Spring REST API is adding extra key-value pair in Response

Question

When I try to get student details by Get Request using Postman, I'm getting extra key-value pair i.e(entity: same-object) present in it. Please help me understand why I'm getting that and how can I remove that from my Response. But when I try to print the object which is fetched in Controller Class (in Line 1) it shows the correct object.

Response :

{
    "id": 2,
    "name": "ABC Person",
    "age": 28,
    "courses_id": 1,
    "entity": {
        "id": 2,
        "name": "ABC Person",
        "age": 28,
        "courses_id": 1
    }
}

Get Request URL :

http://localhost:8300/students/ABC Person

REST API Controller Class:

@RestController
public class StudentController {
    
    @Autowired
    private StudentService studentService;
    
    @GetMapping(value="/students/{name}")
    public ResponseEntity<StudentDTO> getStudentDetails(@PathVariable String name){
        StudentDTO student = studentService.getStudentDetails(name);
        System.out.println(student); // LINE 1
        return new ResponseEntity<>(student,HttpStatus.OK);
    }
}

StudentDTO class:

public class StudentDTO {
    private int id;
    private String name;
    private int age;
    private int courses_id;

    //getter and setter methods

    public static StudentDTO valueOf(Student student) {
        StudentDTO studentDTO = new StudentDTO();
        
        studentDTO.setId(student.getId());
        studentDTO.setName(student.getName());
        studentDTO.setAge(student.getAge());
        studentDTO.setCourses_id(student.getCourses_id());
        
        return studentDTO;
    }
    
    public Student getEntity() {
        Student student = new Student();
        
        student.setId(this.id);
        student.setName(this.name);
        student.setAge(this.age);
        student.setCourses_id(this.courses_id);
        
        return student;
    }
}

@DanielWosch I've edited and added the StudentDTO class FYR. — dpx98, Jun 02 '21 at 11:52

Hai Hoang · Accepted Answer · 2021-06-02T12:10:01.870

4

Add a @JsonIgnore above getEntity. Because Jackson (which spring use as messageconverter) will pick getter method while seriliaze object to json by default.

@JsonIgnore
public Student getEntity() {
    Student student = new Student();
        
    student.setId(this.id);
    student.setName(this.name);
    student.setAge(this.age);
    student.setCourses_id(this.courses_id);
        
    return student;
}

Look like you are trying to map between DTO and JPA Entity. To avoid boilerplate code while converting between them, you can use mapping libraries like mapstruct, modelmapper, etc...

edited Jun 02 '21 at 12:10

answered Jun 02 '21 at 11:53

Hai Hoang

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Yeah it works. But can you check if my understanding is correct. You said like Jackson will pick up all the getter methods and serialize the object to JSON. As I'm having an extra getter method so it also converts that. Right ? – dpx98 Jun 02 '21 at 12:02
Yes, by default, jackson will serialize all the getter methods of the class. To skip one, you need to add `@JacksonIgnore`. Also, you can config the object mapper globally to use fields instead of getters and make it a spring bean: https://stackoverflow.com/questions/7105745/how-to-specify-jackson-to-only-use-fields-preferably-globally – Hai Hoang Jun 02 '21 at 12:07

Spring REST API is adding extra key-value pair in Response

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