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Android AsyncTask, handle unavailable server

I am using this tutorial:
http://hmkcode.com/android-parsing-json-data/ to get JSON data from server on virtual machine. It works fine, when server is turned on, but my app crashes when server is unavailable.
How should I handle this situation?
After pressing button I execute:
httpAsyncTask.execute("http://localhost:3000"); //changed on purpose, it works with given IP
httpAsyncTask class:
private class HttpAsyncTask extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... urls) {
return GET(urls[0]);
}
// onPostExecute displays the results of the AsyncTask.
#Override
protected void onPostExecute(String result) {
Toast.makeText(getBaseContext(), "Worked fine", Toast.LENGTH_LONG).show();
goToMyActivity();
}
}
In debug my app stops at:
HttpResponse httpResponse = httpclient.execute(new HttpGet(url));
int GET method:
public static String GET(String url){
InputStream inputStream = null;
String result = "";
try {
// create HttpClient
HttpClient httpclient = new DefaultHttpClient();
// make GET request to the given URL
HttpResponse httpResponse = httpclient.execute(new HttpGet(url));
// receive response as inputStream
inputStream = httpResponse.getEntity().getContent();
// convert inputstream to string
if (inputStream != null)
result = convertInputStreamToString(inputStream);
else
result = "Did not work!";
} catch (Exception e){
Log.e("Http:",e.toString());
}
return result;
}
Caught exception was null.

use getResponseCode(); of HttpURLConnection class to make sure that the connection is established successfully.
getResponseCode(); would return 200 if the connection is successful.
int responseCode = -1;
feedURL = "your URL"
HttpURLConnection connection;
connection = (HttpURLConnection) feedURL.openConnection();
connection.connect();
responseCode = connection.getResponseCode();
then use if block to check if 200 is returned by connection.getResponseCode().
the constant HttpURLConnection.HTTP_OK can be used instead of hard coding 200.
if (responseCode == HttpURLConnection.HTTP_OK) {
// do your stuff here
}
else {
// Show some error dialog or Toast message
}

Use the catch block to catch the timeout exception (and others):
String message = "";
try {
//HTTP stuff here
if (responseCode == HttpURLConnection.HTTP_OK) {
// do your stuff here
} else {
// Show some error dialog or Toast message
}
} catch (Exception e) {
message = e.getLocalizedMessage();
e.printStackTrace();
}
// Toast message

This function will return null if it gets timeout otherwise will send the response
public static String Get(String url) {
// Create a new HttpClient
HttpParams params = new BasicHttpParams();
// set your timeouts here
HttpConnectionParams.setConnectionTimeout(params, 5000);
HttpConnectionParams.setSoTimeout(params, 10000);
HttpClient httpclient = new DefaultHttpClient(params);
try {
// Execute HTTP GET Request
HttpResponse response = httpclient.execute(new HttpGet(url));
return EntityUtils.toString(response.getEntity());
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}

Android HttpsURLConnection - simple POST request with parameters

I've been trying to get a simple android client server app working, and I've had nothing but trouble. I'm hoping someone can look at this code and see what I'm doing wrong, maybe I'm doing things in the wrong order, or forgetting something? Just adding the relevant parts
HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
conn.addRequestProperty("Content-Type", "application/json");
// set some made up parameters
String str = "{'login':'superman#super.com','password':'password'}";
byte[] outputInBytes = str.getBytes("UTF-8");
OutputStream os = conn.getOutputStream();
os.write( outputInBytes );
os.close();
// connection.setDoOutput(true); //should trigger POST - move above -> crash
conn.setRequestMethod("POST"); // explicitly set POST -move above so we can set params -> crash
conn.setDoInput(true);
The error I get is
'exception: java.net.ProtocolException: method does not support a
request body: GET'
If I just do a POST request without parameters it's fine, so I guess I should move the connection.setDoOutput(true); or conn.setRequestMethod("POST"); higher up, that should work right? When I do that I get the error:
exception: java.net.ProtocolException: Connection already established.
So, if I try to set to POST before adding parameters it doesn't work, if I try to do it after it doesn't work... what am I missing? Is there another way I should be doing this? Am I adding parameters incorrectly? I've been searching for a simple android networking example, and I can't find any, is there any example the official Android site? All I want to do is a very basic network operation, this is so frustrating!
EDIT: I need to use HttpsURLConnection for reasons not included in the above code- I need to authenticate, trust hosts, etc- so I'm really looking for a potential fix for the above code if possible.

