https://stackoverflow.com/questions/6218143/how-to-send-post-request-in-json-using-httpclient-in-android




I'm trying to figure out how to POST JSON from Android by using HTTPClient. I've been trying to figure this out for a while, I have found plenty of examples online, but I cannot get any of them to work. I believe this is because of my lack of JSON/networking knowledge in general. I know there are plenty of examples out there but could someone point me to an actual tutorial? I'm looking for a step by step process with code and explanation of why you do each step, or of what that step does. It doesn't need to be a complicated, simple will suffice.

Again, I know there are a ton of examples out there, I'm just really looking for an example with an explanation of what exactly is happening and why it is doing that way.

If someone knows about a good Android book on this, then please let me know.

Thanks again for the help @terrance, here is the code I described below

public void shNameVerParams() throws Exception{
     String path = //removed
     HashMap  params = new HashMap();

     params.put(new String("Name"), "Value"); 
     params.put(new String("Name"), "Value");

     try {
        HttpClient.SendHttpPost(path, params);
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
 }
    up vote157down voteaccepted

    In this answer I am using an example posted by Justin Grammens.

    About JSON

    JSON stands for JavaScript Object Notation. In JavaScript properties can be referenced both like this object1.name and like this object['name'];. The example from the article uses this bit of JSON.

    The Parts
    A fan object with email as a key and foo@bar.com as a value

    {
      fan:
        {
          email : 'foo@bar.com'
        }
    }

    So the object equivalent would be fan.email; or fan['email'];. Both would have the same value of 'foo@bar.com'.

    About HttpClient Request

    The following is what our author used to make a HttpClient Request. I do not claim to be an expert at all this so if anyone has a better way to word some of the terminology feel free.

    public static HttpResponse makeRequest(String path, Map params) throws Exception 
    {
        //instantiates httpclient to make request
        DefaultHttpClient httpclient = new DefaultHttpClient();
    
        //url with the post data
        HttpPost httpost = new HttpPost(path);
    
        //convert parameters into JSON object
        JSONObject holder = getJsonObjectFromMap(params);
    
        //passes the results to a string builder/entity
        StringEntity se = new StringEntity(holder.toString());
    
        //sets the post request as the resulting string
        httpost.setEntity(se);
        //sets a request header so the page receving the request
        //will know what to do with it
        httpost.setHeader("Accept", "application/json");
        httpost.setHeader("Content-type", "application/json");
    
        //Handles what is returned from the page 
        ResponseHandler responseHandler = new BasicResponseHandler();
        return httpclient.execute(httpost, responseHandler);
    }

    Map

    If you are not familiar with the Map data structure please take a look at the Java Map reference. In short, a map is similar to a dictionary or a hash.

    private static JSONObject getJsonObjectFromMap(Map params) throws JSONException {
    
        //all the passed parameters from the post request
        //iterator used to loop through all the parameters
        //passed in the post request
        Iterator iter = params.entrySet().iterator();
    
        //Stores JSON
        JSONObject holder = new JSONObject();
    
        //using the earlier example your first entry would get email
        //and the inner while would get the value which would be 'foo@bar.com' 
        //{ fan: { email : 'foo@bar.com' } }
    
        //While there is another entry
        while (iter.hasNext()) 
        {
            //gets an entry in the params
            Map.Entry pairs = (Map.Entry)iter.next();
    
            //creates a key for Map
            String key = (String)pairs.getKey();
    
            //Create a new map
            Map m = (Map)pairs.getValue();   
    
            //object for storing Json
            JSONObject data = new JSONObject();
    
            //gets the value
            Iterator iter2 = m.entrySet().iterator();
            while (iter2.hasNext()) 
            {
                Map.Entry pairs2 = (Map.Entry)iter2.next();
                data.put((String)pairs2.getKey(), (String)pairs2.getValue());
            }
    
            //puts email and 'foo@bar.com'  together in map
            holder.put(key, data);
        }
        return holder;
    }

    Please feel free to comment on any questions that arise about this post or if I have not made something clear or if I have not touched on something that your still confused about... etc whatever pops in your head really.

    (I will take down if Justin Grammens does not approve. But if not then thanks Justin for being cool about it.)

