Object is not being updated. Hibernate + Spring

@Controller
public class WorkoutController {

    @Autowired
    private WorkoutService workoutService;
    @Autowired
    private OneRepMaxService oneRepMaxService;
    @Autowired
    private ActualRepsService actualRepsService;
    @Autowired
    private PercentageService percentageService;
    @Autowired
    private ExerciseService exerciseService;



    @RequestMapping("/")
    @SuppressWarnings("unchecked")
    public String showWorkout(Long id, Model model,Workout workout){





        Workout firstWorkout = workoutService.findById(Long.valueOf(83));

        model.addAttribute("firstWorkout",firstWorkout);
        model.addAttribute("workout",workout);

        return "workout";
    }

    @RequestMapping(value="/workoutLogs", method = RequestMethod.POST)
    public String saveWorkout(@ModelAttribute Workout workout,Model model) {


        workoutService.saveNewWorkout(workout);


        return "redirect:/workoutLogs";
    }


    @RequestMapping("/workoutLogs")
    public String showAllSavedWorkoutLogs(Model model){


        return "WorkoutLogs";

    }



}

@Entity
@Table
public class Exercise {

    @Id
    @GeneratedValue
    private Long id;


    private String exerciseName;
    private int weight;
    private int actualReps;

    @ManyToOne
    @JoinColumn(name = "workout_id")
    private Workout workout;

    public Exercise(){}


    public Exercise( String exerciseName, int weight, int actualReps) {
        this.exerciseName = exerciseName;
        this.weight = weight;
        this.actualReps = actualReps;
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getExerciseName() {
        return exerciseName;
    }

    public void setExerciseName(String exerciseName) {
        this.exerciseName = exerciseName;
    }

    public int getWeight() {
        return weight;
    }

    public void setWeight(int weight) {
        this.weight = weight;
    }

    public int getActualReps() {
        return actualReps;
    }

    public void setActualReps(int actualReps) {
        this.actualReps = actualReps;
    }
}

@Entity
public class Workout {

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

    @OneToMany(cascade = CascadeType.ALL)
    @JoinColumn(name = "workout_id")
    private List<Exercise> exercises;

    public Workout(List<Exercise> exercises) {
        this.exercises = exercises;
    }

    public Workout() {
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public List<Exercise> getExercises() {
        return exercises;
    }

    public void setExercises(List<Exercise> exercises) {
        this.exercises = exercises;
    }
    //for each exercise inside a workout print exercise make it all inputs bind the workout
}

@Repository
public class WorkoutDaoImpl implements WorkoutDao {

    @Autowired
    SessionFactory sessionFactory;

    @Override
    @SuppressWarnings("unchecked")
    public List<Workout> findAll() {
        Session session = sessionFactory.openSession();
        List<Workout> workouts = session.createCriteria(Workout.class).list();
        session.close();
        return workouts;
    }

    @Override
    public Workout getFirstWorkoutExerciseName(Long id) {
        return null;
    }

    @Override
    public Workout getWorkout() {
        return null;


    }


    @Override
    public Workout findById(Long id) {
        Session session = sessionFactory.openSession();
        Workout workout = session.get(Workout.class,id);
        Hibernate.initialize(Workout.class);
        session.close();
        return workout;
    }


    @Override
    public void save(Workout workout) {
        Session session = sessionFactory.openSession();

        // Begin a transaction
        session.beginTransaction();

        // Save the category
        session.saveOrUpdate(workout);

        // Commit the transaction
        session.getTransaction().commit();

        // Close the session
        session.close();
    }

    @Override
    public void delete(Workout workout) {

    }



}