Question

Hi guys I’m developing a Restful + JSON servlet, but I got a strange problem, if i try to compile my project source with this method:

public
static
WipdDBTable
parseJSON(String JSONBody)
{
    JSONObject jsonObj;
    JSONTokener jsonTok;
    Iterator it;
    String[] labels;
    String[][] fields;
    int i;

    try  {
        jsonTok = new JSONTokener(JSONBody);
        jsonObj = new JSONObject(jsonTok);

        labels = new String[jsonObj.length()];
        fields = new String[1][labels.length];

        i = 0;
        it = jsonObj.keys(); 
        while(it.hasNext())  {
            String key = it.next().toString();
            labels[i] = key;
            fields[0][i] = jsonObj.get(key);
            i++;
        }

        return new WipdDBTable(labels, fields);
    } catch(JSONException ex)  {
        return null;
    }
}

I get this error:

WipdJSON.java:102: incompatible types
found   : java.lang.Object
required: java.lang.String
                fields[0][i] = jsonObj.get(key);

So I wrote a test class, with apparently the same source, but with this one I don’t get any error:

public class jsontest
{
    public static
    void
    main(String[] args)
    {
        String s1;
        JSONObject jsonObj;
        JSONTokener jsonTok;

        s1 = "{\"lo\":\"ol\",\"json\":{\"1\":\"2\"},\"yo\":{\"lol\":\"lol\"}}";

        try  {
            jsonTok = new JSONTokener(s1);
            jsonObj = new JSONObject(jsonTok);

            Iterator it = jsonObj.keys();
            while(it.hasNext())  {
                String key = it.next().toString();
                System.out.print(key + "=>");
                System.out.println(jsonObj.get(key));
            }
        } catch(JSONException ex)  {
            ex.printStackTrace();
        }

    }
}

Answer 1

jsonObj.get(key); return an Object, you need to cast it to a String if you want to get the value in a String variable. There is a getString method in the JSONObject class:

fields[0][i] = jsonObj.getString(key);

And you don’t get any error in your test class as you’re only outputting the value that is calling the toString() method.