java如何以JSON格式保存对象并将其放入控制器中的列表或映射中

Question

我使用远程REST API： http://bank.pl/api/exchangerates/rates/**{table}/{code}**/

我想下载3个项目，同时输入3种货币的**{code}**代码：美元、欧元、英镑，如{code}3种货币的字符串：美元、欧元、英镑

{table}参数是常量，不改变C

   private final String URI_CURRENCY_PATH_ID = "http://bank.pl/api/exchangerates/rates/C/{code}";
     
    @Autowired
    RestTemplate restTemplate;
     
    // Using RestTemplate
     
    
     
   //"C/{code}"
    Map <String, String> params = new HashMap <String, String> ();
    params.put ("C", "USD");
    Currency currency = restTemplate.getForObject (URI_CURRENCY_PATH_ID, Currency.class, params);

如果我使用POSTMAN，我会得到3个对象：

{"table":"C","currency":"dolar amerykański","code":"USD","rates":[{"no":"186/C/NBP/2021","effectiveDate":"2021-09-24","bid":3.8897,"ask":3.9683}]}

{"table":"C","currency":"euro","code":"EUR","rates":[{"no":"186/C/NBP/2021","effectiveDate":"2021-09-24","bid":4.5664,"ask":4.6586}]}

{"table":"C","currency":"funt szterling","code":"GBP","rates":[{"no":"186/C/NBP/2021","effectiveDate":"2021-09-24","bid":5.3426,"ask":5.4506}]}

是否可以使用列表或地图作为直接保存同时获取3种货币

也许有人会尽可能地帮助解决这个问题

Answer 1

从API来看，它似乎只接受一个参数。在这种情况下，您不能一次调用带有多个参数的API并返回您正在寻找的响应。但是，可以使用不同的参数并行调用API，这样就不必等到一个API调用响应。下面是代码片段，您可以参考它来并行调用API，这基本上解决了您的问题

@Service
public class RestService {

    private final String URI_CURRENCY_PATH_ID = "http://bank.pl/api/exchangerates/rates/C/{code}";

    @Autowired
    private RestTemplate restTemplate;

    Executor executor = Executors.newFixedThreadPool(5);

    public void callApi() {
        Map<String, String> map = new HashMap<>();
        CompletableFuture<Currency> apiCall1 = CompletableFuture.supplyAsync(() -> callRestApi(map), executor).thenApply(jsonNode -> callRestApi(jsonNode));
        CompletableFuture<Currency> apiCall2 = CompletableFuture.supplyAsync(() -> callRestApi(map), executor).thenApply(jsonNode -> callRestApi(jsonNode));
        CompletableFuture<Currency> apiCall3 = CompletableFuture.supplyAsync(() -> callRestApi(map), executor).thenApply(jsonNode -> callRestApi(jsonNode));
        List<Currency> result = Stream.of(apiCall1, apiCall2, apiCall3)
                .map(CompletableFuture::join)
                .collect(Collectors.toList());
    }

    private JsonNode callRestApi(final Map<String, String> params) {
        return restTemplate.getForObject (URI_CURRENCY_PATH_ID, JsonNode.class, params);
    }

    private Currency callRestApi(final JsonNode jsonNode) {
        // deserialize it and return your Currency object
        return new Currency(); // just for example
    }

    // Keep it somewhere in Model package (here just for example)
    private class Currency {
        // define your arguments
    }
}