class ActionDispatch::ShowExceptions
Action Dispatch ShowExceptions
¶ ↑
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 env["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 ActionDispatch::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.
Public Class Methods
# File lib/action_dispatch/middleware/show_exceptions.rb, line 26 def initialize(app, exceptions_app) @app = app @exceptions_app = exceptions_app end
Public Instance Methods
# File 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
Private Instance Methods
# File 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
# File 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
# File 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