log4j:WARN No appenders could be found for logger

在测试JSEL时，调用自定义函数时，出现 异常如下：

log4j:WARN No appenders could be found for logger

log4j:WARN Please initialize the log4j system properly.

解决办法 参考Joshua Taylor的回答 ，链接如下：

http://stackoverflow.com/questions/12532339/no-appenders-could-be-found-for-loggerlog4j

内容如下：

This Short introduction to log4j guide is a little bit old but still valid.

That guide will give you some information about how to use loggers and appenders.

Just to get you going you have two simple approaches you can take.

First one is to just add this line to your main method:

BasicConfigurator.configure();

Second approach is to add this standard log4j.properties (taken from the above mentioned guide) file to your classpath:

# Set root logger level to DEBUG and its only appender to A1.
log4j.rootLogger=DEBUG, A1

# A1 is set to be a ConsoleAppender.
log4j.appender.A1=org.apache.log4j.ConsoleAppender

# A1 uses PatternLayout.
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=%-4r [%t] %-5p %c %x - %m%n