mybatis的简单使用

1、导入依赖

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.29</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.11</version>
        </dependency>

2、编写实体类
3、编写dao接口Userdao
4、编写到接口的映射配置文件UserDao.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">
<!--namespace与dao接口对应，id为接口的方法名，resultType为接口方法的返回值类型-->
<mapper namespace="org.example.mapper.UserMapper">
    <select id="findAll" resultType="org.example.pojo.User">
        select * from user
    </select>
</mapper>

5、编写mybatis的配置文件SqlMapConfig.xml(配置数据库连接和告诉映射文件的位置)

<?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>
    <!-- 配置 mybatis 的环境 -->
    <environments default="mysql">
        <!-- 配置 mysql 的环境 -->
        <environment id="mysql">
            <!-- 配置事务的类型 -->
            <transactionManager type="JDBC"></transactionManager>
            <!-- 配置连接数据库的信息：用的是数据源(连接池) -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/springboot"/>
                <property name="username" value="root"/>
                <property name="password" value="1234"/>
            </dataSource>
        </environment>
    </environments>
    <!-- 告知 mybatis 映射配置的位置 -->
    <mappers>
        <mapper resource="org/example/UserMapper.xml"/>
    </mappers>
</configuration>

6、使用

    @Test
    public void test() throws IOException {
        InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        SqlSessionFactory sessionFactory = builder.build(inputStream);
        SqlSession session = sessionFactory.openSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        for (User user : mapper.findAll()) {
            System.out.println(user);
        }
    }

总结：导依赖，写实体类和接口，写两个配置文件