做一个简单实现mybatis的CRUD增删查改
（提示：途中有啥包没引入的自己根据idea的提示自动引入就好）
一、建立一个普通的maven工程
1、一个普通的maven工程就好，直接next
2、然后设置项目命名，随意起，然后接着往下点就好
（IDEA版本不同创建maven工程的过程有一丢丢不同，随意应变一下就好）
二、配置pom.xml文件
<dependencies>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.5</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.20</version>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.12</version>
</dependency>
</dependencies>
<build>
<resources>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.xml</include>
</includes>
</resource>
</resources>
</build>
三、随便建个简易的数据库
为了方便部分老铁，我就把sql语句也奉上了
CREATE DATABASE `mybatis` ;
USE `mybatis`;
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`id` int(10) NOT NULL AUTO_INCREMENT,
`name` varchar(50) DEFAULT NULL,
`password` varchar(50) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;
insert into `user`(`id`,`name`,`password`) values (1,'giao','admin'),(2,'giao2','321');
四、创建实体类
（Lombok没有用过的要先去idea的插件中心下载一个，直接搜索Lombok就好）
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data//生成get和set方法
@AllArgsConstructor//生成有参构造
@NoArgsConstructor//生成无参构造
public class User {
private int id;
private String name;
private String password;
}
五、创建mybatis的配置文件
<?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>
<environments default="db1">
<environment id="db1">
<!-- 配置JDBC事务-->
<transactionManager type="JDBC"/>
<!-- POOLED配置数据源连接池-->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=UTF-8&serverTimezone=GMT"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
</configuration>
六、创建Mapper接口，也就是Dao接口
（这张图是后来补的，爆红啥的不重要）
import java.util.List;
public interface UserMapper {
public int save(User user);
public int dalete(int id);
public List<User> findAll();
public User findById(int id);
public int update(User user);
}
七、创建Mapper的实现配置文件
<?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:实现接口的全类名-->
<mapper namespace="com.ximen.mappers.UserMapper">
<!-- 增： id：接口方法名 parameterType：传入参数的类型-->
<insert id="save" parameterType="com.ximen.entity.User">
insert into user(name, password) VALUES (#{name},#{password})
</insert>
<!-- 删-->
<delete id="delete" parameterType="int">
delete from user where id=#{id}
</delete>
<!-- 查找所有用户： resultType：返回的结果类型-->
<select id="findAll" resultType="com.ximen.entity.User">
select * from user
</select>
<!-- 通过id查找用户-->
<select id="findById" parameterType="int" resultType="com.ximen.entity.User">
select * from user where id=#{id}
</select>
<!-- 修改-->
<update id="update" parameterType="com.ximen.entity.User">
update user set name=#{name},password=#{password} where id=#{id}
</update>
</mapper>
八、在mybatis的配置文件中注册mapper
(就加上最下面那几句就好啦)
<?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>
<environments default="db1">
<environment id="db1">
<!-- 配置JDBC事务-->
<transactionManager type="JDBC"/>
<!-- POOLED配置数据源连接池-->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.cj.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=UTF-8&serverTimezone=GMT"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/ximen/mappers/UserMapper.xml"/>
</mappers>
</configuration>
九、创建测试类，就可以自己跑跑看啦，代码奉上了
(显示缺少啥包就自己根据idea的提示自动引入就好啦)
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;
public class Test {
public static void main(String[] args) {
//通过类加载器加载配置文件
InputStream inputStream=Test.class.getClassLoader().getResourceAsStream("config.xml");
SqlSessionFactoryBuilder sqlSessionFactoryBuilder=new SqlSessionFactoryBuilder();
SqlSessionFactory sqlSessionFactory = sqlSessionFactoryBuilder.build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
//增
// User user=new User(2,"giao2","123");
// int save = mapper.save(user);
// sqlSession.commit();//提交事务，有数据变动必须提交事务
// System.out.println(save);
// sqlSession.close();//关闭sqlSession避免资源浪费
//删
// int delete = mapper.delete(3);
// sqlSession.commit();
// System.out.println(delete);
// sqlSession.close();
// 查询所有用户 注：有数据变动的才用commit提交事务，像查询的话是没有数据变动的，所以不用commit提交事务
// List<User> users = mapper.findAll();
// for(User user:users){
// System.out.println(user);
// }
// sqlSession.close();
//通过id查找用户
// User user = mapper.findById(2);
// System.out.println(user);
// sqlSession.close();
//修改
// User user = new User(2, "giao2", "321");
// int update = mapper.update(user);
// sqlSession.commit();
// System.out.println(update);
// sqlSession.close();
}
}
基本上简易的mybatis的增删查改就是这样了
