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Class: ActionDispatch::ShowExceptions

Relationships & Source Files
Inherits: Object
Defined in: actionpack/lib/action_dispatch/middleware/show_exceptions.rb

Overview

This middleware rescues any exception returned by the application and calls an exceptions app that will wrap it in a format for the end user.

The exceptions app should be passed as a parameter on initialization of ShowExceptions. Every time there is an exception, ShowExceptions will store the exception in "action_dispatch.exception", rewrite the PATH_INFO to the exception status code, and call the ::Rack app.

In Rails applications, the exceptions app can be configured with config.exceptions_app, which defaults to PublicExceptions.

If the application returns a response with the X-Cascade header set to “pass”, this middleware will send an empty response as a result with the correct status code. If any exception happens inside the exceptions app, this middleware catches the exceptions and returns a failsafe response.

Class Method Summary

Instance Method Summary

Constructor Details

.new(app, exceptions_app) ⇒ ShowExceptions

[ GitHub ] 

  


# File 'actionpack/lib/action_dispatch/middleware/show_exceptions.rb', line 26



def initialize(app, exceptions_app)
  @app = app
  @exceptions_app = exceptions_app
end


  







Instance Method Details



  

    #call(env)  
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/middleware/show_exceptions.rb', line 31



def call(env)
  @app.call(env)
rescue Exception => exception
  request = ActionDispatch::Request.new env
  backtrace_cleaner = request.get_header("action_dispatch.backtrace_cleaner")
  wrapper = ExceptionWrapper.new(backtrace_cleaner, exception)
  request.set_header "action_dispatch.exception", wrapper.unwrapped_exception
  request.set_header "action_dispatch.report_exception", !wrapper.rescue_response?

  if wrapper.show?(request)
    render_exception(request.dup, wrapper)
  else
    raise exception
  end
end


  








  

    #fallback_to_html_format_if_invalid_mime_type(request)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/middleware/show_exceptions.rb', line 67



def fallback_to_html_format_if_invalid_mime_type(request)
  # If the MIME type for the request is invalid then the @exceptions_app may not
  # be able to handle it. To make it easier to handle, we switch to HTML.
  begin
    request.content_mime_type
  rescue ActionDispatch::Http::MimeNegotiation::InvalidType
    request.set_header "CONTENT_TYPE", "text/html"
  end

  begin
    request.formats
  rescue ActionDispatch::Http::MimeNegotiation::InvalidType
    request.set_header "HTTP_ACCEPT", "text/html"
  end
end


  








  

    #pass_response(status)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/middleware/show_exceptions.rb', line 83



def pass_response(status)
  [status, { Rack::CONTENT_TYPE => "text/html; charset=#{Response.default_charset}",
            Rack::CONTENT_LENGTH => "0" }, []]
end


  








  

    #render_exception(request, wrapper)   (private)
  

  [ GitHub ]


  

  


# File 'actionpack/lib/action_dispatch/middleware/show_exceptions.rb', line 48



def render_exception(request, wrapper)
  status = wrapper.status_code
  request.set_header "action_dispatch.original_path", request.path_info
  request.set_header "action_dispatch.original_request_method", request.raw_request_method
  fallback_to_html_format_if_invalid_mime_type(request)
  request.path_info = "/#{status}"
  request.request_method = "GET"
  response = @exceptions_app.call(request.env)
  response[1][Constants::X_CASCADE] == "pass" ? pass_response(status) : response
rescue Exception => failsafe_error
  $stderr.puts "Error during failsafe response: #{failsafe_error}\n  #{failsafe_error.backtrace * "\n  "}"

  [500, { Rack::CONTENT_TYPE => "text/plain; charset=utf-8" },
    ["500 Internal Server Error\n" \
    "If you are the administrator of this website, then please read this web " \
    "application's log file and/or the web server's log file to find out what " \
    "went wrong."]]
end