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https://github.com/richpeck/exception_handler

Ruby on Rails Custom Error Pages
https://github.com/richpeck/exception_handler

email-notification exception-handler http http-error-pages http-errors middleware rails rails-exceptions rails-gem ruby

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Ruby on Rails Custom Error Pages

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README 

        
![Exception Handler](readme/title.jpg "Exception Handler Logo")





  


ExceptionHandler is presently the MOST POPULAR exceptions gem for CUSTOM Rails error pages.


  


    With 290,000+ downloads, it is the *only* gem to provide custom 400/500 exception pages for Rails 5 & 6

  


  


  
Current 0.8.0.0 (August 2018)







  

  

  

  Coverage Status

  






  


  


    

      📝 Introduction -

      ⚠️ Installation -

      🔧 Configuration -

      ☎️ Support -

      ⭐ Changelog

    

  


  







  
📝 Introduction





---



  
ExceptionHandler replaces Rails' default error pages with dynamic views.


  
It does this by injecting config.exceptions_app with our controller - allowing us to populate erroneous responses with our own HTML. To understand how this works, you need to appreciate how Rails handles errors:


  


  
Rails uses ActionDispatch::ShowExceptions (above) to generate error responses.


  
Because web browsers (Rails is a web framework) can only interpret HTTP responses, Ruby/Rails exceptions have to be translated into something a browser can read. This is done by calling the above middleware.


  
--


  
As highlighted, an HTTP response is built independent of the Rails stack. This includes assigning an HTTP status code and HTML response body. It's the response body which ExceptionHandler is designed to override.







  






  
⚠️ Installation





---





  


    💎 RubyGems (Code) |

    💻 Medium (Tutorial)

  


  
# Gemfile

gem 'exception_handler', '~> 0.8.0.0'


  
Because ExceptionHandler is built around a Rails engine, there is nothing to be done to get it working in production. Installing the Gem should translate your production 4xx/5xx error pages into dynamic views.


  
Environments other than production (development/staging) required the dev variable to be true.







  






  
🔧 Configuration





---





   📁 Config    💻 Dev    💾 Database    ✉️   Email    👓 Views    💬 Locales    📋 Layouts    ⛔️ Custom Exceptions




---






The **ONLY** thing you need to manage `ExceptionHandler` is its [`config`](https://github.com/richpeck/exception_handler/blob/master/lib/exception_handler/config.rb) settings.



Whilst the gem **works out of the box** (without any configuration), if you want to manage the [`layouts`](#layouts), [`email`](#email), [`dev`](#dev) or the [`database`](#db), you'll need to set the appropriate values in the config hash.



This is done in `config/application.rb` or `config/environments/[env].rb` ↴



```rb

# config/application.rb



module YourApp

  class Application < Rails::Application



    # => This is an example of ALL available config options

    # => You're able to see exactly how it works here:

    # => https://github.com/richpeck/exception_handler/blob/master/lib/exception_handler/config.rb



    # => Config hash (no initializer required)

    config.exception_handler = {

      dev:        nil, # allows you to turn ExceptionHandler "on" in development

      db:         nil, # allocates a "table name" into which exceptions are saved (defaults to nil)

      email:      nil, # sends exception emails to a listed email (string // "[email protected]")



      # Custom Exceptions

      custom_exceptions: {

        #'ActionController::RoutingError' => :not_found # => example

      },



      # On default 5xx error page, social media links included

      social: {        

        facebook: nil, # Facebook page name   

        twitter:  nil, # Twitter handle  

        youtube:  nil, # Youtube channel name / ID

        linkedin: nil, # LinkedIn name

        fusion:   nil  # FL Fusion handle

      },  



      # This is an entirely NEW structure for the "layouts" area

      # You're able to define layouts, notifications etc ↴



      # All keys interpolated as strings, so you can use symbols, strings or integers where necessary

      exceptions: {



        :all => {

          layout: "exception", # define layout

          notification: true, # (false by default)

          deliver: #something here to control the type of response

        },

        :4xx => {

          layout: nil, # define layout

          notification: true, # (false by default)

          deliver: #something here to control the type of response    

        },    

        :5xx => {

          layout: "exception", # define layout

          notification: true, # (false by default)

          deliver: #something here to control the type of response    

        },

        500 => {

          layout: "exception", # define layout

          notification: true, # (false by default)

          deliver: #something here to control the type of response    

        },



        # This is the old structure

        # Still works but will be deprecated in future versions



        501 => "exception",

        502 => "exception",

        503 => "exception",

        504 => "exception",

        505 => "exception",

        507 => "exception",

        510 => "exception"



      }

    }

  end

end

```  



For a full retinue of the available options, you'll be best looking at the [`config`](https://github.com/richpeck/exception_handler/blob/master/lib/exception_handler/config.rb) file itself.



