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HttpURLConnection POST returning 400 Bad Request

I have tried every single question about it in here, but my code still returning 400, for every request that I try to do and I'm not getting what I'm doing wrong.
HttpURLConnection connection = null;
InputStream in = null;
try {
URL url = new URL(uri);
connection = (HttpURLConnection) url.openConnection();
connection.setReadTimeout(10000);
connection.setConnectTimeout(20000);
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-type", "application/x-www-form-urlencoded");
connection.setDoInput(true);
connection.setDoOutput(true);
String query = "";
if (Validator.isNotNull(paramsMap) && !paramsMap.isEmpty()) {
Uri.Builder builder = new Uri.Builder();
for (Map.Entry<String, String> entry : paramsMap.entrySet()) {
builder.appendQueryParameter(entry.getKey(), entry.getValue());
}
query = builder.build().getEncodedQuery();
}
if (!query.isEmpty()) {
OutputStream os = connection.getOutputStream();
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os, "UTF-8"));
writer.write(query);
writer.flush();
writer.close();
os.close();
}
connection.connect();
int status = connection.getResponseCode();
if (status == 200) {
in = connection.getInputStream();
} else {
in = connection.getErrorStream();
}
} finally {
connection.disconnect();
}
return in;

I would try to get it working using a separate tool (there are quite a few browser plugins that let you create POST requests (Postman, HttpRequester, etc.) Use one of those to figure out exactly what you need to POST to get it to work. Once you have it working in one of the tools, you can do the same thing in your Java code.

OutputStream os = con.getOutputStream() throws NullPointerException

I am trying to build an android app for a website and I need to post some value to this page first.
Here is my code:
private void sendPOST(String user,String pass) throws IOException {
String POST_PARAMS = "username="+user+"&password="+pass;
URL obj = new URL("http://xx.xx.xx.xx/mysite/test.php");
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
con.setRequestMethod("POST");
con.setRequestProperty("User-Agent", "Mozilla/5.0");
//----------------------------------------------------------- For POST only - START---------------------------------------------
con.setDoOutput(true);
OutputStream os = con.getOutputStream();
os.write(POST_PARAMS.getBytes());
os.flush();
os.close();
// ------------------------------------------------------------For POST only - END----------------------------------------------------
int responseCode = con.getResponseCode();
if (responseCode == HttpURLConnection.HTTP_OK) { //success
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
Toast.makeText(getApplicationContext(), response.toString()==""?"No Result":response.toString(), Toast.LENGTH_LONG).show();
} else {
Toast.makeText(getApplicationContext(),"POST request failed", Toast.LENGTH_LONG).show();
}
}
when this line is executed OutputStream os = con.getOutputStream();
a null exception occurs.
I am unable to proceed further. Please suggest what i must do to remove this exception.

put your delevelopment server in another locatation other than localhost (try using the real IP, something like: 192.168.0.1).
sometimes you will receive a successfull connection from HttpUrlConnection.openConnection() (it returns non null object) and this not guarantee the subsequents calls to success. In other words, when you call con.getOutputStream() it throws an exception no matter if con is non-null.

It's the old question but I might have to answer on it because I have face to it today. When you ping http (instead https) have to put in manifest -> application: android:usesCleartextTraffic="true"

I think this would helped you years ago...
try(OutputStream os = con.getOutputStream()) {
byte[] input = POST_PARAMS.getBytes("utf-8");
os.write(input, 0, input.length);
}

maybe you should try to "connect" first before doing anything with your created HttpURLConnection con.
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
con.connect();
do more stuff with con...
I hope this helps you :)

URL obj = new URL("http://xx.xx.xx.xx/mysite/test.php");
URL Class object "obj" can't reach to your mentioned URL properly.
Try this instead:
URL obj = new URL("http://"+"xx.xx.xx.xx/mysite/test.php");

