自定义log4j生成的log文件名

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很多时候，log4j的RollingFileAppender配置如下：

log4j.logger.cn.lettoo.Test=INFO, filelog4j.appender.file=org.apache.log4j.RollingFileAppenderlog4j.appender.file.MaxFileSize=100KBlog4j.appender.file.MaxBackupIndex=10log4j.appender.file.File=test.loglog4j.appender.file.layout=org.apache.log4j.PatternLayout  log4j.appender.file.layout.ConversionPattern=[%d{MM/dd/yyyy HH:mm:ss.SSS} %m%n

RollingFileAppender会自动在一个文件满了之后，生成一个如text.log.1的文件，一直生成到text.log.x（x值可配置log4j.appender.file.MaxBackupIndex＝10）为止，再回写text.log。

当我们有需要在产生一些自定义的log文件名的时候，比如：

引用

test_[process_name]_0_20111031.log
test_[process_name]_1_20111031.log
test_[process_name]_2_20111031.log
......

要在文件名显示是哪一个进程名，第一个文件为0，后面是1，2，3......，并且要加上日期，再使用RollingFileAppender做简单的配置是无论如何也实现不了了。

打开RollingFileAppender.java的源码，我看到它主要是用setFile(),subAppend()和rollOver()这几个方法来实现具体的功能的：

  public // synchronization not necessary since doAppend is alreasy synched  void rollOver() {    File target;    File file;    if (qw != null) {        long size = ((CountingQuietWriter) qw).getCount();        LogLog.debug("rolling over count=" + size);        //   if operation fails, do not roll again until        //      maxFileSize more bytes are written        nextRollover = size + maxFileSize;    }    LogLog.debug("maxBackupIndex="+maxBackupIndex);    boolean renameSucceeded = true;    // 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())       renameSucceeded = file.delete();      // Map {(maxBackupIndex - 1), ..., 2, 1} to {maxBackupIndex, ..., 3, 2}      for (int i = maxBackupIndex - 1; i >= 1 && renameSucceeded; i--) {file = new File(fileName + "." + i);if (file.exists()) {  target = new File(fileName + '.' + (i + 1));  LogLog.debug("Renaming file " + file + " to " + target);  renameSucceeded = file.renameTo(target);}      }    if(renameSucceeded) {      // 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);      renameSucceeded = file.renameTo(target);      //      //   if file rename failed, reopen file with append = true      //      if (!renameSucceeded) {          try {            this.setFile(fileName, true, bufferedIO, bufferSize);          }          catch(IOException e) {              if (e instanceof InterruptedIOException) {                  Thread.currentThread().interrupt();              }              LogLog.error("setFile("+fileName+", true) call failed.", e);          }      }    }    }    //    //   if all renames were successful, then    //    if (renameSucceeded) {    try {      // This will also close the file. This is OK since multiple      // close operations are safe.      this.setFile(fileName, false, bufferedIO, bufferSize);      nextRollover = 0;    }    catch(IOException e) {        if (e instanceof InterruptedIOException) {            Thread.currentThread().interrupt();        }        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());    }  }  /**     This method differentiates RollingFileAppender from its super     class.     @since 0.9.0  */  protected  void subAppend(LoggingEvent event) {    super.subAppend(event);    if(fileName != null && qw != null) {        long size = ((CountingQuietWriter) qw).getCount();        if (size >= maxFileSize && size >= nextRollover) {            rollOver();        }    }   }

