Java写入文本文件无法正常工作

Question

The Java application that I support is logging some details in a flat file. the problem I face some times is that, the entry is very low compared to the previous day. This entry is most essential because our reports are generated based on the file. I went thro code for writing I couldn't figure out any issues. the method which is writing is sync method.

Any suggestions? I can also provide the code for you is you may need?

 public synchronized void log (String connID, String hotline, String callerType,
        String cli, String lastMenu, String lastInput,
        String status, String reason)
   {
    //String absoluteFP = LOG_LOC + ls + this.getFilename();

    //PrintWriter pw = this.getPrintWriter(absoluteFP, true, true);

    try
    {
        pw.print (this.getDateTime ()+ ","+connID +","+hotline+","+callerType+","+ cli+"," +   lastMenu + "," + lastInput + "," + status + "," + reason);               


        //end 1006
        pw.print (ls);
        pw.flush ();
        //pw.close();
    }
    catch (Exception e)
    {
        e.printStackTrace ();
        return;
    }
}

private synchronized PrintWriter getPrintWriter (String absoluteFileName,
        boolean append, boolean autoFlush)
{
    try
    {
        //set absolute filepath
        File folder = new File (absoluteFileName).getParentFile ();//2009-01-23

        File f = new File (absoluteFileName);

        if (!folder.exists ())//2009-01-23
        {
            //System.out.println ("Call Detailed Record folder NOT FOUND! Creating a new);     
            folder.mkdirs ();

            //System.out.println ("Configure log folder");
            this.setHiddenFile (LOG_LOC);//set tmp directory to hidden folder

            if (!f.exists ())
            {
                //System.out.println ("Creating a new Call Detailed Record...");//2009-01-23

                f.createNewFile ();//2009-01-23

                               }
        }
        else
        {
            if (!f.exists ())
            {
                //System.out.println ("Creating a new Call Detailed Record...");//2009-01-23

                f.createNewFile ();//2009-01-23


            }
        }

        FileOutputStream tempFOS = new FileOutputStream (absoluteFileName, append);
        if (tempFOS != null)
        {
            return new PrintWriter (tempFOS, autoFlush);
        }
        else
        {
            return null;
        }
    }
    catch (Exception ex)
    {
        ex.printStackTrace ();
        return null;
    }
}

          /**
             * Set the given absolute file path as a hidden file.
        * @param absoluteFile String
      */
     private void setHiddenFile (String absoluteFile)
       {
    //set hidden file
    //2009-01-22, KC
    Runtime rt = Runtime.getRuntime ();
    absoluteFile = absoluteFile.substring (0, absoluteFile.length () - 1);//2009-01-23
    try
    {
      System.out.println (rt.exec ("attrib +H " + "\"" + absoluteFile +        "\"").getInputStream ().toString ());
    }
    catch (IOException e)
    {
        e.printStackTrace ();
    }
}

private String getDateTime ()
{
    //2011-076-09, KC-format up to milliseconds to prevent duplicate PK in CDR table.
    //return DateUtils.now ("yyyy/MM/dd HH:mm:ss");
    return DateUtils.now ("yyyy/MM/dd HH:mm:ss:SSS");
    //end 0609
}

private String getFilename ()
{
    ///return "CDR_" + port + ".dat";//2010-10-01
    return port + ".dat";//2010-10-01
}

public void closePW ()
{
    if (pw != null)
    {
        pw.close ();
    }
}

Answer 1

You've created a FileOutputStream , but aren't closing that stream. Close that stream and try again. That might be causing the problem.

Messages are getting logged sometime because the garbage collector kicks in at some intervals and closes the FileOutStream . This then allows messages to be logged again. You're getting the unreachable error since you have a return statement in both the if & else blocks. You'll have to take the PrintWriter and FileOutStreamWriter out of the getPrintWriter put it where you usually call the getPrintWriter() . Then you'll be able to close the streams correctly. getPrintWriter should only ensure file exists, so rename it to ensureFileExistance

Answer 2

If you can use Apache Common IO, try this:

public synchronized void log(String connID, String hotline, String callerType,
        String cli, String lastMenu, String lastInput,
        String status, String reason) {
    String absoluteFP = LOG_LOC + ls + this.getFilename();
    File file = new File(absoluteFP);
    String message = this.getDateTime() + "," + connID + "," + hotline + "," + callerType + "," + cli + "," + lastMenu + "," + lastInput + "," + status + "," + reason;
    try {
        // note that you must explicitly add new line character if you want the line to end with newline
        FileUtils.write(file, message + "\n", "UTF-8", true);
    } catch (IOException ex) {
        ex.printStackTrace ();
    }
}

In Common IO 2.1, you can append a file that you are writting to. You can now get rid of the closePW and getPrintwriter and since the log method is synchronized , the file can be written one at a time from the same object. However, if you try to write the same file from different object at the same time, you will end up having overwritting problem.

Also, Common IO create the missing parent folder for you automatically. There is no need to explicitly check and create the folder.