOutputStream(tee);
            channel.connect();

            // wait for it to finish
            thread =
                new Thread() {
                    public void run() {
                        while (!channel.isEOF()) {
                            if (thread == null) {
                                return;
                            }
                            try {
                                sleep(500);
                            } catch (Exception e) {
                                // ignored
                            }
                        }
                    }
                };

            thread.start();
            thread.join(maxwait);

            if (thread.isAlive()) {
                // ran out of time
                thread = null;
                if (getFailonerror()) {
                    throw new BuildException(TIMEOUT_MESSAGE);
                } else {
                    log(TIMEOUT_MESSAGE, Project.MSG_ERR);
                }
            } else {
                // completed successfully
                if (outputProperty != null) {
                    getProject().setProperty(outputProperty, out.toString());
                }
                if (outputFile != null) {
                    writeToFile(out.toString(), append, outputFile);
                }

                // this is the wrong test if the remote OS is OpenVMS,
                // but there doesn't seem to be a way to detect it.
                int ec = channel.getExitStatus();
                if (ec != 0) {
                    String msg = "Remote command failed with exit status " + ec;
                    if (getFailonerror()) {
                        throw new BuildException(msg);
                    } else {
                        log(msg, Project.MSG_ERR);
                    }
                }
            }
        } catch (BuildException e) {
            throw e;
        } catch (JSchException e) {
            if (e.getMessage().indexOf("session is down") >= 0) {
                if (getFailonerror()) {
                    throw new BuildException(TIMEOUT_MESSAGE, e);
                } else {
                    log(TIMEOUT_MESSAGE, Project.MSG_ERR);
                }
            } else {
                if (getFailonerror()) {
                    throw new BuildException(e);
                } else {
                    log("Caught exception: " + e.getMessage(),
                        Project.MSG_ERR);
                }
            }
        } catch (Exception e) {
            if (getFailonerror()) {
                throw new BuildException(e);
            } else {
                log("Caught exception: " + e.getMessage(), Project.MSG_ERR);
            }
        } finally {
            if (session != null && session.isConnected()) {
                session.disconnect();
            }
        }
    }


    /**
     * Writes a string to a file. If destination file exists, it may be
     * overwritten depending on the "append" value.
     *
     * @param from           string to write
     * @param to             file to write to
     * @param append         if true, append to existing file, else overwrite
     * @exception Exception  most likely an IOException
     */
    private void writeToFile(String from, boolean append, File to)
        throws IOException {
        FileWriter out = null;
        try {
            out = new FileWriter(to.getAbsolutePath(), append);
            StringReader in = new StringReader(from);
            char[] buffer = new char[8192];
            int bytesRead;
            while (true) {
                bytesRead = in.read(buffer);
                if (bytesRead == -1) {
                    break;
                }
                out.write(buffer, 0, bytesRead);
            }
            out.flush();
        } finally {
            if (out != null) {
                out.close();
            }
        }
    }

}