Develop Reference

How would I get a particular value from a JSON?

I'm trying to get a particular value from a field within a JSON file. This is my first time working with a JSON file so I'm not sure if I'm doing it correctly.
try {
URL url = new URL(API_URL + city +".json");
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
try {
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
StringBuilder stringBuilder = new StringBuilder();
String line;
while ((line = bufferedReader.readLine()) != null) {
stringBuilder.append(line).append("\n");
}
bufferedReader.close();
return stringBuilder.toString();
}
This block would get the JSON from a weather website and then return the JSON as a string. This string would then be used below. Unfortunately whenever I run this app in Android Studio and go through the logs the logs constantly say that there was no value in weather.
protected void onPostExecute(String response) {
if(response == null) {
response = "THERE WAS AN ERROR";
}
progressBar.setVisibility(View.GONE);
Log.i("INFO", response);
responseView.setText(response);
// TODO: check this.exception
// TODO: do something with the feed
try {
JSONObject object = (JSONObject) new JSONTokener(response).nextValue();
String weather = object.getString("weather");
Toast.makeText(MyActivity.this, "There is rain", Toast.LENGTH_SHORT).show();
} catch (JSONException e) {
e.printStackTrace();
}
}
What I'm trying to do is grab information from the weather section
Here is the JSON link I'm trying to parse from. This text box thought there were too many links in the JSON response for me to post it here. I'm trying to figure out what is going on and any help would be greatly appreciated.

You can print out response to see if it is exactly your JSON or not.
Assume you get the JSON String correctly.
JSONObject object = new JSONObject(response);
String weather = object.getString("weather");
However, if the JSON your obtained is exactly your response, the above code do not work because there is not weather String. The root only contain response and current_observation.
If what you what to get is weather under current_observation, you should use the code below.
JSONObject object = new JSONObject(response);
JSONObject current_obs = object.getJSONObject("current_observation");
String weather = current_obs.getString("weather"); // Clear

JSONObject object = (JSONObject) new JsonObject(responseString);
String weather = object.getString("weather");

First you need to get your response in string.
Now,start json parsing as per response.
OR
You can use Gson class as well for json parsing.
Get json value from JSONObject:
{"weather":"sunny"}
code snippet to parse the JSONObject.
JSONObject object = new JsonObject(response);
String weather= object.getString("weather");
Get json value from JSONArray:
[{"name":"name1","url":"url1"},{"name":"name2","url":"url2"},...]
code snippet to parse the JsonArray.
JSONArray jsonarray = new JSONArray(response);
for (int i = 0; i < jsonarray.length(); i++) {
JSONObject jsonobject = jsonarray.getJSONObject(i);
String name = jsonobject.getString("name");
String url = jsonobject.getString("url");
}
Hope it'll help you.

I have a sample Weather app done using open weather map api. It has all you asked for.
Code here:
http://opensourceandroid.in/weather_forecast.html

Json Parsing in Android with multiple same rows

Well,it is simple yet I am finding confused to extract the info.Could you give a look here:
formatted JSON Data
[
{
"catalogName":"a",
"categoryName":"aa",
"subCategoryName":"aaa",
"price":888.0,
},
{
"catalogName":"b",
"categoryName":"bb",
"subCategoryName":"bbb",
"productName":"hjb",
"price":9.0,
}
]
I would be printing this in my android app.Thanks

Here is how I do in my code:
HttpGet httpGet = new HttpGet(uri);
httpGet.setHeader("Accept", "application/json");
httpGet.setHeader("Content-type", "application/json");
HttpClient httpClient = new DefaultHttpClient();
HttpResponse httpResponse = httpClient.execute(httpGet);
StatusLine statusLine = httpResponse.getStatusLine();
// Check StatusLine result ....
// Convert response to a JSon Array:
ByteArrayOutputStream baos = new ByteArrayOutputStream();
httpResponse.getEntity().writeTo(baos);
baos.close();
JSONArray jsonArray = new JSONArray(baos.toString())
for(int i = 0; i < jsonArray.length(); ++i)
{
// Extract values from JSON row:
JSONObject jsonObject = jsonArray.getJSONObject(i);
String catalogName = jsonObject.has("catalogName") ? jsonObject.getString("catalogName") : "";
String categoryName = jsonObject.has("categoryName") ? jsonObject.getString("categoryName") : "";
String subCategoryName = jsonObject.has("subCategoryName") ? jsonObject.getString("subCategoryName") : "";
String productName = jsonObject.has("productName") ? jsonObject.getString("productName") : "";
double price = jsonObject.has("price") ? jsonObject.getString("price") : 0.;
// Do stuff with data:
...
}
Please note that if a row misses a value (like productName) you must handle it. In the example I assign a default value but maybe it's not the best choice.

