Java即時讀取記錄檔__Java

 

在一台伺服器上寫記錄檔，每當記錄檔寫到一定大小時，比如是1G，會將這個記錄檔改名成另一個名字，並建立一個與原檔案名稱相同的記錄檔，再往這個建立的記錄檔裡寫資料；要求寫一個程式能即時地讀取記錄檔中的內容，並且不能影響寫操作與重新命名操作。

RandomAccessFile類中seek方法可以從指定位置讀取檔案，可以用來實現檔案即時讀取。JDK文檔對RandomAccessFile的介紹

在每一次讀取後，close一下就不會影響重新命名操作了。

寫記錄檔，每秒寫200條記錄，並且記錄寫的時間

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 LogWrite implements Runnable {      private File logFile = null;    private SimpleDateFormat dateFormat =           new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");      public LogWrite(File logFile) {    this.logFile = logFile;}      /**      * 將資訊記錄到記錄檔      * @param logFile 記錄檔      * @param mesInfo 資訊      * @throws IOException       */      public void run(){          if(logFile == null) {              throw new IllegalStateException("logFile can not be null!");          }         try {            if(!logFile.exists()) {          logFile.createNewFile();          }         //啟動一個線程每1秒鐘向記錄檔寫一次資料              ScheduledExecutorService exec = Executors.newScheduledThreadPool(1);              exec.scheduleWithFixedDelay(new Runnable(){                 public void run() {                     try {                     Writer txtWriter = new FileWriter(logFile,true);                  txtWriter.write(dateFormat.format(new Date()) +"\t 99bill test ! \n");                    txtWriter.flush();                       } catch (IOException e) {                         throw new RuntimeException(e);                     }                 }             }, 0, 1, TimeUnit.SECONDS);         } catch (IOException e) { e.printStackTrace();}      }                public static void main(String[] args) throws Exception{                    final File tmpLogFile = new File("mock.log");          final LogWrite logSvr = new LogWrite(tmpLogFile);             //啟動一個線程每5秒鐘向記錄檔寫一次資料   /*       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.NANOSECONDS);*/      }  }  

即時讀取記錄檔，每隔1秒讀一次

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; // 上次檔案大小    private static SimpleDateFormat dateFormat = new SimpleDateFormat(            "yyyy-MM-dd HH:mm:ss");    public LogReader(File logFile) {        this.logFile = logFile;        lastTimeFileSize = logFile.length();    }    /**     * 即時輸出日誌資訊     */    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();            }        }    }}

開啟寫線程、讀線程，將即時資訊列印在控制台。

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();    }}

在讀寫的過程中，我們可以手動將mock.log檔案重新命名，發現依舊可以即時讀。