Java实时监控日志文件并输出的方法详解

想在前台显示数据同步过程中产生的日志文件，在网上找到解决方案，做了代码测试好用。这里做个记录

java.io.RandomAccessFile可以解决同时向文件读和写.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.fbkj.genelog;

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;

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();

String userdir = System.getProperty("user.dir");

final File tmpLogFile = new File(userdir+"/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.fbkj.genelog;

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 {

String userdir = System.getProperty("user.dir");

LogView view = new LogView();

final File tmpLogFile = new File(userdir+"/mock.log");

view.realtimeShowLog(tmpLogFile);

}

}

先执行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.