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How do I parse JSON in Android? [duplicate]

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How do I parse a JSON feed in Android?

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3 Answers
3

Note: this answer has not been updated since 2013. The suggested way to download the json is not recommended for android anymore as the http client has been removed from the sdk as of api 23.
However, the parsing logic below still applies

Android has all the tools you need to parse json built-in. Example follows, no need for GSON or anything like that.

Get your JSON:

DefaultHttpClient httpclient = new DefaultHttpClient(new BasicHttpParams());
HttpPost httppost = new HttpPost(http://someJSONUrl/jsonWebService);
// Depends on your web service
httppost.setHeader("Content-type", "application/json");

InputStream inputStream = null;
String result = null;
try {
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();

inputStream = entity.getContent();
// json is UTF-8 by default
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"), 8);
StringBuilder sb = new StringBuilder();

String line = null;
while ((line = reader.readLine()) != null)
{
sb.append(line + "n");
}
result = sb.toString();
} catch (Exception e) {
// Oops
}
finally {
try{if(inputStream != null)inputStream.close();}catch(Exception squish){}
}


now you have your JSON, so what?

Create a JSONObject:

JSONObject jObject = new JSONObject(result);


To get a specific string

String aJsonString = jObject.getString("STRINGNAME");


To get a specific boolean

boolean aJsonBoolean = jObject.getBoolean("BOOLEANNAME");


To get a specific integer

int aJsonInteger = jObject.getInt("INTEGERNAME");


To get a specific long

long aJsonLong = jObject.getLong("LONGNAME");


To get a specific double

double aJsonDouble = jObject.getDouble("DOUBLENAME");


To get a specific JSONArray:

JSONArray jArray = jObject.getJSONArray("ARRAYNAME");


To get the items from the array

for (int i=0; i < jArray.length(); i++)
{
try {
JSONObject oneObject = jArray.getJSONObject(i);
// Pulling items from the array
String oneObjectsItem = oneObject.getString("STRINGNAMEinTHEarray");
String oneObjectsItem2 = oneObject.getString("anotherSTRINGNAMEINtheARRAY");
} catch (JSONException e) {
// Oops
}
}


Writing JSON Parser Class

public class JSONParser {

static InputStream is = null;
static JSONObject jObj = null;
static String json = "";

// constructor
public JSONParser() {}

public JSONObject getJSONFromUrl(String url) {

// Making HTTP request
try {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);

HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();

} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}

// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}

// return JSON String
return jObj;

}
}


Parsing JSON Data
Once you created parser class next thing is to know how to use that class. Below i am explaining how to parse the json (taken in this example) using the parser class.

2.1. Store all these node names in variables: In the contacts json we have items like name, email, address, gender and phone numbers. So first thing is to store all these node names in variables. Open your main activity class and declare store all node names in static variables.

// url to make request
private static String url = "http://api.9android.net/contacts";

// JSON Node names
private static final String TAG_CONTACTS = "contacts";
private static final String TAG_ID = "id";
private static final String TAG_NAME = "name";
private static final String TAG_EMAIL = "email";
private static final String TAG_ADDRESS = "address";
private static final String TAG_GENDER = "gender";
private static final String TAG_PHONE = "phone";
private static final String TAG_PHONE_MOBILE = "mobile";
private static final String TAG_PHONE_HOME = "home";
private static final String TAG_PHONE_OFFICE = "office";

// contacts JSONArray
JSONArray contacts = null;


2.2. Use parser class to get JSONObject and looping through each json item. Below i am creating an instance of JSONParser class and using for loop i am looping through each json item and finally storing each json data in variable.

// Creating JSON Parser instance
JSONParser jParser = new JSONParser();

// getting JSON string from URL
JSONObject json = jParser.getJSONFromUrl(url);

try {
// Getting Array of Contacts
contacts = json.getJSONArray(TAG_CONTACTS);

// looping through All Contacts
for(int i = 0; i < contacts.length(); i++){
JSONObject c = contacts.getJSONObject(i);

// Storing each json item in variable
String id = c.getString(TAG_ID);
String name = c.getString(TAG_NAME);
String email = c.getString(TAG_EMAIL);
String address = c.getString(TAG_ADDRESS);
String gender = c.getString(TAG_GENDER);

// Phone number is agin JSON Object
JSONObject phone = c.getJSONObject(TAG_PHONE);
String mobile = phone.getString(TAG_PHONE_MOBILE);
String home = phone.getString(TAG_PHONE_HOME);
String office = phone.getString(TAG_PHONE_OFFICE);

}
} catch (JSONException e) {
e.printStackTrace();
}


I've coded up a simple example for you and annotated the source. The example shows how to grab live json and parse into a JSONObject for detail extraction:

try{
// 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);

} catch(Exception e){
// In your production code handle any errors and catch the individual exceptions
e.printStackTrace();
}


Once you have your JSONObject refer to the SDK for details on how to extract the data you require.

readLine()

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