Return response from API as inner JSON objects

I use this code to get a list of countries as full name and ISO code:

public Map<String, Object> getCountryNameCodeList() {

        String[] countryCodes = Locale.getISOCountries();
        Map<String, Object> list = new HashMap<>();

        for (String countryCode : countryCodes) {

            Locale obj = new Locale("", countryCode);

            list.put(obj.getDisplayCountry().toString(), obj.getCountry());
        }

        return list;
    }

Rest API:

@GetMapping("shipping_countries")
public ResponseEntity<Map<String, Object>> getShippingCountries() {

    return new ResponseEntity<Map<String, Object>>(countriesService.getCountryNameCodeList(), HttpStatus.OK);
}

I get the response data in this format:

{
    "Papua New Guinea": "PG",
    "Cambodia": "KH",
    "Kazakhstan": "KZ",
    "Paraguay": "PY",
    .....
}

I would like to get the data this way:

[
  {
    name: "Papua New Guinea",
    value: "PG"
  },
  {
    name: "Unites States",
    value: "US"
  }, 
  ....
]

How I can modify the Java code to return the data this way?

Try this approach. You need to use data transfer object to return customized data.

Create a class DTO.

public class DTO {

	private String key;
	private String value;

	public String getKey() {
		return key;
	}

	public void setKey(String key) {
		this.key = key;
	}

	public String getValue() {
		return value;
	}

	public void setValue(String value) {
		this.value = value;
	}

	@Override
	public String toString() {
		return "DTO [key=" + key + ", value=" + value + "]";
	}

}

Create Rest API in the controller. Example :

@RestController
public class Sample {

	@RequestMapping("shipping_countries")
	public ResponseEntity<List<DTO>> getShippingCountries() {
		Map<String, String> map = new HashMap<>();
		map.put("Papua New Guinea", "PG");
		map.put("Cambodia", "KH");
		List<DTO> list = getCustomisedData(map);
		return ResponseEntity.ok(list);
	}

	private List<DTO> getCustomisedData(Map<String, String> map) {
		List<DTO> dtos = new ArrayList();
		for(Entry<String, String> value: map.entrySet()) {
			DTO dto = new DTO();
			dto.setKey(value.getKey());
			dto.setValue(value.getValue());
			dtos.add(dto);
		}
		return dtos;
	}
}

Output :

The response you are getting is the JSON representation of a map, which is what you return.
The json you want is an array of objects, so if you want to return that- the easiest way will be to return it like that, is to return the set of Map.Entry from your map. Something like that:

@GetMapping("shipping_countries")
public ResponseEntity<Set<Map.Entry<String, Object>>> getShippingCountries() {

    return new ResponseEntity<>(countriesService.getCountryNameCodeList().entrySet(), HttpStatus.OK);
}

Other way can be to create a Json serializer for the response, but it seems like an overkill