--



If using an [`engine`](http://guides.rubyonrails.org/engines.html), you **DON'T need an `initializer`**:

```rb

# lib/engine.rb

module YourModule

  class Engine < Rails::Engine



    # => ExceptionHandler

    # => Works in and out of an initializer

    config.exception_handler = {

      dev: nil, # => this will not load the gem in development

      db:  true # => this will use the :errors table to store exceptions

    }

  end

end

```



The best thing about using a `config` options block is that you are able to only define the options that you require.



If you have particular options you *only* wish to run in `staging`, or have single options for `production` etc, this setup gives you the ability to manage it properly...



---





  
💻 Dev





As explained, `ExceptionHandler` does *not* work in `development` by default.



This is because it overrides the `exceptions_app` middleware hook - which is *only* invoked in `production` or `staging`.





  




To get it working in `development`, you need to override the [`config.consider_all_requests_local`](http://guides.rubyonrails.org/configuring.html#rails-general-configuration) setting (a standard component of Rails) - setting it to "false" ↴





  




This is normally done by changing the setting in your Rails config files. However, to make the process simpler for `ExceptionHandler`- we've added a `dev` option which allows you to override the hook through the context of the gem...



```rb

# config/application.rb

config.exception_handler = { dev: true }

```



This disables [`config.consider_all_requests_local`](http://guides.rubyonrails.org/configuring.html#rails-general-configuration), making Rails behave as it would in production.



Whilst simple, it's not recommended for extended use. Very good for testing new ideas etc.



---





  
💾 DB





To save exceptions to your database, you're able to set the `db` option.



Because we use a `controller` to manage the underlying way the system works, we're able to invoke the likes of a [`model`](https://github.com/richpeck/exception_handler/blob/master/app/models/exception_handler/exception.rb) with other functionality.



Ths is done automatically with the latest version of `ExceptionHandler`.



To do this, once you've populated the option with either `true` or a `string`, run `rails db:migrate` from your console.



Our new [`migration system`](https://github.com/richpeck/exception_handler/tree/readme#migrations) will automatically run the migration.



```rb

# config/application.rb

config.exception_handler = { db: true }

```



This enables `ActiveRecord::Base` on the [`Exception`](app/models/exception_handler/exception.rb) class, allowing us to save to the database.



In order for this to work, your db needs the correct table.



---





  
✉️ Email





`ExceptionHandler` also sends **email notifications**.



If you want to receive emails whenever your application raises an error, you can do so by adding your email to the config:



```rb

# config/application.rb

config.exception_handler = {

  email: "[email protected]"

}

```



> **Please Note** this requires [`ActionMailer`](http://guides.rubyonrails.org/action_mailer_basics.html). If you don't have any outbound SMTP server, [`SendGrid`](http://sendgrid.com) is free.



From version [`0.8.0.0`](https://github.com/richpeck/exception_handler/releases/tag/v0.8.0.0), you're able to define whether email notifications are sent on a per-error basis:



```rb

# config/application.rb

config.exception_handlder = {



  # This has to be present for any "notification" declarations to work

  # Defaults to 'false'

  email: "[email protected]",



  # Each status code in the new "exceptions" block allows us to define whether email notifications are sent

  exceptions: {

    :all => { notification: true },

    :50x => { notification: false },

    500 =>  { notification: false }

  }

}

```

---





  
👓 Views





What *most* people want out of the view is to change the way it ***looks***. This can be done without changing the "view" itself.



To better explain, if [`ExceptionsController`](https://github.com/richpeck/exception_handler/blob/master/app/controllers/exception_handler/exceptions_controller.rb) is invoked (by `exceptions_app`), it has **ONE** method ([`show`](https://github.com/richpeck/exception_handler/blob/master/app/controllers/exception_handler/exceptions_controller.rb#L42)).



This method calls the [`show` view](https://github.com/richpeck/exception_handler/blob/master/app/views/exception_handler/exceptions/show.html.erb), which is *entirely* dependent on the locales for content & the layout for the look.



This means that if you wish to change how the view "looks" - you're *either* going to want to change your [layout][layouts] or the [*locales*](#locales). There is NO reason to change the `show` view itself - it's succinct and entirely modular. Whilst you're definitely at liberty to change it, you'll just be making the issue more complicated than it needs to be.



--



We've also included a number of routes which shows in [`dev`](dev) mode (allowing you to test):





  




---





  
💬 Locales





[Locales](https://github.com/richpeck/exception_handler/blob/Readme/config/locales/exception_handler.en.yml) are used to create interchangeable text (translations/internationalization).



--



In `ExceptionHandler`, it provides the wording for each type of error code.



