Http Response parameter name incorrect using Spring Boot/Angular-CodePudding

I'm trying to display a table listing the Country codes (iso3166) in a postgresql db onto an html page using Spring Boot and Angular, the parameter name in the http response lists "number" when instead I want it to list "nbr".

The SQL table has 4 columns

name (varchar) unique
alpha2 (varchar) PK unique
alpha3 (varchar) unique
nbr (int4)

My Spring Boot Models is the following:

@Entity
@Table(name = "iso3166")
public class Country {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private String alpha2;

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

    @Column(name = "alpha3")
    private String alpha3;

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

    public Country()
    {
    }

    public Country(String name, String alpha2, String alpha3, int nbr)
    {
        this.name = name;
        this.alpha2 = alpha2;
        this.alpha3 = alpha3;
        this.nbr = nbr;
    }

/*
getters and settings   toString()
*/

The repository uses JPARepository

public interface ICountryRepository extends JpaRepository<Country, String> {
}

And the Controller has only the findAll() method

@RestController
@RequestMapping({"/api"})
public class CountryController {
    
    @Autowired
    ICountryRepository countryRepository;

    @GetMapping
    public List<Country> findAll(){
        List<Country> country = countryRepository.findAll();
        return country;
    }
}

Running spring-boot and opening localhost in chrome, the table shows up just fine.

However, looking at the Response tab under Network, it shows up like this Shows the same thing if I go to http://localhost:8080/api

[{"alpha2":"AX","name":"AALAND ISLANDS","alpha3":"ALA","number":248},{"alpha2":"AF","name":"AFGHANISTAN","alpha3":"AFG","number":4},{"alpha2":"AL","name":"ALBANIA","alpha3":"ALB","number":8},{"alpha2":"DZ","name":"ALGERIA","alpha3":"DZA","number":12},{"alpha2":"AS","name":"AMERICAN SAMOA","alpha3":"ASM","number":16},{"alpha2":"AD","name":"ANDORRA","alpha3":"AND","number":20},{"alpha2":"AO","name":"ANGOLA","alpha3":"AGO","number":24},

Why does the Http Response return the "nbr" field as "number" instead? And how can I change it to show up as "nbr" in the Http response? Does something happen in the background in Spring Boot when formulating the http response that I can't control?

CodePudding user response：

It is a number because you defined it as a number here, in Country entity:

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

The best solution is to create another object which is used for HTTP communication. For example: CountryDTO. In CountryDTO you can define nbr field as String. Then you just have to create a mapping between Country and CountryDTO objects.

Why you should always do like this:

You should never send Entities directly to the client.
It keeps your code clean and separated: One object is responsible for holding the database model, and another is responsible for communicating with the client. It is now the same, and it is just pure luck.

CodePudding user response：

Found out what happened, although I don't know the specifics.

spring uses Jackson to serialize, and Jackson uses by default public getters to serialize and name data. Since I named the nbr getter/setters as getNumber() and setNumber, changing it to getNbr() and setNbr() respectively solved the issue.