C#可以连接，但是java无法连接

Question

我正在尝试连接“ https://api.tdax.com/api/orders/?pair=btc_thb ” 这个网址在 chrome、邮递员上工作。我可以用 C# 连接这个 url。但无法连接java。namespace Exchanges.Satang{    class SatangApi    {        private static class WebApi        {            private static readonly HttpClient st_client = new HttpClient();            static WebApi()            {                st_client.Timeout = TimeSpan.FromSeconds(2);            }            public static HttpClient Client { get { return st_client; } }            public static string Query(string url)            {                var resultString = Client.GetStringAsync(url).Result;                return resultString;            }        }        public static string GetOrders(string symbol)        {            const string queryStr = "https://api.tdax.com/api/orders/?pair=";            var response = WebApi.Query(queryStr + symbol);            return response.ToString();        }    }}此 C# 代码运行良好，但以下 Java 代码无法运行，出现 403 错误。    private String publicOperation(String operation) throws IOException, BadResponseException {        StringBuilder result = new StringBuilder();        URL url = new URL(baseUrl+operation);        HttpURLConnection con = (HttpURLConnection) url.openConnection();        //con.setRequestProperty("Content-Type", "application/json");        con.setRequestMethod("GET");        //https://api.tdax.com/api/orders/?pair=btc_thb        int responseCode=con.getResponseCode();        if(responseCode!=HttpURLConnection.HTTP_OK){            throw new BadResponseException(responseCode);        }        BufferedReader rd = new BufferedReader(new InputStreamReader(con.getInputStream()));        String line;        while ((line = rd.readLine()) != null) {            result.append(line);        }        rd.close();        return result.toString();    }

Answer 1

某些服务器期望User-Agent请求中存在标头，以将其视为有效请求。因此，您需要将其添加到您的请求中，如下所示。

con.setRequestProperty("User-Agent", "My-User-Agent");
int responseCode = con.getResponseCode();

该标头的值（My-User-Agent在上面的示例中）可以设置为此端点所需的任何字符串。例如，PostmanPostmanRuntime/7.16.3为此设置了类似的内容。

C# 可能会在内部执行此操作，因此您不必显式设置它。

Answer 2

public String getOrders(SatangCurrencyPairs currencyPair) throws IOException, BadResponseException {

    String operation="orders/?pair="+currencyPair.toString();

    StringBuilder result = new StringBuilder();

    URL url = new URL(baseUrl+operation);

    //URL url_ = new URL("https://api.tdax.com/api/orders/?pair=btc_thb");

    HttpURLConnection con = (HttpURLConnection) url.openConnection();

    con.setRequestProperty("User-Agent", "java client");

    con.setRequestMethod("GET");

    //https://api.tdax.com/api/orders/?pair=btc_thb

    int responseCode=con.getResponseCode();

    if(responseCode!=HttpURLConnection.HTTP_OK){

        throw new BadResponseException(responseCode);

    }

    BufferedReader rd = new BufferedReader(new InputStreamReader(con.getInputStream()));

    String line;

    while ((line = rd.readLine()) != null) {

        result.append(line);

    }

    rd.close();

    return result.toString();

}