使用AngularJS从ASP.NET Web API方法下载文件

Question

在我的Angular JS项目中，我有一个<a>锚标记，单击该锚标记GET会对返回文件的WebAPI方法发出HTTP 请求。

现在，我希望在请求成功后将文件下载给用户。我怎么做？

锚标记：

<a href="#" ng-click="getthefile()">Download img</a>

AngularJS：

$scope.getthefile = function () {        
    $http({
        method: 'GET',
        cache: false,
        url: $scope.appPath + 'CourseRegConfirm/getfile',            
        headers: {
            'Content-Type': 'application/json; charset=utf-8'
        }
    }).success(function (data, status) {
        console.log(data); // Displays text data if the file is a text file, binary if it's an image            
        // What should I write here to download the file I receive from the WebAPI method?
    }).error(function (data, status) {
        // ...
    });
}

我的WebAPI方法：

[Authorize]
[Route("getfile")]
public HttpResponseMessage GetTestFile()
{
    HttpResponseMessage result = null;
    var localFilePath = HttpContext.Current.Server.MapPath("~/timetable.jpg");

    if (!File.Exists(localFilePath))
    {
        result = Request.CreateResponse(HttpStatusCode.Gone);
    }
    else
    {
        // Serve the file to the client
        result = Request.CreateResponse(HttpStatusCode.OK);
        result.Content = new StreamContent(new FileStream(localFilePath, FileMode.Open, FileAccess.Read));
        result.Content.Headers.ContentDisposition = new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment");
        result.Content.Headers.ContentDisposition.FileName = "SampleImg";                
    }

    return result;
}

Answer 1

使用ajax对下载二进制文件的支持不是很好，它仍在作为工作草案进行开发。

简单的下载方法：

您可以使用以下代码简单地让浏览器下载所请求的文件，并且所有浏览器都支持此功能，并且显然会触发WebApi请求。

$scope.downloadFile = function(downloadPath) { 
    window.open(downloadPath, '_blank', '');  
}

Ajax二进制下载方法：

使用ajax下载二进制文件可以在某些浏览器中完成，下面是一个可以在最新版本的Chrome，Internet
Explorer，FireFox和Safari中运行的实现。

它使用arraybuffer响应类型，然后将其转换为JavaScript blob，然后使用该saveBlob方法将其呈现为保存-
尽管当前仅在Internet Explorer中存在-或转换为由浏览器打开的Blob数据URL，从而触发如果支持在浏览器中查看MIME类型，则下载对话框。

Internet Explorer 11支持（已修复）

注意：Internet Explorer 11不喜欢使用msSaveBlob已别名的功能-也许是安全功能，但更可能是漏洞，因此使用var saveBlob = navigator.msSaveBlob||navigator.webkitSaveBlob...etc.确定可用的saveBlob支持会导致异常。因此，为什么下面的代码现在分别进行测试navigator.msSaveBlob。谢谢？微软

// Based on an implementation here: web.student.tuwien.ac.at/~e0427417/jsdownload.html
$scope.downloadFile = function(httpPath) {
    // Use an arraybuffer
    $http.get(httpPath, { responseType: 'arraybuffer' })
    .success( function(data, status, headers) {

        var octetStreamMime = 'application/octet-stream';
        var success = false;

        // Get the headers
        headers = headers();

        // Get the filename from the x-filename header or default to "download.bin"
        var filename = headers['x-filename'] || 'download.bin';

        // Determine the content type from the header or default to "application/octet-stream"
        var contentType = headers['content-type'] || octetStreamMime;

        try
        {
            // Try using msSaveBlob if supported
            console.log("Trying saveBlob method ...");
            var blob = new Blob([data], { type: contentType });
            if(navigator.msSaveBlob)
                navigator.msSaveBlob(blob, filename);
            else {
                // Try using other saveBlob implementations, if available
                var saveBlob = navigator.webkitSaveBlob || navigator.mozSaveBlob || navigator.saveBlob;
                if(saveBlob === undefined) throw "Not supported";
                saveBlob(blob, filename);
            }
            console.log("saveBlob succeeded");
            success = true;
        } catch(ex)
        {
            console.log("saveBlob method failed with the following exception:");
            console.log(ex);
        }

        if(!success)
        {
            // Get the blob url creator
            var urlCreator = window.URL || window.webkitURL || window.mozURL || window.msURL;
            if(urlCreator)
            {
                // Try to use a download link
                var link = document.createElement('a');
                if('download' in link)
                {
                    // Try to simulate a click
                    try
                    {
                        // Prepare a blob URL
                        console.log("Trying download link method with simulated click ...");
                        var blob = new Blob([data], { type: contentType });
                        var url = urlCreator.createObjectURL(blob);
                        link.setAttribute('href', url);

                        // Set the download attribute (Supported in Chrome 14+ / Firefox 20+)
                        link.setAttribute("download", filename);

                        // Simulate clicking the download link
                        var event = document.createEvent('MouseEvents');
                        event.initMouseEvent('click', true, true, window, 1, 0, 0, 0, 0, false, false, false, false, 0, null);
                        link.dispatchEvent(event);
                        console.log("Download link method with simulated click succeeded");
                        success = true;

                    } catch(ex) {
                        console.log("Download link method with simulated click failed with the following exception:");
                        console.log(ex);
                    }
                }

                if(!success)
                {
                    // Fallback to window.location method
                    try
                    {
                        // Prepare a blob URL
                        // Use application/octet-stream when using window.location to force download
                        console.log("Trying download link method with window.location ...");
                        var blob = new Blob([data], { type: octetStreamMime });
                        var url = urlCreator.createObjectURL(blob);
                        window.location = url;
                        console.log("Download link method with window.location succeeded");
                        success = true;
                    } catch(ex) {
                        console.log("Download link method with window.location failed with the following exception:");
                        console.log(ex);
                    }
                }

            }
        }

        if(!success)
        {
            // Fallback to window.open method
            console.log("No methods worked for saving the arraybuffer, using last resort window.open");
            window.open(httpPath, '_blank', '');
        }
    })
    .error(function(data, status) {
        console.log("Request failed with status: " + status);

        // Optionally write the error out to scope
        $scope.errorDetails = "Request failed with status: " + status;
    });
};

用法：

var downloadPath = "/files/instructions.pdf";
$scope.downloadFile(downloadPath);

笔记：

您应该修改WebApi方法以返回以下标头：

• 我已使用x-filename标题发送文件名。为了方便起见，这是一个自定义标头，但是您可以content-disposition使用正则表达式从标头中提取文件名。

• 您还应该content-type为响应设置mime标头，以便浏览器知道数据格式。

我希望这有帮助。