一、数据库连接池架构
二、数据库连接池的过滤器
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
三、druid连接池返回的连接其实是包装类
com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl
com.alibaba.druid.pool.DruidPooledConnection