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.