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Upload File from GWT to another domain , response is always null

I am uploading a File from GWT to a different domain
File Uploads well , But the response i sent from the server always reaches as "null" at the client side
response.setContentType("text/html");
response.setHeader("Access-Control-Allow-Origin", "*");
response.getWriter().print("TEST");
response is NULL only when i upload the file on a different domain ... (on same domain all is OK)
I also see this in GWT documentation
Tip:
The result html can be null as a result of submitting a form to a different domain.
http://www.gwtproject.org/javadoc/latest/com/google/gwt/user/client/ui/FormPanel.SubmitCompleteEvent.html
Is there any way I can receive back a response at my client side when i am uploading file to a different domain

There are 2 possible answer:
Use JSONP Builder
JsonpRequestBuilder requestBuilder = new JsonpRequestBuilder();
requestBuilder.requestObject(url, new AsyncCallback<FbUser>() {
#Override
public void onFailure(Throwable ex) {
throw SOMETHING_EXCEPTION(ex);
}
#Override
public void onSuccess(ResponseModel resp) {
if (resp.isError()) {
// on response error on something
log.error(resp.getError().getMessage())
log.error(resp.getError().getCode())
}
log.info(resp.getAnyData())
}
Not to use GWT to upload, rather use other client like apache HttpClient
public uploadFile() {
HttpClient httpClient = new DefaultHttpClient();
HttpContext localContext = new BasicHttpContext();
HttpPost httpPost = new HttpPost(url);
FileBody bin = new FileBody(new File(UPLOADED_FILE));
long size = bin.getContentLength();
MultipartEntity reqEntity = new MultipartEntity();
reqEntity.addPart("PART", bin);
String content = "-";
try {
httpPost.setEntity(reqEntity);
HttpResponse response = httpClient.execute(httpPost, localContext);
HttpEntity ent = response.getEntity();
InputStream st = ent.getContent();
StringWriter writer = new StringWriter();
IOUtils.copy(st, writer);
content = writer.toString();
} catch (IOException e) {
return "false";
}
return content;
}
Hope it helps

How to pass complex parameter to POST request using Apache HTTP client?

I attempt to send POST request with body like this
{
"method": "getAreas",
"methodProperties": {
"prop1" : "value1",
"prop2" : "value2",
}
}
Here is my code
static final String HOST = "https://somehost.com";
public String sendPost(String method,
Map<String, String> methodProperties) throws ClientProtocolException, IOException {
HttpPost post = new HttpPost(HOST);
List<NameValuePair> urlParameters = new ArrayList<>();
urlParameters.add(new BasicNameValuePair("method", method));
List<NameValuePair> methodPropertiesList = methodProperties.entrySet().stream()
.map(entry -> new BasicNameValuePair(entry.getKey(), entry.getValue()))
.collect(Collectors.toList());
// ??? urlParameters.add(new BasicNameValuePair("methodProperties", methodPropertiesList));
post.setEntity(new UrlEncodedFormEntity(urlParameters));
try (CloseableHttpClient httpClient = HttpClients.createDefault();
CloseableHttpResponse response = httpClient.execute(post)) {
return EntityUtils.toString(response.getEntity());
}
}
But constructor of BasicNameValuePair applies (String, String). So I need another class instead.
Is there any way to add methodPropertiesList to urlParameters?

your request looking like a json structure so post data like below:
class pojo1{
String method;
Map<String,String> methodProperties;
}
String postUrl = "www.site.com";// put in your url
Gson gson = new Gson();
HttpClient httpClient = HttpClientBuilder.create().build();
HttpPost post = new HttpPost(postUrl);
StringEntity postingString = new StringEntity(gson.toJson(pojo1));//gson.tojson() converts your pojo to json
post.setEntity(postingString);
post.setHeader("Content-type", "application/json");
HttpResponse response = httpClient.execute(post);
ref:HTTP POST using JSON in Java

There is a well known approach to this problem.
In most cases you will create your own object describing the thing that you want to send in the HttpPost. So you will have something like:
static final String HOST = "https://somehost.com";
public String sendPost(String method,
Map<String, String> methodProperties) throws ClientProtocolException, IOException {
HttpPost post = new HttpPost(HOST);
MyResource resource = new MyResource();
resource.setMethod(method);
MyNestedResource nestedResource = new MyNestedResource();
nestedResource.setMethodProperties(methodProperties);
resource.setNestedResourceMethodProperties(nestedResource);
StringEntity strEntity = new StringEntity(gson.toJson(resource));
post.setEntity(strEntity);
try (CloseableHttpClient httpClient = HttpClients.createDefault();
CloseableHttpResponse response = httpClient.execute(post)) {
return EntityUtils.toString(response.getEntity());
}
}
And that is usually how you approach more complext json objects with a nested structure. You have to create classes for the resources you want to send (in your example it may be one class and to use map in it, but usually you create a class for the nested object too if it has a specific structure). To get more familiar with the whole picture better cover this tutorial: https://www.baeldung.com/jackson-mapping-dynamic-object