Java HTTP post assistance

I've been working with the Slack API in java and have been trying to get an HTTP method that can be used like my below example block of code. That code block works, but the issue is I need to also include a 200 response code, and can't figure out how to get it to work.
Basically, how can I, In Java, send an HTTP post and also tag on the 200 status code using the URL and the content?
Current code:
public void httpRequest(URL url, String content) {
try {
byte[] contentBytes = content.getBytes("UTF-8");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setDoInput(true);
connection.setDoOutput(true);
connection.setRequestProperty("Accept-Charset", "UTF-8");
connection.setRequestProperty("Content-Type", "application/json");
connection.setRequestProperty("Content-Length", Integer.toString(contentBytes.length));
connection.setRequestProperty("Status", Integer.toString(200));
OutputStream requestStream = connection.getOutputStream();
requestStream.write(contentBytes, 0, contentBytes.length);
requestStream.close();
String response = "";
BufferedReader responseStream;
response = "" + ((HttpURLConnection) connection).getResponseCode();
try {
if (((HttpURLConnection) connection).getResponseCode() == 200) {
responseStream = new BufferedReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));
} else {
responseStream = new BufferedReader(new InputStreamReader(((HttpURLConnection) connection).getErrorStream(), "UTF-8"));
}
response = responseStream.readLine();
responseStream.close();
} catch (NullPointerException ignored) {
}
} catch (IOException e) {
e.printStackTrace();
}
}

The call to setDoOutput(true) triggers a post, i.e. you do not need to add
connection.setRequestMethod("POST");
Adding a status header to the request is possible, as you have done, but typically one associates status codes with http responses, not requests. - And off course, adding such custom header would only make sense if the server was designed to use this information to anything.
See this big, and highly up-voted answer on java.net.HttpURLConnection.
Also, you have some problems relating to your response variable as well as the BufferedReader. You accidentally override the value you initially assigned to the response field, instead of concatening. Also, your readLine() should probably be in a loop:
String tmp;
while ((tmp = responseStream.readLine()) !=null){
response += tmp;
}

Send POST data from JSP page to remote PHP server (and get an answer)

I'm trying to send some data from a JSP page to a PHP one (which should execute some code and return a success message).
I'm using this java function to make some tests:
public String excutePost(String targetURL, String urlParameters)
{
URL url;
HttpURLConnection connection = null;
try {
//Create connection
url = new URL(targetURL);
connection = (HttpURLConnection)url.openConnection();
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-Type",
"application/x-www-form-urlencoded");
connection.setRequestProperty("Content-Length", "" +
Integer.toString(urlParameters.getBytes().length));
connection.setRequestProperty("Content-Language", "en-US");
connection.setUseCaches (false);
connection.setDoInput(true);
connection.setDoOutput(true);
//Send request
DataOutputStream wr = new DataOutputStream (
connection.getOutputStream ());
wr.writeBytes (urlParameters);
wr.flush ();
wr.close ();
//Get Response
InputStream is = connection.getInputStream();
BufferedReader rd = new BufferedReader(new InputStreamReader(is));
String line;
StringBuffer response = new StringBuffer();
while((line = rd.readLine()) != null) {
response.append(line);
response.append('\r');
}
rd.close();
return response.toString();
} catch (Exception e) {
e.printStackTrace();
return null;
} finally {
if(connection != null) {
connection.disconnect();
}
}
}
String urlParameters =
"var=" + URLEncoder.encode("varcontent", "UTF-8");
out.println(excutePost("remoteurl",urlParameters));
Now if i run the page i get the response "null" and none of the code in the php page is executed.
Am I doing something wrong? How can I allow the php page to run the code in it?
Isn't a simple echo $_POST['var'] enough to send the data back to the jsp page?
EDIT: I tried to see if the php page is receiving something by writing the posted variable in a file. But nothing is written in it.
$file = 'debug.txt';
echo file_put_contents($file, $_POST['var']);
and here is the exception i'm getting..
java.net.SocketException: Connection reset

No, an echo is not enough. Put $_POST['var'] in say a text file and serve the updated text file (Edit the text file each time you need to keep track of $_POST['var']). Alternatively you can put it in some DB and check for changes.

Preemptive Basic Auth with HttpUrlConnection?