Here is an example of how to post with a JSON Object:
JSONObject payload=new JSONObject();
try {
payload.put("password", params[1]);
payload.put("userName", params[0]);
} catch (JSONException e) {
e.printStackTrace();
}
String responseString="";
try
{
HttpPost httpPost = new HttpPost("www.theUrlYouQWant.com");
httpPost.setEntity(new StringEntity(payload.toString()));
httpPost.setHeader("Accept", "application/json");
httpPost.setHeader("Content-type", "application/json");
HttpResponse response = new DefaultHttpClient().execute(httpPost);
responseString = EntityUtils.toString(response.getEntity());
}
catch (ClientProtocolException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}
And example of how to get
String responseString = "";
//check if the username exists
StringBuilder builder = new StringBuilder();
HttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet("www.theUrlYouQWant.com");
ArrayList<String> existingUserName = new ArrayList<String>();
try
{
HttpResponse response = client.execute(httpGet);
StatusLine statusLine = response.getStatusLine();
int statusCode = statusLine.getStatusCode();
if (statusCode == 200) {
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(content));
String line;
while ((line = reader.readLine()) != null) {
builder.append(line);
}
}
else
{
Log.e(ParseException.class.toString(), "Failed to download file");
}
}
catch (ClientProtocolException e)
{
e.printStackTrace();
}
catch (IOException e)
{
e.printStackTrace();
}

I followed this tutorial on making http calls:
http://www.androidhive.info/2012/01/android-json-parsing-tutorial/
Works fine with no problems.
Below is a class that I have modified from the sample:
public class ServiceHandler {
static String response = null;
public final static int GET = 1;
public final static int POST = 2;
String TAG = ((Object) this).getClass().getSimpleName();
public ServiceHandler() {
}
/**
* Making service call
*
* #url - url to make request
* #method - http request method
*/
public String makeServiceCall(String url, int method) {
return this.makeServiceCall(url, method, null);
}
/**
* Making service call
*
* #url - url to make request
* #method - http request method
* #params - http request params
*/
public String makeServiceCall(String url, int method,
List<NameValuePair> params) {
try {
// http client
HttpParams httpParameters = new BasicHttpParams();
// Set the timeout in milliseconds until a connection is established.
// The default value is zero, that means the timeout is not used.
int timeoutConnection = 2000;
HttpConnectionParams.setConnectionTimeout(httpParameters, timeoutConnection);
// Set the default socket timeout (SO_TIMEOUT)
// in milliseconds which is the timeout for waiting for data.
int timeoutSocket = 2000;
HttpConnectionParams.setSoTimeout(httpParameters, timeoutSocket);
DefaultHttpClient httpClient = new DefaultHttpClient(httpParameters);
HttpEntity httpEntity = null;
HttpResponse httpResponse = null;
// Checking http request method type
if (method == POST) {
HttpPost httpPost = new HttpPost(url);
// adding post params
if (params != null) {
httpPost.setEntity(new UrlEncodedFormEntity(params));
}
httpResponse = httpClient.execute(httpPost);
} else if (method == GET) {
// appending params to url
if (params != null) {
String paramString = URLEncodedUtils
.format(params, "utf-8");
url += "?" + paramString;
}
Log.e("Request: ", "> " + url);
HttpGet httpGet = new HttpGet(url);
httpResponse = httpClient.execute(httpGet);
}
if (httpResponse != null) {
httpEntity = httpResponse.getEntity();
} else {
Log.e(TAG, "httpResponse is null");
}
response = EntityUtils.toString(httpEntity);
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return response;
}
}
And this is how I use the class:
nameValuePairs = new ArrayList<NameValuePair>();
String param_value = "value";
String param_name = "name";
nameValuePairs.add(new BasicNameValuePair(param_name, param_value));
// Creating service handler class instance
sh = new ServiceHandler();
String json = sh.makeServiceCall(Utils.getUrl, ServiceHandler.GET, nameValuePairs);

Basic Android App Direction

I've created basic android apps in various programming classes that I have taken before using Eclipse and the Java Android SDK.
The app that I'd like to create would require users to enter information that would later be analyzed. I want people to be able to compare this data with other people's data so I'd like every entry that users make to be submitted to a database to later be queried when a person attempts to compare their data.
I'd like direction for how to accomplish this. Should I find a free hosting site and set up a Sql server or is there a better way to accomplish this?
Edit: Just for fun.

