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<tank.zhang@99bill.com>
*@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.