Question

我必须在我的远程linux机器上拖尾日志文件并在浏览器上连续打印输出。我已经设法使用JSch尾随它，我当前正在将输出打印为System out。我现在正在使用servlet（尽管客户端只是使用jsp）。问题是，当我尝试在浏览器上打印尾流时，浏览器会进入冻结状态，好像它正在不断加载某些东西（它是!!）。在浏览器冻结时，sysout日志可以在控制台上完美地打印尾流。这是我的servlet

package sshUploader;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintStream;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Run several ssh commands in a single JSch session
 */
import com.jcraft.jsch.Channel;
import com.jcraft.jsch.JSch;
import com.jcraft.jsch.Session;
import java.io.*;
import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.Hashtable;

/**
 * Servlet implementation class TailLogServlet
 */
@WebServlet(description = "This servlet tails the remote logs", urlPatterns = { "/TailLogServlet" })
public class TailLogServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public TailLogServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        try{
            System.out.println("**************************ADI NEW*****************");
            JSch jsch = new JSch();
              String user = <user>;            //CHANGE ME
              String host = <host>; //CHANGE ME
              String passwd = <pwd>;      //CHANGE ME
              int port = 22;    
              Session session = jsch.getSession(user, host, port);
              session.setPassword(passwd);

              Hashtable<String, String> hashtable  = new Hashtable<String, String>();
              hashtable.put("StrictHostKeyChecking", "no");
              session.setConfig(hashtable);

              session.connect();

              Channel channel = session.openChannel("shell");
              OutputStream ops = channel.getOutputStream();
              PrintStream ps = new PrintStream(ops, true);

              channel.connect();
              InputStream input = channel.getInputStream();

              ps.println("tail -f /home/LogFile.log");
              ps.close();

             // response.setIntHeader("Refresh", 1);
              response.setContentType("text/html");

              /*Calendar calendar = new GregorianCalendar();
              String am_pm;
              int hour = calendar.get(Calendar.HOUR);
              int minute = calendar.get(Calendar.MINUTE);
              int second = calendar.get(Calendar.SECOND);
              if(calendar.get(Calendar.AM_PM) == 0)
                am_pm = "AM";
              else
                am_pm = "PM";

              String CT = hour+":"+ minute +":"+ second +" "+ am_pm;*/

              PrintWriter out = new PrintWriter (response.getOutputStream());//.getWriter();
              out.println("<html><head><title>GuestBookServlet</title></head>");
              out.println("<body>********************");

              int SIZE = 1024;
              byte[] tmp = new byte[SIZE];
              while (true)
              {
                 while (input.available() > 0)
                 {
                    int i = input.read(tmp, 0, SIZE);
                    if(i < 0)
                       break;
                     System.out.print(new String(tmp, 0, i)); // use document.write(new String(tmp, 0, i));
                   // System.out.println("******Adi i :"+i);
                    //out.println("Out by Adi i :"+i);
                   out.println(new String(tmp, 0, i));
                 }
                 if(!channel.isConnected())
                 {
                    System.out.println("exit-status: " + channel.getExitStatus());
                    break;
                 }
                 try
                 {
                    Thread.sleep(300);
                 }
                 catch (Exception ee)
                 {
                 }
             }
              out.println("</body></html>");
              out.close();


              channel.disconnect();
              session.disconnect();
        }catch(Exception e){
            e.printStackTrace();

        }
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
    }

}

这只会在打印流时遇到困难。如果我通过不断更新它来尝试打印当前时间，我能够。它在浏览器中完美体现。有什么出路吗？

修改好的，我已经缩小到了

根本原因

。这是

无限循环

我在这里申请。此循环连续检查输入流中是否有来自远程的任何内容。因此，sysout正确打印，但out.write不正确。如果我删除无限循环，则会打印一行，因为它是远程输入流中唯一的thig。关于如何在浏览器内部无限循环获取输出的任何想法？

