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The source code

/*
 * Copyright (C) The Apache Software Foundation. All rights reserved.
 *
 * This software is published under the terms of the Apache Software
 * License version 1.1, a copy of which has been included with this
 * distribution in the LICENSE.txt file.  */



package org.apache.log4j;

import java.io.IOException;
import java.io.Writer;
import java.io.File;
import org.apache.log4j.helpers.OptionConverter;
import org.apache.log4j.helpers.LogLog;
import org.apache.log4j.helpers.CountingQuietWriter;
import org.apache.log4j.spi.LoggingEvent;

/**
   RollingFileAppender extends FileAppender to backup the log files when
   they reach a certain size.

   @author Heinz Richter
   @author Ceki Gülcü

*/
public class RollingFileAppender extends FileAppender {

  /**
     The default maximum file size is 10MB.
  */
  protected long maxFileSize = 10*1024*1024;

  /**
     There is one backup file by default.
   */
  protected int  maxBackupIndex  = 1;

  /**
     The default constructor simply calls its {@link
     FileAppender#FileAppender parents constructor}.  */
  public
  RollingFileAppender() {
    super();
  }

  /**
    Instantiate a RollingFileAppender and open the file designated by
    filename. The opened filename will become the ouput
    destination for this appender.

    

If the append parameter is true, the file will be appended to. Otherwise, the file desginated by filename will be truncated before being opened. */ public RollingFileAppender(Layout layout, String filename, boolean append) throws IOException { super(layout, filename, append); } /** Instantiate a FileAppender and open the file designated by filename. The opened filename will become the output destination for this appender.

The file will be appended to. */ public RollingFileAppender(Layout layout, String filename) throws IOException { super(layout, filename); } /** Returns the value of the MaxBackupIndex option. */ public int getMaxBackupIndex() { return maxBackupIndex; } /** Get the maximum size that the output file is allowed to reach before being rolled over to backup files. @since 1.1 */ public long getMaximumFileSize() { return maxFileSize; } /** Implements the usual roll over behaviour.

If MaxBackupIndex is positive, then files {File.1, ..., File.MaxBackupIndex -1} are renamed to {File.2, ..., File.MaxBackupIndex}. Moreover, File is renamed File.1 and closed. A new File is created to receive further log output.

If MaxBackupIndex is equal to zero, then the File is truncated with no backup files created. */ public // synchronization not necessary since doAppend is alreasy synched void rollOver() { File target; File file; LogLog.debug("rolling over count=" + ((CountingQuietWriter) qw).getCount()); LogLog.debug("maxBackupIndex="+maxBackupIndex); // If maxBackups <= 0, then there is no file renaming to be done. if(maxBackupIndex > 0) { // Delete the oldest file, to keep Windows happy. file = new File(fileName + '.' + maxBackupIndex); if (file.exists()) file.delete(); // Map {(maxBackupIndex - 1), ..., 2, 1} to {maxBackupIndex, ..., 3, 2} for (int i = maxBackupIndex - 1; i >= 1; i--) { file = new File(fileName + "." + i); if (file.exists()) { target = new File(fileName + '.' + (i + 1)); LogLog.debug("Renaming file " + file + " to " + target); file.renameTo(target); } } // Rename fileName to fileName.1 target = new File(fileName + "." + 1); this.closeFile(); // keep windows happy. file = new File(fileName); LogLog.debug("Renaming file " + file + " to " + target); file.renameTo(target); } try { // This will also close the file. This is OK since multiple // close operations are safe. this.setFile(fileName, false, bufferedIO, bufferSize); } catch(IOException e) { LogLog.error("setFile("+fileName+", false) call failed.", e); } } public synchronized void setFile(String fileName, boolean append, boolean bufferedIO, int bufferSize) throws IOException { super.setFile(fileName, append, this.bufferedIO, this.bufferSize); if(append) { File f = new File(fileName); ((CountingQuietWriter) qw).setCount(f.length()); } } /** Set the maximum number of backup files to keep around.

The MaxBackupIndex option determines how many backup files are kept before the oldest is erased. This option takes a positive integer value. If set to zero, then there will be no backup files and the log file will be truncated when it reaches MaxFileSize. */ public void setMaxBackupIndex(int maxBackups) { this.maxBackupIndex = maxBackups; } /** Set the maximum size that the output file is allowed to reach before being rolled over to backup files.

This method is equivalent to {@link #setMaxFileSize} except that it is required for differentiating the setter taking a long argument from the setter taking a String argument by the JavaBeans {@link java.beans.Introspector Introspector}. @see #setMaxFileSize(String) */ public void setMaximumFileSize(long maxFileSize) { this.maxFileSize = maxFileSize; } /** Set the maximum size that the output file is allowed to reach before being rolled over to backup files.

In configuration files, the MaxFileSize option takes an long integer in the range 0 - 2^63. You can specify the value with the suffixes "KB", "MB" or "GB" so that the integer is interpreted being expressed respectively in kilobytes, megabytes or gigabytes. For example, the value "10KB" will be interpreted as 10240. */ public void setMaxFileSize(String value) { maxFileSize = OptionConverter.toFileSize(value, maxFileSize + 1); } protected void setQWForFiles(Writer writer) { this.qw = new CountingQuietWriter(writer, errorHandler); } /** This method differentiates RollingFileAppender from its super class. @since 0.9.0 */ protected void subAppend(LoggingEvent event) { super.subAppend(event); if((fileName != null) && ((CountingQuietWriter) qw).getCount() >= maxFileSize) this.rollOver(); } }

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