mybatis创建入门流程体验

mysql数据库中建表

drop table if exists tb_user;

create table tb_user(
	id int primary key auto_increment,
	username varchar(20),
	password varchar(20),
	gender char(1),
	addr varchar(30)
);

INSERT INTO tb_user VALUES (1, 'zhangsan', '123', '男', '北京');
INSERT INTO tb_user VALUES (2, '李四', '234', '女', '天津');
INSERT INTO tb_user VALUES (3, '王五', '11', '男', '西安');

IDEA中新建项目模块

pom文件中导入依赖

        <!--mybatis 依赖-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</version>
        </dependency>

        <!--mysql 驱动-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.26</version>
        </dependency>

在resource目录下添加mybatis-config.xml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>

    <typeAliases>
        <package name="com.itheima.pojo"/>
    </typeAliases>

    <!--
    environments：配置数据库连接环境信息。可以配置多个environment，通过default属性切换不同的environment
    -->
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <!--数据库连接信息-->
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql:///mybatis?useSSL=false"/>  <!-- 连接路径为本地mysql-->
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>

    </environments>
    <mappers>
        <!--加载sql映射文件-->
         <mapper resource=""/>

        <!--Mapper代理方式-->
<!--        <package name="UserMapper.xml"/>-->
    </mappers>
</configuration>

创建 pojo类

public class User {

    private Integer id;
    private String username;
    private String password;
    private String gender;
    private String addr;

    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 getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public String getAddr() {
        return addr;
    }

    public void setAddr(String addr) {
        this.addr = addr;
    }

    @Override
    public String toString() {  //重写toString()方法
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                ", gender='" + gender + '\'' +
                ", addr='" + addr + '\'' +
                '}';
    }
}

创建sql表映射的xml文件，通常命名由表名开头。

<?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:名称空间
-->

<mapper namespace="UserMapper">  <!-- 此处自定义命名空间 -->
    <select id="selectAll" resultType="com.mybatis.User">  <!-- 此处id为该表的唯一标识 resultType为查询返回类型包下目录形式的pojo类 -->
        select *
        from tb_user;
    </select>

    <!-- <select id="selectById" resultType="user">   官方原版结构
            select *
            from tb_user where id = #{id};

        </select>-->
</mapper>

在mybatis-config.xml文件中加载刚创建的sql表映射的xml文件

        <!--加载sql映射文件-->
         <mapper resource="UserMapper.xml"/>

写核心测试代码

    public static void main(String[] args) throws IOException {

        //1. 获取SqlSessionFactory  注意此处的代码配置不需要记忆和理解，官方编写好直接复制使用即可
        String resource = "mybatis-config.xml"; //写为mybatis-config.xml配置文件的的路径
        InputStream inputStream = Resources.getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

        //2. 获取SqlSession对象
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //3.执行sql
        List<User> users = sqlSession.selectList("UserMapper.selectAll"); //此处传sql命名空间下的唯一标识

        //4.打印输出查看
        System.out.println(users);

        //5. 释放资源
        sqlSession.close();

    }

运行查看输出结果