I am a very beginner android developer, and I have found that using cloud-stored online database like mongolab.com is very friendly for user submitted data. The communication between database and server will have to be done through JSON parsing and URI requests.
Here is example of code you can bind to a button that will send object stored in field tempData:
public void send(View view) {
String apiURI = "https://api.mongolab.com/api/1/databases/MYDATABASE/collections/USERSUBMITTEDDATA?apiKey="
+ apiKey;
try {
// make web service connection
final HttpPost request = new HttpPost(apiURI);
request.setHeader("Accept", "application/json");
request.setHeader("Content-type", "application/json");
// Build JSON string with GSON library
Gson gson = new Gson();
JsonElement jsonElement = gson.toJsonTree(tempData);
String json = gson.toJson(jsonElement);
StringEntity entity = new StringEntity(json);
Log.d("****Parameter Input****", "Testing:" + json);
request.setEntity(entity);
// Send request to WCF service
final DefaultHttpClient httpClient = new DefaultHttpClient();
new AsyncTask<Void, Void, Void>() {
#Override
public Void doInBackground(Void... arg) {
try {
HttpResponse response = httpClient.execute(request);
Log.d("WebInvoke", "Saving: "
+ response.getStatusLine().toString());
// Get the status of web service
BufferedReader rd = new BufferedReader(
new InputStreamReader(response.getEntity()
.getContent()));
// print status in log
String line = "";
while ((line = rd.readLine()) != null) {
Log.d("****Status Line***", "Webservice: " + line);
}
} catch (Exception e) {
Log.e("SendMail", e.getMessage(), e);
}
return null;
}
}.execute();
} catch (Exception e) {
e.printStackTrace();
}
}
And here is an example of code used to retrieve elements in the database:
public void load() {
String apiURI = "https://api.mongolab.com/api/1/databases/MYDATABASE/collections/USERSUBMITTEDDATA"
+ "?apiKey=" + apiKey;
Log.d("****Status Line***", "" + apiURI);
try {
// make web service connection
final StringBuilder builder = new StringBuilder();
final HttpGet request = new HttpGet(apiURI);
request.setHeader("Accept", "application/json");
request.setHeader("Content-type", "application/json");
final DefaultHttpClient httpClient = new DefaultHttpClient();
new AsyncTask<Void, Void, String>() {
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
doSomethingWithReceivedData(result); //THIS METHOD IS DEFINED IN BODY OF YOUR ACTIVITY
}
#Override
public String doInBackground(Void... arg) {
try {
HttpResponse response = httpClient.execute(request);
StatusLine statusLine = response.getStatusLine();
int statusCode = statusLine.getStatusCode();
if (statusCode == 200) {
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
BufferedReader reader = new BufferedReader(
new InputStreamReader(content));
String line;
while ((line = reader.readLine()) != null) {
builder.append(line);
}
Log.d("****Status Line***", "Success");
return builder.toString();
} else {
Log.d("****Status Line***",
"Failed to download file");
}
} catch (Exception e) {
Log.e("SendMail", e.getMessage(), e);
}
return null;
}
}.execute();
} catch (Exception e) {
e.printStackTrace();
}
}

You should have a data base to store the data. Like mentioned above, the data base is good to be in MySQL (SQL). Your application should have a method that can POST the results to the server, where the server will read the string send and retrieve and store the data.
A good start is to read about JSON
and read also about Asynctask
Also you need to know how to build your sever part. A good idea is to start with PHP, but I am not an expert on that field.
I hope this helps you start your project.

Simple, no DB required.
Usergrid by Apigee is exactly what you are looking for!
You can store each user's details
Retrieve stored data
Send events and receive event callbacks across devices
Best of all - no server side code. Only APIs
FYI This is the direction you should be heading even if you know how to code a server.
PS: I don't work for apigee or usergrid.

