Convert returned JSON String to a JSONArray

Question

I have a web service that performs a database query, converts the result set to a JSON String and returns the strung to the client. This is the code for the converter (I got it from http://biercoff.com/nice-and-simple-converter-of-java-resultset-into-jsonarray-or-xml/):

public static String convertToJSON(ResultSet resultSet)
        throws Exception {
    JSONArray jsonArray = new JSONArray();
    while (resultSet.next()) {
        int total_rows = resultSet.getMetaData().getColumnCount();
        JSONObject obj = new JSONObject();
        for (int i = 0; i < total_rows; i++) {
            obj.put(resultSet.getMetaData().getColumnLabel(i + 1)
                    .toLowerCase(), resultSet.getObject(i + 1));
        }
        jsonArray.add(obj);
    }
    return jsonArray.toJSONString();
}

In the client application when I print the returned string it is in the following format:

[{"Column1":0.333333,"Column2":"FirmA"},{"Column1":0.666667,"Column2":"FirmB"}]

so far all is good. The problem I am having is converting the returned string into a JSON array. I tried this:

JSONArray arr = new JSONArray(JSON_STRING);

but got the following error message: constructor JSONArray in class JSONArray cannot be applied to given types. I tried to first convert in into a JSON object like so:

JSONObject obj = new JSONObject(JSON_STRING);

but got the following error: incompatible types: String cannot be converted to Map. What am I doing wrong? Thanks.

See syntax of a json array w3schools.com/json/json_syntax.asp, the returned string should be in this format arr: [{}, {}] — 6ton
– 6ton, Commented Jan 8, 2015 at 15:13
This is the format of the returned string that I have shown above. I don't see any discrepancy. — user3245747
– user3245747, Commented Jan 8, 2015 at 15:15
You are missing "arr":, instead its just the array value in your string. — 6ton
– 6ton, Commented Jan 8, 2015 at 15:18
6ton I have produced the string in the form: {"Chart":[{"Column1":0.333333,"Column2":"FirmA"} ,{"Column1":0.666667,"Column2":"FirmB"}]} but Im still having the exact problems. — user3245747
– user3245747, Commented Jan 8, 2015 at 21:03

Community · Accepted Answer · 2017-05-23 12:30:31Z

1

Apparently the problem was with the json library that I was using. Once I used the

import org.json.JSONArray;

it all worked out well. I was able to convert the returned string to an array using

JSONArray arr = new JSONArray(JSON_STRING);

and to iterate through the values I used the code provided in this answer: Accessing members of items in a JSONArray with Java which I reproduce here for simplicity:

for (int i = 0; i < arr.length(); ++i) {
    JSONObject rec = arr.getJSONObject(i);
    int id = rec.getInt("id");
    String loc = rec.getString("loc");
    // ...
}

edited May 23, 2017 at 12:30

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answered Jan 9, 2015 at 7:35

user3245747

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2 Comments

Kishan Bheemajiyani Over a year ago

I think that will not be correct with the String because string can be anything u need to convert an array to string.

user3245747 Over a year ago

The method posted in the question returns an array which is converted to a string. When I changed the json library I was using I was able to create an array from the string on the client side. The jar which worked for me came from java2s.com/Code/Jar/j/Downloadjavajsonjar.htm

Kishan Bheemajiyani · Accepted Answer · 2015-01-09 07:48:36Z

0

well you need to do it by this way for example

String jsonText = "[0,{\"1\":{\"2\":{\"3\":{\"4\":[5,{\"6\":7}]}}}}]";
        try {

            JSONArray array = new JSONArray(jsonText);
            System.out.println(array);
            System.out.println(array.length());

        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
    }

answered Jan 9, 2015 at 7:48

Kishan Bheemajiyani

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Comments

Zon · Accepted Answer · 2016-08-25 17:21:33Z

0

Check the correct library used. The mess is that org.json.simple is often suggested by IDE as default for JSONObject and JSONArray.

You can find a link to latest jar for org.json library above.

answered Aug 25, 2016 at 17:21

Zon

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