Mybatis使用注解实现 CRUD

可以在工具类创建时实现自动提交事务
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession(true);
//改成 true 可自动提交事务 ，不需要commit

    }

编写接口，增加注解

public interface UserMapper {
    @Select("Select * from user")
    List<User> getUsers();

    @Select("Select *from user where id=#{id}")
    User getUsersByID(@Param("id") int id);//方法存在多个参数,所有的参数前面必须加上 @Param("id")注解

    @Delete("delete from  user where id = #{id}")
    int deleteUser(@Param("id") int id);

    @Update("update user set name =#{name},pwd=#{pwd} where id =#{id}")
    int updateUser(User user);

}
测试类

public class Text01 {
    @Test
    public  void  getUsers(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> users= mapper.getUsers();
        for (User user : users){
            System.out.println(user);
        }
        sqlSession.close();
    }
    @Test
    public  void  getUsersByID(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User usersByID = mapper.getUsersByID(4);
        System.out.println(usersByID);
        sqlSession.close();
    }
    @Test
    public  void updateUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        mapper.updateUser(new User(1,"哈dsasa哈","888888"));
        sqlSession.close();

    }

    @Test
    public  void  deleteUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);

        mapper.deleteUser(3);
        sqlSession.close();
    }


}

注意！！！
必须将接口绑定注册到mapper核心配置文件中
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关于Param（）注解
1：基本类型的参数或者String类型，需要加上
2：引用类型不用加
3：如果只有一个基本类型的话，可以忽略，但建议加上
4：我们在sql中引用的就是 @Param("xxx")中设定的属性名