    Update

    I just happend to get a comment about how to use the code and realized that there was a mistake in the return type. The method signature was set to return a string but in this case it wasnt returning anything. I changed the signature to HttpResponse and will refer you to this link on Getting Response Body of HttpResponse the path variable is the url and I updated to fix a mistake in the code.

      Here is an alternative solution to @Terrance's answer. You can easly outsource the conversion. The Gson library does wonderful work converting various data structures into JSON and the other way around.

      public static void execute() {
          Map<String, String> comment = new HashMap<String, String>();
          comment.put("subject", "Using the GSON library");
          comment.put("message", "Using libraries is convenient.");
          String json = new GsonBuilder().create().toJson(comment, Map.class);
          makeRequest("http://192.168.0.1:3000/post/77/comments", json);
      }
      
      public static HttpResponse makeRequest(String uri, String json) {
          try {
              HttpPost httpPost = new HttpPost(uri);
              httpPost.setEntity(new StringEntity(json));
              httpPost.setHeader("Accept", "application/json");
              httpPost.setHeader("Content-type", "application/json");
              return new DefaultHttpClient().execute(httpPost);
          } catch (UnsupportedEncodingException e) {
              e.printStackTrace();
          } catch (ClientProtocolException e) {
              e.printStackTrace();
          } catch (IOException e) {
              e.printStackTrace();
          }
          return null;
      }

      Similar can be done by using Jackson instead of Gson. I also recommend taking a look at Retrofitwhich hides a lot of this boilerplate code for you. For more experienced developers I recommend trying out RxAndroid.

        I recommend using this HttpURLConnectioninstead HttpGet. As HttpGet is already deprecated in Android API level 22.

        HttpURLConnection httpcon;  
        String url = null;
        String data = null;
        String result = null;
        try {
          //Connect
          httpcon = (HttpURLConnection) ((new URL (url).openConnection()));
          httpcon.setDoOutput(true);
          httpcon.setRequestProperty("Content-Type", "application/json");
          httpcon.setRequestProperty("Accept", "application/json");
          httpcon.setRequestMethod("POST");
          httpcon.connect();
        
          //Write       
          OutputStream os = httpcon.getOutputStream();
          BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os, "UTF-8"));
          writer.write(data);
          writer.close();
          os.close();
        
          //Read        
          BufferedReader br = new BufferedReader(new InputStreamReader(httpcon.getInputStream(),"UTF-8"));
        
          String line = null; 
          StringBuilder sb = new StringBuilder();         
        
          while ((line = br.readLine()) != null) {  
            sb.append(line); 
          }         
        
          br.close();  
          result = sb.toString();
        
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } 

          Too much code for this task, checkout this library https://github.com/kodart/Httpzoid Is uses GSON internally and provides API that works with objects. All JSON details are hidden.

          Http http = HttpFactory.create(context);
          http.get("http://example.com/users")
              .handler(new ResponseHandler<User[]>() {
                  @Override
                  public void success(User[] users, HttpResponse response) {
                  }
              }).execute();

            There are couple of ways to establish HHTP connection and fetch data from a RESTFULL web service. The most recent one is GSON. But before you proceed to GSON you must have some idea of the most traditional way of creating an HTTP Client and perform data communication with a remote server. I have mentioned both the methods to send POST & GET requests using HTTPClient.

            /**
             * This method is used to process GET requests to the server.
             * 
             * @param url 
             * @return String
             * @throws IOException
             */
            public static String connect(String url) throws IOException {
            
                HttpGet httpget = new HttpGet(url);
                HttpResponse response;
                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 = 60*1000;
                HttpConnectionParams.setConnectionTimeout(httpParameters, timeoutConnection);
                // Set the default socket timeout (SO_TIMEOUT) 
                // in milliseconds which is the timeout for waiting for data.
                int timeoutSocket = 60*1000;
            
                HttpConnectionParams.setSoTimeout(httpParameters, timeoutSocket);
                HttpClient httpclient = new DefaultHttpClient(httpParameters);
                try {
            
                    response = httpclient.execute(httpget);
            
                    HttpEntity entity = response.getEntity();
                    if (entity != null) {
                        InputStream instream = entity.getContent();
                        result = convertStreamToString(instream);
                        //instream.close();
                    }
                } 
                catch (ClientProtocolException e) {
                    Utilities.showDLog("connect","ClientProtocolException:-"+e);
                } catch (IOException e) {
                    Utilities.showDLog("connect","IOException:-"+e);