log4j用properties文件配置，无法应用过滤器的解决方法

properties文件仍然有错误

log4j:WARN Failed to set property [filter] to value "org.apache.log4j.varia.LevelRangeFilter". 
log4j:ERROR Could not instantiate class [FATAL].

后来我在国外论坛上找到了答案

The PropertyConfigurator does not handle the advanced configuration features supported by the DOMConfigurator such as support for Filters, custom ErrorHandlers, nested appenders such as the AsyncAppender, etc.

翻译如下：

PropertyConfigurator 不能处理那些DOMConfigurator支持的高级配置功能，例如过滤器支持、自定义错误处理器、嵌套Appender（例如AsyncAppender）等等

看来xml配置才是log4j的王道。果然换了xml配置就可以使用了。

参考地址：http://stackoverflow.com/questions/1257641/cant-set-levelrangefilter-for-log4j