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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 <tt>local_request?</tt> method in your own controller.
# Custom rescue behavior is achieved by overriding the <tt>rescue_action_in_public</tt> and <tt>rescue_action_locally</tt> 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 = {
'ActionController::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.
#
# <tt>rescue_from</tt> 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 <tt>local_request?</tt>). 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 <tt>status_code</tt> 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 <tt>public/500.html</tt>.
# 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 and 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), 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 # errors from action performed
return if 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
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