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记录一个点：
很多时候，生产环境的log4j appender会设置bufferIO。但是系统意外挂了就会丢失部分日志。通过下面的语句flush log4j的日志：
LogManager.shutdown();
或者：
public static void flushAllLogs()
{
try
{
Set<FileAppender> flushedFileAppenders = new HashSet<FileAppender>();
Enumeration currentLoggers = LogManager.getLoggerRepository().getCurrentLoggers();
while(currentLoggers.hasMoreElements())
{
Object nextLogger = currentLoggers.nextElement();
if(nextLogger instanceof Logger)
{
Logger currentLogger = (Logger) nextLogger;
Enumeration allAppenders = currentLogger.getAllAppenders();
while(allAppenders.hasMoreElements())
{
Object nextElement = allAppenders.nextElement();
if(nextElement instanceof FileAppender)
{
FileAppender fileAppender = (FileAppender) nextElement;
if(!flushedFileAppenders.contains(fileAppender) && !fileAppender.getImmediateFlush())
{
flushedFileAppenders.add(fileAppender);
//log.info("Appender "+fileAppender.getName()+" is not doing immediateFlush ");
fileAppender.setImmediateFlush(true);
currentLogger.info("FLUSH");
fileAppender.setImmediateFlush(false);
}
else
{
//log.info("fileAppender"+fileAppender.getName()+" is doing immediateFlush");
}
}
}
}
}
}
catch(RuntimeException e)
{
log.error("Failed flushing logs",e);
}
}
PS：可能要增加一个java代码的钩子， 在系统关闭的时候触发。
//增加关闭钩子
Runtime.getRuntime().addShutdownHook(new Thread(){
public void run(){
//STH TODO
}
});
//移除关闭钩子
Runtime.getRuntime().removeShutdownHook(hook);
其实是“参考” stackoverflow的：
http://stackoverflow.com/questions/3060240/how-do-you-flush-a-buffered-log4j-fileappender
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原文地址：http://www.cnblogs.com/ELMND/p/5140184.html
