File upload error: current request is not a multipart request

Want to upload a file ,spring boot coordination Ajax To carry out . But report a mistake ：Current request is not a multipart request

This is a screenshot of the error ：

This kind of mistake happened at that time , I was shocked , I thought I found many ways to solve .

There are the following ways , Of course, these did not solve my problem , But part of it works , Just list it first ：

1. Add information at the head of the page ：

<meta http-equiv="Content-Type" content="multipart/form-data; charset=utf-8" />

         This method Unresolved problem ！

2. stay form Form add attribute ：enctype

<form method="post" enctype="multipart/form-data">
    <input type="file" name="file" />
</form>

This method Unresolved problem ！

3. Back end ：@RequestParam MultipartFile file Change it to @RequestPart MultipartFile file

This method Unresolved problem ！

There are individual methods ... Neither.

Here's the solution , Before me ajax Code ：

$('#upload-ok').click(function () {
        var form = document.getElementById("upload-form");
        var file = new FormData(form);
        $.ajax({
            url: "/addFile",
            type: "POST",
            processData:false,
            contentType:false,
            data:{
                "file":file
            },
            success: function (date) {
                xxxxxx
            },
            error: function (date) {
                xxxxxx
            }
        })
    })

Correct code ：

$('#upload-ok').click(function () {
        var form = document.getElementById("upload-form");
        var file = new FormData(form);
        $.ajax({
            url: "/addFile",
            type: "POST",
            processData:false,
            contentType:false,
            // Important part ,data It's the whole form , Don't wrap it in braces ; No custom variable name 
            data:file,
            success: function (date) {
                xxxxxx
            },
            error: function (date) {
                xxxxxx
            }
        })
    })

That's it , solve ！！！