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.
