Unlock Remote Server Access in Spring Boot 3 with JSch: Read Files & Run Commands

This article introduces the Java JSch library for Spring Boot 3, which enables Java applications to connect to remote servers for file access and command execution.

1. Introduction

The library allows reading files directly from a remote Linux host, executing arbitrary commands, and opening an interactive shell session.

Read remote files without downloading them locally.

Execute commands on the remote host.

Obtain a shell prompt for interactive use.

2. Practical Cases

Environment Preparation

Add the JSch dependency to your Maven project:

<code>&lt;dependency&gt;
    &lt;groupId&gt;com.github.mwiede&lt;/groupId&gt;
    &lt;artifactId&gt;jsch&lt;/artifactId&gt;
    &lt;version&gt;0.2.23&lt;/version&gt;
&lt;/dependency&gt;</code>

2.1 Read Remote Host File

Prepare a file pack.txt on the remote host (e.g., /root/jsch/pack.txt ) and read its content using JSch:

<code>private static final String USER = "root";
private static final String HOST = "192.168.1.188";
private static final int PORT = 22;
private static final String PASSWORD = "xxxooo001";</code>

<code>try {
    JSch jsch = new JSch();
    Session session = jsch.getSession(USER, HOST, PORT);
    session.setPassword(PASSWORD);
    session.setConfig("StrictHostKeyChecking", "no");
    session.connect();
    ChannelSftp sftpChannel = (ChannelSftp) session.openChannel("sftp");
    sftpChannel.connect();
    InputStream inputStream = sftpChannel.get("/root/jsch/pack.txt");
    try (BufferedReader br = new BufferedReader(new InputStreamReader(inputStream))) {
        String line;
        while ((line = br.readLine()) != null) {
            System.out.println(line);
        }
    }
    sftpChannel.disconnect();
    session.disconnect();
} catch (Exception e) {
    e.printStackTrace();
}</code>

The console output will display the file content, e.g.,

<code>xxxooo
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2.2 Execute Remote Host Command

Run a command such as ls /root/software on the remote host:

<code>// Establish session (session variable must be initialized)
String command = "ls /root/software";
Channel channel = session.openChannel("exec");
((ChannelExec) channel).setCommand(command);
channel.setInputStream(null);
((ChannelExec) channel).setErrStream(System.err);
InputStream in = channel.getInputStream();
channel.connect();
byte[] tmp = new byte[1024];
while (true) {
    while (in.available() > 0) {
        int i = in.read(tmp, 0, 1024);
        if (i < 0) break;
        System.out.print(new String(tmp, 0, i));
    }
    if (channel.isClosed()) {
        if (in.available() > 0) continue;
        break;
    }
    Thread.sleep(1000);
}
channel.disconnect();
session.disconnect();</code>

If the command is invalid (e.g., lls /root/software ), the console will show an error such as:

<code>bash: lls: command not found</code>

2.3 Get Shell Prompt

Open an interactive shell channel to obtain a prompt where users can type commands freely:

<code>try {
    JSch jsch = new JSch();
    Session session = jsch.getSession(USER, HOST, PORT);
    session.setPassword(PASSWORD);
    session.setConfig("StrictHostKeyChecking", "no");
    session.connect();
    Channel channel = session.openChannel("shell");
    channel.setInputStream(System.in);
    channel.setOutputStream(System.out);
    channel.connect(3 * 1000);
} catch (Exception e) {
    e.printStackTrace();
}</code>

After connecting, the terminal displays a shell prompt, allowing you to execute any command on the remote host.

All examples are built with Spring Boot 3.4.0 and JSch 0.2.23, and the collection promises continuous updates with new cases.