What is the best way to use preemptive basic http authentication using HttpUrlConnection. (Assume for now I can't use HttpClient).
EDIT for clarification: I'm setting the un/pw correctly in the request header using Base64 encoding. Are there any additional flags or properties that need to be set, or is the fact that I'm setting the basic auth headers for the request all that is needed for preemptive basic auth?

If you are using Java 8 or later, java.util.Base64 is usable:
HttpURLConnection connection = (HttpURLConnection) new URL(url).openConnection();
String encoded = Base64.getEncoder().encodeToString((username+":"+password).getBytes(StandardCharsets.UTF_8)); //Java 8
connection.setRequestProperty("Authorization", "Basic "+encoded);
Then use the connection as normal.
If you're using Java 7 or lower, you'll need a method to encode a String to Base64, such as:
byte[] message = (username+":"+password).getBytes("UTF-8");
String encoded = javax.xml.bind.DatatypeConverter.printBase64Binary(message);
Yes, that's all you have to do in order to use Basic Auth. The code above to set the Request Property should be done immediately after opening the connection and before getting the Input or Output streams.

Incidentally, in case someone else runs into the same, the android problem, is also present if you use org.apache.commons.codec.binary.Base64 and do Base64.encodeBase64String(). You need to do Base64.encodeBase64() and get a byte[] then construct the string.
It caught me offguard entirely that the results would be different for the line ending between those two methods.

You can use java.net.Authenticator to configure basic auth. globally for every request send by your application, see :
http://docs.oracle.com/javase/7/docs/technotes/guides/net/http-auth.html
http://developer.android.com/reference/java/net/Authenticator.html#getPasswordAuthentication()

you need to do this just copy paste it be happy
HttpURLConnection urlConnection;
String url;
// String data = json;
String result = null;
try {
String username ="danish.hussain#gmail.com";
String password = "12345678";
String auth =new String(username + ":" + password);
byte[] data1 = auth.getBytes(UTF_8);
String base64 = Base64.encodeToString(data1, Base64.NO_WRAP);
//Connect
urlConnection = (HttpURLConnection) ((new URL(urlBasePath).openConnection()));
urlConnection.setDoOutput(true);
urlConnection.setRequestProperty("Content-Type", "application/json");
urlConnection.setRequestProperty("Authorization", "Basic "+base64);
urlConnection.setRequestProperty("Accept", "application/json");
urlConnection.setRequestMethod("POST");
urlConnection.setConnectTimeout(10000);
urlConnection.connect();
JSONObject obj = new JSONObject();
obj.put("MobileNumber", "+97333746934");
obj.put("EmailAddress", "danish.hussain#dhl.com");
obj.put("FirstName", "Danish");
obj.put("LastName", "Hussain");
obj.put("Country", "BH");
obj.put("Language", "EN");
String data = obj.toString();
//Write
OutputStream outputStream = urlConnection.getOutputStream();
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));
writer.write(data);
writer.close();
outputStream.close();
int responseCode=urlConnection.getResponseCode();
if (responseCode == HttpsURLConnection.HTTP_OK) {
//Read
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream(), "UTF-8"));
String line = null;
StringBuilder sb = new StringBuilder();
while ((line = bufferedReader.readLine()) != null) {
sb.append(line);
}
bufferedReader.close();
result = sb.toString();
}else {
// return new String("false : "+responseCode);
new String("false : "+responseCode);
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}

I was having this problem too.
And Now I have solved this problem.
My code is :
URL url = new URL(stringUrl);
String authStr = "MyAPIKey"+":"+"Password";
System.out.println("Original String is " + authStr);
// encode data on your side using BASE64
byte[] bytesEncoded = Base64.encodeBase64(authStr .getBytes());
String authEncoded = new String(bytesEncoded);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestProperty("Authorization", "Basic "+authEncoded);
It may help many others.
Best of luck.

Regarding the Base64 encoding problem, I found this library: http://sourceforge.net/projects/migbase64/
I have not fully vetted it but I am using it for the Basic Authentication solution shown above (as well as for image encoding/decoding), and it works well. It provides a parameter for whether or not to include the newline.