Java實時監控日誌文件並輸出的方法詳解

想在前臺顯示數據同步過程當中產生的日誌文件，在網上找到解決方案，作了代碼測試好用。這裏作個記錄html

java.io.RandomAccessFile能夠解決同時向文件讀和寫.爲了模擬這個問題,編寫LogSvr和 LogView類,LogSvr不斷向mock.log日誌文件寫數據,而 LogView則實時輸出日誌變化部分的數據.java

代碼1:日誌產生類

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");

    /**
     * 將信息記錄到日誌文件
     * @param logFile 日誌文件
     * @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();
        }

        //啓動一個線程每5秒鐘向日志文件寫一次數據
        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);
    }
}

代碼2:顯示日誌的類

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
    /**
     * 實時輸出日誌信息
     * @param logFile 日誌文件
     * @throws IOException
     */
    public void realtimeShowLog(File logFile) throws IOException{
        //指定文件可讀可寫
        final RandomAccessFile randomFile = new RandomAccessFile(logFile,"rw");
        //啓動一個線程每10秒鐘讀取新增的日誌信息
        ScheduledExecutorService exec =
                Executors.newScheduledThreadPool(1);
        exec.scheduleWithFixedDelay(new Runnable(){
            public void run() {
                try {
                    //得到變化部分的
                    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);
    }
}

先執行LogSvr類,LogSvr類會啓動一個線程,每5秒鐘向mock.log日誌文件寫一次數據,dom

而後再執行LogView類,LogView每隔1秒鐘讀一次,若是數據有變化則輸出變化的部分.測試

參考 https://www.qedev.com/dev/245197.html spa