Develop Reference

Read json array from a json object with gson

I want to get a list of JSON objects with JSON from a API. For example affiliate.itunes
but with gson I can't go throw a jsonObject and i have to use java JSONObject and JSONArray class for this mater.
Is it possible to handle this completely with gson lib ?
This is json file that I copied into my android raw folder
and this is my code
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
GsonBuilder builder = new GsonBuilder();
Gson gson = builder.create();
InputStream inputStream = getResources().openRawResource(R.raw.file);
String jsonStr = streamToString(inputStream);
try {
JSONObject jsonObject = new JSONObject(jsonStr);
JSONArray jsonArray = jsonObject.getJSONArray("results");
Type type = new TypeToken<List<BandJsonResult>>(){}.getType();
List<BandJsonResult> jsonResults = gson.fromJson(jsonArray.toString(),type);
for(int i = 0 ; i < jsonResults.size() ; i++){
Log.e("JSON " + i ,jsonResults.get(i).toString());
}
} catch (JSONException e) {
e.printStackTrace();
}
}
private String streamToString(InputStream stream) {
InputStreamReader reader = new InputStreamReader(stream);
BufferedReader bufferedReader = new BufferedReader(reader);
StringBuilder result = new StringBuilder();
String line = "";
try {
while ((line = bufferedReader.readLine()) != null) {
result.append(line);
}
}catch (IOException ex){
ex.printStackTrace();
}
return result.toString();
}
}

Gson uses reflection by default to (de-)serialize classes (unless you provide custom adapters), see also this example in the Gson user guide. Based on the screenshot you could add these two classes:
// You can give these classes any name
class ApiResponse {
// Uses the field names for (de-)serialization by default, but you can also
// specify custom names using #SerializedName
private int resultCount;
private List<BandResult> results;
}
class BandResult {
// You can also use enums and then either name the enum constants the same
// as the values, or annotate the enum constants with #SerializedName
private String wrapperType;
private String kind;
private int artistId;
...
}
And then use them when calling Gson.fromJson:
ApiResponse apiResponse = gson.fromJson(jsonStr, ApiResponse.class);

why can't I parsing value 'fields' in my code?

When I run my app, In logcat, "Problem parsing the earthquake Json results
org.json.JSONException: No value for fields"
Could you check my JSON code..? I'm beginner of JSON Parsing, So I searched a lot inf But I'm not sure about my code.
public class Utils {
private static List<News> extractFromJson(String newsJSON) {
if (TextUtils.isEmpty(newsJSON)) {
return null;
}
List<News> news = new ArrayList<>();
try {
// Create a JSONObject from the JSON response string
JSONObject baseJsonResponse = new JSONObject(newsJSON);
JSONObject response = baseJsonResponse.getJSONObject("response");
JSONArray jsonArray = response.getJSONArray("results");
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject currentNews = jsonArray.getJSONObject(i);
JSONObject fields = currentNews.getJSONObject("fields");
Drawable thumbnail = LoadImageFromUrl (fields.getString("thumbnail"));
String section = currentNews.getString("sectionName");
String title = currentNews.getString("webTitle");
String url = currentNews.getString("webUrl");
String date = currentNews.getString("webPublicationDate");
news.add(new News( section, title, url, date,thumbnail));
}
return news;
} catch (JSONException e) {
Log.e("Utils", "Problem parsing the news Json results", e);
}
return null;
}
private static Drawable LoadImageFromUrl(String imageurl) {
Drawable drawable = null;
InputStream inputStream = null;
try {
inputStream = new URL(imageurl).openStream();
drawable = Drawable.createFromStream(inputStream, null);
inputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
return drawable;
}
}

Try this to validate
Problem occur may be you dont have a field jsonobject in your json list. It may be not present in the some of other jsonobjects. So check if jsonobject has actual field jsonobject before parsing.
Use this condition whenever your json value might give null sometimes.
if(currentNews.has("fields"))
{
JSONObject fields = currentNews.getJSONObject("fields");
}
else
{
Log.d("JSON_TAG","NO FIELD JSON OBJECT");
}

