java - FileNotFoundException while getting the InputStream object from HttpURLConnection

Question

I am trying to send a post request to a url using HttpURLConnection (for using cUrl in java). The content of the request is xml and at the end point, the application processes the xml and stores a record to the database and then sends back a response in form of xml string. The app is hosted on apache-tomcat locally.

When I execute this code from the terminal, a row gets added to the db as expected. But an exception is thrown as follows while getting the InputStream from the connection

java.io.FileNotFoundException: http://localhost:8080/myapp/service/generate
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1401)
    at org.kodeplay.helloworld.HttpCurl.main(HttpCurl.java:30)

Here is the code

public class HttpCurl {
    public static void main(String [] args) {

        HttpURLConnection con;

        try {
            con = (HttpURLConnection) new URL("http://localhost:8080/myapp/service/generate").openConnection();
            con.setRequestMethod("POST");
            con.setDoOutput(true);
            con.setDoInput(true);

            File xmlFile = new File("test.xml");

            String xml = ReadWriteTextFile.getContents(xmlFile);                

            con.getOutputStream().write(xml.getBytes("UTF-8"));
            InputStream response = con.getInputStream();

            BufferedReader reader = new BufferedReader(new InputStreamReader(response));
            for (String line ; (line = reader.readLine()) != null;) {
                System.out.println(line);
            }
            reader.close();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
  }

Its confusing because the exception is traced to the line InputStream response = con.getInputStream(); and there doesn't seem to be any file involved for a FileNotFoundException.

When I try to open a connection to an xml file directly, it doesn't throw this exception.

The service app uses spring framework and Jaxb2Marshaller to create the response xml.

The class ReadWriteTextFile is taken from here

Thanks.

Edit: Well it saves the data in the DB and sends back a 404 response status code at the same time.

I also tried doing a curl using php and print out the CURLINFO_HTTP_CODE which turns out to be 200.

Any ideas on how do I go about debugging this ? Both service and client are on the local server.

Resolved: I could solve the problem after referring to an answer on SO itself.

It seems HttpURLConnection always returns 404 response when connecting to a url with a non standard port.

Adding these lines solved it

con.setRequestProperty("User-Agent","Mozilla/5.0 ( compatible ) ");
con.setRequestProperty("Accept","*/*");

Answer 1

I don't know about your Spring/JAXB combination, but the average REST webservice won't return a response body on POST/PUT, just a response status. You'd like to determine it instead of the body.

Replace

InputStream response = con.getInputStream();

by

int status = con.getResponseCode();

All available status codes and their meaning are available in the HTTP spec, as linked before. The webservice itself should also come along with some documentation which overviews all status codes supported by the webservice and their special meaning, if any.

If the status starts with 4nn or 5nn, you'd like to use getErrorStream() instead to read the response body which may contain the error details.

InputStream error = con.getErrorStream();