spi的思想，加载配置文件的Filter
druid.filters.default=com.alibaba.druid.filter.stat.StatFilter druid.filters.stat=com.alibaba.druid.filter.stat.StatFilter druid.filters.mergeStat=com.alibaba.druid.filter.stat.MergeStatFilter druid.filters.counter=com.alibaba.druid.filter.stat.StatFilter druid.filters.encoding=com.alibaba.druid.filter.encoding.EncodingConvertFilter druid.filters.log4j=com.alibaba.druid.filter.logging.Log4jFilter druid.filters.log4j2=com.alibaba.druid.filter.logging.Log4j2Filter druid.filters.slf4j=com.alibaba.druid.filter.logging.Slf4jLogFilter druid.filters.commonlogging=com.alibaba.druid.filter.logging.CommonsLogFilter druid.filters.commonLogging=com.alibaba.druid.filter.logging.CommonsLogFilter druid.filters.wall=com.alibaba.druid.wall.WallFilter druid.filters.config=com.alibaba.druid.filter.config.ConfigFilter
com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl
com.alibaba.druid.pool.DruidPooledConnection
参考：https://www.jianshu.com/p/3f2401d14c78
https://www.jianshu.com/p/4df8d4019055
原文：https://www.cnblogs.com/shangxiaofei/p/10746302.html
