mybatis初体验（细节满满）

1.创建数据表（库名为：mayikt）

CREATE TABLE `mayikt_user` (
  `id` int NOT NULL AUTO_INCREMENT,
  `username` varchar(20) DEFAULT NULL,
  `userpwd` varchar(20) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8mb3

2.创建maven项目

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创建完成后配置pom.xml文件：

<dependencies>
        
        <dependency>
            <groupId>org.mybatisgroupId>
            <artifactId>mybatisartifactId>
            <version>3.5.13version>
        dependency>
        
        <dependency>
            <groupId>com.mysqlgroupId>
            <artifactId>mysql-connector-jartifactId>
            <version>8.1.0version>
        dependency>
 
    dependencies>

3.在main文件夹下的resources文件夹下创建mybatis-config.xml（该配置文件名称是可以改） 存放就是我们数据库相关连接信息

"1.0" encoding="UTF-8" ?>
configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<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://127.0.0.1:3306/mayikt?serverTimezone=GMT%2B8"/>
                <property name="username" value="root"/>
                <property name="password" value=""/>
            dataSource>
        environment>
    environments>
    <mappers>
        <mapper resource="mapper/userMapper.xml"/>
    mappers>
configuration>

 4.定义mapper ----编写我们mybatis 相关 sql语句 每个表 对应一个mapper

"1.0" encoding="UTF-8" ?>
mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="userMapper">
    <select id="getByUsers" resultType="com.entity.UserEntity">
        select * from mayikt_user
    select>
mapper>

 5.定义java对象--需要注意下 类中的 成员属性与数据库表中字段 映射 默认 类中的 成员属性数据库表中字段名称对应的

/*
 * Copyright (c) 2020, 2023,  All rights reserved.
 *
 */
package com.entity;
 
/**
 * 
Project: mybatis-dome - UserEntity
 * 
Powered by scl On 2023-09-08 10:18:39
 * 
描述：
 *
 * @author 孙臣龙 [1846080280@qq.com]
 * @version 1.0
 * @since 17
 */
public class UserEntity {
   private Integer id;
   private String username;
   private String userpwd;
 
    public Integer getId() {
        return id;
    }
 
    public void setId(Integer id) {
        this.id = id;
    }
 
    public String getUsername() {
        return username;
    }
 
    public void setUsername(String username) {
        this.username = username;
    }
 
    public String getUserpwd() {
        return userpwd;
    }
 
    public void setUserpwd(String userpwd) {
        this.userpwd = userpwd;
    }
 
    @Override
    public String toString() {
        return "UserEntity{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", userpwd='" + userpwd + '\'' +
                '}';
    }
}

 6.测试，使用 mybatis api开始执行该 sql语句即可 得到结果

/*
 * Copyright (c) 2020, 2023,  All rights reserved.
 *
 */
package com.test;
 
import com.entity.UserEntity;
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.List;
 
/**
 * 
Project: mybatis-dome - Test01
 * 
Powered by scl On 2023-09-08 10:29:37
 * 
描述：
 *
 * @author 孙臣龙 [1846080280@qq.com]
 * @version 1.0
 * @since 17
 */
public class Test01 {
    public static void main(String[] args) throws IOException {
        // 1.读取加载mybatis-config.xml
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        // 2.获取到获取到
        SqlSession sqlSession = sqlSessionFactory.openSession();
        // 3.根据 mapper id=getByUsers 执行该s  ql 语句 通过  sql语句得到我们的对象 orm
        List userEntitys = sqlSession.selectList("getByUsers", UserEntity.class);
        System.out.println(userEntitys);
        sqlSession.close();
    }
}