module ActionController #:nodoc: # Actions that fail to perform as expected throw exceptions. These exceptions can either be rescued for the public view # (with a nice user-friendly explanation) or for the developers view (with tons of debugging information). The developers view # is already implemented by the Action Controller, but the public view should be tailored to your specific application. # # The default behavior for public exceptions is to render a static html file with the name of the error code thrown. If no such # file exists, an empty response is sent with the correct status code. # # You can override what constitutes a local request by overriding the local_request? method in your own controller. # Custom rescue behavior is achieved by overriding the rescue_action_in_public and rescue_action_locally methods. module Rescue LOCALHOST = '127.0.0.1'.freeze DEFAULT_RESCUE_RESPONSE = :internal_server_error DEFAULT_RESCUE_RESPONSES = { 'ActionController::RoutingError' => :not_found, 'ActionController::UnknownAction' => :not_found, 'ActiveRecord::RecordNotFound' => :not_found, 'ActiveRecord::StaleObjectError' => :conflict, 'ActiveRecord::RecordInvalid' => :unprocessable_entity, 'ActiveRecord::RecordNotSaved' => :unprocessable_entity, 'ActionController::MethodNotAllowed' => :method_not_allowed, 'ActionController::NotImplemented' => :not_implemented, 'ActionController::InvalidAuthenticityToken' => :unprocessable_entity } DEFAULT_RESCUE_TEMPLATE = 'diagnostics' DEFAULT_RESCUE_TEMPLATES = { 'ActionView::MissingTemplate' => 'missing_template', 'ActionController::RoutingError' => 'routing_error', 'ActionController::UnknownAction' => 'unknown_action', 'ActionView::TemplateError' => 'template_error' } def self.included(base) #:nodoc: base.cattr_accessor :rescue_responses base.rescue_responses = Hash.new(DEFAULT_RESCUE_RESPONSE) base.rescue_responses.update DEFAULT_RESCUE_RESPONSES base.cattr_accessor :rescue_templates base.rescue_templates = Hash.new(DEFAULT_RESCUE_TEMPLATE) base.rescue_templates.update DEFAULT_RESCUE_TEMPLATES base.class_inheritable_array :rescue_handlers base.rescue_handlers = [] base.extend(ClassMethods) base.class_eval do alias_method_chain :perform_action, :rescue end end module ClassMethods def process_with_exception(request, response, exception) #:nodoc: new.process(request, response, :rescue_action, exception) end # Rescue exceptions raised in controller actions. # # rescue_from receives a series of exception classes or class # names, and a trailing :with option with the name of a method # or a Proc object to be called to handle them. Alternatively a block can # be given. # # Handlers that take one argument will be called with the exception, so # that the exception can be inspected when dealing with it. # # Handlers are inherited. They are searched from right to left, from # bottom to top, and up the hierarchy. The handler of the first class for # which exception.is_a?(klass) holds true is the one invoked, if # any. # # class ApplicationController < ActionController::Base # rescue_from User::NotAuthorized, :with => :deny_access # self defined exception # rescue_from ActiveRecord::RecordInvalid, :with => :show_errors # # rescue_from 'MyAppError::Base' do |exception| # render :xml => exception, :status => 500 # end # # protected # def deny_access # ... # end # # def show_errors(exception) # exception.record.new_record? ? ... # end # end def rescue_from(*klasses, &block) options = klasses.extract_options! unless options.has_key?(:with) block_given? ? options[:with] = block : raise(ArgumentError, "Need a handler. Supply an options hash that has a :with key as the last argument.") end klasses.each do |klass| key = if klass.is_a?(Class) && klass <= Exception klass.name elsif klass.is_a?(String) klass else raise(ArgumentError, "#{klass} is neither an Exception nor a String") end # Order is important, we put the pair at the end. When dealing with an # exception we will follow the documented order going from right to left. rescue_handlers << [key, options[:with]] end end end protected # Exception handler called when the performance of an action raises an exception. def rescue_action(exception) log_error(exception) if logger erase_results if performed? # Let the exception alter the response if it wants. # For example, MethodNotAllowed sets the Allow header. if exception.respond_to?