Mybatis 简单入门

1、安装依赖包:MyBatis

  <dependency>
  　　<groupId>org.mybatis</groupId>
  　　<artifactId>mybatis</artifactId>
     <version>3.5.4</version>
 </dependency>

2、MyBatis核心配置：建议放resouces

<?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.doubleh.pojo"></package>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <!--mysql driver固定写法；之前是com.mysql.jdbc.Driver但是被弃用了-->
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <!--数据库连接串；注意&这里是&amp;-->
                <property name="url" value="jdbc:mysql://localhost:3306/mybatis?serverTimezone=UTC&amp;useUnicode=true&amp;characterEncoding=utf-8&amp;useSSL=true"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/doubleh/mapper/UserMapper.xml" ></mapper>
    </mappers>
</configuration>

3、创建获取SqlSession的工具类

SqlSession 完全包含了面向数据库执行 SQL 命令所需的所有方法。你可以通过 SqlSession 实例来直接执行已映射的 SQL 语句。

public class MybatisHelper {
    private static  SqlSessionFactory sqlSessionFactory = null;
    static{
        try {
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }

}

4、创建数据实体类、数据访问接口和数据操作映射配置

//数据访问接口
public interface UserDao {
    List<User> getUserList();
}

<?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">
<!--命名空间绑定一个对应的数据访问接口-->
<mapper namespace="com.doubleh.mybatis.dao.UserDao">
  <!--id 对应执行的方法,resultType 返回结果，只需要写泛型类即可-->
    <select id="getUserList" resultType="com.doubleh.mybatis.pojo.User">
        select * from mybatis.user
    </select>
</mapper>

5、执行Sql

//第一步:通过MyBatis工具类获取SqlSession对象
SqlSession sqlSession = MybatisHelper.getSqlSession();
//第二步：获取对应方法
UserDao mapper = sqlSession.getMapper(UserDao.class);
//第三步:执行sql
List<User> userList = mapper.getUserList();
for (User u :userList){
    System.out.println(u);
}
//第四步：关闭
sqlSession.close();