parsing JSON array gives error

Question

I have the following Javascript object:

var o = {
      "username":"username",
      "args": [
          "1", "2", "3"
      ]
};

And send it like:

xhr.send(JSON.stringify(o));

My java class:

public class Command implements Serializable {
    private String username;
    private String[] args;
    //getters, setters constructors etc.
}

And in my servlet:

@Override
public void doPost(HttpServletRequest request, HttpServletResponse response){
    Command c;

    try {
        c = gson.fromJson(request.getReader(), Command.class);
    } catch(Exception e) {
            .
            .
            .

Gives the error: Expected BEGIN_ARRAY but was STRING at line 1 column X, where column number X is where the "[ appears in stringified JSON.

From what I understand this should be a very simple and straightforward thing. What am I doing wrong?

EDIT: I think it may be related to JSON.stringify() behavior with Javascript arrays of strings.

JSON.stringify(o) returns:

"{"username":"username","args":"[\"1\", \"2\", \"3\"]"}"

Yes: your "args" property is a string, not an array

Maurice Perry
– Maurice Perry

2014-08-21 12:23:17 +00:00
Commented Aug 21, 2014 at 12:23 — Maurice Perry
– Maurice Perry, Commented Aug 21, 2014 at 12:23
What do you exactly mean by it?

uylmz
– uylmz

2014-08-21 12:33:17 +00:00
Commented Aug 21, 2014 at 12:33 — uylmz
– uylmz, Commented Aug 21, 2014 at 12:33
The value starts with a quote, not a bracket

Maurice Perry
– Maurice Perry

2014-08-21 12:45:37 +00:00
Commented Aug 21, 2014 at 12:45 — Maurice Perry
– Maurice Perry, Commented Aug 21, 2014 at 12:45

Sagar D · Accepted Answer · 2014-08-21 12:30:20Z

2

Normal JavaScript arrays are designed to hold data with numeric indexes. Try using Object instead of an array.

Try using the below code for constructing the object and check the output :

var o = {};           // Object
o['username'] = 'username';
o['args'] = [];          // Array
o['args'].push('1');
o['args'].push('2');
o['args'].push('3');
var json = JSON.stringify(o);
alert(json);

edited Aug 21, 2014 at 12:30

answered Aug 21, 2014 at 10:42

Sagar D

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3 Comments

uylmz Over a year ago

I think it's not valid Javascript.

Sagar D Over a year ago

Sorry about the previous answer

uylmz Over a year ago

It's not related to character encoding. It's related to JSON.stringify function with string arrays I think.

Mike_G · Accepted Answer · 2014-08-25 17:43:39Z

2

I think you have one too many quotes in your stringify result. When I construct the object like this:

 var o = {
            username: "username",
            args: ["1","2","3"]
        };

the result from calling JSON.stringify(o)

is this

"{\"username\":\"username\",\"args\":[\"1\",\"2\",\"3\"]}"

notice there are no quotes around my square brackets.

answered Aug 25, 2014 at 17:43

Mike_G

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2 Comments

uylmz Over a year ago

Both IE 11 and Opera consoles give me the result with too many quotes.

Mike_G Over a year ago

that's strange because I am using IE 11. I tested in Chrome and received the same results.

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