即使操作成功，Ajax post 也返回 404

Question

I am making an ajax post call to my backing spring controller. I see that the data is saved successfully in the db as a result of post but on the browser console I see that POST throws 404. Also, once the call returns from the spring controller, error function of ajax call is envoked.

Can someone please tell me what I am missing here.

$('#submitMessage').submit(function(e){
    e.preventDefault();
    var formData = {};
    var msg=document.getElementById('iconLeft4-1');
    var url = "${context}/wasadmin/support/ajax/send";
    formData['comment']=msg.value;
    formData['commented_by']='1';
    formData['supportId']='1';
    formData['userType']='O';
    console.log(JSON.stringify(formData));
    $.ajax({
        type : 'POST',
        contentType: "application/json",
        url : url,
        dataType : 'json',
        data:JSON.stringify(formData),
        success:function(data,status,xhr){
            console.log('saved successfully');

            },
        error:function(data,status,xhr){
            console.log('error occured');  // This gets  printed
            }

        });

Controller

@PostMapping(value="/ajax/send")
    public void sendSupportMessage(@RequestBody SupportConversationDTO supportConversationDTO) {
        supportConversationService.save(supportConversationDTO);
        return;
    }

Answer 1

In your ajax request you are using dataType:'json' , jQuery's Ajax-Related Methods Description Says

// The type of data we expect back
    dataType : "json",

But from your controller, you are returning void!!!

You need to update your ajax request, remove dataType and update success:function

$.ajax({
    type : 'POST',
    contentType: "application/json",
    url : url,
    data:JSON.stringify(formData),
    success:function(data) {
        console.log('saved successfully');
    },
    error:function(data,status,xhr) {
        console.log('error occured');
    }
});

Then change your controller code, return something from it and add @ResponseBody

@PostMapping(value="/ajax/send")
@ResponseBody
public String sendSupportMessage(@RequestBody SupportConversationDTO supportConversationDTO) {
    supportConversationService.save(supportConversationDTO);
    return "success";
}