In Rails 3.0, a Rails::Application object was introduced which is nothing more than an Engine but with the responsibility of coordinating the whole boot process.
Rails::Application is responsible for executing all railties, engines and plugin initializers. It also executes some bootstrap initializers (check Rails::Application::Bootstrap) and finishing initializers, after all the others are executed (check Rails::Application::Finisher).
Besides providing the same configuration as Rails::Engine and Rails::Railtie, the application object has several specific configurations, for example “allow_concurrency”, “cache_classes”, “consider_all_requests_local”, “filter_parameters”, “logger”, “reload_plugins” and so forth.
Check Rails::Application::Configuration to see them all.
The application object is also responsible for holding the routes and reloading routes whenever the files change in development.
The Application is also responsible for building the middleware stack.
The application is also responsible for setting up and executing the booting process. From the moment you require “config/application.rb” in your app, the booting process goes like this:
1) require "config/boot.rb" to setup load paths 2) require railties and engines 3) Define Rails.application as "class MyApp::Application < Rails::Application" 4) Run config.before_configuration callbacks 5) Load config/environments/ENV.rb 6) Run config.before_initialize callbacks 7) Run Railtie#initializer defined by railties, engines and application. One by one, each engine sets up its load paths, routes and runs its config/initializers/* files. 9) Custom Railtie#initializers added by railties, engines and applications are executed 10) Build the middleware stack and run to_prepare callbacks 11) Run config.before_eager_load and eager_load if cache classes is true 12) Run config.after_initialize callbacks
# File lib/rails/application.rb, line 62 def inherited(base) raise "You cannot have more than one Rails::Application" if Rails.application super Rails.application = base.instance Rails.application.add_lib_to_load_path! ActiveSupport.run_load_hooks(:before_configuration, base.instance) end
# File lib/rails/application.rb, line 77 def initialize super @initialized = false @reloaders = [] end
# File lib/rails/application.rb, line 229 def call(env) env["ORIGINAL_FULLPATH"] = build_original_fullpath(env) super(env) end
Rails.application.env_config stores some of the Rails initial environment parameters. Currently stores:
* "action_dispatch.parameter_filter" => config.filter_parameters, * "action_dispatch.secret_token" => config.secret_token, * "action_dispatch.show_exceptions" => config.action_dispatch.show_exceptions, * "action_dispatch.show_detailed_exceptions" => config.consider_all_requests_local, * "action_dispatch.logger" => Rails.logger, * "action_dispatch.backtrace_cleaner" => Rails.backtrace_cleaner
These parameters will be used by middlewares and engines to configure themselves.
# File lib/rails/application.rb, line 177 def env_config @app_env_config ||= super.merge({ "action_dispatch.parameter_filter" => config.filter_parameters, "action_dispatch.secret_token" => config.secret_token, "action_dispatch.show_exceptions" => config.action_dispatch.show_exceptions, "action_dispatch.show_detailed_exceptions" => config.consider_all_requests_local, "action_dispatch.logger" => Rails.logger, "action_dispatch.backtrace_cleaner" => Rails.backtrace_cleaner }) end
Load the application console and invoke the registered hooks. Check
Rails::Railtie.console
for more info.
# File lib/rails/application.rb, line 151 def load_console(app=self) initialize_console super self end
Load the application runner and invoke the registered hooks. Check
Rails::Railtie.runner
for more info.
# File lib/rails/application.rb, line 159 def load_runner(app=self) initialize_runner super self end
Load the application and its railties tasks and invoke the registered
hooks. Check Rails::Railtie.rake_tasks
for more info.
# File lib/rails/application.rb, line 143 def load_tasks(app=self) initialize_tasks super self end
Reload application routes regardless if they changed or not.
# File lib/rails/application.rb, line 107 def reload_routes! routes_reloader.reload! end
# File lib/rails/application.rb, line 221 def to_app self end
Returns an array of file paths appended with a hash of directories-extensions suitable for ActiveSupport::FileUpdateChecker API.
# File lib/rails/application.rb, line 117 def watchable_args files = [] files.concat config.watchable_files dirs = {} dirs.merge! config.watchable_dirs ActiveSupport::Dependencies.autoload_paths.each do |path| dirs[path.to_s] = [:rb] end [files, dirs] end
# File lib/rails/application.rb, line 319 def build_original_fullpath(env) path_info = env["PATH_INFO"] query_string = env["QUERY_STRING"] script_name = env["SCRIPT_NAME"] if query_string.present? "#{script_name}#{path_info}?#{query_string}" else "#{script_name}#{path_info}" end end
# File lib/rails/application.rb, line 242 def default_middleware_stack require 'action_controller/railtie' ActionDispatch::MiddlewareStack.new.tap do |middleware| if rack_cache = config.action_controller.perform_caching && config.action_dispatch.rack_cache require "action_dispatch/http/rack_cache" middleware.use ::Rack::Cache, rack_cache end if config.force_ssl require "rack/ssl" middleware.use ::Rack::SSL, config.ssl_options end if config.serve_static_assets middleware.use ::ActionDispatch::Static, paths["public"].first, config.static_cache_control end middleware.use ::Rack::Lock unless config.allow_concurrency middleware.use ::Rack::Runtime middleware.use ::Rack::MethodOverride middleware.use ::ActionDispatch::RequestId middleware.use ::Rails::Rack::Logger, config.log_tags # must come after Rack::MethodOverride to properly log overridden methods middleware.use ::ActionDispatch::ShowExceptions, config.exceptions_app || ActionDispatch::PublicExceptions.new(Rails.public_path) middleware.use ::ActionDispatch::DebugExceptions middleware.use ::ActionDispatch::RemoteIp, config.action_dispatch.ip_spoofing_check, config.action_dispatch.trusted_proxies if config.action_dispatch.x_sendfile_header.present? middleware.use ::Rack::Sendfile, config.action_dispatch.x_sendfile_header end unless config.cache_classes app = self middleware.use ::ActionDispatch::Reloader, lambda { app.reload_dependencies? } end middleware.use ::ActionDispatch::Callbacks middleware.use ::ActionDispatch::Cookies if config.session_store if config.force_ssl && !config.session_options.key?(:secure) config.session_options[:secure] = true end middleware.use config.session_store, config.session_options middleware.use ::ActionDispatch::Flash end middleware.use ::ActionDispatch::ParamsParser middleware.use ::ActionDispatch::Head middleware.use ::Rack::ConditionalGet middleware.use ::Rack::ETag, "no-cache" if config.action_dispatch.best_standards_support middleware.use ::ActionDispatch::BestStandardsSupport, config.action_dispatch.best_standards_support end end end
# File lib/rails/application.rb, line 238 def reload_dependencies? config.reload_classes_only_on_change != true || reloaders.map(&:updated?).any? end