ruby - 如何通过 Net::HTTP::Get 下载二进制文件？

Question

我正在尝试使用以下 Ruby 脚本通过 HTTP 下载二进制文件。

#!/usr/bin/env ruby
require 'net/http'
require 'uri'

def http_download(resource, filename, debug = false)
  uri = URI.parse(resource)
  puts "Starting HTTP download for: #{uri}"
  http_object = Net::HTTP.new(uri.host, uri.port)
  http_object.use_ssl = true if uri.scheme == 'https'
  begin
    http_object.start do |http|
      request = Net::HTTP::Get.new uri.request_uri
      Net::HTTP.get_print(uri) if debug
      http.read_timeout = 500
      http.request request do |response|
        open filename, 'w' do |io|
          response.read_body do |chunk|
            io.write chunk
          end
        end
      end
    end
  rescue Exception => e
    puts "=> Exception: '#{e}'. Skipping download."
    return
  end
  puts "Stored download as #{filename}."
end

但是它下载的是 HTML 源代码而不是二进制文件。当我在浏览器中输入 URL 时，二进制文件被下载。这是脚本失败的 URL:

http://dcatlas.dcgis.dc.gov/catalog/download.asp?downloadID=2175&downloadTYPE=KML

我执行脚本如下

pry> require 'myscript'
pry> resource = "http://dcatlas.dcgis.dc.gov/catalog/download.asp?downloadID=2175&downloadTYPE=KML"
pry> http_download(resource,"StreetTreePt.KML", true)

如何下​​载二进制文件？

重定向实验

我找到了这个 redirection check这看起来很合理。当我集成到响应 block 中时，它失败并出现以下错误:

Exception: 'undefined method `host' for "save_download.asp?filename=StreetTreePt.KML":String'. Skipping download.

在上面贴出的“原始”函数中没有发生异常。

Answer 1

Net::HTTP 的文档显示 how to handle redirects :

Following Redirection

Each Net::HTTPResponse object belongs to a class for its response code.

For example, all 2XX responses are instances of a Net::HTTPSuccess subclass, a 3XX response is an instance of a Net::HTTPRedirection subclass and a 200 response is an instance of the Net::HTTPOK class. For details of response classes, see the section “HTTP Response Classes” below.

Using a case statement you can handle various types of responses properly:

def fetch(uri_str, limit = 10)
  # You should choose a better exception.
  raise ArgumentError, 'too many HTTP redirects' if limit == 0

  response = Net::HTTP.get_response(URI(uri_str))

  case response
  when Net::HTTPSuccess then
    response
  when Net::HTTPRedirection then
    location = response['location']
    warn "redirected to #{location}"
    fetch(location, limit - 1)
  else
    response.value
  end
end

print fetch('http://www.ruby-lang.org')

或者，您可以使用 Ruby 的 OpenURI , 它会自动处理。或者，Curb gem 会做到的。大概 Typhoeus和 HTTPClient也是。

根据您在问题中显示的代码，您获得的异常只能来自:

http_object = Net::HTTP.new(uri.host, uri.port)

这不太可能，因为 uri 是一个 URI 对象。如果您需要帮助解决该问题，则需要显示完整的代码。