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\"]"}"

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\"]"}"

• javascript
• java
• arrays
• json
• gson

• Yes: your "args" property is a string, not an array – Maurice Perry Commented Aug 21, 2014 at 12:23
• What do you exactly mean by it? – uylmz Commented Aug 21, 2014 at 12:33
• The value starts with a quote, not a bracket – Maurice Perry Commented Aug 21, 2014 at 12:45

2 Answers 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);

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.