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r - R：从 Companies House API 获取 pdf 文档

问题描述

我正在尝试使用 R 从 API 中获取文档。感谢本文中对流程的说明。我已经部分成功地执行了上述步骤，但最后一步仍然无法访问文档的内容：

  1. 找到您感兴趣的文件归档（例如，为公司提出归档历史请求1）。解析“links”字段中文档链接的响应：{“document_metadata”：“link URI fragment here”}。

没问题：

library(httr)
library(jsonlite)
library(openssl)

### retrieving filing history ####
company_num = 'FC013908'
key = 'my_key'
fh_path = paste0('/company/', str_to_upper(company_num), "/filing-history")
fh_url <- modify_url("https://api.companieshouse.gov.uk/", path = fh_path)
fh_test <- GET(fh_url, authenticate(key, "")) #status_code = 200
fh_parsed <- jsonlite::fromJSON(content(fh_test, "text",encoding = "utf-8"), flatten = TRUE)
docs <- fh_parsed$items

完毕。

2 对于给定的文档，通过 CH Document API3 请求文档元数据。解析响应以获取可用的文档（mime）类型以及指向实际文档数据（文档 URI 片段）的链接。

这里没有问题：

md_meta_url = docs$links.document_metadata[1]  
key_pass <- paste0(key,":")
decoded_auth <- paste0('Basic ', base64_encode(key_pass))

md_test <- GET(md_meta_url,
               add_headers(Authorization = decoded_auth)
               )
md_test #status_code = 200!
md_parsed <- jsonlite::fromJSON(content(md_test, "text",encoding = "utf-8"), flatten = TRUE)

这样我可以获取内容 URL：

cont_url = md_parsed$links$document

请求实际的文档9，指定 mime 类型（例如“application/pdf”）。

我在不遵循重定向的情况下执行此操作，并且正如预期的那样，我得到了带有 location标题的 302 状态代码：

accept = 'application/pdf'
cont_test <- GET(cont_url, 
           add_headers(Authorization = decoded_auth,
                       Accept = accept),
           config(followlocation = FALSE)
)

final_url <- cont_test$headers$location

> final_url
[1] "https://s3-eu-west-1.amazonaws.com/document-api-images-prod/docs/LjBouRHeXXpIYAvqYIPWL06iXaliPz6Pucp1OXCXQhI/application-pdf?AWSAccessKeyId=ASIAJX7TVURFXZTY5DNQ&Expires=1529483765&Signature=uUQx6RTW7XBLqx4L6pYr5tOUySg%3D&x-amz-security-token=FQoDYXdzEP%2F%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaDGxe7meYGe3OYhNwcSK3AwcVYJUXaUMf19oVO9s4qNPWN8AHjNNd5rrZhgE9YTkF1OmzyZSL5xHbls664kDP%2Bxd7dz9PIU5O1D%2BVxoDyoYcFiS6acDnO28KpfFE56lUZNfedf1jys%2FP0SJ8f%2F50Cbn93bfOlm0MZA9%2BQ2DYQvPfkWSvrDjMyCXHbu57gpZHjQKPNRTgzGXzUUCvFwREytGMM4eThhn4Glvvx%2FA8IiLbnsvgmEKw9iAj7KWIenhoJq3cTRytUpVeipLnQoBVLau8dFYkKdAHZaYM2Tlx0z6ObRb%2BGdm7W7eOVA1bFXuUXmUmnAHruDIwwLlgOVN2IJ9CxmJU22lY8jrEm%2BUivtrdp2oofn32PryBEJ8jJOg9cIpLbBBx%2FeOkng9zJwnZbute7Nmh%2BnaY2btsId6JjraFNsTvR%2B1qEZX9uuznUdJdqgVfTMj2gGrAmntwk0JAkILlvamzjWC%2F9vAqK7Xvt8aC6hlIMB2vdzTCU9Jf%2FrIMTClTJkk0BzBuvJ86t1l%2BXb4rF5Pab%2FegFpJ6nvZKqde%2F77wMMiTyG35EndmYx4AWqTIh9EofYwKZa9uciNvRT0E2%2BYnT5jZMo%2BdWn2QU%3D"

但是，当我尝试

再次向 Amazon 请求此 URI，并再次传递您想要的内容类型。我收到 400 错误：

 final_test <- GET(final_url, 
                 add_headers(Authorization = decoded_auth,
                             Accept = accept
                             ))

