Question

我想从此页面获取数据：

http://www.canadapost.ca/cpotools/apps/track/personal/findByTrackNumber?trackingNumber=0656887000494793

但该页面转发到：

http://www.canadapost.ca/cpotools/apps/track/personal/findByTrackNumber?execution=eXs1

因此，当我使用来自OpenUri的open尝试获取数据时，会引发RuntimeError错误，说HTTP redirection loop:

我不确定如何在重定向并抛出该错误后获取该数据。

Answer 1

您需要一个像Mechanize这样的工具。从它的描述：

Mechanize库用于自动化与网站的互动。机械化自动存储和发送cookie，跟随重定向，可以关注链接，并提交表单。形成可以填充和提交字段。机械化也跟踪您访问过的网站历史。

这正是您所需要的。所以，

sudo gem install mechanize

然后

require 'mechanize'
agent = WWW::Mechanize.new
page = agent.get "http://www.canadapost.ca/cpotools/apps/track/personal/findByTrackNumber trackingNumber=0656887000494793"

page.content # Get the resulting page as a string
page.body # Get the body content of the resulting page as a string
page.search(".somecss") # Search for specific elements by XPath/CSS using nokogiri

你已经准备好摇滚了。

Answer 2

该网站似乎正在使用会话进行一些重定向逻辑。如果您没有发回他们在第一次请求时发送的会话cookie，您将最终进入重定向循环。恕我直言，这对他们来说是一个糟糕的实施。

然而，我试图将cookie传递给他们，但我没有让它工作，所以我不能完全确定这就是这就是。

Answer 3

虽然机械化是一个很好的工具，但我更喜欢“烹饪”我自己的东西。

如果您认真解析，可以查看此代码。它每天在国际层面上抓取成千上万的网站，据我所研究和调整，没有一种更稳定的方法可以让你在以后高度定制你的需求。

require "open-uri"
require "zlib"
require "nokogiri"
require "sanitize"
require "htmlentities"
require "readability"

def crawl(url_address)
self.errors = Array.new
begin
  begin
    url_address = URI.parse(url_address)
  rescue URI::InvalidURIError
    url_address = URI.decode(url_address)
    url_address = URI.encode(url_address)
    url_address = URI.parse(url_address)
  end
  url_address.normalize!
  stream = ""
  timeout(8) { stream = url_address.open(SHINSO_HEADERS) }
  if stream.size > 0
    url_crawled = URI.parse(stream.base_uri.to_s)
  else
    self.errors << "Server said status 200 OK but document file is zero bytes."
    return
  end
rescue Exception => exception
  self.errors << exception
  return
end
# extract information before html parsing
self.url_posted       = url_address.to_s
self.url_parsed       = url_crawled.to_s
self.url_host         = url_crawled.host
self.status           = stream.status
self.content_type     = stream.content_type
self.content_encoding = stream.content_encoding
self.charset          = stream.charset
if    stream.content_encoding.include?('gzip')
  document = Zlib::GzipReader.new(stream).read
elsif stream.content_encoding.include?('deflate')
  document = Zlib::Deflate.new().deflate(stream).read
#elsif stream.content_encoding.include?('x-gzip') or
#elsif stream.content_encoding.include?('compress')
else
  document = stream.read
end
self.charset_guess = CharGuess.guess(document)
if not self.charset_guess.blank? and (not self.charset_guess.downcase == 'utf-8' or not self.charset_guess.downcase == 'utf8')
  document = Iconv.iconv("UTF-8", self.charset_guess, document).to_s
end
document = Nokogiri::HTML.parse(document,nil,"utf8")
document.xpath('//script').remove
document.xpath('//SCRIPT').remove
for item in document.xpath('//*[translate(@src, "ABCDEFGHIJKLMNOPQRSTUVWXYZ", "abcdefghijklmnopqrstuvwxyz")]')
  item.set_attribute('src',make_absolute_address(item['src']))
end
document = document.to_s.gsub(/<!--(.|\s)*?-->/,'')
self.content = Nokogiri::HTML.parse(document,nil,"utf8")
end

使用OpenUri，我如何获取重定向页面的内容？

3 个答案: