Populate transient field from many-to-many db table

Question

Consider 4 classes:

User

@Entity
@Table(name = "users")
public class User implements UserDetails {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "user_id")
    private long id;

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

    @Column(name = "email")
    private String email;

    @Column(name = "password")
    private String password;

    @Column(name = "created_at")
    @Temporal(TemporalType.DATE)
    private LocalDate createdAt;

    @Column(name = "locked")
    private boolean locked;

    @Column(name = "enabled")
    private boolean enabled;

    @ManyToMany
    @JoinTable(
            name = "users_course",
            joinColumns = @JoinColumn(name = "user_id"),
            inverseJoinColumns = @JoinColumn(name = "course_id")
    )
    private List<Course> courses;

    @ManyToMany
    @JoinTable(
            name = "users_lesson",
            joinColumns = @JoinColumn(name = "user_id"),
            inverseJoinColumns = @JoinColumn(name = "lesson_id")
    )
    private List<Lesson> lessons;

    @ManyToMany
    @JoinTable(
            name = "users_exercise",
            joinColumns = @JoinColumn(name = "user_id"),
            inverseJoinColumns = @JoinColumn(name = "exercise_id")
    )
    private List<Exercise> exercises;

Course

@Entity
@Table(name = "course")
public class Course{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

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

    @Column(name = "description")
    private String description;

    @JsonManagedReference
    @OneToMany(mappedBy = "course",
               cascade = CascadeType.ALL,
               fetch = FetchType.LAZY)
    private List<Lesson> lessons;

}

Lesson

@Entity
@Table(name = "lesson")
public class Lesson {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private long id;

    @JsonBackReference
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "course_id")
    private Course course;

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

    @JsonManagedReference
    @OneToMany(mappedBy = "lesson", cascade = CascadeType.ALL, fetch = FetchType.LAZY)
    private List<Exercise> exercises;

}

Exercise

@Entity
@Table(name = "exercise")
public class Exercise {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private long id;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "lesson_id")
    @JsonBackReference
    private Lesson lesson;

    @Column(name = "exercise")
    private String exercise;

    @Transient
    private boolean access;

    @Transient
    private double typingSpeed;

    @Transient
    private double mistakeCount;


}

Tables in db

I want to fill access, mistakeCount and typingSpeed fields. When I'm getting all exercises for the user these fields have default value. How can I fill them? Is there way to get values from users_exercises table and put them to these field?

I saw that some people created class like UserExercise (exemple of my case), but I'm not sure that it is right