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Mybatis接口实现sql执行
使用过 mybatis 框架的小伙伴们都知道,mybatis 是个半 orm 框架,通过写 mapper 接口就能自动实现数据库的增删改查,但是对其中的原理一知半解,接下来就让我们深入框架的底层一探究竟
1、环境搭建
首先引入 mybatis 的依赖,在 resources 目录下创建 mybatis 核心配置文件 mybatis-config.xml
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "https://mybatis.org/dtd/mybatis-3-config.dtd"> <configuration> <!-- 环境、事务工厂、数据源 --> <environments default="dev"> <environment id="dev"> <transactionManager type="JDBC"/> <dataSource type="UNPOOLED"> <property name="driver" value="org.apache.derby.jdbc.EmbeddedDriver"/> <property name="url" value="jdbc:derby:db-user;create=true"/> </dataSource> </environment> </environments> <!-- 指定 mapper 接口--> <mappers> <mapper class="com.myboy.demo.mapper.user.UserMapper"/> </mappers> </configuration>
在 com.myboy.demo.mapper.user 包下新建一个接口 UserMapper
public interface UserMapper { UserEntity getById(Long id); void insertOne(@Param("id") Long id, @Param("name") String name, @Param("json") List<String> json); }
在 resources 的 com.myboy.demo.mapper.user 包下创建 UserMapper.xml
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "https://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.myboy.demo.mapper.user.UserMapper"> <select id="getById" resultType="com.myboy.demo.db.entity.UserEntity"> select * from demo_user where id = #{id} </select> <insert id="insertOne"> insert into demo_user (id, name, json) values (#{id}, #{name}, #{json}) </insert> </mapper>
创建 main 方法测试
try(InputStream in = Resources.getResourceAsStream("com/myboy/demo/sqlsession/mybatis-config.xml")){ SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(in); sqlSession = sqlSessionFactory.openSession(); # 拿到代理类对象 UserMapper mapper = sqlSession.getMapper(UserMapper.class); # 执行方法 UserEntity userEntity = mapper.getById(2L); System.out.println(userEntity); sqlSession.close(); }catch (Exception e){ e.printStackTrace(); }