如果我继承这个类，然后在子类里实现它的这三个方法，不就可以实现我要的功能了吗？
代码如下：

public class MWLogFileAppender extends RollingFileAppender {    private long nextRollover = 0;    public void rollOver() {        File target;        File file;        if (qw != null) {            long size = ((CountingQuietWriter) qw).getCount();            LogLog.debug("rolling over count=" + size);            // if operation fails, do not roll again until            // maxFileSize more bytes are written            nextRollover = size + maxFileSize;        }        LogLog.debug("maxBackupIndex=" + maxBackupIndex);        boolean renameSucceeded = true;        // 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);            file = new File(getRollingFileName(fileName, maxBackupIndex));            if (file.exists())                renameSucceeded = file.delete();            // Map {(maxBackupIndex - 1), ..., 2, 1} to {maxBackupIndex, ..., 3,            // 2}            for (int i = maxBackupIndex - 1; i >= 1 && renameSucceeded; i--) {                //file = new File(fileName + "." + i);                file = new File(getRollingFileName(fileName, i));                if (file.exists()) {                    //target = new File(fileName + '.' + (i + 1));                    target = new File(getRollingFileName(fileName, i+1));                    LogLog.debug("Renaming file " + file + " to " + target);                    renameSucceeded = file.renameTo(target);                }            }            if (renameSucceeded) {                // Rename fileName to fileName.1                //target = new File(fileName + "." + 1);                target = new File(this.getRollingFileName(fileName, 1));                this.closeFile(); // keep windows happy.                file = new File(fileName);                LogLog.debug("Renaming file " + file + " to " + target);                renameSucceeded = file.renameTo(target);                //                // if file rename failed, reopen file with append = true                //                if (!renameSucceeded) {                    try {                        this.setFile(fileName, true, bufferedIO, bufferSize);                    } catch (IOException e) {                        if (e instanceof InterruptedIOException) {                            Thread.currentThread().interrupt();                        }                        LogLog.error("setFile(" + fileName                                + ", true) call failed.", e);                    }                }            }        }        //        // if all renames were successful, then        //        if (renameSucceeded) {            try {                // This will also close the file. This is OK since multiple                // close operations are safe.                this.setFile(fileName, false, bufferedIO, bufferSize);                nextRollover = 0;            } catch (IOException e) {                if (e instanceof InterruptedIOException) {                    Thread.currentThread().interrupt();                }                LogLog.error("setFile(" + fileName + ", false) call failed.", e);            }        }    }    private String getRollingFileName(String fileName, int index) {        Pattern p = Pattern.compile("_\\d+\\.");         Matcher m=p.matcher(fileName);                return m.replaceFirst(String.format("_%d.", index));    }    public synchronized void setFile(String fileName, boolean append,            boolean bufferedIO, int bufferSize) throws IOException {        String processName = "01";        SimpleDateFormat format = new SimpleDateFormat("MMddyyyy");        String dateString = format.format(new Date(System.currentTimeMillis()));        String processId = String.valueOf(Thread.currentThread().getId());        String temp = String.format(fileName, processName, dateString,                processId);        //System.out.println(temp);        super.setFile(temp, append, bufferedIO, bufferSize);    }    protected void subAppend(LoggingEvent event) {        super.subAppend(event);        if (fileName != null && qw != null) {            long size = ((CountingQuietWriter) qw).getCount();            if (size >= maxFileSize && size >= nextRollover) {                rollOver();            }        }    }}

在setFile方法里，通过String的替换来实现我要的自定义字符串的功能，当然，这里只是一个示例。
文件满了之后生成新的文件编号，不再在log后面加数据，而是在文件名体现，我这里加了一个getRollingFileName()来根据正则表达式来替换。

当然，配置文件可以修改如下了：

log4j.logger.cn.lettoo.Test=INFO, filelog4j.appender.file=org.apache.log4j.RollingFileAppenderlog4j.appender.file.MaxFileSize=100KBlog4j.appender.file.MaxBackupIndex=10log4j.appender.file.File=test-%s_%s_0.%s.loglog4j.appender.file.layout=org.apache.log4j.PatternLayout  log4j.appender.file.layout.ConversionPattern=[%d{MM/dd/yyyy HH:mm:ss.SSS} %m%n

虽然以上的做法满足了我的要求，但是我感觉也有缺点，主要是：

配置文件必须要按我自定义的格式来写，即log4j.appender.file.File=test-%s_%s_0.%s.log不能搞错了
RollingFileAppender的几个方法扩展的都不好，还把原来的代码copy过来修改的。

转载地址：http://lettoo.iteye.com/blog/1226671

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