@GetMapping("/proctor/{proctorId}/{organizationId}")
     public ResponseEntity<List<ExamResponse>> getExamsForProctor(@PathVariable Long proctorId, @PathVariable Long organizationId) {
+        if (proctorId == null || proctorId <= 0 || organizationId == null || organizationId <= 0) {
+            return ResponseEntity.badRequest().build();
+        }
         List<ExamResponse> exams = examSetterService.getExamsForProctor(proctorId, organizationId);
         return ResponseEntity.ok(exams);
     }

     @GetMapping("/{examId}/candidates")
     public ResponseEntity<Set<CandidateResponse>> getCandidatesForExam(@PathVariable Long examId) {
+        if (examId == null || examId <= 0) {
+            return ResponseEntity.badRequest().build();
+        }
         Set<CandidateResponse> candidates = examSetterService.getCandidatesForExam(examId);
         return ResponseEntity.ok(candidates);
     }

     @PostMapping("/{candidateId}/{examId}/proctorComments")
+    @Consumes(MediaType.APPLICATION_JSON_VALUE)
-    public ResponseEntity<String> addComment(@PathVariable Long candidateId, @PathVariable Long examId, @RequestBody String content) {
+    public ResponseEntity<String> addComment(
+        @PathVariable Long candidateId,
+        @PathVariable Long examId,
+        @Valid @RequestBody ProctorCommentRequest request
+    ) {
+        if (candidateId == null || candidateId <= 0 || examId == null || examId <= 0) {
+            return ResponseEntity.badRequest().body("Invalid candidate or exam ID");
+        }
+        if (request.getContent() == null || request.getContent().trim().isEmpty()) {
+            return ResponseEntity.badRequest().body("Comment content cannot be empty");
+        }
-        examSetterService.addCommentToCandidate(candidateId, examId, content);
+        examSetterService.addCommentToCandidate(candidateId, examId, request.getContent());
         return ResponseEntity.ok("Comment added successfully");
     }

    @OneToMany(mappedBy = "exam", cascade = CascadeType.ALL, orphanRemoval = true)
+   @JsonIgnore
-   private List<ProctorComment> proctorComments;
+   private List<ProctorComment> proctorComments = new ArrayList<>();
+
+   public void addProctorComment(ProctorComment comment) {
+       proctorComments.add(comment);
+       comment.setExam(this);
+   }
+
+   public void removeProctorComment(ProctorComment comment) {
+       proctorComments.remove(comment);
+       comment.setExam(null);
+   }

+@Transactional
 public void addCommentToCandidate(Long candidateId, Long examId, String content) {
     Candidate candidate = candidateRepository.findById(candidateId)
-            .orElseThrow(() -> new RuntimeException("Candidate not found"));
+            .orElseThrow(() -> new EntityNotFoundException("Candidate not found with id: " + candidateId));
     Exam exam = examRepository.findById(examId)
-            .orElseThrow(() -> new RuntimeException("Exam not found"));
+            .orElseThrow(() -> new EntityNotFoundException("Exam not found with id: " + examId));

     ProctorComment comment = new ProctorComment();
     comment.setCandidate(candidate);
     comment.setExam(exam);
     comment.setContent(content);
     comment.setCreatedAt(LocalDateTime.now());

     proctorCommentRepository.save(comment);
 }