(:handle_response!) exception.handle_response!(response) end if consider_all_requests_local || local_request? rescue_action_locally(exception) else rescue_action_in_public(exception) end end # Overwrite to implement custom logging of errors. By default logs as fatal. def log_error(exception) #:doc: ActiveSupport::Deprecation.silence do if ActionView::TemplateError === exception logger.fatal(exception.to_s) else logger.fatal( "\n\n#{exception.class} (#{exception.message}):\n " + clean_backtrace(exception).join("\n ") + "\n\n" ) end end end # Overwrite to implement public exception handling (for requests answering false to local_request?). By # default will call render_optional_error_file. Override this method to provide more user friendly error messages.s def rescue_action_in_public(exception) #:doc: render_optional_error_file response_code_for_rescue(exception) end # Attempts to render a static error page based on the status_code thrown, # or just return headers if no such file exists. For example, if a 500 error is # being handled Rails will first attempt to render the file at public/500.html. # If the file doesn't exist, the body of the response will be left empty. def render_optional_error_file(status_code) status = interpret_status(status_code) path = "#{Rails.public_path}/#{status[0,3]}.html" if File.exist?(path) render :file => path, :status => status else head status end end # True if the request came from localhost, 127.0.0.1. Override this # method if you wish to redefine the meaning of a local request to # include remote IP addresses or other criteria. def local_request? #:doc: request.remote_addr == LOCALHOST && request.remote_ip == LOCALHOST end # Render detailed diagnostics for unhandled exceptions rescued from # a controller action. def rescue_action_locally(exception) add_variables_to_assigns @template.instance_variable_set("@exception", exception) @template.instance_variable_set("@rescues_path", File.dirname(rescues_path("stub"))) @template.send!(:assign_variables_from_controller) @template.instance_variable_set("@contents", @template.render(:file => template_path_for_local_rescue(exception), :use_full_path => false)) response.content_type = Mime::HTML render_for_file(rescues_path("layout"), response_code_for_rescue(exception)) end # Tries to rescue the exception by looking up and calling a registered handler. def rescue_action_with_handler(exception) if handler = handler_for_rescue(exception) if handler.arity != 0 handler.call(exception) else handler.call end true # don't rely on the return value of the handler end end private def perform_action_with_rescue #:nodoc: perform_action_without_rescue rescue Exception => exception rescue_action_with_handler(exception) || rescue_action(exception) end def rescues_path(template_name) "#{File.dirname(__FILE__)}/templates/rescues/#{template_name}.erb" end def template_path_for_local_rescue(exception) rescues_path(rescue_templates[exception.class.name]) end def response_code_for_rescue(exception) rescue_responses[exception.class.name] end def handler_for_rescue(exception) # We go from right to left because pairs are pushed onto rescue_handlers # as rescue_from declarations are found. _, handler = *rescue_handlers.reverse.detect do |klass_name, handler| # The purpose of allowing strings in rescue_from is to support the # declaration of handler associations for exception classes whose # definition is yet unknown. # # Since this loop needs the constants it would be inconsistent to # assume they should exist at this point. An early raised exception # could trigger some other handler and the array could include # precisely a string whose corresponding constant has not yet been # seen. This is why we are tolerant to unknown constants. # # Note that this tolerance only matters if the exception was given as # a string, otherwise a NameError will be raised by the interpreter # itself when rescue_from CONSTANT is executed. klass = self.class.const_get(klass_name) rescue nil klass ||= klass_name.constantize rescue nil exception.is_a?(klass) if klass end case handler when Symbol method(handler) when Proc handler.bind(self) end end def clean_backtrace(exception) if backtrace = exception.backtrace if defined?(RAILS_ROOT) backtrace.map { |line| line.sub RAILS_ROOT, '' } else backtrace end end end end end