一、配置属性文件log4j.properties

log4j.rootLogger=INFO,stdout,R

log4j.appender.stdout=org.apache.log4j.ConsoleAppender

log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

# Pattern to output the caller's file name and line number.

log4j.appender.stdout.layout.ConversionPattern=%-d{yyyy-MM-dd HH\:mm\:ss} %5p [%t] (%F\:%L) - %m%n

log4j.appender.R=org.apache.log4j.DailyRollingFileAppender

log4j.appender.R.File=/home/log/system

log4j.appender.R.DatePattern ='.'yyyy-MM-dd'.log'

log4j.appender.R.layout=org.apache.log4j.PatternLayout

log4j.appender.R.layout.ConversionPattern=%-d{yyyy-MM-dd HH\:mm\:ss} [%c]-[%p] [%t] (%F\:%L) ->%m %n

二、项目初始化log4j

PropertyConfigurator.configure(log4j);

.......

此步骤略。

三、修改log4j源代码中DailyRollingFileAppender.java文件。

将log4j的源文件加入项目中。修改：

/**

* Rollover the current file to a new file.

*/

void rollOver() throws IOException {

/* Compute filename, but only if datePattern is specified */

if (datePattern == null) {

errorHandler.error("Missing DatePattern option in rollOver().");

return;

}

String datedFilename = fileName + sdf.format(now);

// It is too early to roll over because we are still within the

// bounds of the current interval. Rollover will occur once the

// next interval is reached.

if (scheduledFilename.equals(datedFilename)) {

return;

}

// close current file, and rename it to datedFilename

this.closeFile();

File target = new File(scheduledFilename);

if (target.exists()) {

target.delete();

}

File file = new File(fileName);

// boolean result = file.renameTo(target);  boolean result = copy(file, target);  if (result) {

LogLog.debug(fileName + " -> " + scheduledFilename);

} else {

LogLog.error("Failed to rename [" + fileName + "] to ["

+ scheduledFilename + "].");

}

try {

// This will also close the file. This is OK since multiple

// close operations are safe.

this.setFile(fileName, false, this.bufferedIO, this.bufferSize);

} catch (IOException e) {

errorHandler.error("setFile(" + fileName + ", false) call failed.");

}

scheduledFilename = datedFilename;

}

修改删除黄色代码，并添加蓝色代码。

并加入方法copy。

boolean copy(File src, File dst) throws IOException {

try {

InputStream in = new FileInputStream(src);

OutputStream out = new FileOutputStream(dst);

// Transfer bytes from in to out

byte[] buf = new byte[8192];

int len;

while ((len = in.read(buf)) > 0) {

out.write(buf, 0, len);

}

in.close();

out.close();

return true;

} catch (FileNotFoundException e) {

LogLog.error("源文件不存在,或者目标文件无法被识别.");

return false;

} catch (IOException e) {

LogLog.error("文件读写错误.");

return false;

}

}

原因：

如果不修改DailyRollingFileAppender中的renameTo方法，发报错：Log4j的log4j:ERROR Failed to rename错误。