一个数据库连接池，能捕获close方法，初始的时候指定初始化多少个连接，如果超过连接个数，则会自动递增连接个数，同时，在代码中可以直接调用close方法，程序会自动捕获-a database connection pool that can capture close, the initial initialization time specified number of connections exceeds the number connections, connections will be automatically increased the number, and in the code can directly call close, the program will automatically capture