Develop Reference

How to deal with a large JSON object on Android

I'm making an Android app that runs a ASP.NET WebService. Webservice sends a JSON object and app parses the object and displays on the screen. In one case, JSON object is too big and I get Failed Binder Transaction error. My solution is to get that JSON object and embed it in the app code, so that it wouldn't need to get that JSON object from the server. Can you tell any other things that I can do for this problem?
Or can you tell me how to get that JSON object from Webservice? Thanks.

Sending the large size data from server to mobile. JSON is light weight.
If you want to pass the data using more efficient way then passes it in pagination.
If you want to use more lighter protocol than JSON then implement the below google protocol which are really useful, which are supporting major languages.
Below are smaller Serialised data structure. Google's data interchange protocol.
1.Google Protocol
2.Flat Buffers
3.Nano-proto buffers
Hope this will be useful you.

If data is large then try to save it in the database, then deal with it using SQLite. (but not recommended if its dynamic)
To parse json object use gson or jackson. This will help reduce the memory consumption significantly as the json data being parsed partially.
get Gson, jackson here
https://sites.google.com/site/gson/gson-user-guide
http://jackson.codehaus.org/
A jackson example
http://www.mkyong.com/java/jackson-streaming-api-to-read-and-write-json/

First thing: If there is a crash or exception in your code, you'll probably want to post that. "Failed Binder Exception" is a bit too vague to understand what you're doing.
If you really want to ship your Android app with JSON embeddd inside it (to avoid having to fetch it from a server, consider storing it as an asset and access it using AssetManager. You basically drop the file with the json in your app's assets folder and read them out with AssetManager.
If you still want to download it from the server and act on it, consider using streaming APIs to download and parse the JSON. Android's JSONObject does not do this and it insists on having the entire JSON string in memory before it can be parsed.
If you want to stream directly from a URL download into a streaming parser (such as GSON), try something along these lines. First get an InputStream from the URL you're trying to fetch:
URL u = new URL(url);
URLConnection conn = u.openConnection();
InputStream is = new BufferedInputStream(conn.getInputStream());
Then feed that InputStream directly to your streaming parser. This should prevent the need to pull the entire response into memory before parsing, but you'll still need enough memory to contain all the objects that the parser creates:
GsonBuilder gb = new GsonBuilder(); // configure this as necessary
Gson gson = gb.create();
final Result response = gson.fromJson(
new InputStreamReader(is, Charset.forName("UTF-8")),
Result.class
);
"Result" here is a class that will contain the data from the JSON response. You'll have to make sure all the mappings work for your data, so read up on GSON and do whatever works for your case.
You can also use GSON to parse the JSON data if you store it in an asset. Just hand it the InputStream of the asset data and it works the same way.

