java为什么从JSch中的shell通道输出读取永远不会以1结束？

Question

我创建了一个名为Obj的对象，它通过一个安全的Shell通道发送消息。我可以用UTF-8发送字符，这意味着输出流必须处理多字节字符。这就是我决定使用缓冲输出流编写器的原因。这是不相关的，因此代码只引用代码中带有注释的部分

我希望输入流也能处理多字节字符。我知道InputStreamReader的read（）函数将返回与UTF-16代码点或-1对应的整数。我当前的实现循环和测试用于-1。它不停地循环。为什么?

以下是我的源代码：

public class Obj {

    public String sendMessage(char[] message) {
     
        final int CONNECTION_TIMEOUT_MILLISECONDS = 300;
        final int IN_BUFFER_SIZE = 2048;
        int codePoint;
        StringBuilder sbResponse = new StringBuilder();

        try {
            ChannelShell channel = SshChannelFactory.getChannel(this);
            if (channel == null) {
                System.out.println("Unable to acquire channel for object \"{}\"", this);
                throw new RuntimeException();
            }
            channel.connect(CONNECTION_TIMEOUT_MILLISECONDS);
            System.out.println("Successfully opened channel to \"{}\"", channel.getHost());
        }
        
        /**
         * Write some stuff in this try block.
         */
        //try {
        //} catch
        
        /**
         * Read the response in this try block.
         */
        char[] buffer = new char[IN_BUFFER_SIZE];
        int bytesReadOffset = 0;
        try {
            BufferedReader fromServerStream = new BufferedReader(new InputStreamReader(channel.getInputStream(), Charset.forName("UTF-8")), IN_BUFFER_SIZE);
            while ((codePoint = fromServerStream.read()) != -1) {
                sbResponse.append((char) codePoint);
            } catch (IOException e) {
              e.printStackTrace();
            }
        return sbResponse.toString();
}

public class SshChannelFactory {

    public static ChannelShell getChannel(Obj obj) {
        return createSshChannel(obj);
    }

    private static Session createSshSession(Obj obj) {
        final JSch jsch = new JSch();
        java.util.Properties config = new java.util.Properties();
        config.put("StrictHostKeyChecking", "no");
        try {
            
            Session session = jsch.getSession(obj.getUser(), obj.getHost(), obj.getPort());
            session.connect();
            return session;
        } catch (JschException e) {
          e.printStackTrace();
          throw new RuntimeException();
        }
    }
    
    private static ChannelShell createSshChannel() {
        Session session = SSHSessionFactory.createSshSession(Obj obj)
        try {
            ChannelShell channel = (ChannelShell) session.openChannel("shell");
            channel.setPty(true);
            channel.setInputStream(null);
            channel.setOutputStream(null);
            return channel;
        } catch (JSchException e) {
            e.printStackTrace();
            throw new RuntimeException();
        }
    }
}

Answer 1

“shell”通道打开一个shell

我们不知道您的代码实际上做了什么。但是我假设您向shell发送一些要执行的命令，然后尝试读取命令输出。一旦命令输出结束，您可能希望得到-1<你不会的。

shell输出流仅在shell结束时结束。为此，您需要发送一些命令，如exit

---

一般来说，您不应该使用“shell”频道。它旨在实现一个交互式shell会话（就像您正在实现自己的SSH终端一样）。这是你很少做的事

要自动执行命令，请使用“exec”通道

另见What is the difference between the 'shell' channel and the 'exec' channel in JSch