MyBatis Demo
先创建一个 Maven 项目，名称为 MyBatis01。
之后创建并连接 MySQL 数据库，然后执行 sql 脚本：
sql
CREATE DATABASE `mybatis`;
USE `mybatis`;
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`id` int(20) NOT NULL,
`name` varchar(30) DEFAULT NULL,
`pwd` varchar(30) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
insert into `user`(`id`,`name`,`pwd`) values (1,'小孔','123456'),(2,'张三','abcdef'),(3,'李四','987654');导入与 MyBatis 相关的依赖：
java
<dependencies>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.26</version>
</dependency>
<!--mybatis-->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.2</version>
</dependency>
<!--junit-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
</dependencies>
<build>
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>false</filtering>
</resource>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
<filtering>false</filtering>
</resource>
</resources>
</build>编写 MyBatis 核心配置文件，在 resources 目录下创建 mybatis-config.xml 文件，配置自己的数据库内容，包括地址、用户名、密码、驱动等：
java
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<!--configuration核心配置文件-->
<configuration>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/your_database_name?useSSl=trur&sueUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai"/>
<property name="username" value="your_username"/>
<property name="password" value="your_password"/>
</dataSource>
</environment>
</environments>
</configuration>编写 MyBatis 工具类，创建 utils 目录，并新建 MybatiesUtils 类：
java
package com.khr.utils;
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.IOException;
import java.io.InputStream;
//sqlSessionFactory -->sqlSession
public class MybatisUtils {
private static SqlSessionFactory sqlSessionFactory;
//使用mybatis第一步，获取sqlSessionFactory对象
static {
try {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
} catch (IOException e) {
e.printStackTrace();
}
}
//既然有了sqlSessionFactory,顾名思义，我们就可以从中获得sqlSession的实例了
//sqlSession 完全包含了面向数据库执行SQL命令所需的所有方法
public static SqlSession getSqlSession(){
return sqlSessionFactory.openSession();
}
}编写 MyBatis 实体类，创建 pojo 目录，并新建 User 类：
java
package com.khr.pojo;
public class User {
private int id; //id
private String name; //姓名
private String pwd; //密码
public User(){
}
public User(int id, String name, String pwd) {
this.id = id;
this.name = name;
this.pwd = pwd;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPwd() {
return pwd;
}
public void setPwd(String pwd) {
this.pwd = pwd;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", name='" + name + '\'' +
", pwd='" + pwd + '\'' +
'}';
}
}编写 Mapper 接口类，创建 dao 目录，并新建UserDao 接口：
java
package com.khr.dao;
import com.khr.pojo.User;
import java.util.List;
public interface UserDao {
List<User> getUserList();
}在 dao 目录下创建 UserMapper.xml 配置文件：
java
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--namespace=绑定一个对应的Dao/Mapper接口-->
<mapper namespace="com.khr.dao.UserDao">
<!--select查询语句-->
<select id="getUserList" resultType="com.khr.pojo.User">
select * from mybatis.user
</select>
</mapper>将刚才创建的 UserMapper.xml 注册到 mybatis-config.xml 文件中，此后每编写一个 Mapper.xml 文件都要注册一次：
java
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<!--configuration核心配置文件-->
<configuration>
......
<mappers>
<mapper resource="com/khr/dao/UserMapper.xml"/>
</mappers>
</configuration>编写测试类 UserDaoTest：
java
package com.khr.dao;
import com.khr.pojo.User;
import com.khr.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import java.util.List;
public class UserDaoTest {
//第一步：获得sqlSession对象
SqlSession sqlSession;
@Test
public void test(){
try {
sqlSession = MybatisUtils.getSqlSession();
//方式一：getMapper
UserDao mapper = sqlSession.getMapper(UserDao.class);
List<User> userList = mapper.getUserList();
for (User user : userList) {
System.out.println(user);
}
}catch (Exception e){
e.printStackTrace();
}finally {
//关闭sqlSession
sqlSession.close();
}
}
}运行结果：
