Develop Reference

Android send POST request in Java to ASP.net Web API

When I used HttpUrlConnection to send POST request from Android to ASP.net Web API. It seems not working.
String baseUrl = "http://<IP Address>/Save/Document";
URL url = new URL(baseUrl);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod("POST");
conn.setRequestProperty("Content-Type", "application/json; charset=utf-8");
DataOutputStream os = new DataOutputStream(conn.getOutputStream());
JSONObject ap = new JSONObject();
// Where data is a JSON string
// Like [{Test: 1}, {Test: 2}]
ap.put("",new Gson().toJson(data));
OutputStreamWriter ap_osw= new OutputStreamWriter(conn.getOutputStream());
ap_osw.write(ap.toString());
ap_osw.flush();
ap_osw.close();
BufferedReader br = new BufferedReader(new InputStreamReader(
(conn.getInputStream())));
StringBuilder response = new StringBuilder();
while ((output = br.readLine()) != null) {
response.append(output);
response.append('\r');
}
String mes = response.toString();
Log.i("INFO", mes);
conn.disconnect();
When executing the above code, it will have an FileNotFoundException in
conn.getInputStream()
I also tried to implement source code in HttpClient style.
HttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(baseUrl);
try {
StringEntity se = new StringEntity((new Gson()).toJson(data));
httpPost.setEntity(se);
httpPost.setHeader("Accept", "application/json");
httpPost.setHeader("Content-Type", "application/json");
HttpResponse response = httpClient.execute(httpPost);
InputStream inputStream = response.getEntity().getContent();
String result = "";
if (inputStream != null)
result = convertInputStreamToString(inputStream);
else
result = "Did not work!";
Log.i("RESPONSE", result);
} catch (Exception ex) {
Log.i("Exception", ex.getMessage());
}
return output;
And this time, it shows "The requested resource does not support http method 'get'".
I have no ideas how to implement the POST request method to send data from Android to ASP.net Web API. Any recommendations?
Finally, the following coding is my ASP.net Web API for reference.
[HttpPost]
[Route("Save/Document")]
public HttpResponseMessage Post([FromBody]string model)
{
var resp = new HttpResponseMessage(HttpStatusCode.OK);
resp.Content = new StringContent(model, System.Text.Encoding.UTF8, "text/plain");
return resp;
}

Finally, I got a solution to fix this problem. It is due to the POST data in request body can not be read from Web API.
When the request Content-Type is "application/json",
Using string, The request body should be a plain text (e.g. "Text Message").
[FromBody] string inStr
Using self-defined class, The request body should be a json string
(e.g { KEY: VALUE })
[FromBody] YourClass inObj
Using array of self-defined class, The request body should be a json array string (e.g [{ KEY: VALUE }])
[FromBody] YourClass[] inObj
And the self-defined class should be like as following:-
class YourClass {
public string KEY { get; set; }
}
Btw. Thanks for all reply and useful information.

Why am I getting 500 response code on passing wrong email or password to service in android?

I have been running into a very strange problem. I am trying to implement log in service in my app. When I pass right email and password service returns response as expected(means no error comes) but when I delibrately pass wrong email or password geInputStream() method throws FileNotFoundException. I don't know what is the reason behind this.Further more, before calling getInputStream() method i checked status code as well(this is the case when I am passing wrong email and password intentionally).The status code was 500. I checked for 500 and that was internal server error. My question is why is that so? I mean when intentionally passing wrong email or password why internal server occurred? One more thing I would like to mention that I have checked the same service on post man it is working fine as expected. If i pass wrong email or password postman returns the expected error. Below is the code I am using
private String invokeWebservice() {
String data = null;
HttpURLConnection conn = null;
BufferedReader in = null;
try {
String webservice = Constants.BASE_URL + serviceName;
LogUtility.debugLog("webservice just called "+ webservice);
URL url = new URL(webservice);
conn = (HttpURLConnection) url.openConnection();
conn.setReadTimeout(10000);
conn.setConnectTimeout(15000);
conn.setUseCaches(false);
if (isPost) {
conn.setDoOutput(true);
conn.setRequestMethod("POST");
conn.setRequestProperty("Content-Type", "application/json");
conn.setRequestProperty("Accept", "application/json");
Writer writer = new BufferedWriter(new OutputStreamWriter(conn.getOutputStream(), "UTF-8"));
if (jsonObject != null)
writer.write(jsonObject.toString());
writer.close();
}
in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
StringBuffer sb = new StringBuffer("");
String l = "";
String nl = System.getProperty("line.separator");
while ((l = in.readLine()) != null)
sb.append(l + nl);
in.close();
data = sb.toString();
return data;
} catch (Exception e) {
LogUtility.errorLog("exception while calling web service");
} finally {
try {
if (conn != null)
conn.disconnect();
if (in != null)
in.close();
} catch (Exception ex) {
// LogUtility.errorLogWithException(ex, ex.getMessage());
}
}
return data;
}
Any help?

