connection pool:
1. Concept
In the actual development process, it is very performance-intensive to acquire and release connections. In order to solve this situation, connection pools are usually used to share connections.
Use the connection pool to manage the connection pool, so that the connection can be reused. When the connection is used, the close method is used, not really closing the connection pool, but putting it back into the connection pool
Java provides a public interface for connection pools: javax.sql.DataSource, each connection pool must implement this interface for its own connection pool products
Common connection pool products: c3p0, dbcp