gson throws MalformedJsonException

Question

I'm using gson to convert a json string to a Java-Object. The value of result2 is exactly the same as the value of result1. (Copied from debugger; Backslashs added)

The following exception is thrown while converting result1: com.google.gson.JsonSyntaxException: com.google.gson.stream.MalformedJsonException: Expected EOF at line 1 column 170

Converting result2 works fine.

The json string is valid according to jsonlint.com.

public static Userinfo getUserinfo()
{
    String result1 = http.POST("https://www.bitstamp.net/api/balance/",
                                postdata, true);
    String result2 = "{\"btc_reserved\": \"0\", \"fee\": \"0.5000\", \"btc_available\": \"0.10000000\", \"usd_reserved\": \"0\", \"btc_balance\": \"0.10000000\", \"usd_balance\": \"30.00\", \"usd_available\": \"30.00\"}";
    Gson gson = new Gson();
    Userinfo userinfo1 = gson.fromJson(result1, Userinfo.class); //throws Exception
    Userinfo userinfo2 = gson.fromJson(result2, Userinfo.class); //works fine

    return userinfo1;
}
private class Userinfo {

    public Userinfo(){
    }

    public float usd_balance;
    public float btc_balance ;
    public float usd_reserved;
    public float btc_reserved;
    public float usd_available;
    public float btc_available;
    public float fee;
    public float last_update;
}

Daniel Martin · Accepted Answer · 2014-04-15T11:38:18.847

114

I suspect that result1 has some characters at the end of it that you can't see in the debugger that follow the closing } character. What's the length of result1 versus result2? I'll note that result2 as you've quoted it has 169 characters.

GSON throws that particular error when there's extra characters after the end of the object that aren't whitespace, and it defines whitespace very narrowly (as the JSON spec does) - only \t, \n, \r, and space count as whitespace. In particular, note that trailing NUL (\0) characters do not count as whitespace and will cause this error.

If you can't easily figure out what's causing the extra characters at the end and eliminate them, another option is to tell GSON to parse in lenient mode:

Gson gson = new Gson();
JsonReader reader = new JsonReader(new StringReader(result1));
reader.setLenient(true);
Userinfo userinfo1 = gson.fromJson(reader, Userinfo.class);

edited Apr 15 '14 at 11:38

answered Jul 15 '12 at 00:11

Daniel Martin

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Thank you! My HTTP Class downloaded the json string in a 256 byte char buffer which was then converted to a string (result1). Because of that, result1 had a length of 255 instead of 169. – Non Jul 15 '12 at 20:13
I had the same problem; the whole EOF thing in the exception kind of threw me, my problem was just pure and simple badly formed JSON. – Kong Sep 22 '13 at 06:26
3

I had the same problem, but I obtained my JSON via a FileChannel. I was pretty sure encoding was allright. What I did was to call trim() method on the String red from file on HDD, this solved the problem. – Apr 14 '14 at 18:20
3

@ThePaul - you probably had extra NUL (that is, '\0') characters at the end of your string. String.trim() removes not just spaces, but also any character less than 32, whereas GSON counts those characters as trailing garbage. (And it then complains "I saw the closing brace, so should next see an EOF, but I saw some other stuff instead ") – Daniel Martin Apr 15 '14 at 11:33
1

Make sure you are importing the right json reader, other libraries have classes of the same name – Joe Maher Dec 23 '15 at 01:04

ryenus · Answer 2 · 2020-05-14T03:06:23.697

20

From my recent experience, JsonReader#setLenient basically makes the parser very tolerant, even to allow malformed JSON data.

But for certain data retrieved from your trusted RESTful API(s), this error might be caused by trailing white spaces. In such cases, simply trim the data would avoid the error:

String trimmed = result1.trim();

Then gson.fromJson(trimmed, T) might work. Surely this only covers a special case, so YMMV.

edited May 14 '20 at 03:06

answered Sep 17 '14 at 11:04

ryenus

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hi @ryenus , if i two words wtih space inbetween then what to do? – Qasim Jun 17 '15 at 17:55
6

What if white spaces mattered in the string response? Tirmming is not good in that case. You'll be losing the integrity of your data. – Anis LOUNIS aka AnixPasBesoin Feb 03 '17 at 16:10

score 4 · Answer 3 · answered Jul 14 '12 at 14:01

4

In the debugger you don't need to add back slashes, the input field understands the special chars.

In java code you need to escape the special chars

answered Jul 14 '12 at 14:01

Mark Bakker

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I copied the value of result1 from the debugger and added backslashes afterwards to escape the special chars in result2 ;) – Non Jul 14 '12 at 14:07
Could it be there is a space char or \n\r infront or appended to the json string. It should be something simple – Mark Bakker Jul 14 '12 at 16:28
What's the result of result1.equals(result2)? – Programmer Bruce Jul 14 '12 at 18:04
@ProgrammerBruce: result1.equals(result2)=false. Both strings contained the same characters, but result1 was longer then result2 (caused by my http class; see above). – Non Jul 15 '12 at 20:28

gson throws MalformedJsonException

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