MyBatis-01-Demo

数据库 DDL

CREATE DATABASE `mybatis_demo01`;
-- mybatis_demo01.`user` definition

CREATE TABLE `user` (
  `id` int NOT NULL AUTO_INCREMENT,
  `username` varchar(100) DEFAULT NULL,
  `birthday` datetime DEFAULT NULL,
  `sex` char(1) DEFAULT NULL,
  `address` varchar(100) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

pom

<dependency>
  <groupId>org.mybatis</groupId>
  <artifactId>mybatis</artifactId>
  <version>3.5.9</version>
</dependency>

<dependency>
  <groupId>mysql</groupId>
  <artifactId>mysql-connector-java</artifactId>
  <version>8.0.28</version>
</dependency>

<dependency>
  <groupId>org.projectlombok</groupId>
  <artifactId>lombok</artifactId>
  <version>1.18.32</version>
</dependency>

Mybatis 配置文件

mybatis-config.xml

<?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="default">
    <environment id="default">
      <!-- 事务类型 -->
      <transactionManager type="JDBC"/>
      <!-- 数据源类型 -->
      <dataSource type="POOLED">
        <!-- 数据库连接基本信息 -->
        <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
        <property name="url"
              value="jdbc:mysql://127.0.0.1:3306/mybatis_demo01?useUnicode=true&amp;characterEncoding=utf8&amp;connectTimeout=1000&amp;socketTimeout=3000&amp;autoReconnect=true&amp;useSSL=false&amp;serverTimezone=UTC"/>
        <property name="username" value="root"/>
        <property name="password" value="123456"/>
      </dataSource>
    </environment>
  </environments>

  <!-- 映射配置文件位置 -->
  <mappers>
    <!-- 注解 OR 包路径的 XML -->
    <!--<mapper class=""></mapper>-->
    <!-- XML 路径 -->
    <!-- 这样不行, 那么 Mybatis 支持哪些形式的呢，只能配置一个吗？通配符呢 -->
    <!--<mapper resource="classpath:mapper/*"/>-->
    <mapper resource="mapper/UserMapper.xml"/>
    <!-- XML 路径 -->
    <!--<mapper url=""></mapper>-->
    <!-- 注解 PR 包路径的 XML, 包下的都扫描 -->
    <!--<package name=""/>-->
  </mappers>
</configuration>

mapper/UserMapper.xml

<?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">
<mapper namespace="cn.lemon.dao.UserDao">

  <resultMap id="BaseResultMap" type="cn.lemon.domain.User">
    <id property="id" column="id" jdbcType="INTEGER"/>
    <result property="username" column="username" jdbcType="VARCHAR"/>
    <result property="birthday" column="birthday" jdbcType="TIMESTAMP"/>
    <result property="sex" column="sex" jdbcType="CHAR"/>
    <result property="address" column="address" jdbcType="VARCHAR"/>
  </resultMap>

  <sql id="Base_Column_List">
    id,username,birthday,
    sex,address
  </sql>
  <!-- 返回类型必须写（非JavaBean也必须写吗），JavaBean 一般要使用 resultMap（阿里巴巴的规范） -->
  <select id="findAll" resultType="cn.lemon.domain.User">
    select *
    from user;
  </select>
</mapper>

Java 代码

User

package cn.lemon.domain;

import lombok.Data;

import java.io.Serializable;
import java.util.Date;

@Data
public class User implements Serializable {
  /**
   *
   */
  private Integer id;

  /**
   * 用户名称
   */
  private String username;

  /**
   * 生日
   */
  private Date birthday;

  /**
   * 性别
   */
  private String sex;

  /**
   * 地址
   */
  private String address;

  private static final long serialVersionUID = 1L;

}

UserDao

package cn.lemon.dao;

import cn.lemon.domain.User;

import java.util.List;


public interface UserDao {

  /**
   * 查询所有用户
   *
   * @return 用户列表，无则返回空列表
   */
  List<User> findAll();

}

测试

package cn.lemon.dao;

import cn.lemon.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.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.List;

public class UserDaoTest {

  public static void main(String[] args) throws IOException {
    // 使用流程
    // 1. 读取配置文件
    InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
    // 2. 创建 SqlSessionFactory 工厂
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
    // 3. 生产 SqlSession 对象
    SqlSession sqlSession = sqlSessionFactory.openSession();
    // 4. 获取 代理对象
    UserDao userDao = sqlSession.getMapper(UserDao.class);
    // 5. 执行方法
    List<User> users = userDao.findAll();
    System.out.println(Arrays.toString(users.toArray()));
    // 6. 释放资源
    sqlSession.close();
    inputStream.close();
  }
}