I'm trying to covert Java object to json using Gson library, but its not working as expected and returning empty string,
my code:
String ie = new String("Jack");
Gson gson = new Gson();
String intentcalue = gson.toJson(ie);
it returns:
{}
Please let me know if anything wrong with library, I tried with other Objects as well all returning null value like for Intent Object, ApplicationInfo etc
If you want convert string to json object, your string must be json as well.
For example:
String ie = new String("{\"name\": \"Jack\"}");
Gson gson = new Gson();
String intentcalue = gson.toJson(ie);
Related
I'm trying to convert Generic ArrayList in JSONArray but it is displaying null value.
but this is working fine if i'm trying to display specific value from ArrayList.
ArrayList<myClass> experience = new ArrayList<>();
... //adding some values
Log.v("testing", experience.get(0).company); //this is showing value
JSONArray json = new JSONArray(experience);
Log.v("testing", json.toString()); //this is showing [null]
There might be a problem recognizing andn converting your "myClass" bean to json.
Try using gson library to create json and to parse it back to object .
Can use GSON library like this:
Gson gson = new GsonBuilder().create();
JsonArray myCustomArray = gson.toJsonTree(myCustomList).getAsJsonArray();
Replace with Below Code and try it will work.
Gson gson = new GsonBuilder().setPrettyPrinting().create();
String json = gson.toJson(experience);
Log.e("Jason Array", json);
I have the following code:
public static void postHttpStream(ArrayListMultimap<String, String> fcmbuildProperties){
HttpClient client = new HttpClient();
Gson gson = new Gson();
System.out.println(fcmbuildProperties);
String jsonString = gson.toJson(fcmbuildProperties);
System.out.println(jsonString);
}
where fcmbuildProperties is an ArrayListMultimap. I try to convert that to JSON here: String jsonString = gson.toJson(fcmbuildProperties); But this returns an empty array. What do I need to do instead?
This is the input that fcmbuildProperties contain : {build.name=[test_project], build.timestamp=[1425600727488], build.number=[121]}
I need to convert this to Json. with key/values.
Use ArrayListMultimap#asMap()
String jsonString = gson.toJson(fcmbuildProperties.asMap());
Gson considers ArrayListMultimap as a Map and ignores its internal state which actually manages the multimap. asMap returns a corresponding Map instance which you can serialize as expected.
I am putting some java objects in the Json at server side
like this :
ArrayList<VisjsNode>visjsNodes = new ArrayList<VisjsNode>();
ArrayList<VisjsConnection> visjsConnections = new ArrayList<VisjsConnection>();
String jsondata = null;
org.json.JSONObject object = new org.json.JSONObject();
try {
object.put("nodes", visjsNodes);
object.put("connections", visjsConnections);
jsondata = object.toString();
Now is there a way I can get these objects back from this json (jsondata) at client side
I am doing this:
com.google.gwt.json.client.JSONValue jsonValue = JSONParser.parseStrict(jsondata);
com.google.gwt.json.client.JSONObject jsonObject = jsonValue.isObject();
jsonValue = jsonObject.get("nodes");
Now I am trying this to get ArrayList back , by doing this
ArrayList<VisjsNode>visjsNodesFromjson = jsonValue ;
But its not compiling ,it says Incompatable types...
Can you please guide how we can retrieve the Java Object back from Json ..
That's because you're using two different JsonObject class. First you use the one which comes from org.json (org.json.JsonObject) and the other is com.google.gwt.json.client.JSONObject. Nevertheless, they're named similar, they're completely different classes.
This question already has answers here:
Java JSON serialization - best practice
(3 answers)
Closed 9 years ago.
I have a list of user objects in a Collection, but I want to convert this into JSON format so that on my html page I can read that json data by using javascript.
List<UserWithEmbeddedContact> users=(List<UserWithEmbeddedContact>) q.execute();
if(!users.isEmpty()) {
for(UserWithEmbeddedContact user:users) {
System.out.println("username="+user.getUsername()+
" password="+user.getPassword()+" mobile="+user.getMobile());
}
}
GSON is your answer:
From their wiki:
Gson is a Java library that can be used to convert Java Objects into their JSON representation. It can also be used to convert a JSON string to an equivalent Java object. Gson can work with arbitrary Java objects including pre-existing objects that you do not have source-code of.
Ex:
List<UserWithEmbeddedContact> users = (List<UserWithEmbeddedContact>) q.execute();
final Type listType = new TypeToken<List<UserWithEmbeddedContact>>(){}.getType();
final String json = new Gson().toJson(users, listType);
Use json-lib for Java. It's very easy.
try this, it will convert java instance variables into JSON
import com.google.gson.Gson;
public class ObjectToJSON {
// declaring variables to be converted into JSON
private int data1 = 100;
private String data2 = "hello";
private String[] details = { "IBM", "pune", "ind", "12345" };
public static void main(String[] args) {
// Creating the class object
ObjectToJSON obj = new ObjectToJSON();
// Creating Gson class object
Gson gson = new Gson();
// convert java object to JSON format and receiving the JSON String
String json = gson.toJson(obj);
System.out.println(json);
}
}
I wanted to save an ArrayList to SharedPreferences so I need to turn it into a string and back, this is what I am doing:
// Save to shared preferences
SharedPreferences sharedPref = this.getPreferences(Activity.MODE_PRIVATE);
SharedPreferences.Editor editor = this.getPreferences(Activity.MODE_PRIVATE).edit();
editor.putString("myAppsArr", myAppsArr.toString());
editor.commit();
I can retrieve it with String arrayString = sharedPref.getString("yourKey", null); but I don't know how to convert arrayString back into an ArrayList. How can it be done?
My array looks something like:
[item1,item2,item3]
You have 2 choices :
Manually parse the string and recreate the arraylist. This would be pretty tedious.
Use a JSON library like Google's Gson library to store and retrieve objects as JSON strings. This is a lightweight library, well regarded and popular. It would be an ideal solution in your case with minimal work required. e.g.,
// How to store JSON string
Gson gson = new Gson();
// This can be any object. Does not have to be an arraylist.
String json = gson.toJson(myAppsArr);
// How to retrieve your Java object back from the string
Gson gson = new Gson();
DataObject obj = gson.fromJson(arrayString, ArrayList.class);
Try this
ArrayList<String> array = Arrays.asList(arrayString.split(","))
This will work if comma is used as separator and none of the items have it.
The page http://mjiayou.com/2015/07/22/exception-gson-internal-cannot-be-cast-to/ contains the following:
Type type = new TypeToken<List<T>>(){}.getType();
List<T> list = gson.fromJson(jsonString, type)
perhaps it will be helpful.
//arraylist convert into String using Gson
Gson gson = new Gson();
String data = gson.toJson(myArrayList);
Log.e(TAG, "json:" + gson);
//String to ArrayList
Gson gson = new Gson();
arrayList=gson.fromJson(data, new TypeToken<List<Friends>>()
{}.getType());
I ended up using:
ArrayList<String> appList = new ArrayList<String>(Arrays.asList(appsString.split("\\s*,\\s*")));
This doesn't work for all array types though. This option differs from:
ArrayList<String> array = Arrays.asList(arrayString.split(","));
on that the second option creates an inmutable array.
Update to Dhruv Gairola's answer for Kotlin
val gson = Gson();
val jsonString = gson.toJson(arrayList)