循序漸進學.Net Core Web Api開發系列【5】:檔案上傳
系列目錄
一、概述
本篇介紹通過.NET core WebApi實現檔案上傳。
二、Controller端程式碼
直接上程式碼:
[Route("api/files")] [Produces("application/json")] public class FileController : Controller { private readonly IHostingEnvironment _hostingEnvironment; public FileController(IHostingEnvironment hostingEnvironment) { _hostingEnvironment= hostingEnvironment; } [HttpPost("iform")] public ResultObject UploadIForm(List<IFormFile> files) { List<String> filenames = new List<string>(); foreach (var file in files) { var fileName = file.FileName; Console.WriteLine(fileName); fileName= $"/UploadFile/{fileName}"; filenames.Add(fileName); fileName = _hostingEnvironment.WebRootPath + fileName; using (FileStream fs = System.IO.File.Create(fileName)) { file.CopyTo(fs); fs.Flush(); } }return new ResultObject { state = "Success", resultObject = filenames }; }
為了同時返回上傳的檔名和操作狀態,我們定義了一個ResultObject的類來返回資訊。
public class ResultObject { public String state { get; set; } public Object resultObject { get; set; } }
返回上傳的檔名稱列表的目的是因為後臺可能會給檔案重新命名,以避免衝突,新的檔名稱需要讓前臺知道。
後臺的files是通過傳入的引數獲得的,還有其他兩種方法可以獲取到檔案,效果一樣:
[HttpPost] public ResultObject UploadAjax() { var files = Request.Form.Files; ... }
或:
public ResultObject UploadForm(IFormCollection form) { var files = form.Files; ... }
除了獲取到files的方式不同,其他操作完全一致。
三、前端程式碼
<!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <title></title> <script src="lib/jquery/dist/jquery.min.js"></script> <script src="lib/jquery-form/dist/jquery.form.min.js"></script> <script type="text/javascript"> function AjaxFormDataUploadfile() { var fileUpload = $("#files").get(0); var files = fileUpload.files; var data = new FormData();
for (var i = 0; i < files.length; i++) { data.append("files", files[i]); } $.ajax({ type: "POST", url: "/api/files/iform", contentType: false, processData: false, data: data, success: function (message) { alert("success"); }, error: function () { alert("上傳檔案出現錯誤!"); } }); } </script> </head> <body> <form id="myform" method="post" action="/api/files/iform" enctype="multipart/form-data"> <input type="file" id="files" name="files" multiple /> <br /><br /> <input id="formupload" type="button" value="Form Data Upload" onclick="AjaxFormDataUploadfile();" /><br /><br /> </form> </body> </html>
兩個注意點:
1、form要提供enctype="multipart/form-data" 屬性
2、如果要上傳多個檔案,檔案表單需要提供multiple屬性
這裡我們通過FormData物件的append操作來構建提交的資料,根據我上一篇部落格提到的,這裡提交資料還有其他兩個辦法:
function formuploadfile() { $("#myform").ajaxSubmit(); }
或者:
function Ajaxuploadfile() { var formdata = new FormData(document.getElementById("myform")); $.ajax({ type: "POST", url: "/api/files/iform", contentType: false, processData: false, data: formdata, success: function (result) { alert("success"); $.each(result.resultObject, function (i, filename) { alert(filename); }); }, error: function () { alert("上傳檔案出現錯誤!"); } }); }
具體選擇哪種方式,要看前端的需求,個人認為 var formdata = new FormData(document.getElementById("myform")); 比較方便。
四、上傳大檔案
上傳大檔案和上傳小檔案程式碼是一樣的,關鍵是上傳大檔案時間太長,需要前端提供進度報告,不然使用者體驗太差。
解決的方案是利用ajax的HXR物件。
<!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <title></title> <script src="lib/jquery/dist/jquery.min.js"></script> <script src="lib/jquery-form/dist/jquery.form.min.js"></script> <script type="text/javascript"> function AjaxuploadfileWithprogress() { var formdata = new FormData(document.getElementById("myform")); $.ajax({ type: "POST", url: "/api/files/iform", contentType: false, processData: false, data: formdata, success: function (result) { alert("success"); $.each(result.resultObject, function (i, filename) { alert(filename); }); }, error: function () { alert("上傳檔案出現錯誤!"); }, xhr: function () { var xhr = $.ajaxSettings.xhr(); if (onprogress && xhr.upload) { xhr.upload.addEventListener("progress", onprogress, false); return xhr; } } }); } function onprogress(evt) { var loaded = evt.loaded; //已經上傳大小 var tot = evt.total; //附件總大小 var per = Math.floor(100 * loaded / tot); //百分比 $("#son").html(per + "%"); $("#son").css("width", per + "%"); } </script> <style type="text/css"> #parent { width: 550px; height: 10px; border: 2px solid #09F; } #son { width: 0; height: 100%; background-color: #09F; text-align: center; line-height: 10px; font-size: 20px; font-weight: bold; } </style> </head> <body> <form id="myform" method="post" action="/api/files/iform" enctype="multipart/form-data"> <div> <div> <br /> <p>表單多個上傳檔案:</p><br /> <input type="file" id="files" name="files" multiple /> <br /><br /> <input id="formuploadprogress" type="button" value="Ajax Upload Progress" onclick="AjaxuploadfileWithprogress();" /><br /><br /> <div id="parent"> <div id="son"></div> </div> </div> </div> </form> </body> </html>
此時,可以看到上傳進度條了,可以選擇一個大檔案測試一下。或者把瀏覽器的傳輸速度調低也可以進行除錯。
五、為Swagger提供檔案上傳除錯功能支援
目前swagger是不支援List<IFormFile>型別的,為了方便除錯,我們為swagger提供該型別的支撐。
新增類:
public class SwaggerFileUploadListFilter : IOperationFilter { public void Apply(Operation operation, OperationFilterContext context) { if (!context.ApiDescription.HttpMethod.Equals("POST", StringComparison.OrdinalIgnoreCase) && !context.ApiDescription.HttpMethod.Equals("PUT", StringComparison.OrdinalIgnoreCase)) { return; } var fileParameters = context.ApiDescription.ActionDescriptor.Parameters.Where(n => n.ParameterType == typeof(List<IFormFile>)).ToList(); if (fileParameters.Count < 0) { return; } operation.Consumes.Add("multipart/form-data");
foreach (var fileParameter in fileParameters) { var parameter = operation.Parameters.Single(n => n.Name == fileParameter.Name); operation.Parameters.Remove(parameter); NonBodyParameter p = new NonBodyParameter { Name = parameter.Name, In = "formData", Description = parameter.Description, Required = parameter.Required, Type = "file" }; operation.Parameters.Add(p); } } }
在Startup類的ConfigureServices方法裡註冊該過濾器:
public void ConfigureServices(IServiceCollection services) { services.AddMvc(); services.AddCors(); services.AddSwaggerGen(option => { option.SwaggerDoc("v1", new Info { Version = "v1", Title = "SaleService介面文件", Description = "RESTful API for SaleService.", TermsOfService = "None", Contact = new Contact { Name = "seabluescn", Email = "[email protected]", Url = "" } }); option.OperationFilter<SwaggerFileUploadListFilter>(); //Set the comments path for the swagger json and ui. var basePath = PlatformServices.Default.Application.ApplicationBasePath; var xmlPath = Path.Combine(basePath, "SaleService.xml"); option.IncludeXmlComments(xmlPath); }); }
此時可以通過swagger選擇檔案了
但有個缺點是隻能上傳一個檔案,如何實現可以選擇多個檔案還不會搞。