After spending some time now I was able to solve my problem.Posting my answer for others. Passing wrong email and password to the service was right and server was consuming those parameters as well and because there was an error(because email and password) that is why it was returning 500 code. So, I checked for status code if it was 200 then I used getInputStream() method and else i called getErrorStream() method. By this way i got the stream that has property for error(this property contains error detail). Below is the code i used
if (conn.getResponseCode() != HttpURLConnection.HTTP_OK) {
in = new BufferedReader(new InputStreamReader(conn.getErrorStream()));
} else {
in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
}
Hope it helps other as well.

Receiving "501 Not Implemented" when using HttpURLConnection

My project is targeted to SDK 23, and from now on, as far as I know, I have to use HttpURLConnection instead of HttpClient to make post requests, but I keep getting 501 response code from my webservice (I'm pretty sure it's fully functional, I have no doubt) when making post requests to store users in a remote mysql database. Here follows the main connection code:
class DatabaseConnector extends AsyncTask<String, Void, String> {
private final String CONNECTION_URL = "webservice_address";
#Override
protected String doInBackground(String... params) {
String response = "initial value";
try {
URL url = new URL(CONNECTION_URL);
HttpURLConnection con = (HttpURLConnection) url.openConnection();
con.setDoOutput(true);
con.setDoInput(true);
con.setUseCaches(false);
con.setRequestProperty("Content-Type", "application/json");
con.setRequestProperty("Accept", "application/json");
con.setReadTimeout(10000);
con.setConnectTimeout(15000);
con.setRequestMethod("POST");
JSONObject json = new JSONObject();
json.put("query", params[0]);
JSONObject conn = new JSONObject();
conn.put("database", "database");
conn.put("hostname", "hostname");
conn.put("password", "password");
conn.put("username", "username");
conn.put("port", "port");
json.put("conn", conn.toString());
OutputStreamWriter wr = new OutputStreamWriter(con.getOutputStream());
wr.write(json.toString());
wr.flush();
wr.close();
con.connect();
//display what returns the POST request
StringBuilder sb = new StringBuilder();
int HttpResult = con.getResponseCode();
System.out.println("Response CODE: "+ con.getResponseCode());
if (HttpResult == HttpURLConnection.HTTP_OK) {
System.out.println("Passed1");
BufferedReader br = new BufferedReader(new InputStreamReader(con.getInputStream(), "utf-8"));
while ((response = br.readLine()) != null) {
sb.append(response + "\n");
}
br.close();
System.out.println("E: " + sb.toString());
response = sb.toString();
} else {
System.out.println("E2: "+con.getResponseMessage());
response = "Error1: "+con.getResponseMessage();
}
} catch (Exception e) {
response = "Error2: "+e.toString();
}
return response;
}
}
And in my fragment I make the network calls:
try {
String result = new DatabaseConnector().execute("SELECssT 1").get();
Toast.makeText(ContentActivity.this, "Result: "+result, Toast.LENGTH_LONG).show();
} catch (Exception ex) {
Toast.makeText(ContentActivity.this, "Error3: "+ex.toString(), Toast.LENGTH_LONG).show();
}
Nevermind that wrong sql statement, it's meant to be like that, I want the webservice to echo back that syntax error. I have tried many stuff, codes, examples, but it doesn't seem to work.
The point is: I keep getting error code 501 Not Implemented. Why? And how can I fix that?
EDIT:
Any tips or comments on how to improve the way I make network calls on android is welcome, I'm pretty new to that. I'm using a Async call but somehow it's still executing in the main thread, cause the debugger complains:
09-25 19:17:32.714 28853-28853/br.com.developer.package I/Choreographer﹕ Skipped 80 frames! The application may be doing too much work on its main thread.
Thank you all.

