Question

在我的应用中，我希望能够将文件直接从浏览器上传到我的AWS S3存储桶。我的后端是rails，但我想避免额外跳到我的服务器，并避免使用像paperclip，carrierwave，carrierwave_direct等宝石来保持简单。我大概是从heroku跟踪这个tutorial。

我正在使用aws-sdk gem和jquery.fileupload.js lib。

问题在于，当我尝试上传时，我从AWS返回了400个错误请求。

我不认为这是一个CORS问题。我在我的存储桶上配置了CORS，我可以看到一个成功的OPTIONS请求，然后是文件上传的POST请求，它返回400错误请求。

以下是复制问题的简化演示。

这是控制器动作。它生成一个AWS :: S3 :: PresignedPost对象，因此视图可以使用它将文件直接发布到S3。

  def new
    Aws.config.update({
      region: 'us-east-1',
      credentials: Aws::Credentials.new('[FILTERED]', '[FILTERED]'),
    })
    s3 = Aws::S3::Resource.new
    bucket = s3.bucket('mybucket')
    @presigned_post = bucket.presigned_post(key: "attachments/#{SecureRandom.uuid}/${filename}")
    @thing = Thing.new
  end

这是由上面呈现的视图new.html.erb，上传表单和用于处理上传的javascript。

<div class='container'>
  <%= form_for(@thing, html: { class: 'direct_upload' }) do |f| %>
    <%= f.label 'Thing' %>
    <%= f.file_field :attachment_url %>
    <%= f.submit %>
  <% end %>
</div>

<script type="text/javascript">
  $(function() {
    var $form = $('form.direct_upload'),
      upload_url = '<%= escape_javascript(@presigned_post.url.to_s) %>',
      upload_form_data = '<%= escape_javascript(@presigned_post.fields.to_json.html_safe) %>';

    console.log('URL: ', upload_url);
    console.log('Form data: ', upload_form_data);

    if ($form.length) {
      $form.find('input[type=file]').each(function(index, input) {
        var $file_field = $(input);

        $file_field.fileupload({
          fileInput: $file_field,
          url: upload_url,
          type: 'POST',
          autoUpload: false,
          formData: upload_form_data,
          paramName: 'file',
          dataType: 'XML',

          add: function(e, data) {
            console.log('add callback fired.');
            $form.submit(function(e) {
              e.preventDefault();
              console.log('form submitted.');
              data.submit();
            });
          },
          start: function(e) {
            console.log('start callback fired');
          },
          done: function(e, data) {
            console.log('done callback fired');
          },
          fail: function(e, data) {
            console.log('fail callback fired');
            console.log(e);
            console.log(data);
          }
        });
      });
    }
  });
</script>

这是从S3回来的回复：

<Error>
  <Code>InvalidArgument</Code>
  <Message>Bucket POST must contain a field named 'key'.  If it is specified, please check the order of the fields.</Message>
  <ArgumentName>key</ArgumentName>
  <ArgumentValue></ArgumentValue>
  <RequestId>[filtered]</RequestId>
  <HostId>[filtered]</HostId>
</Error>

当页面加载时，您可以在javascript控制台中看到预期的输出：

URL:  https://mybucket.s3.amazonaws.com/
Form data:  {"key":"attachments/d6313635-9735-4b84-9985-f9f62a036de8/${filename}","policy":"[FILTERED]","x-amz-credential":"[FILTERED]/us-east-1/s3/aws4_request","x-amz-algorithm":"AWS4-HMAC-SHA256","x-amz-date":"20150809T134239Z","x-amz-signature":"[FILTERED]"}

如您所见，有一个关键字段。

将文件添加到文件输入字段时，add回调会触发并绑定表单的提交操作，如预期的那样。提交表单后，请求将转到S3，但然后fail回调将触发，因为返回了400。

这question可能描述了问题所在，但我无法根据提供的信息解决问题。

以下是从Chrome开发者工具中复制的请求/回复信息。

Remote Address:54.231.17.17:443
Request URL:https://mybucket.s3.amazonaws.com/
Request Method:POST
Status Code:400 Bad Request