IOException: Internal Server Error when trying to consume rest service

I want to create a restful web service in java using jersey API and consume it in android application. I got this question on SO but it talks about java client whereas I have android client.
My service looks like this:
#Path("/no")
public class CheckNumber {
#POST
#Produces("application/json")
#Consumes("application/json")
public String getDetails(#PathParam("cNo") String cNo) {
String CardNo="";
try {
JSONObject jsonObj = new JSONObject(cNo);
CardNo=jsonObj.getString("CardNo");
} catch (ParseException e1) {
e1.printStackTrace();
}
//Do something
return "someValue";
}
}
Now comes the client side:
public class MainActivity extends Activity {
JSONObject json = new JSONObject();
String wsdl = "http://192.168.1.105:8080/restdemo/check/no/";
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
new RequestTask().execute("1234567890");
}
class RequestTask extends AsyncTask<String, String, String> {
#Override
protected String doInBackground(String... uri) {
HttpClient httpclient = new DefaultHttpClient();
HttpResponse response;
String add = "{\"CardNo\":\"" + uri[0] + "\"}";
HttpPost postMethod = new HttpPost(wsdl);
String responseString = null;
try {
postMethod.addHeader("Content-Type", "application/json");
HttpEntity entity = new StringEntity(add);
postMethod.setEntity(entity);
response = httpclient.execute(postMethod);
StatusLine statusLine = response.getStatusLine();
if (statusLine.getStatusCode() == HttpStatus.SC_OK) {
ByteArrayOutputStream out = new ByteArrayOutputStream();
response.getEntity().writeTo(out);
out.close();
responseString = out.toString();
} else {
response.getEntity().getContent().close();
throw new IOException(statusLine.getReasonPhrase());
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
return responseString;
}
#Override
protected void onPostExecute(String result) {
super.onPostExecute(result);
}
}
}
I'm just starting with rest web services. I successfully created a sample rest service which consumes string and returns string and used this service in android app.
But when I try to pass json string using POST method. It's giving following errorin log:
java.io.IOException: Internal Server Error
at com.example.restclient.MainActivity$RequestTask.doInBackground(MainActivity.java:85)
where MainActivity.java:85 is throw new IOException(statusLine.getReasonPhrase()); which implies that statusLine.getStatusCode() is not returning HttpStatus.SC_OK. Instead it's returning status code = 500.
Any help appreciated.

It will be good to see the server side log to understand better.
Try creating the entity with UTF8 and set the content-type in the string entity rather than in the postMethod
StringEntity stringEntity = new StringEntity(myJsonDocStr, HTTP.UTF_8);
stringEntity.setContentType("application/json");

Try this code, It works for me
Boolean NetworkLostFlag = false;
HttpParams httpParameters = new BasicHttpParams();
int timeoutConnection = 10000;
HttpConnectionParams.setConnectionTimeout(httpParameters,
timeoutConnection);
int timeoutSocket = 12000;
HttpConnectionParams.setSoTimeout(httpParameters, timeoutSocket);
HttpClient httpclient = new DefaultHttpClient(httpParameters);
HttpPost httppost = new HttpPost(strUrl");
try {
httppost.setEntity(new UrlEncodedFormEntity(new BasicNameValuePair(arg1, val1), "UTF-8"));
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
if (entity != null) {
InputStream instream = entity.getContent();
try {
// do something useful
StringBuffer buffer = new StringBuffer();
byte[] b = new byte[4096];
for (int n; (n = instream.read(b)) != -1;) {
buffer.append(new String(b, 0, n));
}
result = buffer.toString();
} catch (Exception e) {
NetworkLostFlag = true;
// TODO: handle exception
} finally {
instream.close();
}
}
} catch (Exception e) {
NetworkLostFlag = true;
e.printStackTrace();
}

Send key-value parametres and json message body throught http post request

I need to send http POST request from mobile android application to the server side applcation.
This request need to contain json message in body and some key-value parametres.
I am try to write this method:
public static String makePostRequest(String url, String body, BasicHttpParams params) throws ClientProtocolException, IOException {
Logger.i(HttpClientAndroid.class, "Make post request");
HttpPost httpPost = new HttpPost(url);
StringEntity entity = new StringEntity(body);
httpPost.setParams(params);
httpPost.setEntity(entity);
HttpResponse response = getHttpClient().execute(httpPost);
return handleResponse(response);
}
Here i set parametres to request throught method setParams and set json body throught setEntity.
But it isn't work.
Can anybody help to me?

You can use a NameValuePair to do this..........
Below is the code from my project where I used NameValuePair to sent the xml data and receive the xml response, this will provide u some idea about how to use it with JSON.
public String postData(String url, String xmlQuery) {
final String urlStr = url;
final String xmlStr = xmlQuery;
final StringBuilder sb = new StringBuilder();
Thread t1 = new Thread(new Runnable() {
public void run() {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(urlStr);
try {
List<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>(
1);
nameValuePairs.add(new BasicNameValuePair("xml", xmlStr));
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse response = httpclient.execute(httppost);
Log.d("Vivek", response.toString());
HttpEntity entity = response.getEntity();
InputStream i = entity.getContent();
Log.d("Vivek", i.toString());
InputStreamReader isr = new InputStreamReader(i);
BufferedReader br = new BufferedReader(isr);
String s = null;
while ((s = br.readLine()) != null) {
Log.d("YumZing", s);
sb.append(s);
}
Log.d("Check Now",sb+"");
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
});
t1.start();
try {
t1.join();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("Getting from Post Data Method "+sb.toString());
return sb.toString();
}