如果要使用池的話,就必須使用OracleConnectionCacheImpl,共有三種池的策略:
DYNAMIC_SCHEME(是動態增加.用完如果超過上限則關掉)
The cache will create connections above the specified maximum limit when necessary but will in turn close connections as they are returned to the cache until the number of connections is within the maximum limit. Connections will never be cached above the maximum limit. This is the default setting.
FIXED_RETURN_NULL_SCHEME (直接返回Null)
The cache will return a null connection once the maximum connection limit has been exceeded.
FIXED_WAIT_SCHEME (始終等待)
The cache will wait until there is a connection available and will then return it to the calling application.