is there anything that i don't know about Json in Code

i'm trying to do some work with methods of json in android.
i read the documentation of json and its methods but when i use them,they don't do what i expected they do.
public class getData_jason extends AsyncTask{
String KholaseKQuery;
String User;
public getData_jason(String link,String user) {
KholaseKQuery = link;
User = user;
}
#Override
protected String doInBackground(Object[] params) {
try{
URL mylink = new URL(KholaseKQuery);
URLConnection connect = mylink.openConnection();
BufferedReader read = new BufferedReader(new InputStreamReader(connect.getInputStream()));
StringBuilder sB = new StringBuilder();
String eline;
while((eline = read.readLine())!= null)
{
sB.append(eline);
}
//MainActivity.jason_rs = sB.toString();
MainActivity.result = sB.toString();
MainActivity.is = true;
JSONObject jObj;
try{
jObj = new JSONObject(MainActivity.result.replace("callback(","")).getJSONObject("response");
JSONArray jsonArray = jObj.optJSONArray("Username");
for (int i = 0;i < jsonArray.length();i++){
JSONObject jsonObject = jsonArray.getJSONObject(i);
if (jsonObject.getBoolean("ali")){
MainActivity.jason_rs = jsonObject.optString("Name");
//MainActivity.jason_rs = jsonObject.getString("Name");
}
}
}catch (Exception e){
}
}catch (Exception e){
/*Any Exception Here*/
}
return "";
}
}
when the process of reading from database is finished,in the result string is:
{"Username":["Name":"ali","Name":"hasan"]},{"Password":["aliali","hasanhasan"]}
so when i want to get ali name from the jsonObject,the value of jason_rs is null.
plz guid me what is that i don't know yet about using json or i do it wrong.

Your "json" is invalid. You can't have the same key more than once in a hash, on the other hand you also can't have keys (certainly not strings) in an array. You can validate it on http://jsonlint.com

Android parse JSONObject

I've got a little problem with parsing json into my android app.
This is how my json file looks like:
{
"internalName": "jerry91",
"dataVersion": 0,
"name": "Domin91",
"profileIconId": 578,
"revisionId": 0,
}
As You can see this structure is a little bit weird. I dont know how to read that data in my app. As I noticed those are all Objects not arrays :/

You can always use good old json.org lib. In your Java code :
First read your json file content into String;
Then parse it into JSONObject:
JSONObject myJson = new JSONObject(myJsonString);
// use myJson as needed, for example
String name = myJson.optString("name");
int profileIconId = myJson.optInt("profileIconId");
// etc

UPDATE 2018
After 5 years there is a new "standard" for parsing json on android. It's called moshi and one can consider it GSON 2.0. It's very similar but with design bugs fixed that are the first obstacles when you start using it.
https://github.com/square/moshi
First add it as a mvn dependency like this:
<dependency>
<groupId>com.squareup.moshi</groupId>
<artifactId>moshi-kotlin</artifactId>
<version>1.6.0</version>
</dependency>
After adding it we can use like so (taken from the examples):
String json = ...;
Moshi moshi = new Moshi.Builder().build();
JsonAdapter<BlackjackHand> jsonAdapter = moshi.adapter(BlackjackHand.class);
BlackjackHand blackjackHand = jsonAdapter.fromJson(json);
System.out.println(blackjackHand);
More infos on their GitHub page :)
[old]
I would recommend using Gson.
Here are some links for tutorials:
how to convert java objecto from json format using GSON
Parse JSON file using GSON
Simple GSON example
Converting JSON data to Java object
An alternative to Gson you could use Jackson.
Jackson in 5 minutes
how to convert java object to and from json
This libraries basically parse your JSON to a Java class you specified.

to know if string is JSONArray or JSONObject
JSONArray String is like this
[{
"internalName": "blaaa",
"dataVersion": 0,
"name": "Domin91",
"profileIconId": 578,
"revisionId": 0,
},
{
"internalName": "blooo",
"dataVersion": 0,
"name": "Domin91",
"profileIconId": 578,
"revisionId": 0,
}]
and this String as a JSONOject
{
"internalName": "domin91",
"dataVersion": 0,
"name": "Domin91",
"profileIconId": 578,
"revisionId": 0,
}
but how to call elements from JSONArray and JSONObject ?
JSNOObject info called like this
first fill object with data
JSONObject object = new JSONObject(
"{
\"internalName\": \"domin91\",
\"dataVersion\": 0,
\"name\": \"Domin91\",
\"profileIconId\": 578,
\"revisionId\": 0,
}"
);
now lets call information from object
String myusername = object.getString("internalName");
int dataVersion = object.getInt("dataVersion");
If you want to call information from JSONArray you must know what is the object position number or you have to loop JSONArray to get the information for example
looping array
for ( int i = 0; i < jsonarray.length() ; i++)
{
//this object inside array you can do whatever you want
JSONObject object = jsonarray.getJSONObject(i);
}
if i know the object position inside JSONArray ill call it like this
//0 mean first object inside array
JSONObject object = jsonarray.getJSONObject(0);

