how do i add String array to JSON

Question

I am currently writing some code in a servlet that gets data from the database and returns it to the client. What I am having problems with is inserting the array of dates I have collected and adding them to my JSON object that I will return to the client.

Here is the code I'm trying but it keeps giving errors

dates = ClassdatesDAO.getdate(dates);
ArrayList<String> ClassDates = new ArrayList<String>();
ClassDates = dates.getClassdates();
response.setContentType("application/json");
JSONObject Dates = new JSONObject();
Dates.put("dates", new JSONArray(ClassDates));

In my IDE I get this error over the ClassDates in the JSONArray

The constructor JSONArray(ArrayList) is undefined

As an aside, replace the first two lines with List<String> classDates = dates.getClassdates();. There's no point creating an instance, if you re-assign the reference on the next line — Nick Holt
– Nick Holt, Commented Mar 24, 2014 at 15:29
new JSONArray should work, if it's the org.json version. It has a constructor for java.util.Collection, and an ArrayList is a Collection. — Hot Licks
– Hot Licks, Commented Mar 24, 2014 at 15:46
BTW, variable names in Java should begin with a lower-case letter. Classes should start with an Upper-Case letter. — Hot Licks
– Hot Licks, Commented Mar 24, 2014 at 15:49

Keerthivasan · Accepted Answer · 2014-03-24 15:26:04Z

1

You are passing ArrayList instance instead of an Array. So, convert the list into an array and then pass it as an argument like this

Dates.put("dates", new JSONArray(ClassDates.toArray(new String[ClassDates.size()])));

Note : json API has a method signature accepting java.util.Collection. So, you are using some other library or older version

answered Mar 24, 2014 at 15:26

Keerthivasan

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SceLus · Accepted Answer · 2014-03-24 15:27:52Z

0

      JSONObject Dates = new JSONObject();
      JSONArray datesJSONArray = new JSONArray();
      for (String date : ClassDates)
          datesJSONArray.put(date);
      try {
        Dates.put("dates", datesJSONArray);
      } catch (JSONException e) {
        e.printStackTrace();
      }

answered Mar 24, 2014 at 15:27

SceLus

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