The following class ApiUrlClass.java has all methods you require. Please read the comments of the class which I wrote. That will help you to do what you require. This also utilises transparent.
import android.graphics.Bitmap;
import android.net.Uri;
import android.os.Build;
import android.util.Log;
import org.apache.http.entity.mime.HttpMultipartMode;
import org.apache.http.entity.mime.content.ByteArrayBody;
import org.apache.http.entity.mime.content.ContentBody;
import org.apache.http.entity.mime.content.StringBody;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.ByteArrayOutputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.SocketTimeoutException;
import java.net.URL;
import java.net.UnknownHostException;
import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLPeerUnverifiedException;
/*
Usage of the class
Create all the necessary API Call methods you need.
And either use a Thread or AsyncTask to call the following.
JSONObject response = ApiUrlCalls.login("username", "passowrd");
After the response is obtained, check for status code like
if(response.getInt("status_code") == 200){
//TODO: code something
} else {
//TODO: code something
}
*/
public class ApiUrlCalls {
private String HOST = "https://domain/path/"; //This will be concated with the function needed. Ref:1
/*
Now utilizing the method is so simple. Lets consider a login function, which sends username and password.
See below for example.
*/
public static JSONObject login(String username, String password){
String functionCall = "login";
Uri.Builder builder = new Uri.Builder()
.appendQueryParameter("username", username)
.appendQueryParameter("password", password);
/*
The return calls the apiPost method for processing.
Make sure this should't happen in the UI thread, orelse, NetworkOnMainThread exception will be thrown.
*/
return apiPost(builder, functionCall);
}
/*
This method is the one which performs POST operation. If you need GET, just change it
in like Connection.setRequestMethod("GET")
*/
private static JSONObject apiPost(Uri.Builder builder, String function){
try {
int TIMEOUT = 15000;
JSONObject jsonObject = new JSONObject();
try {
URL url = null;
String response = "";
/*
Ref:1
As mentioned, here below, in case the function is "login",
url looks like https://domain/path/login
This is generally a rewrited form by .htaccess in server.
If you need knowledge on RESTful API in PHP, refer
http://stackoverflow.com/questions/34997738/creating-restful-api-what-kind-of-headers-should-be-put-out-before-the-response/35000332#35000332
I have answered how to create a RESTful API. It matches the above URL format, it also includes the .htaccess
*/
url = new URL(HOST + function);
HttpsURLConnection conn = null;
conn = (HttpsURLConnection) url.openConnection();
assert conn != null;
conn.setReadTimeout(TIMEOUT);
conn.setConnectTimeout(TIMEOUT);
conn.setRequestMethod("POST");
conn.setDoInput(true);
conn.setDoOutput(true);
String query = builder.build().getEncodedQuery();
OutputStream os = conn.getOutputStream();
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os, "UTF-8"));
writer.write(query);
writer.flush();
writer.close();
os.close();
conn.connect();
int responseCode = conn.getResponseCode();
String responseMessage = conn.getResponseMessage();
jsonObject.put("status_code", responseCode);
jsonObject.put("status_message", responseMessage);
/*The if condition below will check if status code is greater than 400 and sets error status
even before trying to read content, because HttpUrlConnection classes will throw exceptions
for status codes 4xx and 5xx. You cannot read content for status codes 4xx and 5xx in HttpUrlConnection
classes.
*/
if (jsonObject.getInt("status_code") >= 400) {
jsonObject.put("status", "Error");
jsonObject.put("msg", "Something is not good. Try again later.");
return jsonObject;
}
String line;
BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
while ((line = br.readLine()) != null) {
response += line;
}
//Log.d("RESP", response);
/*
After the actual payload is read as a string, it is time to change it into JSON.
Simply when it starts with "[" it should be a JSON array and when it starts with "{"
it is a JSONObject. That is what hapenning below.
*/
if(response.startsWith("[")) {
jsonObject.put("content", new JSONArray(response));
}
if(response.startsWith("{")){
jsonObject.put("content", new JSONObject(response));
}
} catch(UnknownHostException e) {
//No explanation needed :)
jsonObject.put("status", "UnknownHostException");
jsonObject.put("msg", "Check your internet connection");
} catch (SocketTimeoutException){
//This is when the connection timeouts. Timeouts can be modified by TIMEOUT variable above.
jsonObject.put("status", "Timeout");
jsonObject.put("msg", "Check your internet connection");
} catch (SSLPeerUnverifiedException se) {
//When an untrusted SSL Certificate is received, this happens. (Only for https.)
jsonObject.put("status", "SSLException");
jsonObject.put("msg", "Unable to establish secure connection.");
se.printStackTrace();
} catch (IOException e) {
//This generally happens when there is a trouble in connection
jsonObject.put("status", "IOException");
jsonObject.put("msg", "Check your internet connection");
e.printStackTrace();
} catch(FileNotFoundException e){
//There is no chance that this catch block will execute as we already checked for 4xx errors
jsonObject.put("status", "FileNotFoundException");
jsonObject.put("msg", "Some 4xx Error");
e.printStackTrace();
} catch (JSONException e){
//This happens when there is a troble reading the content, or some notice or warnings in content,
//which generally happens while we modify the server side files. Read the "msg", and it is clear now :)
jsonObject.put("status", "JSONException");
jsonObject.put("msg", "We are experiencing a glitch, try back in sometime.");
e.printStackTrace();
} return jsonObject;
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
}

You could embed your JSON in your app's code as you suggested, but this will be a bad approach if the JSON is dynamic. Then you would need to push an update for your app whenever the JSON changes.
A better solution would be to paginate the JSON that you generate from your WebService, i.e., break the JSON into smaller parts that you can fetch sequentially in separate API calls.

