Question

I’m trying to pass data to my controller using Ajax and JSON.

I’ve got an HTML table and I’ve got to send multiple coordinates of that table to my controller. So I made a Javascript array containing anonymous objects of this kind :

{ 
    DAY: someIndex, 
    HOUR: someOtherIndex 
}

and let this array be called coordinates, I serialized it like this:

JSON.stringify(coordinates)

so then in an ajax call (type: POST) I used data: JSON.stringify(coordinates).

In my document ready I used :

$.ajaxSetup({
    headers : {
        Accept : "application/json; charset=utf-8"
    }
}); 

And my controller looks like this:

@RequestMapping(value = "/{id}", method = RequestMethod.POST)
public @ResponseBody
String update(@PathVariable int id, @RequestBody String coordinates, HttpServletResponse response) {

    // Do something here to convert it in my complex structure

}

However I don’t know what the type should be for the parameter coordinates.

I’m using GSON. And I wasn’t able to deserialize it easily. I tried using this solution, but it wouldn’t work. (Kept asking to cast types for some reason.)

Since I didn’t think it’d be possible to deserialize this correctly, I tried to serialize the coordinates as another format (just a JSON array of strings where the coordinates are split by a token (;) here

So my array the javascript objects are created like this in a foreach:

coordinates.push( someIndex.toString() + ";" + someOtherIndex.toString() );

And I kept the stringify part.

So now when I POST the data to my controller, I output the value with System.out.println(coordinates) and the output looks weird.

%5B%220%3B8%22%5D=

for this object in the Javascript console : ["0;8"].

So my questions :

1. Is this a good approach?
2. Is it possible to deserialize a JSON array into some java types? Such as List<Coordinate> ? ( I’ve tried using this type instead of String in my controller, but it would give me an error 415 - Unsupported media type)
3. If I’m using the String approach, is there a way to translate that gibberish into something I want?

Answer 1

You get %5B%220%3B8%22%5D= on server side, cause jQuery by default serializes data to query string.

You need to set the content type of the request to application/json using contentType jQuery option.

Then you’ll probably want to take a look at some implementation of GsonHttpMessageConverter for simpler RequestBody conversion. Here is one and it looks like there’s one in spring for android so maybe you can use that.