By default, the English name of the error is used (`"404"` will appear as `"Not Found"`) - if you want to create custom messages, you're able to do so by referencing the error's ["status_code"](https://github.com/rack/rack/blob/master/lib/rack/utils.rb#L492) within your locales file:



```yml

# config/locales/en.yml

en:

  exception_handler:

    not_found:              "Your message here" # -> 404 page

    unauthorized:           "You need to login to continue"

    internal_server_error:  "This is a test to show the %{status} of the error"

```



You get access to [`%{message}` and `%{status}`](https://github.com/richpeck/exception_handler/blob/master/app/views/exception_handler/exceptions/show.html.erb#L1), both inferring from an [`@exception`](https://github.com/richpeck/exception_handler/blob/master/app/controllers/exception_handler/exceptions_controller.rb#L20) object we invoke in the controller...



 - `%{message}` is the error's actual message ("XYZ file could not be shown")

 - `%{status}` is the error's status code ("Internal Server Error")



--



By default, only `internal_server_error` is customized by the gem:



```yml

# config/locales/en.yml

en:

  exception_handler:

    internal_server_error: "%{status} Error %{message}"

```

---





  
📋 Layouts





The most attractive feature of `ExceptionHandler` (for most) is its ability to manage [`layouts`](https://guides.rubyonrails.org/layouts_and_rendering.html#structuring-layouts) for HTTP status.



--



The reason for this is due to the way in which Rails works → the "layout" is a "wrapper" for the returned HTML (the "styling" of a page). If you have no layout, it will render the "view" HTML and nothing else.



This means if you want to change the "look" of a Rails action, you simply have to be able to change the `layout`. You should not change the view at all.



To this end, `ExceptionHandler` has been designed around providing a [SINGLE VIEW](app/controllers/exception_handler/exceptions_controller.rb#L44) for exceptions. This view does not need to change (although you're welcome to use a [`generator`][generators] to do so) - the key is the `layout` that's assigned...



- [`4xx`](https://en.wikipedia.org/wiki/List_of_HTTP_status_codes#4xx_Client_errors) errors are given a `nil` layout (by default) (inherits from `ApplicationController` in your main app)

- [`5xx`](https://en.wikipedia.org/wiki/List_of_HTTP_status_codes#5xx_Server_errors) errors are assigned our own [`exception`](app/views/layouts/exception.html.erb) layout:



```rb

# config/application.rb

config.exception_handler = {



  # The new syntax allows us to assign different values to each HTTP status code

  # At the moment, only 'layout' & 'notification' are supported

  # We plan to include several more in the future...



  exceptions: {

    all: { layout: nil } # -> this will inherit from ApplicationController's layout

  }

}

```



The `layout` system has changed between [`0.7.7.0`](releases/tag/v0.7.7.0) and [`0.8.0.0`](releases/tag/v0.8.0.0).



Building on the former's adoption of HTTP status-centric layouts, it is now the case that we have the `all`, `5xx` and `4xx` options - allowing us to manage the layouts for blocks of HTTP errors respectively:



```rb

# config/application.rb

config.exception_handler = {



  # Old (still works)

  # No "all" / "4xx"/"5xx" options

  layouts: {

    500 => 'exception',

    501 => 'exception'

  },



  # New

  exceptions: {

    :all => { layout: 'exception' },

    :4xx => { layout: 'exception' },

    :5xx => { layout: 'exception' }, # -> this overrides the :all declaration

    500  => { layout: nil } # -> this overrides the 5xx declaration

  }

}

```



We've bundled the [`exception`](app/views/layouts/exception.html.erb) layout for `5xx` errors because since these denote internal server errors, it's best to isolate the view system as much as possible. Whilst you're at liberty to change it, we've found it sufficient for most use-cases.



---





  
⛔️ Custom Exceptions





As mentioned, Rails' primary role is to convert Ruby exceptions into HTTP errors.



Part of this process involves mapping Ruby/Rails exceptions to the equivalent HTTP status code.



This is done with [`config.action_dispatch.rescue_responses`](https://github.com/rack/rack/blob/master/lib/rack/utils.rb#L492).





  




Whilst this works well, it may be the case that you want to map your own classes to an HTTP status code (default is `Internal Server Error`).



If you wanted to keep this functionality inside `ExceptionHandler`, you're able to do it as follows:



```rb

# config/application.rb

config.exception_handler = {

  custom_exceptions: {

    'CustomClass::Exception' => :not_found

  }

}

```



Alternatively, you're able to still do it with the default Rails behaviour:



```rb

# config/application.rb

config.action_dispatch.rescue_responses = { 'CustomClass::Exception' => :not_found }

```

---





  
💼 Generators





If you want to edit the `controller`, `views`, `model` or `assets`, you're able to invoke them in your own application.



