Getting 400 bad request error in Jquery Ajax POST

I am trying to send an Ajax POST request using Jquery but I am having 400 bad request error.

Here is my code:

$.ajax({
  type: 'POST',
  url: "http://localhost:8080/project/server/rest/subjects",
  data: {
    "subject:title":"Test Name",
    "subject:description":"Creating test subject to check POST method API",
    "sub:tags": ["facebook:work", "facebook:likes"],
    "sampleSize" : 10,
    "values": ["science", "machine-learning"]
  },
  error: function(e) {
    console.log(e);
  }
});

It Says: Can not build resource from request. What am I missing ?

Finally, I got the mistake and the reason was I need to stringify the JSON data I was sending. I have to set the content type and datatype in XHR object. So the correct version is here:

$.ajax({
  type: 'POST',
  url: "http://localhost:8080/project/server/rest/subjects",
  data: JSON.stringify({
    "subject:title":"Test Name",
    "subject:description":"Creating test subject to check POST method API",
    "sub:tags": ["facebook:work", "facebook:likes"],
    "sampleSize" : 10,
    "values": ["science", "machine-learning"]
  }),
  error: function(e) {
    console.log(e);
  },
  dataType: "json",
  contentType: "application/json"
});

May be it will help someone else.

Yes. You need to stringify the JSON data orlse 400 bad request error occurs as it cannot identify the data.

400 Bad Request

> Bad Request. Your browser sent a request that this server could not > understand.

Plus you need to add content type and datatype as well. If not you will encounter 415 error which says Unsupported Media Type.

> 415 Unsupported Media Type

Try this.

var newData =   {
				  "subject:title":"Test Name",
				  "subject:description":"Creating test subject to check POST method API",
                  "sub:tags": ["facebook:work", "facebook:likes"],
                  "sampleSize" : 10,
                  "values": ["science", "machine-learning"]
				  };

var dataJson = JSON.stringify(newData);

$.ajax({
  type: 'POST',
  url: "http://localhost:8080/project/server/rest/subjects",
  data: dataJson,
  error: function(e) {
    console.log(e);
  },
  dataType: "json",
  contentType: "application/json"
});

With this way you can modify the data you need with ease. It wont confuse you as it is defined outside the ajax block.

In case anyone else runs into this. I have a web site that was working fine on the desktop browser but I was getting 400 errors with Android devices.

It turned out to be the anti forgery token.

$.ajax({
        url: "/Cart/AddProduct/",
        data: {
            __RequestVerificationToken: $("[name='__RequestVerificationToken']").val(),
            productId: $(this).data("productcode")
        },

The problem was that the .Net controller wasn't set up correctly.

I needed to add the attributes to the controller:

    [AllowAnonymous]
    [IgnoreAntiforgeryToken]
    [DisableCors]
    [HttpPost]
    public async Task<JsonResult> AddProduct(int productId)
    {

The code needs review but for now at least I know what was causing it. 400 error not helpful at all.

The question is a bit old... but just in case somebody faces the error 400, it may also come from the need to post csrfToken as a parameter to the post request.

You have to get name and value from craft in your template :

<script type="text/javascript">
    window.csrfTokenName = "{{ craft.config.csrfTokenName|e('js') }}";
    window.csrfTokenValue = "{{ craft.request.csrfToken|e('js') }}";
</script>

and pass them in your request

data: window.csrfTokenName+"="+window.csrfTokenValue

You need to build query from "data" object using the following function

function buildQuery(obj) {
		var Result= '';
		if(typeof(obj)== 'object') {
			jQuery.each(obj, function(key, value) {
				Result+= (Result) ? '&' : '';
				if(typeof(value)== 'object' && value.length) {
					for(var i=0; i<value.length; i++) {
						Result+= [key+'[]', encodeURIComponent(value[i])].join('=');
					}
				} else {
					Result+= [key, encodeURIComponent(value)].join('=');
				}
			});
		}
		return Result;
	}

and then proceed with

var data= {
"subject:title":"Test Name",
"subject:description":"Creating test subject to check POST method API",
"sub:tags": ["facebook:work, facebook:likes"],
"sampleSize" : 10,
"values": ["science", "machine-learning"]
}

$.ajax({
  type: 'POST',
  url: "http://localhost:8080/project/server/rest/subjects",
  data: buildQuery(data),
  error: function(e) {
    console.log(e);
  }
});