Using Sushil Mittal answer here is my solution
static final String HOST = "https://somehost.com";
public String sendPost(String method, Map<String, String> methodProperties) throws ClientProtocolException, IOException {
HttpPost post = new HttpPost(HOST);
Gson gson = new Gson();
Params params = new Params(method, methodProperties);
StringEntity entity = new StringEntity(gson.toJson(params));
post.setEntity(entity);
try (CloseableHttpClient httpClient = HttpClients.createDefault();
CloseableHttpResponse response = httpClient.execute(post)) {
return EntityUtils.toString(response.getEntity());
}
}
class Params {
String method;
Map<String, String> methodProperties;
public Params(String method, Map<String, String> methodProperties) {
this.method = method;
this.methodProperties = methodProperties;
}
//getters
}

Unable to make http POST request in java?

static HttpClient httpclient = new DefaultHttpClient();
static HttpPost httppost = new HttpPost("http://servername:6405/biprws/logon/long");
public static void main(String[] args) throws ClientProtocolException, IOException {
ArrayList<NameValuePair> postParameters = new ArrayList<NameValuePair>();
postParameters.add(new BasicNameValuePair("userName", "Administrator"));
postParameters.add(new BasicNameValuePair("password", "test"));
postParameters.add(new BasicNameValuePair("auth", "secEnterprise"));
httppost.setEntity(new UrlEncodedFormEntity(postParameters));
httppost.addHeader("accept", "application/json");
httppost.addHeader("Content-Type", "application/json");
HttpResponse response = httpclient.execute(httppost);
Header s = response.getFirstHeader("logontoken");
String s1 = s.getValue();
System.out.println(s1);// null pointer exception here
}
Running the code above i am not able to add request body to the POST request. How can i achieve this?
Alternative method i followed:
HttpClient client1 = new DefaultHttpClient();
HttpPost post = new HttpPost("http://servername:6405/biprws/logon/long");
String json = "{\"UserName\":\"Administrator\",\"Password\":\"test\",\"Auth\":\"secEnterprise\"}";
StringEntity entity = new StringEntity(json,"UTF-8");
entity.setContentType("application/json");
post.setEntity(entity);
System.out.println(entity);
post.setHeader("Accept", "application/json");
HttpResponse response = client1.execute(post);
BufferedReader rd1 = new BufferedReader(
new InputStreamReader(response.getEntity().getContent()));
String result1 = null;
String line1 = "";
result1 = rd1.readLine();
System.out.println(result1);
Still i am not able to make request.

You are successfully receiving a response which does not contain the "logontoken" header. Very possibly because the response is not an HTTP 200 OK response. Why? We don't know, it all depends on the protocol that your server implements on top of HTTP.
That having been said, the use of both httppost.setEntity(new UrlEncodedFromEntity(postParameters)) and httppost.addHeder("Content-Type", "application/json") does not look right to me. A URL-encoded form entity is not of json content type. So, either convert your post parameters to json, or lose the content-type header.

Oauth token requests before provider credentials issuance

Please forgive me if I ask something stupid, I am a novice here. I need to implement OAuth in my Java application to authenticate against launchpad.net API. The documentation specifies an initiation of a token request with three parameters : oauth_consumer_key e.g. (name of my application), oauth_signature_method e.g. "PLAINTEXT" and oauth_signature e.g. The string "&". I realised that most OAuth libraries require that
I have already acquired a Consumer key and Consumer Id/Secret from
the OAuth provider (e.g as issued in Twitter), and most examples are organised in this manner. However, launchpad.net will issue these parameters only after issuance of request token (they use no third party provider). How can I proceed?I am currently stuck after trying some libraries that threw errors. Many thanks for any useful information. The official launchpad library is in python.
My initial code is below:
public class Quicky {
public static void main(String[] args) throws Exception {
CloseableHttpClient httpclient = HttpClients.createDefault();
try {
HttpGet httpGet = new HttpGet("https://launchpad.net/+request-token");
CloseableHttpResponse response1 = httpclient.execute(httpGet);
try {
System.out.println("Your current GET request status:" + response1.getStatusLine());
HttpEntity entity1 = response1.getEntity();
EntityUtils.consume(entity1);
} finally {
response1.close();
}
HttpRequest request;
HttpPost httpPost = new HttpPost("https://launchpad.net/+request-token");
PostMethod poster = new PostMethod();
List <NameValuePair> postParams = new ArrayList <NameValuePair>();
postParams.add(new BasicNameValuePair("oauth_customer_key", "XXXX"));
postParams.add(new BasicNameValuePair("oauth_signature_method", "PLAINTEXT"));
postParams.add(new BasicNameValuePair("oauth_signature", "&"));
httpPost.setEntity(new UrlEncodedFormEntity(postParams, "utf-8"));
// httpPost.setEntity(entity1);
httpclient.execute(httpPost);
HttpParameters requestParams = (HttpParameters) postParams;
CloseableHttpResponse response2 = httpclient.execute(httpPost);
try {
System.out.println("Your current POST request status:" + response2.getStatusLine());
HttpEntity entity2 = response2.getEntity();
// do something useful with the response body
// and ensure it is fully consumed
EntityUtils.consume(entity2);
} finally {
response2.close();
}
} finally {
httpclient.close();
}
}
}

