一、Mybatis的入门案例
- 首先，先在数据库demo里面创建一个user的表
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`id` int(0) NOT NULL AUTO_INCREMENT,
`username` varchar(32) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '用户名称',
`birthday` datetime(0) NULL DEFAULT NULL COMMENT '生日',
`sex` char(1) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '性别',
`address` varchar(256) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '地址',
PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 49 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;
INSERT INTO `user` VALUES (41, '老王', '2018-02-27 17:47:08', '男', '北京');
INSERT INTO `user` VALUES (42, '小二王', '2018-03-02 15:09:37', '女', '北京金燕龙');
INSERT INTO `user` VALUES (43, '小二王', '2018-03-04 11:34:34', '女', '北京金燕龙');
INSERT INTO `user` VALUES (45, '传智播客', '2018-03-04 12:04:06', '男', '北京金燕龙');
INSERT INTO `user` VALUES (46, '老王', '2018-03-07 17:37:26', '男', '北京');
INSERT INTO `user` VALUES (48, '小马宝莉', '2018-03-08 11:44:00', '女', '北京修正');
SET FOREIGN_KEY_CHECKS = 1;
-
然后，创建测试类MybatisTest：
第一步：读取配置文件
第二步：创建SqlSessionFactory工厂
第三步：创建SqlSession
第四步：创建Dao接口的代理对象
第五步：执行dao中的方法
第六步：释放资源 -
结合上篇Mybatis入门相关概念及环境搭建文章，然后在test文件里面创建测试类MybatisTest，目录结构如下：
package com.itheima.test;
import com.itheima.dao.IUserDao;
import com.itheima.domain.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.InputStream;
import java.util.List;
/**
* mybatis的入门案例
*/
public class MybatisTest {
public static void main(String[] args) throws Exception {
//1.读取配置文件
InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
//2.创建SqlSessionFactory工厂
SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
SqlSessionFactory factory = builder.build(in);
//3.使用工厂生产SqlSession对象
SqlSession session = factory.openSession();
//4.使用SqlSession创建Dao接口的代理对象
IUserDao userDao = session.getMapper(IUserDao.class);
//5.使用代理对象执行方法
List<User> users = userDao.findAll();
for (User user : users){
System.out.println(user);
}
//6.释放资源
session.close();
in.close();
}
}
-
入门案例的分析：
-
控制台输出：
2020-04-20 22:33:37,461 0 [ main] DEBUG ache.ibatis.logging.LogFactory - Logging initialized using 'class org.apache.ibatis.logging.log4j.Log4jImpl' adapter.
2020-04-20 22:33:37,500 39 [ main] DEBUG source.pooled.PooledDataSource - PooledDataSource forcefully closed/removed all connections.
2020-04-20 22:33:37,500 39 [ main] DEBUG source.pooled.PooledDataSource - PooledDataSource forcefully closed/removed all connections.
2020-04-20 22:33:37,500 39 [ main] DEBUG source.pooled.PooledDataSource - PooledDataSource forcefully closed/removed all connections.
2020-04-20 22:33:37,500 39 [ main] DEBUG source.pooled.PooledDataSource - PooledDataSource forcefully closed/removed all connections.
2020-04-20 22:33:37,576 115 [ main] DEBUG ansaction.jdbc.JdbcTransaction - Opening JDBC Connection
2020-04-20 22:33:39,414 1953 [ main] DEBUG source.pooled.PooledDataSource - Created connection 210506412.
2020-04-20 22:33:39,414 1953 [ main] DEBUG ansaction.jdbc.JdbcTransaction - Setting autocommit to false on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@c8c12ac]
2020-04-20 22:33:39,417 1956 [ main] DEBUG m.itheima.dao.IUserDao.findAll - ==> Preparing: select * from user;
2020-04-20 22:33:39,438 1977 [ main] DEBUG m.itheima.dao.IUserDao.findAll - ==> Parameters:
2020-04-20 22:33:39,456 1995 [ main] DEBUG m.itheima.dao.IUserDao.findAll - <== Total: 6
User{id=41, username='老王', birthday=Wed Feb 28 01:47:08 CST 2018, sex='男', address='北京'}
User{id=42, username='小二王', birthday=Fri Mar 02 23:09:37 CST 2018, sex='女', address='北京金燕龙'}
User{id=43, username='小二王', birthday=Sun Mar 04 19:34:34 CST 2018, sex='女', address='北京金燕龙'}
User{id=45, username='传智播客', birthday=Sun Mar 04 20:04:06 CST 2018, sex='男', address='北京金燕龙'}
User{id=46, username='老王', birthday=Thu Mar 08 01:37:26 CST 2018, sex='男', address='北京'}
User{id=48, username='小马宝莉', birthday=Thu Mar 08 19:44:00 CST 2018, sex='女', address='北京修正'}
2020-04-20 22:33:39,461 2000 [ main] DEBUG ansaction.jdbc.JdbcTransaction - Resetting autocommit to true on JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@c8c12ac]
2020-04-20 22:33:39,461 2000 [ main] DEBUG ansaction.jdbc.JdbcTransaction - Closing JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@c8c12ac]
2020-04-20 22:33:39,461 2000 [ main] DEBUG source.pooled.PooledDataSource - Returned connection 210506412 to pool.
Process finished with exit code 0
- 注意事项：
不要忘记在映射配置中告知mybatis要封装到哪个实体类中
配置的方式：指定实体类的全限定类名
二、Mybatis基于注解的入门案例：
- 结构目录：
- 把IUserDao.xml移除，在dao接口的方法上使用@Select注解，并且指定SQL语句
- 同时需要在SqlMapConfig.xml中的mapper配置时，使用class属性指定dao接口的全限定类名。
- 明确：
我们在实际开发中，都是越简便越好，所以都是采用不写dao实现类的方式。
不管使用XML还是注解配置。
但是Mybatis它是支持写dao实现类的。
