前端程式碼：

<form id="form_upload">
        <input id="upload_img_id" type="file" name="fileName"/>
        <button ng-click="uploadFile()" type="button">
        上傳
        </button>
</form>

angularjs程式碼

this.uploadFile = function(){
        //重點1：form_upload是form表單的id
        var
 
 formData = new FormData(document.getElementById("form_upload"));
        //重點2：upload_img_id是檔案input的id
        var file = document.getElementById("upload_img_id").files[0];
        //重點3：向formData中新增資料:
        formData.append("file",file);

        //下面是angularjs的程式碼，可以換成其他前端程式碼實現，重點是formData上傳
        return
 
 $http({
            method:'post',
            url:'/seller/fileload/uploadFile.do',
            data:formData,
            headers:{'Content-Type':undefined} ,// Content-Type : text/html  text/plain
            transformRequest:angular.identity
            //瀏覽器會幫我們把Content-Type 設定為 multipart/form-data.
        });
    }
 

端java程式碼（SpringBoot的），SpringBoot自帶檔案上傳，可以直接用

//重點4：@RequestParam("fileName")這個跟前端的input標籤的name一致
@RequestMapping(value = "uploadFile.do", method = RequestMethod.POST)
    @ResponseBody
    public String fileUpload(@RequestParam("fileName") MultipartFile file){
        System.out.println(file.getOriginalFilename()+">>>>>>>>>");
        if(file.isEmpty()){
            return "false";
        }
        String fileName = file.getOriginalFilename();//z.png
        int size = (int) file.getSize();
        //fileName=fileName.substring(fileName.lastIndexOf("\\")+1);

        String path = System.getProperty("user.dir");//   /Users/apple/Desktop/IDEAWORKSPACE/day2/shoppingmall2
        File dest = new File(path+"/target/classes/static/img" + "/" + fileName);
        if(!dest.getParentFile().exists()){ //判斷檔案父目錄是否存在
            dest.getParentFile().mkdir();
        }
        try {
            file.transferTo(dest); //儲存檔案
            return "{\"img_path\":\"http://localhost:8080/img/"+fileName+"\"}";
        } catch (IllegalStateException e) {
            e.printStackTrace();
            return "false";
        } catch (IOException e) {
            e.printStackTrace();
            return "false";
        }
    }