This part do in onBackground in AsyncTask
JSONParser jParser = new JSONParser();
JSONObject json = jParser.getJSONFromUrl(url);
try {
result = json.getString("internalName");
data=json.getString("dataVersion");
ect..
} catch (JSONException e) {
e.printStackTrace();
}
JsonParser
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, "utf-8"), 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;
}
}

I suggest you to use a library like gson as #jmeier wrote on his answer. But if you want to handle json with android's defaults, you can use something like this:
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
String s = new String("{\"internalName\": \"domin91\",\"dataVersion\": 0,\"name\": \"Domin91\",\"profileIconId\": 578,\"revisionId\": 0,}");
try {
MyObject myObject = new MyObject(s);
Log.d("MY_LOG", myObject.toString());
} catch (JSONException e) {
Log.d("MY_LOG", "ERROR:" + e.getMessage());
}
}
private static class MyObject {
private String internalName;
private int dataVersion;
private String name;
private int profileIconId;
private int revisionId;
public MyObject(String jsonAsString) throws JSONException {
this(new JSONObject(jsonAsString));
}
public MyObject(JSONObject jsonObject) throws JSONException {
this.internalName = (String) jsonObject.get("internalName");
this.dataVersion = (Integer) jsonObject.get("dataVersion");
this.name = (String) jsonObject.get("name");
this.profileIconId = (Integer) jsonObject.get("profileIconId");
this.revisionId = (Integer) jsonObject.get("revisionId");
}
#Override
public String toString() {
return "internalName=" + internalName +
"dataVersion=" + dataVersion +
"name=" + name +
"profileIconId=" + profileIconId +
"revisionId=" + revisionId;
}
}
}

Please checkout ig-json parser or Logan Square for fast and light JSON library.
For comparison, this is the stats from Logan Square developer.

Here you can parse any file from assets folder
fetch file from assets folder
public void loadFromAssets(){
try {
InputStream is = getAssets().open("yourfile.json");
readJsonStream(is);
} catch (IOException e) {
e.printStackTrace();
}
}
Convert JSON to your class object
public void readJsonStream(InputStream in) throws IOException {
Gson gson = new Gson();
JsonReader reader = new JsonReader(new InputStreamReader(in, "UTF-8"));
reader.setLenient(true);
int size = in.available();
Log.i("size", size + "");
reader.beginObject();
long starttime=System.currentTimeMillis();
while (reader.hasNext()) {
try {
Yourclass message = gson.fromJson(reader, Yourclass.class);
}
catch (Exception e){
Toast.makeText(this, e.getCause().toString(), Toast.LENGTH_SHORT).show();
}
}
reader.endObject();
long endtime=System.currentTimeMillis();
long diff=endtime-starttime;
int seconds= (int) (diff/1000);
Log.i("elapsed",seconds+"");
reader.close();
}

conversion from string to JSON object Android

I am working on an Android application. In my app I have to convert a string to JSON Object, then parse the values. I checked for a solution in Stackoverflow and found similar issue here link
The solution is like this
`{"phonetype":"N95","cat":"WP"}`
JSONObject jsonObj = new JSONObject("{\"phonetype\":\"N95\",\"cat\":\"WP\"}");
I use the same way in my code . My string is
{"ApiInfo":{"description":"userDetails","status":"success"},"userDetails":{"Name":"somename","userName":"value"},"pendingPushDetails":[]}
string mystring= mystring.replace("\"", "\\\"");
And after replace I got the result as this
{\"ApiInfo\":{\"description\":\"userDetails\",\"status\":\"success\"},\"userDetails\":{\"Name\":\"Sarath Babu\",\"userName\":\"sarath.babu.sarath babu\",\"Token\":\"ZIhvXsZlKCNL6Xj9OPIOOz3FlGta9g\",\"userId\":\"118\"},\"pendingPushDetails\":[]}
when I execute JSONObject jsonObj = new JSONObject(mybizData);
I am getting the below JSON exception
org.json.JSONException: Expected literal value at character 1 of
Please help me to solve my issue.