Answer 1

好的，我终于在花了一些时间之后就做到了。在客户交付繁忙的时候在这里更新。以下是步骤编写了一个名为TailLogServlet.java的servlet，它具有拖尾远程日志的代码。准备了一个名为showTailLogs.jsp的jsp，它每2秒通过ajax调用一次这个servlet，并在浏览器上打印响应。此调用在jsp的 body onLoad 函数中完成这是servlet和jsp：

的 showTailLogs.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <link rel="stylesheet" type="text/css" href="css/myStyle.css"> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <script type="text/javascript" src="jquery.js"></script> <title>Show Tail Logs</title> <script> var binDone = false; var lastUpdate = "Starting logs"; function tail2() { if (!binDone) { $.post("/<<Context>>/TailLogServlet", { logUID:"<%= request.getParameter("logUID")%>", logPwd:"<%= request.getParameter("logPwd")%>", host:"<%= request.getParameter("host")%>", logFileName:"<%= request.getParameter("logFileName")%>" }, function(data,status){ $("#thePlace").append(data); if (data.indexOf(lastUpdate)>-1) { binDone = true; } }); } } </script> </head> <body onLoad='tail2(); setInterval("tail2()", 2000)'> <div id="wrapper" class="radius"> <div id="imageContainer"> <img alt="my Image" class="myLogo" src="myLogo.jpg" /> <h1>Show Tail Logs</h1> </div> <div id="navContainer" style="color:white"> Logs Update automatically. Please don't press refresh button... </div> <div> <div id="thePlace"></div> </div> </body> </div> </html>

的 TailLogServlet.java

package sshUploader; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.io.PrintStream; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /** * Run several ssh commands in a single JSch session */ import com.jcraft.jsch.Channel; import com.jcraft.jsch.JSch; import com.jcraft.jsch.Session; import java.io.*; import java.util.Calendar; import java.util.GregorianCalendar; import java.util.Hashtable; /** * Servlet implementation class TailLogServlet */ @WebServlet(description = "This servlet tails the remote logs", urlPatterns = { "/TailLogServlet" }) public class TailLogServlet extends HttpServlet { private static final long serialVersionUID = 1L; /** * @see HttpServlet#HttpServlet() */ public TailLogServlet() { super(); // TODO Auto-generated constructor stub } /** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */ protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { try { //System.out.println("*************GETTT TailLogServlet Hit. logFileName :"+request.getParameter("logFileName")); PrintWriter pw=response.getWriter(); response.setContentType("text/html"); response.setHeader("Cache-Control", "no-cache"); JSch jsch = new JSch(); String user = request.getParameter("logUID"); //CHANGE ME String host = request.getParameter("host");//CHANGE ME String passwd = request.getParameter("logPwd"); //CHANGE ME int port = 22; Session session = jsch.getSession(user, host, port); session.setPassword(passwd); Hashtable<String, String> hashtable = new Hashtable<String, String>(); hashtable.put("StrictHostKeyChecking", "no"); session.setConfig(hashtable); session.connect(); Channel channel = session.openChannel("shell"); OutputStream ops = channel.getOutputStream(); PrintStream ps = new PrintStream(ops, true); channel.connect(); InputStream input = channel.getInputStream(); ps.println("tail -f "+request.getParameter("logFileName")); ps.close(); int SIZE = 1024; byte[] tmp = new byte[SIZE]; long startTime = System.currentTimeMillis(); while ((System.currentTimeMillis()-startTime)< 3*1000){ while (input.available() > 0) { int i = input.read(tmp, 0, SIZE); if(i < 0) break; System.out.println(new String(tmp, 0, i)); pw.println(new String(tmp, 0, i)); } pw.flush(); } }catch(Exception e) { e.printStackTrace(); } } /** * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response) */ protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub //System.out.println("*************POSTTTTT TailLogServlet Hit. logFileName :"+request.getParameter("logFileName")); doGet(request, response); } }

代码可能有一些不需要的导入，因为我还没有完成清理。

在浏览器上打印远程文件

1 个答案: