Question

I have setup a java servlet which accepts parameters from the URL and have it working properly:

public class GetThem extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws IOException, ServletException
{
    try {

            double lat=Double.parseDouble(request.getParameter("lat"));
            double lon=Double.parseDouble(request.getParameter("lon"));
            response.setContentType("text/html");
            PrintWriter out = response.getWriter();
            out.println(lat + " and " + lon);

        } catch (Exception e) {

            e.printStackTrace();
    }
  }       
}

So visiting this link:
http://www.example.com:8080/HttpPost/HttpPost?lat=1&lon=2 would output:

  "1.0 and 2.0"

I’m currently calling it from another java program using this code:

try{
            URL objectGet = new URL("http://www.example.com:8080/HttpPost/HttpPost?lat=" + Double.toString(dg.getLatDouble()) + "&lon=" + Double.toString(dg.getLonDouble()));
            URLConnection yc = objectGet.openConnection();
            BufferedReader in = new BufferedReader(
                    new InputStreamReader(
                    yc.getInputStream()));
            in = new BufferedReader(
            new InputStreamReader(
            yc.getInputStream()));
            ...

Now I want to change it so that I’m not using the URL parameters to pass this data to the server. I want to send much larger messages to this server. I am aware that I need to use http post rather than http get to achieve this but am not sure how to do it.

Do I need to change anything on the server side which is receiving data? What do I need to do on the client side which is posting this data?

Any help would be greatly appreciate thanks.
Ideally I’d like to send this data in JSON format.

Answer 1

Below there’s sample from the first link found by “java HTTP POST example” in google.

try {
    // Construct data
    StringBuilder dataBuilder = new StringBuilder();
    dataBuilder.append(URLEncoder.encode("key1", "UTF-8")).append('=').append(URLEncoder.encode("value1", "UTF-8")).
       append(URLEncoder.encode("key2", "UTF-8")).append('=').append(URLEncoder.encode("value2", "UTF-8"));

    // Send data
    URL url = new URL("http://hostname:80/cgi");
    URLConnection conn = url.openConnection();
    conn.setDoOutput(true);
    OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream());
    wr.write(dataBuilder.toString());
    wr.flush();

    // Get the response
    BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));
    String line;
    while ((line = rd.readLine()) != null) {
        // Process line...
    }
    wr.close();
    rd.close();
} catch (Exception e) {
}