Preferably try to break the Json Object to smaller object and get from webService ,
or get data in parts and if u cant do that
You have to use a streaming JSON parser.
For Android u can use these 2:
GSON
Jackson
GSON Streaming is explained at: https://sites.google.com/site/gson/streaming
I personally like Gson .

Json call making in android

I am new bee in Android , so the knowledge regarding android is not so vast.
I am trying to implement Json call in android and i am using the foolowing code to get the list of all the contacts in the database.
package com.example.library;
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.UnsupportedEncodingException;
public class SecondActivity extends Activity {
Button show_data;
JSONObject my_json_obj;
String path,firstname,lastname;
{
path = "http://192.168.71.129:3000/contacts";
HttpClient client = new DefaultHttpClient();
HttpConnectionParams.setConnectionTimeout(client.getParams(), 10000);
HttpEntity entity;
HttpResponse response = null;
HttpURLConnection urlconn;
my_json_obj = new JSONObject();
}
}
I dont know if this is the right method but this code was already existing in another project and i have just made some change.
Please guide me through this one as i have gone through many stackoverflow and google answers,but it is very confusing as i am just a beginner and dont have knowledge of json calls in android.

I could give you a chunk of code and say "Hey try this", but like you stated that you are very new to Android so I simply wont.
I think its of more value that you can learn something beter by trying then simply copy pasting code(most of the time)
There are a couple of things you need to consider when you do network request and parsing data.
Network request you must always do this in a seperate thread then the UI thread, because if you dont youll get a NetworkOnMainUiThreadException if I am correct out the top of my head.
The same applies for parsing the data you have retrieved from your request.
I dont see any parsing of data in your current code but I just wanted to give you a headsup because you will prob do this at some point in your application.
Here you can find a tutorial how to do threading with the AsyncTask. this is "the way" how it should be done in Android, they realy made it easy for you.
When reading that tutorial you will get the basic knowlage to do stuff in this class.
When you get the concept of threading and how to work with this newly added skill I would suggest reading and following up on this json tutorial here.
I hope this helps

try this, result variable has your responce
try {
HttpClient client = new DefaultHttpClient();
HttpGet request = new HttpGet("paset_your_url_here");
HttpResponse response = client.execute(request);
BufferedReader in = new BufferedReader
(new InputStreamReader(response.getEntity().getContent()));
StringBuffer sb = new StringBuffer("");
String line = "";
String NL = System.getProperty("line.separator");
while ((line = in.readLine()) != null) {
sb.append(line + NL);
}
in.close();
result = sb.toString();
Log.i("", "-----------------------"+result);
} catch(Exception e) {
e.printStackTrace();
}finally {
if (in != null) {
try {
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
if you want to prase json then first do googling and if you get your answer by this then vote up :)

What are the best methods to consume a web service from android?

Can anyone tell me which is the best, ease and flexible method to consume web service from android? I'm using eclipse.