How to handle 500 Internal Server Error when using JSON

I am relatively new to Android and I am using JSON to get data from a server. On the first loop at line 22, the StringBuilder contains, 500 Internal Server Error and then the jArray ends up coming back null. How can I handle this error?
public static JSONObject getJSON() {
String jsonString = "";
InputStream inStream = null;
//http post
JSONObject jArray = null;
try {
HttpClient httpClient = new DefaultHttpClient(new BasicHttpParams());
HttpPost httpPost = new HttpPost(WS_URL);
httpPost.setHeader("Content-type", "application/json");
HttpResponse response = httpClient.execute(httpPost);
HttpEntity entity = response.getEntity();
inStream = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(inStream, "UTF-8"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
inStream.close();
jsonString = sb.toString();
jArray = new JSONObject(jsonString);
//outputTransactions(jArray);
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
return jArray;
}

Though its a late reply but it might help others. You need to check the response status from the server before parsing it as JSON.
For ex.
int status_code=response.getStatusLine().getStatusCode();
if(status_code!=200){
Log.d("MYLOG","ERROR! Response status is"+status_code);
}
else{
inStream = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(inStream, "UTF-8"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
inStream.close();
// Rest of your code......
}
or Optionally you can check the status code and display the error to the user
Like:
else if(status_code==404){
Log.d("MYLOG","Sorry! Page not found! Check the URL ");
}else if(status_code==500){
Log.d("MYLOG","Server is not responding! Sorry try again later..");
}
Hope it helps for newbies like you :-)

A "500 Internal Server" error means the server had a problem responding to your request. You are not getting a JSON string response.
Then when you try to create your jArray, the string is not valid JSON and the JSONObject cannot parse it - it returns "null" as you say.
You can parse the server response to see if it contains this string, and then create whatever jArray object you want, but you can't get a JSON object from a non-JSON string.

Take a look at this answer: https://stackoverflow.com/a/8148785/1974614
You should check the statusCode against 500

You should consider use a library to handle the REST requests like: http://square.github.io/retrofit/
If you use a library like that you can get an object from json when a success response is available and other when an error occur.
MyApi mylogin = restAdapter.create(MyApi.class); //this is how retrofit create your api
mylogin.login(username,password,new Callback<String>() {
#Override
public void success(String s, Response response) {
//process your response if login successfull you can call Intent and launch your main activity
}
#Override
public void failure(RetrofitError retrofitError) {
retrofitError.printStackTrace(); //to see if you have errors
}
});
}

I got the same problem like you and I solved it because I missed a part while adding GSON .jar files to adding my serverside project. I think you should carrefully add external libraries to your project too like me.With these links I could aware of problem .
LINK 1
LINK 2

Not able to POST to REST API

Today I'm making my first attempt of sending a POST request with a JSON to save some data, and I'm not being able to do so.
My app works by signing in, and then save, modify and delete data. It's already done in iOS, but since I'm new to Android, I'm not sure how to do it.
Here's my POST function:
public String POST(String targetURL, String urlParameters, String user, String pwd) {
URL url;
String u = targetURL;
HttpURLConnection connection = null;
try {
// Create connection
// u=URLEncoder.encode(u, "UTF-8");
url = new URL(u);
connection = (HttpURLConnection) url.openConnection();
// cambiarlo luego al usuario q esta logeado
String login = user + ":" + pwd;
String encoding = new String(org.apache.commons.codec.binary.Base64.encodeBase64(org.apache.commons.codec.binary.StringUtils.getBytesUtf8(login)));
connection.setRequestMethod("POST");
connection.setRequestProperty("Authorization", "Basic " + encoding);
connection.setRequestProperty("Content-Type", "plain/text");// hace q sirva con el string de json
connection.setRequestProperty("Content-Length", "" + Integer.toString(urlParameters.getBytes().length));
connection.setRequestProperty("Content-Language", "en-US");
connection.setUseCaches(false);
connection.setDoInput(true);
connection.setDoOutput(true);
connection.setReadTimeout(120000);
// 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();
this.setResponseCode(connection.getResponseCode());
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();
}
}
}
The method above is executed with Asynctask, and even if I use it to Login using Spring security, it works, and even I can save for internal usage the username, password, and secret token.
I dunno if I need to put the token in a header or something, because I already did that, with no positive results.
I'm supposing that the only permission I need to execute this is the internet one, so in my manifest file I specified that permission.
I'm going crazy with this issue, please help!
Thanks in advance.
EDIT:
Sorry guys, I'm kinda new to this way of asking, and also, not an English native speaker :P
The output I receive after sending the request, is the HTML of the page that handles logging in into the web app... I need like a json response or something like that to make sure the request was saved correctly

Try handling your cookies
CookieManager cookieManager = new CookieManager();
CookieHandler.setDefault(cookieManager);
This should be a singleton.