JSONArray jsonArray=new JSONArray("YOUR_JSON_ARRAY_NAME"); //Must be case sensitive
for(int i=0;i<jsonArray.length();i++){
JSONObject current_job= jsonArray.getJSONObject(i);
String catalogName= current_job.getString("catalogName");
//same for other fields. KEY must be case sensitive
...
...
}

This is a JSONArray :-) Parse it with this:
String json = /** your JSON **/
JSONArray array = new JSONArray(json);
And now you can take the data out of the object with getJSONObject(int index) :-)

I suggest using a JSON parsing library, such as Gson. It is fast and very simple to use.
https://github.com/google/gson
If you have a following class:
class Catalog{
private String catalogName;
private String categoryName;
private String subCategoryName;
private String productName;
private double price;
/** Getter, setters, optional: toString, constructor... **/
}
To parse it simply call:
Type listType = new TypeToken<List<Catalog>>() {}.getType();
List<Catalog> yourList = new Gson().fromJson(YOUR_JSON_STRING, listType);
Instead of this "confusing" code for listType you can use also Class (see documentation), but this is not possible in your case, as provided JSON format is a direct list of elements, it is not wrapped. For using a class you would have to wrap this JSON with another element.

Parsing JsonArray With JsonObject

I have some JSON with the following structure:
{
"items":[
{
"product":{
"product_id":"some",
"price_id":"some",
"price":"some",
"title_fa":"some",
"title_en":"Huawei Ascend Y300",
"img":"some",
"has_discount_from_price":"0",
"discount_from_price":null,
"type_discount_from_price":null,
"has_discount_from_product":"0",
"discount_from_product":null,
"type_discount_from_product":null,
"has_discount_from_category":"0",
"discount_from_category":null,
"type_discount_from_category":null,
"has_discount_from_brand":"0",
"discount_from_brand":null,
"type_discount_from_brand":null,
"weight":null,
"features":[
{
"feature_value":"#000000",
"feature_id":"some",
"feature_title":"some"
},
{
"feature_value":"some",
"feature_id":"1652",
"feature_title":"some"
}
]
},
"number":1,
"feature_id":"56491,56493",
"price_inf":{
"has_discount":0,
"discount_type":0,
"final_price":"400000",
"value_discount":0
},
"cart_id":13
}
]
}
I'm trying to access the elements "product_id" and "price_id" with the following Java code:
try{
JSONArray feedArray=response.getJSONArray("items");
for (int i=0;i<feedArray.length();i++){
JSONObject feedObj=feedArray.getJSONObject(i);
JSONObject pro=feedObj.getJSONObject("product");
Product product = new Product();
product.setPrice(pro.getDouble("price_id"));
product.setTitle_fa(pro.getString("price_id"));}}
but i see product not found error.what is wrong in my parser?

First of all your JSON is valid. So no worries there.
Now regarding your problem, because you haven't posted the logs so I can't tell what the exact problem is. But using this code snippet you can get the desired values.
try {
JSONArray itemsJsonArray = jsonObject.getJSONArray("items");
for (int i = 0; i < itemsJsonArray.length(); i++){
JSONObject itemJsonObject = itemsJsonArray.getJSONObject(i);
JSONObject productObject = itemJsonObject.getJSONObject("product");
String productId = productObject.getString("product_id");
String priceId = productObject.getString("price_id");
}
} catch (JSONException e) {
e.printStackTrace();
}

Validate and create Pojo for your json here
use
Data data = gson.fromJson(this.json, Data.class);
follow https://stackoverflow.com/a/5314988/5202007
By the way your JSON is invalid .