Since you only care about consuming a webservice, I assume you already know how to send data from the web server. Do you use JSON or XML, or any other kind of data format?
I myself prefer JSON, especially for Android.
Your question still lacks some vital information.
I personally use apache-mime4j and httpmime-4.0.1 libraries for web services.
With these libraries I use the following code
public void get(String url) {
HttpResponse httpResponse = null;
InputStream _inStream = null;
HttpClient _client = null;
try {
_client = new DefaultHttpClient(_clientConnectionManager, _httpParams);
HttpGet get = new HttpGet(url);
httpResponse = _client.execute(get, _httpContext);
this.setResponseCode(httpResponse.getStatusLine().getStatusCode());
HttpEntity entity = httpResponse.getEntity();
if(entity != null) {
_inStream = entity.getContent();
this.setStringResponse(IOUtility.convertStreamToString(_inStream));
_inStream.close();
Log.i(TAG, getStringResponse());
}
} catch(ClientProtocolException e) {
e.printStackTrace();
} catch(IOException e) {
e.printStackTrace();
} finally {
try {
_inStream.close();
} catch (Exception ignore) {}
}
}
I make a request via _client.execute([method], [extra optional params])
The result from the request is put in a HttpResponse object.
From this object you can get the status code and the entity containing the result.
From the entity I take the content. The content would in my case be the actualy JSON string. You retrieve this as an InputStream, convert the stream to a string and do whatever you want with it.
For example
JSONArray result = new JSONArray(_webService.getStringResponse()); //getStringResponse is a custom getter/setter to retrieve the string converted from an inputstream in my WebService class.
Depending on how you build your JSON. mine is nested deeply with objects in the array etc.
But handling this is basic looping.
JSONObject objectInResult = result.getJSONObject(count);//count would be decided by a while or for loop for example.
You can extract data from the current JSON object in this case like:
objectInResult.getString("name"); //assume the json object has a key-value pair that has name as a key.

to parse "JSON" I recommend the following library is the faster and better.
Jackson Java JSON-processor

Android parse json from url and store it

Hi there i'm creating my first android app and i'm wanting to know what is the best and most efficient way of parsing a JSON Feed from a URL.Also Ideally i want to store it somewhere so i can keep going back to it in different parts of the app. I have looked everywhere and found lots of different ways of doing it and i'm not sure which to go for. In your opinion whats the best way of parsing json efficiently and easily?

I'd side with whatsthebeef on this one, grab the data and then serialize to disk.
The code below shows the first stage, grabbing and parsing your JSON into a JSON Object and saving to disk
// Create a new HTTP Client
DefaultHttpClient defaultClient = new DefaultHttpClient();
// Setup the get request
HttpGet httpGetRequest = new HttpGet("http://example.json");
// Execute the request in the client
HttpResponse httpResponse = defaultClient.execute(httpGetRequest);
// Grab the response
BufferedReader reader = new BufferedReader(new InputStreamReader(httpResponse.getEntity().getContent(), "UTF-8"));
String json = reader.readLine();
// Instantiate a JSON object from the request response
JSONObject jsonObject = new JSONObject(json);
// Save the JSONOvject
ObjectOutput out = new ObjectOutputStream(new FileOutputStream(new File(getCacheDir(),"")+"cacheFile.srl"));
out.writeObject( jsonObject );
out.close();
Once you have the JSONObject serialized and save to disk, you can load it back in any time using:
// Load in an object
ObjectInputStream in = new ObjectInputStream(new FileInputStream(new File(new File(getCacheDir(),"")+"cacheFile.srl")));
JSONObject jsonObject = (JSONObject) in.readObject();
in.close();

Your best bet is probably GSON
It's simple, very fast, easy to serialize and deserialize between json objects and POJO, customizable, although generally it's not necessary and it is set to appear in the ADK soon. In the meantime you can just import it into your app. There are other libraries out there but this is almost certainly the best place to start for someone new to android and json processing and for that matter just about everyone else.
If you want to persist you data so you don't have to download it every time you need it, you can deserialize your json into a java object (using GSON) and use ORMLite to simply push your objects into a sqlite database. Alternatively you can save your json objects to a file (perhaps in the cache directory)and then use GSON as the ORM.

This is pretty straightforward example using a listview to display the data. I use very similar code to display data but I have a custom adapter. If you are just using text and data it would work fine. If you want something more robust you can use lazy loader/image manager for images.

