==> Preparing: select * from user
==> Parameters:
<== Columns: id, username, password, name, age
<== Row: 1, daqiao, 123456, 大乔, 22
<== Row: 2, xiaoqiao, 123456, 小乔, 18
<== Row: 3, diaochan, 123456, 貂蝉, 24
<== Row: 4, lvbu, 123456, 吕布, 28
<== Row: 5, zhaoyun, 12345678, 赵云, 27
<== Total: 5
日志输出
spring.application.name=webai01# 数据库配置信息
spring.datasource.url=jdbc:mysql://localhost:3306/db01
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.username=root
spring.datasource.password=123456
#日志输出
mybatis.configuration.log-impl=org.apache.ibatis.logging.stdout.StdOutImpl
数据库连接池（Connection Pool）= “一批已握好手的连接”，
程序需要时直接借，用完归还，避免“每次 new 连接→三次握手→断开”的开销。
在 Spring Boot 里的默认实现
HikariCP（spring-boot-starter-jdbc / mybatis-spring-boot-starter 自带）。
什么都不用配就能用，官方号称“最快的连接池”。
数据库连接池
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@23ca36d] was not registered for synchronization because synchronization is not active
2025-08-30T10:33:20.309+08:00 INFO 12576 --- [webai01] [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Starting...
2025-08-30T10:33:20.720+08:00 INFO 12576 --- [webai01] [ main] com.zaxxer.hikari.pool.HikariPool : HikariPool-1 - Added connection com.mysql.cj.jdbc.ConnectionImpl@409732fb
2025-08-30T10:33:20.722+08:00 INFO 12576 --- [webai01] [ main] com.zaxxer.hikari.HikariDataSource : HikariPool-1 - Start completed.
