How to handle 404 not found errors in Nokogiri

问题:

I am using Nokogiri to scrape web pages. Few urls need to be guessed and returns 404 not found error when they don't exist. Is there a way to capture this exception?

http://yoursite/page/38475 #=> page number 38475 doesn't exist

I tried the following which didn't work.

url = "http://yoursite/page/38475"
doc = Nokogiri::HTML(open(url)) do
  begin
    rescue Exception => e
      puts "Try again later"
  end
end

回答1:

It doesn't work, because you are not rescuing part of code (it's open(url) call) that raises an error in case of finding 404 status. The following code should work:

url = 'http://yoursite/page/38475'
begin
  file = open(url)
  doc = Nokogiri::HTML(file) do
    # handle doc
  end
rescue OpenURI::HTTPError => e
  if e.message == '404 Not Found'
    # handle 404 error
  else
    raise e
  end
end

BTW, about rescuing Exception: Why is it a bad style to `rescue Exception => e` in Ruby?