Remove the slashes:
String json = {"phonetype":"N95","cat":"WP"};
try {
JSONObject obj = new JSONObject(json);
Log.d("My App", obj.toString());
} catch (Throwable t) {
Log.e("My App", "Could not parse malformed JSON: \"" + json + "\"");
}

This method works
String json = "{\"phonetype\":\"N95\",\"cat\":\"WP\"}";
try {
JSONObject obj = new JSONObject(json);
Log.d("My App", obj.toString());
Log.d("phonetype value ", obj.getString("phonetype"));
} catch (Throwable tx) {
Log.e("My App", "Could not parse malformed JSON: \"" + json + "\"");
}

try this:
String json = "{'phonetype':'N95','cat':'WP'}";

You just need the lines of code as below:
try {
String myjsonString = "{\"phonetype\":\"N95\",\"cat\":\"WP\"}";
JSONObject jsonObject = new JSONObject(myjsonString );
//displaying the JSONObject as a String
Log.d("JSONObject = ", jsonObject.toString());
//getting specific key values
Log.d("phonetype = ", jsonObject.getString("phonetype"));
Log.d("cat = ", jsonObject.getString("cat");
}catch (Exception ex) {
StringWriter stringWriter = new StringWriter();
ex.printStackTrace(new PrintWriter(stringWriter));
Log.e("exception ::: ", stringwriter.toString());
}

just try this ,
finally this works for me :
//delete backslashes ( \ ) :
data = data.replaceAll("[\\\\]{1}[\"]{1}","\"");
//delete first and last double quotation ( " ) :
data = data.substring(data.indexOf("{"),data.lastIndexOf("}")+1);
JSONObject json = new JSONObject(data);

To get a JSONObject or JSONArray from a String I've created this class:
public static class JSON {
public Object obj = null;
public boolean isJsonArray = false;
JSON(Object obj, boolean isJsonArray){
this.obj = obj;
this.isJsonArray = isJsonArray;
}
}
Here to get the JSON:
public static JSON fromStringToJSON(String jsonString){
boolean isJsonArray = false;
Object obj = null;
try {
JSONArray jsonArray = new JSONArray(jsonString);
Log.d("JSON", jsonArray.toString());
obj = jsonArray;
isJsonArray = true;
}
catch (Throwable t) {
Log.e("JSON", "Malformed JSON: \"" + jsonString + "\"");
}
if (object == null) {
try {
JSONObject jsonObject = new JSONObject(jsonString);
Log.d("JSON", jsonObject.toString());
obj = jsonObject;
isJsonArray = false;
} catch (Throwable t) {
Log.e("JSON", "Malformed JSON: \"" + jsonString + "\"");
}
}
return new JSON(obj, isJsonArray);
}
Example:
JSON json = fromStringToJSON("{\"message\":\"ciao\"}");
if (json.obj != null) {
// If the String is a JSON array
if (json.isJsonArray) {
JSONArray jsonArray = (JSONArray) json.obj;
}
// If it's a JSON object
else {
JSONObject jsonObject = (JSONObject) json.obj;
}
}

Using Kotlin
val data = "{\"ApiInfo\":{\"description\":\"userDetails\",\"status\":\"success\"},\"userDetails\":{\"Name\":\"somename\",\"userName\":\"value\"},\"pendingPushDetails\":[]}\n"
try {
val jsonObject = JSONObject(data)
val infoObj = jsonObject.getJSONObject("ApiInfo")
} catch (e: Exception) {
}

Here is the code, and you can decide which
(synchronized)StringBuffer or
faster StringBuilder to use.
Benchmark shows StringBuilder is Faster.
public class Main {
int times = 777;
long t;
{
StringBuffer sb = new StringBuffer();
t = System.currentTimeMillis();
for (int i = times; i --> 0 ;) {
sb.append("");
getJSONFromStringBuffer(String stringJSON);
}
System.out.println(System.currentTimeMillis() - t);
}
{
StringBuilder sb = new StringBuilder();
t = System.currentTimeMillis();
for (int i = times; i --> 0 ;) {
getJSONFromStringBUilder(String stringJSON);
sb.append("");
}
System.out.println(System.currentTimeMillis() - t);
}
private String getJSONFromStringBUilder(String stringJSONArray) throws JSONException {
return new StringBuffer(
new JSONArray(stringJSONArray).getJSONObject(0).getString("phonetype"))
.append(" ")
.append(
new JSONArray(employeeID).getJSONObject(0).getString("cat"))
.toString();
}
private String getJSONFromStringBuffer(String stringJSONArray) throws JSONException {
return new StringBuffer(
new JSONArray(stringJSONArray).getJSONObject(0).getString("phonetype"))
.append(" ")
.append(
new JSONArray(employeeID).getJSONObject(0).getString("cat"))
.toString();
}
}

May be below is better.
JSONObject jsonObject=null;
try {
jsonObject=new JSONObject();
jsonObject.put("phonetype","N95");
jsonObject.put("cat","wp");
String jsonStr=jsonObject.toString();
} catch (JSONException e) {
e.printStackTrace();
}