MyBatis与jpa的比较：
mybatis的优势在于SQL的自由度上，SQL优化和返回对象的大小都是可控的。spring-data-JPA则在开发效率上有优势。
mybatis在springboot中开启驼峰式命名：
mybatis.configuration.map-underscore-to-camel-case=true
MyBatis的映射：
普通映射
@Select("select * from mybatis_Student where id=#{id}")
public Student getStudent(int id);
@Insert("insert into mybatis_Student (name, age, remark, pic,grade_id,address_id) values (#{name},#{age},#{remark}, #{pic},#{grade.id},#{address.id})")
public int insert(Student student);
@Update("update mybatis_Student set name=#{name},age=#{age} where id=#{id}")
public int update(Student student);
@Delete("delete from mybatis_Student where id=#{id}")
public int delete(int id)
结果集映射
@Select("select * from mybatis_Student")
@Results({
@Result(id=true,property="id",column="id"),
@Result(property="name",column="name"),
@Result(property="age",column="age")
})
public List<Student> getAllStudents();
关系映射
a.一对一
@Select("select * from mybatis_Student")
@Results({
@Result(id=true,property="id",column="id"),
@Result(property="name",column="name"),
@Result(property="age",column="age"),
@Result(property="address",column="address_id",one=@One(select="com.skymr.mybatis.mappers.AddressMapper.getAddress"))
})
public List<Student> getAllStudents();
b.一对多
@Select("select * from mybatis_grade where id=#{id}")
@Results({
@Result(id=true,column="id",property="id"),
@Result(column="grade_name",property="gradeName"),
@Result(property="students",column="id",many=@Many(select="com.skymr.mybatis.mappers.Student2Mapper.getStudentsByGradeId"))
})
public Grade getGrade(int id);
利用@Provider实现动态SQL