Response Headers
Access-Control-Allow-Methods:GET, POST, PUT
Access-Control-Allow-Origin:*
Connection:close
Content-Type:application/xml
Date:Sun, 09 Aug 2015 12:29:57 GMT
Server:AmazonS3
Transfer-Encoding:chunked
Vary:Origin, Access-Control-Request-Headers, Access-Control-Request-Method
x-amz-id-2:ymrt0MUlhf3bKqVWj+O5jhaUPXNEXy9HQh9PABmqzDkkb4Ods3Hy1LA++8G/Svri3LcOktpnGeE=
x-amz-request-id:545E755033D285F2

Request Headers
Accept:application/xml, text/xml, */*; q=0.01
Accept-Encoding:gzip, deflate
Accept-Language:en-US,en;q=0.8
Connection:keep-alive
Content-Length:331
Content-Type:multipart/form-data; boundary=----WebKitFormBoundary9vtTme67oAg1OMyL
Host:braidio.s3.amazonaws.com
Origin:http://localhost:3000
Referer:http://localhost:3000/things/new
User-Agent:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/44.0.2403.125 Safari/537.36

Request Payload
------WebKitFormBoundary9vtTme67oAg1OMyL
Content-Disposition: form-data; name="file"; filename="my_text.txt"
Content-Type: text/plain


------WebKitFormBoundary9vtTme67oAg1OMyL--

如您所见，请求有效负载仅包含文件，而不包含密钥。可能是文件需要在post请求中的所有其他字段之后，这就是为什么S3没有看到关键字段，正如answer中所建议的那样。

一些相关的宝石：

* jquery-rails (4.0.4)
* rails (4.2.3)
* aws-sdk (2.1.13)
* aws-sdk-core (2.1.13)
* aws-sdk-resources (2.1.13)

还使用jquery.fileupload.js 5.42.3

我不确定如何使这个工作。

提前致谢！

Answer 1

我找到了解决方案。

我在前端捕获的后端生成的表单数据：

upload_form_data = '<%= escape_javascript(@presigned_post.fields.to_json.html_safe) %>'

必须将

从JSON字符串转换为JavaScript对象：

upload_form_data_obj = JSON.parse(upload_form_data);

显然，$.fileupload函数需要formData的对象，而不是字符串。

随着更改的到位，所需的表单数据将包含在POST到S3中并且成功。

以下是有效的javascript代码：

$(function() {
var $form = $('form.direct_upload'),
  upload_url,
  upload_form_data,
  upload_form_data_obj;

if ($form.length) {
  upload_url = '<%= escape_javascript(@presigned_post.url) %>'
  upload_form_data = '<%= escape_javascript(@presigned_post.fields.to_json.html_safe) %>';
  upload_form_data_obj = JSON.parse(upload_form_data);

  console.log('URL: ', upload_url);
  console.log('Form data: ', upload_form_data_obj);

  $form.find('input[type=file]').each(function(index, input) {
    var $file_field = $(input);
    $file_field.fileupload({
      fileInput: $file_field,
      url: upload_url,
      type: 'POST',
      autoUpload: false,
      formData: upload_form_data_obj, // needed to be an object, not a string
      paramName: 'file',
      dataType: 'JSON',

      add: function(e, data) {
        console.log('add callback fired.');
        $form.submit(function(e) {
          e.preventDefault();

          console.log('form submitted.');
          console.log(data);
          data.submit();
        });
      },
      start: function(e) {
        console.log('start callback fired');
      },
      done: function(e, data) {
        console.log('done callback fired');
      },
      fail: function(e, data) {
        console.log('fail callback fired');
        console.log(e);
        console.log(data);
      }
    });
  });
}
});

使用jquery.fileupload

1 个答案: