Java实时读取日志文件

写日志文件，每秒写200条记录，并且记录写的时间

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.text.SimpleDateFormat;
import java.util.Date;

public class LogReader implements Runnable {
    private File logFile = null;
    private long lastTimeFileSize = 0; // 上次文件大小
    private static SimpleDateFormat dateFormat = new SimpleDateFormat(
            "yyyy-MM-dd HH:mm:ss");

    public LogReader(File logFile) {
        this.logFile = logFile;
        lastTimeFileSize = logFile.length();
    }

    /**
     * 实时输出日志信息
     */
    public void run() {
        while (true) {
            try {
                long len = logFile.length();
                if (len < lastTimeFileSize) {
                    System.out.println("Log file was reset. Restarting logging from start of file.");
                    lastTimeFileSize = len;
                } else if(len > lastTimeFileSize) {
                    RandomAccessFile randomFile = new RandomAccessFile(logFile, "r");
                    randomFile.seek(lastTimeFileSize);
                    String tmp = null;
                    while ((tmp = randomFile.readLine()) != null) {
                        System.out.println(dateFormat.format(new Date()) + "/t"
                                + tmp);
                    }
                    lastTimeFileSize = randomFile.length();
                    randomFile.close();
                }
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            
            try {
                Thread.sleep(50);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }

}

实时读取日志文件，每隔1秒读一次

import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.text.SimpleDateFormat;
import java.util.Date;

public class LogReader implements Runnable {
    private File logFile = null;
    private long lastTimeFileSize = 0; // 上次文件大小
    private static SimpleDateFormat dateFormat = new SimpleDateFormat(
            "yyyy-MM-dd HH:mm:ss");

    public LogReader(File logFile) {
        this.logFile = logFile;
        lastTimeFileSize = logFile.length();
    }

    /**
     * 实时输出日志信息
     */
    public void run() {
        while (true) {
            try {
                RandomAccessFile randomFile = new RandomAccessFile(logFile, "r");
                randomFile.seek(lastTimeFileSize);
                String tmp = null;
                while ((tmp = randomFile.readLine()) != null) {
                    System.out.println(dateFormat.format(new Date()) + "/t"
                            + tmp);
                }
                lastTimeFileSize = randomFile.length();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            try {
                Thread.sleep(500);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }

}

开启写线程、读线程，将实时信息打印在控制台。

import java.io.File;

public class RunRun {
    public static void main(String[] args) {
        File logFile = new File("mock.log");
        Thread wthread = new Thread(new LogWrite(logFile));
        wthread.start();
        Thread rthread = new Thread(new LogReader(logFile));
        rthread.start();
    }
}

在读写的过程中，我们可以手动将mock.log文件重命名，发现依旧可以实时读。