Générer correcte JSON de Java Object - Jackson

Question

Je le résultat suivant pour la requête select * from student where courseName = 'Science';

Résultats:

student_id | name | points | course_name | course_id | 
+----------+--------+--------+---------------+-----------+ 
     1107| Matt | 3000 |  Science | 10  | 
|  1108| Charley| 12348 |  Science | 20  | 

2 rows in set, 2 warnings (0.00 sec) 

Une partie du code de mise en œuvre ressemble actuellement:

List<StudentDetails> studentDetailss = StudentDetailsRepository 
    .findByCourseId(Request.getCourseId()); 
List<Student> student = new ArrayList<>(); 
List<Item> studentList = new ArrayList<>(); 
Response response = new Response(); 

for (StudentDetails student : studentDetailss) { 
    IndividualItem studentItem = new IndividualItem(); 
    studentItem.setId(student.getId()); 

    Offer offer = new Offer(); 
    offer.setName(studentDetailss.getName()); 
    offer.setTotalPoints(studentDetailss.getPoints()); 
    offer.setCourseName(studentDetailss.getCourseName()); 
    offer.setCourseId(studentDetailss.getCourseId()); 

    Student.add(offer); 
    studentItem.setOfferList(Student); 
    studentList.add(studentItem); 
    Response.setItems(studentList); 
    } 

json_text = mapper.writeValueAsString(Response); 

Au-dessus de code affiche le mauvais JSON comme:

{"items":[{"id":"1107","details":[{"name":"Matt", "points":3000,"course_name":"Science","course_id":10},{"name": "Charley",points":12348,"course_name":"Science","course_id":20}]},{"id":"1108","details":[{"name":"Matt", "points":3000,"course_name":"Science","course_id":10},{"name": "Charley",points":12348,"course_name":"Science","course_id":20}]}]} 

Mais je dois générer suivant JSON au lieu de ce qui précède celui-ci:

{"items":[{"id":"1107","details":[{"name":"Matt", "points":3000,"course_name":"Science","course_id":10}]},{"id":"1108","details":[{"name": "Charley",points":12348,"course_name":"Science","course_id":20}]}]} 

(Note: Il est pas le code réel - juste un échantillon du code)

Answer 1

Le problème ci-dessus a été résolu par initialiser la liste du tableau « étudiant » à l'intérieur de la boucle:

le code a changé comme:

List<StudentDetails> studentDetailss = StudentDetailsRepository 
    .findByCourseId(Request.getCourseId()); 
List<Item> studentList = new ArrayList<>(); 
Response response = new Response(); 

for (StudentDetails student : studentDetailss) { 
    IndividualItem studentItem = new IndividualItem(); 
    studentItem.setId(student.getId()); 

    Offer offer = new Offer(); 
    offer.setName(studentDetailss.getName()); 
    offer.setTotalPoints(studentDetailss.getPoints()); 
    offer.setCourseName(studentDetailss.getCourseName()); 
    offer.setCourseId(studentDetailss.getCourseId()); 

    Student.add(offer); 
    studentItem.setOfferList(Student); 
    studentList.add(studentItem); 
    Response.setItems(studentList); 
    } 

json_text = mapper.writeValueAsString(Response);