MySQL jdbc.url 认知

useUnicode　　默认为 true

characterEncoding　　仅在 useUnicode=true 时起作用，默认 autodetect，常设为 UTF-8

autoReconnect　　默认 false，官方： 

The use of this feature is not recommended, 
because it has side effects related to session state and data consistency when applications don't handle SQLExceptions properly, 
and is only designed to be used when you are unable to configure your application to handle SQLExceptions resulting from dead and stale connections properly.

autoReconnectForPools　　默认 false

useServerPrepStmts　　是否开启服务端 prepared statements，默认 false。配合 cachePrepStmts=true 等配置，缓存 sql 预编译脚本，提升执行效率；相应会多占用内存

cachePrepStmts=true&prepStmtCacheSize=250&prepStmtCacheSqlLimit=2048　　开启缓存预编译的 sql，根据 LRU 策略最大缓存 250 条，只缓存长度在 2048 以下的 sql

useSSL　　某些版本 MySQL 需要显示声明 true/false