mybatis入门例子-极简

添加依赖pom.xml

<dependencies>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.0</version>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>
    <!-- 提供mysql驱动 -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.38</version>
    </dependency>
</dependencies>

mybatis配置

<?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>
    <settings>
        <!-- changes from the defaults -->
        <setting name="lazyLoadingEnabled" value="false"/>
    </settings>
    <typeAliases>
        <!--这里给实体类取别名，方便在mapper配置文件中使用 -->
        <typeAlias alias="user" type="com.example.entity.User"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/db1"/>
                <property name="username" value="root"/>
                <property name="password" value="admin"/>
            </dataSource>
        </environment>
    </environments>
    <!--这里添加的是执行CRUD操作的接口对应的配置文件(xml文件) -->
    <mappers>
        <mapper resource="mapper/UserMapper.xml"/>
    </mappers>
</configuration>

实体类User

public class User {
    private Long id;
    private String userId;
    private String userName;
    private Integer age;
    private String email;
    private Date addTime;
    private Date modifyTime;
    private Integer isDel;
...
}

mapper配置

<?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="com.example.mapper.UserMapper">
    <resultMap id="BaseResultMap" type="com.example.entity.User">
        <id column="id" jdbcType="BIGINT" property="id"/>
        <result column="user_id" jdbcType="VARCHAR" property="userId"/>
        <result column="user_name" jdbcType="VARCHAR" property="userName"/>
        <result column="age" jdbcType="INTEGER" property="age"/>
        <result column="email" jdbcType="VARCHAR" property="email"/>
        <result column="add_time" jdbcType="TIMESTAMP" property="addTime"/>
        <result column="modify_time" jdbcType="TIMESTAMP" property="modifyTime"/>
        <result column="is_del" jdbcType="TINYINT" property="isDel"/>
    </resultMap>
    <sql id="Base_Column_List">
    id, user_id, user_name, age, email, add_time, modify_time, is_del
  </sql>
    <select id="selectByPrimaryKey" parameterType="java.lang.Long" resultMap="BaseResultMap">
        select
        <include refid="Base_Column_List"/>
        from user
        where id = #{id,jdbcType=BIGINT}
    </select>
</mapper>

Mapper

import com.example.entity.User;

public interface UserMapper {
    User selectByPrimaryKey(Long id);
}

测试

import com.example.entity.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 org.junit.Before;
import org.junit.Test;

import java.io.InputStream;

public class UserMapperTest {
    // 指定MyBatis配置文件
    final String RESOURCE = "mybatis-config.xml";
    SqlSessionFactory sessionFactory = null;

    @Before
    public void before() {
        try {

            // 1、指定MyBaties配置文件
            InputStream inputstream = Resources.getResourceAsStream(RESOURCE);
            // 2、创建SqlSessionFactory()
            sessionFactory = new SqlSessionFactoryBuilder().build(inputstream);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Test
    public void test() {

        // 3、获取SqlSession
        SqlSession session = sessionFactory.openSession();
        UserMapper userMapper = session.getMapper(UserMapper.class);
        User user = userMapper.selectByPrimaryKey(1L);
        System.out.println(String.format("userId:%s,userName:%s,age:%s", user.getId(), user.getUserName(), user.getAge()));
    }

}