Rack中间件中的"env"变量是什么？

Question

我知道Rack中间件过滤器是一个带有初始化和调用方法的Ruby类.我知道call方法采用"env"参数.像这样的东西:

class MyFilter
  def initialize(app)
  end

  def call(env)
  end
end

我的问题是:"env"参数究竟发送给"call"的是什么？这与Rails ENV环境(即开发,测试,生产)相同.

谢谢!

Answer 1

env只是一个哈希.机架本身和各种中间件为其增加了价值.

要了解哈希中各种键的含义,请查看机架规范.

这是一个env哈希示例:

{
  "GATEWAY_INTERFACE" => "CGI/1.1",
  "PATH_INFO" => "/index.html",
  "QUERY_STRING" => "",
  "REMOTE_ADDR" => "::1",
  "REMOTE_HOST" => "localhost",
  "REQUEST_METHOD" => "GET",
  "REQUEST_URI" => "http://localhost:3000/index.html",
  "SCRIPT_NAME" => "",
  "SERVER_NAME" => "localhost",
  "SERVER_PORT" => "3000",
  "SERVER_PROTOCOL" => "HTTP/1.1",
  "SERVER_SOFTWARE" => "WEBrick/1.3.1 (Ruby/2.0.0/2013-11-22)",
  "HTTP_HOST" => "localhost:3000",
  "HTTP_USER_AGENT" => "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:26.0) Gecko/20100101 Firefox/26.0",
  "HTTP_ACCEPT" => "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
  "HTTP_ACCEPT_LANGUAGE" => "zh-tw,zh;q=0.8,en-us;q=0.5,en;q=0.3",
  "HTTP_ACCEPT_ENCODING" => "gzip, deflate",
  "HTTP_COOKIE" => "jsonrpc.session=3iqp3ydRwFyqjcfO0GT2bzUh.bacc2786c7a81df0d0e950bec8fa1a9b1ba0bb61",
  "HTTP_CONNECTION" => "keep-alive",
  "HTTP_CACHE_CONTROL" => "max-age=0",
  "rack.version" => [1, 2],
  "rack.input" => #<StringIO:0x007fa1bce039f8>,
  "rack.errors" => #<IO:<STDERR>>,
  "rack.multithread" => true,
  "rack.multiprocess" => false,
  "rack.run_once" => false,
  "rack.url_scheme" => "http",
  "HTTP_VERSION" => "HTTP/1.1",
  "REQUEST_PATH" => "/index.html"
}

为了方便使用,请检查Rack :: Request,这样可以更轻松地访问env哈希中的值.

Answer 2

我建议您可以尝试使用简单的编程来打印'env'变量.

require "rubygems"
require "rack" 
def pp(hash)
  hash.map {|key,value| "#{key} => #{value}"}.sort.join("<br/>") 
end
Rack::Handler::WEBrick.run lambda {|env| [200,{},[pp(env)]]} , :Port=>3000

输入localhost:3000链接

Answer 3

该env变量是一个哈希,它包含许多有用的信息,包括请求头和主体,以及可能由上游中间件添加的运行时环境数据.