Java实时监控日志文件并输出

   最近有一个银行数据漂白系统,要求操作人员在页面调用远端Linux服务器的shell,并将shell输出的信息保存到一个日志文件,前台页面要实时显示日志文件的内容.这个问题难点在于如何判断哪些数据是新增加的,通过查看JDK 的帮助文档,java.io.RandomAccessFile
可以解决这个问题.为了模拟这个问题,编写LogSvr和 LogView类,LogSvr不断向mock.log日志文件写数据,而 LogView则实时输出日志变化部分的数据.

代码1:日志产生类

package com.bill99.seashell.domain.svr;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
/**
 *<p>title: 日志服务器</p>
 *<p>Description: 模拟日志服务器</p>
 *<p>CopyRight: CopyRight (c) 2010</p>
 *<p>Company: 99bill.com</p>
 *<p>Create date: 2010-6-18</P>
 *@author Tank Zhang<[email protected]>
 *@version v0.1 2010-6-18
 */
public class LogSvr {

    private SimpleDateFormat dateFormat =
        new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");

    /**
     * 将信息记录到日志文件
     * @param logFile 日志文件
     * @param mesInfo 信息
     * @throws IOException
     */
    public void logMsg(File logFile,String mesInfo) throws IOException{
        if(logFile == null) {
            throw new IllegalStateException("logFile can not be null!");
        }
        Writer txtWriter = new FileWriter(logFile,true);
        txtWriter.write(dateFormat.format(new Date()) +"\t"+mesInfo+"\n");
        txtWriter.flush();
    }

    public static void main(String[] args) throws Exception{

        final LogSvr logSvr = new LogSvr();
        final File tmpLogFile = new File("mock.log");
        if(!tmpLogFile.exists()) {
            tmpLogFile.createNewFile();
        }
        //启动一个线程每5秒钟向日志文件写一次数据
        ScheduledExecutorService exec =
            Executors.newScheduledThreadPool(1);
        exec.scheduleWithFixedDelay(new Runnable(){
            public void run() {
                try {
                    logSvr.logMsg(tmpLogFile, " 99bill test !");
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
        }, 0, 5, TimeUnit.SECONDS);
    }
}

 代码2:显示日志的类

 

 

package com.bill99.seashell.domain.client;

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class LogView {
    private long lastTimeFileSize = 0;  //上次文件大小
    /**
     * 实时输出日志信息
     * @param logFile 日志文件
     * @throws IOException
     */
    public void realtimeShowLog(File logFile) throws IOException{
        //指定文件可读可写
        final RandomAccessFile randomFile = new RandomAccessFile(logFile,"rw");
        //启动一个线程每10秒钟读取新增的日志信息
        ScheduledExecutorService exec =
            Executors.newScheduledThreadPool(1);
        exec.scheduleWithFixedDelay(new Runnable(){
            public void run() {
                try {
                    //获得变化部分的
                    randomFile.seek(lastTimeFileSize);
                    String tmp = "";
                    while( (tmp = randomFile.readLine())!= null) {
                        System.out.println(new String(tmp.getBytes("ISO8859-1")));
                    }
                    lastTimeFileSize = randomFile.length();
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
        }, 0, 1, TimeUnit.SECONDS);
    }

    public static void main(String[] args) throws Exception {
        LogView view = new LogView();
        final File tmpLogFile = new File("mock.log");
        view.realtimeShowLog(tmpLogFile);
    }

}

 

执行LogSvr类,LogSvr类会启动一个线程,每5秒钟向mock.log日志文件写一次数据,然后再执行LogView类,LogView每隔1秒钟读一次,如果数据有变化则输出变化的部分.

 

结果输出:

2010-06-19 17:25:54  99bill test !
2010-06-19 17:25:59  99bill test !
2010-06-19 17:26:04  99bill test !
2010-06-19 17:26:09  99bill test !
2010-06-19 17:26:14  99bill test !
2010-06-19 17:26:19  99bill test !

 

 

PS:

  代码修改过, 有朋友下载了我的代码,说如果是中文会乱码,将日志输出类的第30行的代码  
  System.out.println(tmp)改成 System.out.println(new String(tmp.getBytes("ISO8859-1"))),就会正常显示中文.