Delete request from custom Java client acts differently than e.g. Postman

Question

I have a java application that is making an HTTP DELETE to an external REST service. This error gets back to me from the server (running C#):

"Value cannot be null.\r\nParameter name: source\n   at System.Linq.Enumerable.Count[TSource](IEnumerable`1 source)\r\n   at AppCloud_Framework.Controllers.NotificationItemsController.DeleteNotificationItem(NotificationItem[] notificationItems) in C:\\Users\\jonas\\OneDrive\\VS Projects\\AppCloud Framework\\AppCloud Framework\\Controllers\\NotificationItemsController.cs:line 101\nValue:null"

The thing is, when I setup Postman to make the HTTP request to the same URL, with the same Payload and same HTTP method, the action is successful.

I do not have access to the server to investigate further so I need to find the resolution from the client side. Anyway it appears to be a client side issue.

I've been trying to find the problem myself but haven't succeeded. All I could come up with was to add "application/json" to Accept and Content-Type header properties.

My HTTP client:

public static Response execute(String url, Method method, String body) {
    Response response = new Response();

    try {
        ////////////////////////////////////////
         // Create a trust manager that does not validate certificate chains
        TrustManager[] trustAllCerts = new TrustManager[] { new X509TrustManager() {
            public java.security.cert.X509Certificate[] getAcceptedIssuers() {
                return null;
            }
            public void checkClientTrusted(X509Certificate[] certs, String authType) {
            }
            public void checkServerTrusted(X509Certificate[] certs, String authType) {
            }
        } };
        // Install the all-trusting trust manager
        final SSLContext sc = SSLContext.getInstance("SSL");
        sc.init(null, trustAllCerts, new java.security.SecureRandom());
        HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());
        // Create all-trusting host name verifier
        HostnameVerifier allHostsValid = new HostnameVerifier() {
            public boolean verify(String hostname, SSLSession session) {
                return true;
            }
        };

        // Install the all-trusting host verifier
        HttpsURLConnection.setDefaultHostnameVerifier(allHostsValid);

        ////////////////////////////////////////


        URL urlObj = new URL(url);
        HttpsURLConnection conn = (HttpsURLConnection) urlObj.openConnection();

        conn.setInstanceFollowRedirects(false);
        conn.setRequestMethod(method.toString());
        conn.setRequestProperty("Content-Type", "application/json");
        conn.setRequestProperty("Accept", "application/json");
        //conn.setRequestProperty("Authorization", _authToken);

        if (method == Method.POST || method == Method.PUT || method == Method.DELETE) {
            conn.setDoOutput(true);
            final OutputStream os = conn.getOutputStream();
            os.write(body.getBytes());
            os.flush();
            os.close();
        }

        int status = conn.getResponseCode();
        //log.info("HTTP request status code: "+status);
        InputStream is;
        if (status>399){
            is = conn.getErrorStream();
        }else{
            is = conn.getInputStream();
        }
        if (is==null) return null;
        BufferedReader rd = new BufferedReader(new InputStreamReader(is,
                "UTF-8"));

        String line;
        while ((line = rd.readLine()) != null) {
            response.body += line;
        }
        rd.close();

        response.statusCode = conn.getResponseCode();
        conn.disconnect();
    } catch (Exception e) {
        //log.error(e.getMessage());
        e.printStackTrace();
        System.out.println("");
        response.exception = e.getMessage();
    }
    return response;
}

I am making a request with this body(disregard the encoding issue, source of that is somewhere else):

[{"hash":"150a17e99f67ce29fcc600c92eee831d","instanceid":"cb440a6f-44ef-4f05-ab41-143153655b6e","text":"{\"C_FirstAndLastName\":\"und\",\"ContactID\":\"1374231\",\"C_Fax\":\"\"}","queueDate":"2016-10-04T03:18:37"},{"hash":"1a94d9b5acff1a27dfe45be4ca5d9138","instanceid":"fdsfdsf-44ef-4f05-ab41-143153655b6e","text":"{\"C_FirstAndLastName\":\"J?â??rgen\",\"ContactID\":\"323093\",\"C_Fax\":\"fsdfsd-B401-4AD3-AEA1-fdsfsdfsd\"}","queueDate":"2016-10-04T03:18:37"},{"hash":"8e592fb16d464bfd0f90f69818944198","instanceid":"fdsfsdf-44ef-4f05-ab41-143153655b6e","text":"{\"C_FirstAndLastName\":\"Claus\",\"ContactID\":\"2495844\",\"C_Fax\":\"fdsfsdgsd-304D-4E91-8586-fsdfsdfsd\"}","queueDate":"2016-10-04T03:18:37"},{"hash":"d6d226255e62690e50abbfa15c4b5462","instanceid":"cb440a6f-44ef-4f05-ab41-143153655b6e","text":"{\"C_FirstAndLastName\":\"Test J??rgen\",\"ContactID\":\"323093\",\"C_Fax\":\"fdsfsdfsd-B401-4AD3-AEA1-fdsfsdfsdf\"}","queueDate":"2016-10-04T03:18:49"}]

Answer 1

All I had to do was to define encoding in the output stream. Not sure if anyone could help me with that as I have just tried many things and some of it worked, but unfortunately nothing was pointing me into this direction.

os.write(body.getBytes("UTF-8"));