Since an http request is time consuming, using an async task will be the best idea. Otherwise the main thread may throw errors. The class shown below can do the download asynchronously
private class jsonLoad extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... urls) {
String response = "";
for (String url : urls) {
DefaultHttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(url);
try {
HttpResponse execute = client.execute(httpGet);
InputStream content = execute.getEntity().getContent();
BufferedReader buffer = new BufferedReader(new InputStreamReader(content));
String s = "";
while ((s = buffer.readLine()) != null) {
response += s;
}
} catch (Exception e) {
e.printStackTrace();
}
}
return response;
}
#Override
protected void onPostExecute(String result) {
// Instantiate a JSON object from the request response
try {
JSONObject jsonObject = new JSONObject(result);
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
File file = new File(getApplicationContext().getFilesDir(),"nowList.cache");
try {
file.createNewFile();
FileOutputStream writer = openFileOutput(file.getName(), Context.MODE_PRIVATE);
writer.write(result);
writer.flush();
writer.close();
}
catch (IOException e) { e.printStackTrace(); return false; }
}
}
Unlike the other answer, here the downloaded json string itself is saved in file. So Serialization is not necessary
Now loading the json from url can be done by calling
jsonLoad jtask=new jsonLoad ();
jtask.doInBackground("http:www.json.com/urJsonFile.json");
this will save the contents to the file.
To open the saved json string
File file = new File(getApplicationContext().getFilesDir(),"nowList.cache");
StringBuilder text = new StringBuilder();
try {
BufferedReader br = new BufferedReader(new FileReader(file));
String line;
while ((line = br.readLine()) != null) {
text.append(line);
text.append('\n');
}
br.close();
}
catch (IOException e) {
//print log
}
JSONObject jsonObject = new JSONObject(text);

Creating a JSON response from Google Application Engine

Purely as an academic exercise I wanted to convert one of my existing GAE applets to return the response back to Android in JSON and parse it accordingly.
The original XML response containing a series of booleans was returned thus:
StringBuilder response = new StringBuilder();
response.append("<?xml version=\"1.0\" encoding=\"utf-8\"?>");
response.append("<friend-response><added>");
response.append(friendAdded);
response.append("</added><removed>");
response.append(friendRemoved);
response.append("</removed><found>");
response.append(friendFound);
response.append("</found></friend-response>");
I want to replace this with a JSON response that looks something like this:
{ "friendResponse" : [ { "added":true, "removed":false, "found":true } ]}
I think I can generate the array contents as follows (I haven't tested it yet) but I don't know how to create the top-level friendResponse array itself. I can't seem to find any good examples of creating JSON responses in Java using the com.google.appengine.repackaged.org.json library. Can anyone help put me on the right path?
boolean friendAdded, friendRemoved, friendFound;
/* Omitted the code that sets the above for clarity */
HttpServletResponse resp;
resp.setContentType("application/json");
resp.setHeader("Cache-Control", "no-cache");
JSONObject json = new JSONObject();
try {
//How do I create this as part of a friendResponse array?
json.put("added", friendAdded);
json.put("removed", friendRemoved);
json.put("found", friendFound);
json.write(resp.getWriter());
} catch (JSONException e) {
System.err
.println("Failed to create JSON response: " + e.getMessage());
}

You need to use JSONArray to create the (single-element) array that will store your object:
try {
JSONObject friendResponse = new JSONObject();
friendResponse.put("added", friendAdded);
friendResponse.put("removed", friendRemoved);
friendResponse.put("found", friendFound);
JSONArray friendResponseArray = new JSONArray();
friendResponseArray.put(friendResponse);
JSONObject json = new JSONObject();
json.put("friendResponse", friendResponseArray);
json.write(resp.getWriter());
} catch (JSONException e) {
System.err
.println("Failed to create JSON response: " + e.getMessage());
}

You can use GSON: https://sites.google.com/site/gson/gson-user-guide#TOC-Object-Examples
With this framework, you can serialize an object to json, and vice versa.