Convert from JSON Object into java records and then passed into relational database

Question

I am requesting data using RestTemplate and get a JSON Object.

I want to insert this data into a relational database. My thoughts after I have been reading was to convert this to java records. It is a nested JSON Object where I want to insert the different levels into different tables.

I am building this project using Sping Boot,

I would like to insert the the following data:

id, owner, model, year into a table namned cars

and then I want to insert the events inte an event table. type, cost, date into a table namned events

{
    "meta": {
        "total_count": 2,
        "current_count": 2,
        "per_page": 10,
        "start": 1,
        "end": 2,
        "current_page": 1,
        "page_count": 1
    },
        "data": [
            {
                "id": 1,
                "owner": "Charles John",
                "model": "Volvo,
                "year": 2020 
                "services": {
                    "events": [
                        {
                            "type": "repair",
                            "cost": 1000
                            "date": "2022-01-12"
                        },
                        {
                            "type": "cleaning",
                            "cost": 200
                            "date": "2022-01-15"

                        },
                        {
                            "type": "washing",
                            "cost": 100
                            "date": "2022-03-05"                            
                        }
                    ]
                }
            },
            {
                "id": 2,
                "owner": "John Carlsson",
                "model": "Mercedes,
                "year": 2021 
                "services": {
                    "events": [
                        {
                            "type": "repair",
                            "cost": 4000
                            "date": "2022-02-12"

                        },
                        {
                            "type": "cleaning",
                            "cost": 200
                            "date": "2022-02-27"

                        }
                    ]
                }
            }
    ]
}

My RestTemplate looks something similar to this:

public void getCarEvents() {


    RestTemplate rt = new RestTemplate();
    
    HttpEntity<?> request = createAuth();
    
    String result = restTemplate.getForObject(buildUri("/cars").toString(), String.class);
    
    ResponseEntity<CarsResponse> carsResponse = restTemplate.exchange(result, HttpMethod.GET, request, new ParameterizedTypeReference<CarsResponse> {});
    
    List<CarsResponse> response = carsResponse.getBody();

...
...
...
}

Where CarsResponse looks something like this:

public record CarsResponse(
    Meta meta;
    ArrayList<Car> data
    ) {}

whre Car looks like this:

public record Car(
    int id,
    String name,
    int age,
    Services services
    ) {}


public record Services(
    ArrayList<Event> events
    ) {}


public record Event (
    String type,
    int cost,
    String date,
    ){}

Should I also make a class for Car and Event like the following?

@Entity
@Table(name = "event")
public class Event{

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

@Column(name = "cost")
private int cost;

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

//Getter, Setter, Constructor, toString()

}

I have only found example where they have more simple JSON Object and not found any with a nested version. Where do I go from here. How do I only get the data from Event so I only insert this data into that table?

Also I would like to get the Id from Car inserted into the Event table to so I now for which car the event has been done for.

score 0 · Answer 1 · answered Jun 07 '22 at 11:09

At first I would highly recommend into checking this question and particular it's first answer since you want to consume a REST API that produces a nested JSON. Basically, all answers are correct, but personally I found that one useful. You must create a POJO class just like this:

@Entity
@Table
@JsonIgnoreProperties(ignoreUnknown = true)
public class Car {
   
   @Id
   @SequenceGenerator(
        name = "car_sequence",
        sequenceName = "car_sequence",
        allocationSize = 1
        )
   @GeneratedValue(
        strategy = GenerationType.SEQUENCE,
        generator = "car_sequence"
        )
   private int id;
   private String owner;
   private String model;
   private Long year;
   // add getters and setters
}

The first two annotations have to do with the database stuff and transform the class as an entity and it's variables as columns for DB. The third annotation ignores any values from the JSON fields that are irrelevant from the variables you want and mention in your class. The annotations about id variable help to identify it as the primary key of your table and the rest are created for auto-increment in your db.

Of course, you must first add the JPA dependency in your project as well as the database's dependency. Also you need the Jackson Databind dependency as well.

Hope this helps!!!

Convert from JSON Object into java records and then passed into relational database

1 Answers1