How JSch executes Shell commands remotely

This article will give you a detailed introduction to how to remotely execute Shell commands using JSch. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to everyone.

JSch is the abbreviation of Java Secure Channel. JSch is a pure Java implementation of SSH2. It allows you to connect to an SSH server and use port forwarding, X11 forwarding, file transfer, etc. Of course, you can also integrate its functionality into your own applications. The framework jsch is a very old framework. It was updated in 2016 and is no longer updated now.

JSch uses shell to execute commands. There are two methods

• ChannelExec: Execute one command at a time. Generally, this is enough for us.

• ChannelShell: Can execute multiple commands. It is not used much in daily development. You can use it as needed;

ChannelExec channelExec = (ChannelExec) session.openChannel("exec");//只能执行一条指令（也可执行符合指令）
ChannelShell channelShell = (ChannelShell) session.openChannel("shell");//可执行多条指令 不过需要输入输出流

1. ChannelExec

• Separate each command with;. Note: The execution of each command will not affect the execution of other commands. In other words, each command will be executed, but there is no guarantee that every command will be executed successfully.

• Separate each command with &&. Note: If the previous command is executed successfully, the following command will be executed. This ensures that after all commands are executed, the execution process is successful.

• Separate each command with ||. Note: || means or, the next command will be executed only after the execution of the previous command fails, until a command is executed successfully.

2. ChannelShell

For ChannelShell, multiple instructions can be executed in the form of an input stream, just like using an interactive shell on the local computer (it usually For: interactive use). If you want to stop, there are two ways:

• Send an exit command to tell the program that this interaction is over;

• Use bytes The available method in the stream is used to obtain the total size of the data, and then it is read in a loop.

Usage Example

1. Introduce pom dependency

<dependency>
   <groupId>com.jcraft</groupId>
   <artifactId>jsch</artifactId>
   <version>0.1.53</version>
</dependency>

2. jsch Usage Example

A Shell tool is encapsulated here Class, used to execute shell commands. The specific usage details are explained in the code comments. You can copy and use it directly. The code is as follows:

package org.example.shell;/**
 * Created by qianghaohao on 2021/3/28
 */import com.jcraft.jsch.ChannelExec;import com.jcraft.jsch.JSch;import com.jcraft.jsch.Session;import java.io.BufferedReader;import java.io.IOException;import java.io.InputStreamReader;/**
 * @description:
 * @author: qianghaohao
 * @time: 2021/3/28
 */public class Shell {
    private String host;
    private String username;
    private String password;
    private int port = 22;
    private int timeout = 60 * 60 * 1000;

    public Shell(String host, String username, String password, int port, int timeout) {
        this.host = host;
        this.username = username;
        this.password = password;
        this.port = port;
        this.timeout = timeout;
    }

    public Shell(String host, String username, String password) {
        this.host = host;
        this.username = username;
        this.password = password;
    }

    public String execCommand(String cmd) {
        JSch jSch = new JSch();
        Session session = null;
        ChannelExec channelExec = null;
        BufferedReader inputStreamReader = null;
        BufferedReader errInputStreamReader = null;
        StringBuilder runLog = new StringBuilder("");
        StringBuilder errLog = new StringBuilder("");
        try {
            // 1. 获取 ssh session
            session = jSch.getSession(username, host, port);
            session.setPassword(password);
            session.setTimeout(timeout);
            session.setConfig("StrictHostKeyChecking", "no");
            session.connect();  // 获取到 ssh session

            // 2. 通过 exec 方式执行 shell 命令
            channelExec = (ChannelExec) session.openChannel("exec");
            channelExec.setCommand(cmd);
            channelExec.connect();  // 执行命令

            // 3. 获取标准输入流
            inputStreamReader = new BufferedReader(new InputStreamReader(channelExec.getInputStream()));
            // 4. 获取标准错误输入流
            errInputStreamReader = new BufferedReader(new InputStreamReader(channelExec.getErrStream()));

            // 5. 记录命令执行 log
            String line = null;
            while ((line = inputStreamReader.readLine()) != null) {
                runLog.append(line).append("\n");
            }

            // 6. 记录命令执行错误 log
            String errLine = null;
            while ((errLine = errInputStreamReader.readLine()) != null) {
                errLog.append(errLine).append("\n");
            }

            // 7. 输出 shell 命令执行日志
            System.out.println("exitStatus=" + channelExec.getExitStatus() + ", openChannel.isClosed="
                    + channelExec.isClosed());
            System.out.println("命令执行完成，执行日志如下:");
            System.out.println(runLog.toString());
            System.out.println("命令执行完成，执行错误日志如下:");
            System.out.println(errLog.toString());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (inputStreamReader != null) {
                    inputStreamReader.close();
                }
                if (errInputStreamReader != null) {
                    errInputStreamReader.close();
                }

                if (channelExec != null) {
                    channelExec.disconnect();
                }
                if (session != null) {
                    session.disconnect();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        return runLog.toString();
    }}

Usage of the above tool class:

package org.example;import org.example.shell.Shell;/**
 * Hello world!
 *
 */public class App {
    public static void main( String[] args ) {
        String cmd = "ls -1";
        Shell shell = new Shell("192.168.10.10", "ubuntu", "11111");
        String execLog = shell.execCommand(cmd);
        System.out.println(execLog);
    }}

Recommended: "java video tutorial》

The above is the detailed content of How JSch executes Shell commands remotely. For more information, please follow other related articles on the PHP Chinese website!