Java httpserver在收到POST请求时崩溃

Question

I am trying to write a simple HTTP server in Java that can handle POST requests. While my server successfully receives the GET, it crashes on the POST.

Here is the server

public class RequestHandler {
    public static void main(String[] args) throws Exception {
        HttpServer server = HttpServer.create(new InetSocketAddress(8080), 0);
        server.createContext("/requests", new MyHandler());
        server.setExecutor(null); // creates a default executor
        server.start();
    }

    static class MyHandler implements HttpHandler {
        public void handle(HttpExchange t) throws IOException {
            String response = "hello world";
            t.sendResponseHeaders(200, response.length());
            System.out.println(response);
            OutputStream os = t.getResponseBody();
            os.write(response.getBytes());
            os.close();
        }
    }
}

And here is the Java code I use to send the POST

// HTTP POST request
private void sendPost() throws Exception {

    String url = "http://localhost:8080/requests";
    URL obj = new URL(url);
    HttpsURLConnection con = (HttpsURLConnection) obj.openConnection();

    //add reuqest header
    con.setRequestMethod("POST");
    con.setRequestProperty("User-Agent", USER_AGENT);
    con.setRequestProperty("Accept-Language", "en-US,en;q=0.5");

    String urlParameters = "sn=C02G8416DRJM&cn=&locale=&caller=&num=12345";

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

    int responseCode = con.getResponseCode();
    System.out.println("\nSending 'POST' request to URL : " + url);
    System.out.println("Post parameters : " + urlParameters);
    System.out.println("Response Code : " + responseCode);

    BufferedReader in = new BufferedReader(
            new InputStreamReader(con.getInputStream()));
    String inputLine;
    StringBuffer response = new StringBuffer();

    while ((inputLine = in.readLine()) != null) {
        response.append(inputLine);
    }
    in.close();

    //print result
    System.out.println(response.toString());
}

Each time the POST request crashes on this line

HttpsURLConnection con = (HttpsURLConnection) obj.openConnection();

but when I change the URL to the one provided in the example where I found this it works.

Answer 1

Instead of

HttpsURLConnection con = (HttpsURLConnection) obj.openConnection();

Use

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

You are connecting to a URL which is not HTTPS. When you call obj.openConnection() , it decides whether the connection is HTTP or HTTPS, and returns the appropriate object. When it's http , it won't return an HttpsURLConnection , so you cannot convert to it.

However, since HttpsURLconnection extends HttpURLConnection , using HttpURLConnection will work for both http and https URLs. The methods that you are calling in your code all exist int the HttpURLConnection class.