Foreign key is always null in one to many relation - Spring Boot Data with JPA

Question

I have two entity classes Country and Language having bi-directional one to many relationship.

Below are the entity classes:

Answer 1

You can do it in this way also. Here it doesn't create new objects. In the same object which is parsing it creates the relationship in language objects.

@PostMapping("/country")
public Country postCountryDetails(@RequestBody Country country) {

    if( country.getLanguages().size() > 0 )
    {
        country.getLanguages().stream().forEach( countryItem -> {
            countryItem.setCountry( country );
        } );
    }
    return country;
}

Answer 2

You can do it in this way :

Country newCountry = new Country(country.getName());

ArrayList < Language > langList = new ArrayList<>();

for (Language lang : country.getLanguages()) {
     langList.add( new Language(language.getName(), newCountry ) ) ;
}

newCountry.setLanguages( langList );

iCountryRepository.save(newCountry);

PS : Don't forget to add appropriate constructors. Also it is mandatory to add a default constructor if you are doing constructor overloading like this :

public Country() {}

public Country(String name) {this.name = name } 

Answer 3

Update the setter for languages in Country class to the below :

 public void setLanguages(List<Language> languages) {
        this.languages = languages;
        languages.forEach(entity -> entity.setCountry(this));
    }