you are getting a json object from your response not json array you need to make following changes
JSONObject temp =new JSONObject(response);
JSONArray feedArray=temp.getJSONArray("items");

Try converting response string to JSONObject first
try{
JSONObject temp =new JSONObject(responseString); // response is a string
JSONArray feedArray=.getJSONArray("items");
....
}
You may try to use GSON library for parsing a JSON string. Here's an example how to use GSON,
Gson gson = new Gson(); // Or use new GsonBuilder().create();
MyType target = new MyType();
String json = gson.toJson(target); // serializes target to Json
MyType target2 = gson.fromJson(json, MyType.class); // deserializes json into target2

How to parse a specific response of a RESTful WS using JSON

I am learning how to parse a response from a restful web service It is supposed to retreive a JSON string so I can parse it, I am using the apache libs in android. Following some questions here in StackOverflow I do the following:
HttpClient httpClient = new DefaultHttpClient();
HttpGet request = new HttpGet(URL);
ResponseHandler<String> handler = new BasicResponseHandler();
try{
result = httpClient.execute(request, handler); ...
with that I can retreive the result of the WS as this:
"[{\"CodigoRTA\":\"0\",\"MensajeRTA\":\"\",\"Respuesta\":\"[{\\"codigo\\":\\"05\\",\\"nombre\\":\\"ANTIOQUIA\\"},{\\"codigo\\":\\"76\\",\\"nombre\\":\\"VALLE DEL CAUCA\\"}]\"}]"
the thing is that I am trying to parse it with JSONObject and JSONArray without success; When I try to use the JSONObject the errorhandler says that it cannot convert the string into JSONObject, so I look up for an answer or a similar problem and found that if the result starts with [] square brackets represents starting of an JSONArray node and curly bracket {} represents JSONObject, so I try to use this code:
//JSONObject jsonObject = new JSONObject(result);
JSONArray jArray = new JSONArray(result);
for(int i=0; i<jArray.length(); i++) {
JSONObject json_data = jArray.getJSONObject(i);
codeDepartment[i] = json_data.getInt("codigo");
NameDepartment[i] = json_data.getString("nombre");
}
without success either, it now says that "it cannot convert String into JSONArray. So any idea of what can I use? any help would be really appreciated.

Well, it seems that the server response is similar to Json response, the thing is all of the \ that it contains. One thing you could do is to replace or remove 1 of the \ backslash and then try to asign the new value to the JSONArray. Something like this:
result = httpClient.execute(request, handler);
result = result.replace("here the info you want to replace", "here with new values to replace with ");
JSONArray jArray = new JSONArray(result);
hope it help you.

How to check if response from server is JSONAobject or JSONArray? [duplicate]

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Determine whether JSON is a JSONObject or JSONArray
I have a server that returns some JSONArray by default, but when some error occurs it returns me JSONObject with error code. I'm trying to parse json and check for errors, I have piece of code that checks for error:
public static boolean checkForError(String jsonResponse) {
boolean status = false;
try {
JSONObject json = new JSONObject(jsonResponse);
if (json instanceof JSONObject) {
if(json.has("code")){
int code = json.optInt("code");
if(code==99){
status = true;
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
return status ;
}
but I get JSONException when jsonResponse is ok and it's a JSONArray (JSONArray cannot be converted to JSONOBject)How to check if jsonResponse will provide me with JSONArray or JSONObject ?

Use JSONTokener. The JSONTokener.nextValue() will give you an Object that can be dynamically cast to the appropriate type depending on the instance.
Object json = new JSONTokener(jsonResponse).nextValue();
if(json instanceof JSONObject){
JSONObject jsonObject = (JSONObject)json;
//further actions on jsonObjects
//...
}else if (json instanceof JSONArray){
JSONArray jsonArray = (JSONArray)json;
//further actions on jsonArray
//...
}

You are trying the convert String response you get from Server into JSONObject which is causing the Exception. As you said you will get the JSONArray from Server, you try to convert into JSONArray. Please refer this link which will help you when to convert string response to JSONObject and JSONArray. If you response starts with [ (Open Square Bracket) then convert it to JsonArray as below
JSONArray ja = new JSONArray(jsonResponse);
if your response starts with { (open flower Bracket) then convert it to
JSONObject jo = new JSONObject(jsonResponse);