How to convert ArrayList

Question

I want to convert my ArrayList<object> to a JSON String and back to ArrayList<object>

But I really don't know how to do that :

Something like :

Convert
ArrayList<data> arrayData = new ArrayList<data>();
 JSONObject retObject = new JSONObject();
    retObject.put("data", new JSONArray(arrayData ));

    Return convert

idk...

Which library are you using ? It is a very straight forward job in GSON ! — AllTooSir, Jun 05 '14 at 09:22
Check: http://stackoverflow.com/questions/17037340/converting-jsonarray-to-arraylist — radimpe, Jun 05 '14 at 09:27
i want to put my Arraylist into a Cookie which only supports strings — Domi, Jun 05 '14 at 09:51
You should mention such details when asking the question the next time, at least then you provide an understandable context for your question. But while we're on this topic: you can just as easily translate the data into a string where you are creating the cookie, it does not necessarily have to happen before transmission of the data. — Gimby, Jun 05 '14 at 09:57

score 4 · Accepted Answer · edited Jun 05 '14 at 09:30

You can consider using 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);

hexin · Answer 2 · 2014-06-05T09:52:52.473

0

Using Jackson:

ObjectMapper mapper = new ObjectMapper();
String listAsJson = mapper.writeValueAsString(oldList);
List<Object> newList= mapper.readValue(listAsJson ,new TypeReference<List<Object>>() {});

edited Jun 05 '14 at 09:52

answered Jun 05 '14 at 09:27

hexin

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Not quite JSON, I don't think. – hd1 Jun 05 '14 at 09:32
No worries, mate, just delete the response before you get voted down – hd1 Jun 05 '14 at 09:52
I changed it to Jackson, could be? – hexin Jun 05 '14 at 09:53
I'm not going to vote it down, but personally, I prefer [xstream](http://xstream.codehaus.org/). – hd1 Jun 05 '14 at 09:55
I use xstream for xml parsing and manipulating, in case of json it depends on project – hexin Jun 05 '14 at 10:10
To each their own, @hexin – hd1 Jun 05 '14 at 10:18

hari · Answer 3 · 2014-06-05T09:37:09.893

-1

ArrayList<Product> arrayData = new ArrayList<Product>();
Gson gson = new Gson();

convert list to json object

String jsonCartList = gson.toJson(cartList);

convert json to your list

List<Product> prodList = gson.fromJson(jsonCartList, Product.class);

edited Jun 05 '14 at 09:37

answered Jun 05 '14 at 09:31

hari

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Wouldn't the last line cause a type mismatch? – Matthias Apr 11 '16 at 16:00

3 Answers3