Null value added to JSON request by servlet

Question

I request a servlet and it returns me JSON structure correctly but combined with "null"

null{"name":Maria,"totalPrice":17.49}

How can I remove null value in the first line?

I am using the following code to get JSON-Servlet:

BufferedReader reader = new BufferedReader(new InputStreamReader(
    ((HttpURLConnection) (new URL(the_url)).openConnection()).getInputStream(),
        Charset.forName("UTF-8")));

String line;
String returnString = null;

while ((line = reader.readLine()) != null) {
    returnString += line;
}

reader.close();
out.write(returnString);

about null - could it be so it returns JSONP? Try to access servlet url with ?jsonp=test or ?callback=test — Sergei Chicherin, Dec 02 '13 at 13:42

score 2 · Accepted Answer · answered Dec 02 '13 at 13:29

You're starting with a null String variable, not an empty one, so when you add them together the null value gets replaced with "null". Use returnString = "" instead. Better yet, use a StringBuilder:

StringBuilder result = new StringBuilder();

while ((line = reader.readLine()) != null) {
    result.append(line);
}

reader.close();
out.write(result);

score 0 · Answer 2 · edited May 23 '17 at 11:49

0

Simply use for example

String yourNewJsonString = stringWithNull.substring(4);

as char with number 4 is { in your String.

BTW, please read Parsing JSON Object in Java and use it for parsing JSON.

edited May 23 '17 at 11:49

Community

1
1

answered Dec 02 '13 at 13:30

Eel Lee

3,513
2
31
49

score 0 · Answer 3 · edited May 23 '17 at 12:19

0

Today I've replied a similar question (How do I pre parse a JSON String? )

The only problem here is that you have to pretend that the producer of JSON data produces them in a consistent manner. Work (if you can) on the JSON provider, not your client.

(being pragmatic) the reply form @eel-lee is what I would do if fixing the Servlet is unviable (?? really ??).

edited May 23 '17 at 12:19

Community

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answered Dec 02 '13 at 13:36

Giupo

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Null value added to JSON request by servlet

3 Answers3