> final_test
Response [https://s3-eu-west-1.amazonaws.com/document-api-images-prod/docs/LjBouRHeXXpIYAvqYIPWL06iXaliPz6Pucp1OXCXQhI/application-pdf?AWSAccessKeyId=ASIAJX7TVURFXZTY5DNQ&Expires=1529483765&Signature=uUQx6RTW7XBLqx4L6pYr5tOUySg%3D&x-amz-security-token=FQoDYXdzEP%2F%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaDGxe7meYGe3OYhNwcSK3AwcVYJUXaUMf19oVO9s4qNPWN8AHjNNd5rrZhgE9YTkF1OmzyZSL5xHbls664kDP%2Bxd7dz9PIU5O1D%2BVxoDyoYcFiS6acDnO28KpfFE56lUZNfedf1jys%2FP0SJ8f%2F50Cbn93bfOlm0MZA9%2BQ2DYQvPfkWSvrDjMyCXHbu57gpZHjQKPNRTgzGXzUUCvFwREytGMM4eThhn4Glvvx%2FA8IiLbnsvgmEKw9iAj7KWIenhoJq3cTRytUpVeipLnQoBVLau8dFYkKdAHZaYM2Tlx0z6ObRb%2BGdm7W7eOVA1bFXuUXmUmnAHruDIwwLlgOVN2IJ9CxmJU22lY8jrEm%2BUivtrdp2oofn32PryBEJ8jJOg9cIpLbBBx%2FeOkng9zJwnZbute7Nmh%2BnaY2btsId6JjraFNsTvR%2B1qEZX9uuznUdJdqgVfTMj2gGrAmntwk0JAkILlvamzjWC%2F9vAqK7Xvt8aC6hlIMB2vdzTCU9Jf%2FrIMTClTJkk0BzBuvJ86t1l%2BXb4rF5Pab%2FegFpJ6nvZKqde%2F77wMMiTyG35EndmYx4AWqTIh9EofYwKZa9uciNvRT0E2%2BYnT5jZMo%2BdWn2QU%3D]
  Date: 2018-06-20 08:37
  Status: 400
  Content-Type: application/xml
  Size: 523 B
<BINARY BODY>

不用说，执行

browseURL(final_test$url)

返回Access Denied错误。我怀疑这可能与类似于此处描述的 Amazon 授权问题有关。任何想法如何解决这个最后的障碍？

谢谢！

标签： rapihttrrequest-headers

解决方案

答案是@voracityemail在回答我关于 Companies House Developers Hub的问题时提供的。基本上，最终调用不需要 Authorization 标头，因此如果您运行以下代码final_test：

final_test <- GET(final_url, add_headers(Accept = accept))

它将返回200代码

> final_test
Response [https://s3-eu-west-1.amazonaws.com/document-api-images-prod/docs/Rl1qKy2kNqdskHUIsqU9u0bGzH2goTfJfnCrNg4S0lg/application-pdf?AWSAccessKeyId=ASIAJMG7NTZHYC4NH3MA&Expires=1530093768&Signature=EteMSmwXS%2FqqdOFRmYY%2Fgf187Aw%3D&x-amz-security-token=FQoDYXdzELf%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEaDOMKrcNPR6jb5bnzGSK3A1yzaoVZWhgAeXYCN9WJnxx8b%2BTKCEEZyZui3aR5j0WoNWIQhW9GIQ8R4xTGVkRjwQIhzgDp%2BRCfXGQ0CfPCOfseaQri5m%2BWTEWBgjfToL7%2FMdcC1IINMTFRrih1APE%2FmmTcQaW7SvyZWv3Q4bVQB%2FtOsiX5k8rWVsT7%2FecfQmnJMljcKF0%2F3vDRTtLRURTCtrdegfnIFrSqXkelLxVVypKY9UeURBgxAgngOgoP7YhYt3wD%2BEz5rBdNfMvF1Zuv91hLGDyBaKuV4fRKMRXlymDHCwNgNZl3JeyuAmnX8pexK6PJzH7MerM8QX8LoPfge1yutvqEj0%2FjRSYEShOWUebecQ2tJqWIEOZly0Ji8fc%2BMtFDO1FWZBrMl6lXgkwTMpELnTH5%2BP4ULMdFfEz30bWSnAuTGXcAxsoFWsFTIE2uO35zgkOsAUT2un4UNGnL2S8XexWbgwq%2B%2Bhtxo9ruP9WA8mTpjBkup2Qe5EpvUiNwGX9APjThi7QFTllVWWvpKgzKTSBh%2Btua9xK8RgiNAYDgEa5k%2BH%2FmWIP56WglBE6r3HGsXgbi%2Bff8Rg8z2lVFLo8f9hVv%2BCYoptXM2QU%3D]
  Date: 2018-06-27 10:02
  Status: 200
  Content-Type: application/pdf
  Size: 21.7 kB
<BINARY BODY>

接着

browseURL(final_test$url)

将在浏览器中打开指定的文档。胜利！

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