Proper Way to layer Spring JPA based DAO using Spring Boot Framework

Am new to Spring Boot & JPA...

Let's say I have two entities mapped to two tables which are joined in a database.

Student-1------<-Course

Also, lets presume that the database is already created and populated.

This depicts that one student has many courses...

My Student Entity:

@Entity
public class Student {

    @OneToMany(mappedBy="student")
    private List<Courses> courses;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "Student_Id")
    private long studentId;

    @Column(name = "Student_Name")
    private String studentName;

    protected Student() { }

    // Getters & Setters
}

My Course Entity:

@Entity
public class Course {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "Course_Id")
    private long courseId;

    @Id
    @Column(name = "Student_Id")
    private long studentId;

    @ManyToOne
    @PrimaryKeyJoinColumn(name="Student_Id", referencedColumnName="Student_Id")
    private Student student;

    @Column(name = "Course_Name")
    private String courseName;

    // Getters & Setters

}

In Spring Boot's Tutorial Guides, it illustrates how to extend a CrudRepository interface, but it doesn't specify how to setup a Spring based DAO which contains custom finder methods which use HQL and EntityManager inside it.

Is the following DAO and DaoImpl correct?

public interface CourseDao {
    List<Course> findCoursesByStudentName(String studentName);
}

@Repository
public class CourseDaoImpl implements CourseDao {

    @PersistenceContext
    EntityManager em;

    public List<Course> findCoursesByStudentName(String studentName) {
        String sql = "select c.courseName" +
                     "from Course c, Student s " +
                     "where c.course_id = s.student_id " +
                     "and s.studentName = :studentName ";

        Query query = em.createQuery(sql);
        query.setParameter("studentName", studentName);
        return query.getResultList();
    }
}   

And then in the client code, for example, in the main class:

 public class Application {

    @Autowired
    CustomerDao dao;

    public static void main (String args []) {
        List<Course> courses = dao.findCoursesByStudentName("John");
    }   
 }

Is this the standard way to use HQL inside Spring DAOs ? I've seend examples of the @Transactional annotation being prepended to the DAO class's impl (e.g. CustomerDAOImpl) ?

Please let me know if this is the write way to structure my Spring Boot app or am I supposed to extend / add to the CrudRepository only?

If someone could correct my example and point me to a URL which talks about HQL using Entities that are joined, I would be very grateful.

The Spring Boot guides didn't depict joins or DAOs - I just need to learn how to properly create finder methods which emulate select statement which return lists or data structures.

Thanks for taking the time to read this...