将请求发送到Java中的Google Elevation API

Question

I'm try to send Post request to Google elevation API and expecting response

private final String ELEVATION_API_URL =  "https://maps.googleapis.com/maps/api/elevation/json";

private final String USER_AGENT = "Mozilla/5.0";

String urlParameters = "locations=6.9366681,79.9393521&sensor=true&key=<API KEY>";


URL obj = new URL(ELEVATION_API_URL);
            java.net.HttpURLConnection con = (java.net.HttpURLConnection)obj.openConnection();

            //add reuqest header
            con.setRequestMethod("POST");
            con.setRequestProperty("User-Agent", USER_AGENT);
            con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            con.setRequestProperty("Content-Language", "en-US");  

            String urlParameters = request;

            // Send post request
            con.setDoOutput(true);
            DataOutputStream wr = new DataOutputStream(con.getOutputStream());
            wr.writeBytes(urlParameters);
            wr.flush();
            wr.close();

            int responseCode = con.getResponseCode();

I'm sending request in this manner but I'm getting response code as 400.This is working when request sent from browser. What is wrong with this code.

Answer 1

To Allow me to get XML back I made the following changes to your project

StringBuilder response = new StringBuilder(); // placed on the top of your Class

**wr.writeBytes(urlParameters.toString());** // as you have it in your code
System.out.println("ResponseMessage : " + connection.getResponseMessage());
System.out.println("RequestMethod : " + connection.getRequestMethod());

in = new BufferedReader(new InputStreamReader(connection.getInputStream()));

String inputLine;

while ((inputLine = in.readLine()) != null) {

    response.append(inputLine);

}

in.close();

wr.flush();

wr.close();

// I changed the URL to :
private final String ELEVATION_API_URL = " https://maps.googleapis.com/maps/api/elevation/xml ";

//**I get XML in the response** 

return response.toString();

Answer 2

I think there is a problem with the url parameters.

Firstly because sending an empty elevation api request does return a code 400 ( Invalid request. Missing the 'path' or 'locations' parameter. ).

Secondly because this works (returning 200) :

public void test() throws Exception {
    String ELEVATION_API_URL =  "https://maps.googleapis.com/maps/api/elevation/json";

    String USER_AGENT = "Mozilla/5.0";

    String urlParameters = "locations=6.9366681,79.9393521&sensor=true";


    URL obj = new URL(ELEVATION_API_URL + "?" + urlParameters);
    HttpURLConnection con = (HttpURLConnection) obj.openConnection();

    //add reuqest header
    con.setRequestMethod("POST");
    con.setRequestProperty("User-Agent", USER_AGENT);
    con.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
    con.setRequestProperty("Content-Language", "en-US");

    //String urlParameters = request;

    // Send post request
    con.setDoOutput(true);
    DataOutputStream wr = new DataOutputStream(con.getOutputStream());
    wr.writeBytes(urlParameters);
    wr.flush();
    wr.close();

    int responseCode = con.getResponseCode();
}