TransactionException in Hibernate and MySQL

在過一段時間後會出現如上錯誤訊息，這是因為MySQL已經切斷閒置的連線，所以可以利用connection pool的配置來處理這個問題。
Mysql服務器預設的「wait_timeout」是8小時(待查證)，所以mysql配置中my.ini 的wait_timeout值一定要大於等於connection pool的idle_timeout 值，否則mysql會在wait_timeout的時間後關閉連接，然而連接池還認為該連接可用，這樣就會產生以上圖內的錯誤。
MySQL :
interactive_timeout=XX
The number of seconds the server waits for activity on an interactive connection before closing it.

wait_timeout=XX
The number of seconds the server waits for activity on a noninteractive connection before closing it.

DBCP
timeBetweenEvictionRunsMillis 每毫秒檢查一次連接池中閒置的連接(spec :The number of milliseconds to sleep between runs of the idle object evictor thread. When non-positive, no idle object evictor thread will be run.)預設是-1

minEvictableIdleTimeMillis 連接池中連接可閒置的時間(spec:The minimum amount of time an object may sit idle in the pool before it is eligable for eviction by the idle object evictor (if any). )

上面兩個設定要一起使用，意思是說每timeBetweenEvictionRunsMillis毫秒檢查一次連接池中空閒的連接,把空閒時間超過 minEvictableIdleTimeMillis毫秒的連接斷開,直到連接池中的連接數到minIdle為止