对一些前端工程师来讲,使用javascript上传文件到Azure存储中可能是需要掌握的技能,希望这篇博客能给到帮助。
在开始前我们需要了解以下几点:
共享访问签名(Shared Access Signature(SAS)
共享访问签名
共享访问签名,是用于提供对Windows Azure Storage中的Container,Blob,Table以及Queue在特定时间范围内进行有限权限访问的URL。通常情况下,我们访问Azure存储都是以账户名和密码的方式来实现的,通过这种方式也给使用者包括增删改在内的最大的访问权限,但是在实际情况中,我们可能希望用户只有读的权限,同时我们也不希望将账户名和密码泄露出去,共享访问签名很好的解决了这类问题。我们在使用Javascript上传时就是通过共享访问签名的URL来进行的。
Azure 存储服务的跨域资源共享 (CORS) 支持
大概在2014年3月份的时候Azure已经支持CORS,经过测试目前中国版和国际版都已经支持,我们在使用Javascript上传的时候是将资源以PUT的方式上传到类似于http://***.blob.core.chinacloudapi.cn这样域名的地方,这就涉及到CORS的问题,在默认情况下Azure存储是禁用CORS的,所以我们需要使用版本 2013-08-15 或更高版本设置适当的服务属性,并向服务属性中添加 CORS 规则,如果我们没有启用CORS规则,我们可能会得到403错误,使用Fiddler工具会得到更详细的错误信息:”CORS not enabled or no matching rule found for this request”。
通过上面的描述,我们在开始编程前,我们需要SAS URL,还需要为我们的blob配置CORS规则,这些我们可以通过Azure SDK来实现,关于这部分我就不介绍了,详细请阅读:#SAS:http://www.windowsazure.cn/zh-cn/documentation/articles/storage-dotnet-shared-access-signature-part-2/
如果我们不太了解C#,我们可以借助Azure Storage Explorer来进行配置,下面我介绍下简单的配置:
1) 得到SAS URL
打开Azure Storage Explorer点击“Security”,选择SAS失效的时间,并选择赋予相应的权限,如上图高亮标注的部分。
2) 配置CORS规则
打开Azure Storage Explorer鼠标停留在”Blob Containers”,这时会出现CORS设置按钮,点击新增CORS规则,并如上图设置,关于具体的设置信息,请阅读:https://msdn.microsoft.com/zh-cn/library/azure/dn535601.aspx?f=255&MSPPError=-2147217396,图中的设置是我测试的字段,可作为参考。
下面是具体的代码
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
<!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>File Uploader</title> <script src="Scripts/jquery-1.10.2.min.js"></script> <script> var maxBlockSize = 256 * 1024;//Each file will be split in 256 KB. var numberOfBlocks = 1; var selectedFile = null; var currentFilePointer = 0; var totalBytesRemaining = 0; var blockIds = new Array(); var blockIdPrefix = "block-"; var submitUri = null; var bytesUploaded = 0; $(document).ready(function () { $("#output").hide(); $("#file").bind('change', handleFileSelect); if (window.File && window.FileReader && window.FileList && window.Blob) { // Great success! All the File APIs are supported. } else { alert('The File APIs are not fully supported in this browser.'); } }); //Read the file and find out how many blocks we would need to split it. function handleFileSelect(e) { maxBlockSize = 256 * 1024; currentFilePointer = 0; totalBytesRemaining = 0; var files = e.target.files; selectedFile = files[0]; $("#output").show(); $("#fileName").text(selectedFile.name); $("#fileSize").text(selectedFile.size); $("#fileType").text(selectedFile.type); var fileSize = selectedFile.size; if (fileSize < maxBlockSize) { maxBlockSize = fileSize; console.log("max block size = " + maxBlockSize); } totalBytesRemaining = fileSize; if (fileSize % maxBlockSize == 0) { numberOfBlocks = fileSize / maxBlockSize; } else { numberOfBlocks = parseInt(fileSize / maxBlockSize, 10) + 1; } console.log("total blocks = " + numberOfBlocks); var baseUrl = $("#sasUrl").val(); var indexOfQueryStart = baseUrl.indexOf("?"); submitUri = baseUrl.substring(0, indexOfQueryStart) + '/' + selectedFile.name + baseUrl.substring(indexOfQueryStart); console.log(submitUri); } var reader = new FileReader(); reader.onloadend = function (evt) { if (evt.target.readyState == FileReader.DONE) { // DONE == 2 var uri = submitUri + '&comp=block&blockid=' + blockIds[blockIds.length - 1]; var requestData = new Uint8Array(evt.target.result); $.ajax({ url: uri, type: "PUT", data: requestData, processData: false, beforeSend: function (xhr) { xhr.setRequestHeader('x-ms-blob-type', 'BlockBlob'); xhr.setRequestHeader('Content-Length', requestData.length); }, success: function (data, status) { console.log(data); console.log(status); bytesUploaded += requestData.length; var percentComplete = ((parseFloat(bytesUploaded) / parseFloat(selectedFile.size)) * 100).toFixed(2); $("#fileUploadProgress").text(percentComplete + " %"); uploadFileInBlocks(); }, error: function (xhr, desc, err) { console.log(desc); console.log(err); } }); } }; function uploadFileInBlocks() { if (totalBytesRemaining > 0) { console.log("current file pointer = " + currentFilePointer + " bytes read = " + maxBlockSize); var fileContent = selectedFile.slice(currentFilePointer, currentFilePointer + maxBlockSize); var blockId = blockIdPrefix + pad(blockIds.length, 6); console.log("block id = " + blockId); blockIds.push(btoa(blockId)); reader.readAsArrayBuffer(fileContent); currentFilePointer += maxBlockSize; totalBytesRemaining -= maxBlockSize; if (totalBytesRemaining < maxBlockSize) { maxBlockSize = totalBytesRemaining; } } else { commitBlockList(); } } function commitBlockList() { var uri = submitUri + '&comp=blocklist'; console.log(uri); var requestBody = '<?xml version="1.0" encoding="utf-8"?><BlockList>'; for (var i = 0; i < blockIds.length; i++) { requestBody += '<Latest>' + blockIds[i] + '</Latest>'; } requestBody += '</BlockList>'; console.log(requestBody); $.ajax({ url: uri, type: "PUT", data: requestBody, beforeSend: function (xhr) { xhr.setRequestHeader('x-ms-blob-content-type', selectedFile.type); xhr.setRequestHeader('Content-Length', requestBody.length); }, success: function (data, status) { console.log(data); console.log(status); }, error: function (xhr, desc, err) { console.log(desc); console.log(err); } }); } function pad(number, length) { var str = '' + number; while (str.length < length) { str = '0' + str; } return str; } </script> </head> <body> <form> <div style="margin-left: 20px;"> <h1>File Uploader</h1> <p> <strong>SAS URI</strong>: <br /> <span class="input-control text"> <input type="text" id="sasUrl" style="width: 50%" value="" /> </span> </p> <p> <strong>File To Upload</strong>: <br /> <span class="input-control text"> <input type="file" id="file" name="file" style="width: 50%" /> </span> </p> <div id="output"> <strong>File Properties:</strong> <br /> <p> Name: <span id="fileName"></span> </p> <p> File Size: <span id="fileSize"></span> bytes. </p> <p> File Type: <span id="fileType"></span> </p> <p> <input type="button" value="Upload File" onclick="uploadFileInBlocks()" /> </p> <p> <strong>Progress</strong>: <span id="fileUploadProgress">0.00 %</span> </p> </div> </div> <div> </div> </form> </body> </html>
代码主要是将文件切成小块,并使用Put blob操作上传相应的小块,最后使用Put blob list将上传的各个小块组成资源文件。