This is done - as with other gems - with a single [`generator`](https://github.com/richpeck/exception_handler/blob/master/lib/generators/exception_handler/views_generator.rb) which takes a series of arguments:



    rails g exception_handler:views

    rails g exception_handler:views -v views

    rails g exception_handler:views -v controllers

    rails g exception_handler:views -v models

    rails g exception_handler:views -v assets

    rails g exception_handler:views -v views controllers models assets



If you don't include any switches, this will copy **all** `ExceptionHandler`'s folders put into your app.



Each switch defines which folders you want (EG `-v views` will only copy `views` dir).



---





  
✔️ Migrations





You **DON'T** need to generate a migration anymore.



From [`0.7.5`](https://github.com/richpeck/exception_handler/releases/tag/0.7.5), the `migration` generator has been removed in favour of our own [migration system](lib/exception_handler/engine.rb#L58).



The reason we did this was so not to pollute your migrations folder with a worthless file. Our migration doesn't need to be changed - we only have to get it into the database and the gem takes care of the rest...



> If you set the [`db`][db] option in config, run `rails db:migrate` and the migration will be run.



To rollback, use the following:



    rails db:migrate:down VERSION=000000



The drawback to this is that if you remove `ExceptionHandler` before you rollback the migration, it won't exist anymore.



You can **only** fire the `rollback` when you have `ExceptionHandler` installed.





  






  
☎️ Support





---





  
You're welcome to contact me directly at [email protected].


  
Alternatively, you may wish to post on our GitHub Issues, or StackOverflow.


  
--


  
Medium







  






  
⭐ Changelog





---



[**1.0.0.0**](https://github.com/richpeck/exception_handler/releases/tag/v1.0.0.0)

  - [ ] TBA



[**0.8.0.0**](https://github.com/richpeck/exception_handler/releases/tag/v0.8.0.0)

 - [x] [README](https://github.com/richpeck/exception_handler/issues/52) (focus on utility)

 - [x] Introduction of `4xx`,`5xx`,`:all` for layouts config

 - [x] Changed `layouts` to `exceptions` in config    

 - [x] Email improvement

 - [x] Streamlined migration

 - [x] Updated model



[**0.7.7.0**](https://github.com/richpeck/exception_handler/releases/tag/v0.7.7.0)

 - [x] [HTTP status layouts](#layouts)



**0.7.0.0**

 - [x] Wildcard mime types

 - [x] [Custom exceptions](#custom_exceptions)

 - [x] Test suite integration

 - [x] [Model backend](#database)

 - [x] Sprockets 4+

 - [x] New layout

 - [x] Readme / wiki overhaul



**0.6.5.0**

 - [x] Streamlined interface

 - [x] ActiveRecord / Middleware overhaul

 - [x] Supports Sprockets 4+ ([`manifest.js`](http://eileencodes.com/posts/the-sprockets-4-manifest/))

 - [x] Email integration

 - [x] Asset overhaul & improvement

 - [x] Removed dependencies



**0.5.0.0**

 - [x] Locales

 - [x] Email notifications

 - [x] Full test suite

 - [x] Rails 4.2 & Rails 5.0 native ([`request.env`](https://github.com/rails/rails/commit/05934d24aff62d66fc62621aa38dae6456e276be) fix)

 - [x] Controller fixed

 - [x] `DB` fixed

 - [x] Legacy initializer support ([more](https://github.com/richpeck/exception_handler/wiki/1-Setup))

 - [x] Rails asset management improvement

 - [x] Reduced gem file size



**0.4.7.0**

 - [x] New config system

 - [x] Fixed controller layout issues

 - [x] Streamlined middleware

 - [x] New layout & interface



 

 


   

 



 [![404 + 500 Errors][banner]][rubygems]



 


   ExceptionHandler provides custom error pages gem for Rails 5+

   


   No other gem is as simple or effective at providing branded exception pages in production

 



 


   

   

   

   Coverage Status

   

 



 


   ➡️ Download & Info ⬅️

 



 

 


   

 



:copyright:         



[banner]:readme/banner.jpg



[rubygems]: http://rubygems.org/gems/exception_handler



[10x]: https://en.wikipedia.org/wiki/List_of_HTTP_status_codes#1xx_Informational_responses

[20x]: https://en.wikipedia.org/wiki/List_of_HTTP_status_codes#2xx_Success

[30x]: https://en.wikipedia.org/wiki/List_of_HTTP_status_codes#3xx_Redirection

[40x]: https://en.wikipedia.org/wiki/List_of_HTTP_status_codes#4xx_Client_errors

[50x]: https://en.wikipedia.org/wiki/List_of_HTTP_status_codes#5xx_Server_errors



[db]: #db

[email]: #email

[dev]: #dev

[layouts]: #layouts

[locales]: #locales

[configuration]: #configuration

[generators]: #generators

[custom-exceptions]: #custom-exceptions