I finally resolved the issue error messages after some research and code re-factoring. The correct code is below, maybe it could be useful to someone out there.
public class LaunchPadTokenRetriever {
public static void main(String[] args) throws ClientProtocolException, IOException{
CloseableHttpClient httpclient = HttpClients.createDefault();
HttpPost httpPost = new HttpPost("https://launchpad.net/+request-token");
httpPost.addHeader("Content-Type", "application/x-www-form-urlencoded");
List <NameValuePair> urlParams = new ArrayList <NameValuePair>();
urlParams.add(new BasicNameValuePair("oauth_signature", "&"));
urlParams.add(new BasicNameValuePair("oauth_consumer_key", "tester"));
urlParams.add(new BasicNameValuePair("oauth_signature_method", "PLAINTEXT"));
httpPost.setEntity(new UrlEncodedFormEntity(urlParams));
CloseableHttpResponse response = httpclient.execute(httpPost);
System.out.println(response);
try {
System.out.println(response.getStatusLine());
HttpEntity entity = response.getEntity();
ResponseHandler<String> responseHandler = new BasicResponseHandler();
String responseBody = httpclient.execute(httpPost, responseHandler);
System.out.println("Initial credentials ---> "+ responseBody);
System.out.println();
String getresponse = responseBody;
EntityUtils.consume(entity);
} finally {
response.close();
}
}
}

authentication with Java and apache HttpClient 4.5.1

my problem is, that i don't get, how to log in with Java and Apache HttpComponents (HttpClient v4.5.1) into a specific site: Site im trying to log in. I have the username (test_admin) and the password (testing) to log in but i think this is not enough and i need something more. I think this has something to do with the field security_token i see when i make a get request to the uri, but i dont know how to keep that or how to save that and what to do with it afterwards. There is also a hidden input field with the name login-ticket, but i dont know what's that for either. I want to login, because i need to see the courses and add some new ones. After trying with several code implementations im stick with this code:
public static void setGet(CloseableHttpClient httpClient) throws UnsupportedOperationException, IOException
{
HttpGet httpGet = new HttpGet("http://demo.studip.de/dispatch.php/admin/courses");
CloseableHttpResponse httpResponse = httpClient.execute(httpGet);
System.out.println("GET Response Status:: "
+ httpResponse.getStatusLine().getStatusCode());
showEntity(httpResponse,httpResponse.getEntity());
}
public static HttpEntity setParam(int count, String[] params, String[] values)
{
List<NameValuePair> formparams = new ArrayList<NameValuePair>();
for (int i = 0; i < count; i++)
{
formparams.add(new BasicNameValuePair(params[i],values[i]));
System.out.println("Paramater------------------> "+params[i]+" Values-------------> "+values[i]);
}
UrlEncodedFormEntity entity = new UrlEncodedFormEntity(formparams, Consts.UTF_8);
return entity;
}
public static void setPost(HttpClient httpC) throws ClientProtocolException, IOException
{
HttpPost httppost = new HttpPost("http://demo.studip.de/dispatch.php/admin/courses");
//String[] params = {"loginname", "password"};
//String[] values = {"test_admin", "testing"};
//HttpEntity entity = setParam(2, params, values );
HttpResponse response = httpC.execute(httppost);
System.out.println("POST Response Status:: "
+ response.getStatusLine().getStatusCode());
showEntity(response, response.getEntity());
}
public static void showEntity(HttpResponse httpResp, HttpEntity httpClient) throws IOException
{
httpClient = httpResp.getEntity();
if (httpClient != null)
httpClient = new BufferedHttpEntity(httpClient);
System.out.print(EntityUtils.toString(httpClient));
}
public static void main(String[] args) throws InterruptedException, IOException {
CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
credentialsProvider.setCredentials(AuthScope.ANY,
new UsernamePasswordCredentials("test_admin", "testing"));
CloseableHttpClient hc =
HttpClientBuilder.create().setDefaultCredentialsProvider(credentialsProvider).build();
setGet(hc);
// HttpClient httpclient = HttpClients.createDefault();
setPost(hc);
setGet(hc);
}
The problem now ist that i get everytime the same answer from the server i only see the login page in the response, where the server asks me to login with username and password.

Which code you get from the server 401,403,301,302 or 200?