Grails vs. Rails

Ruby On Rails and Grails are two popular MVC webframeworks. Rails uses the Ruby language, and Grails uses Groovy. In this post I compare Grails vs Rails.


Ruby On Rails (in short just “Rails”) is a webframework that uses the Ruby language. It uses a push MVC design pattern, which means that a controller/action receives a client HTTP request, then creates or search (in a DB) for model objects containing data, and forwards those objects to the view where a HTML page is rendered for the HTTP client.

The other webframework, Grails, is also a push MVC webframework that uses some ideas of Rails. In fact, it was previously called Groovy On Rails. Grails uses the Groovy language instead of Ruby.

About the comparison

The way I look at these frameworks is influenced by my prior knowledge and preferences:
-I have a Java background
-I strongly prefer static typed over dynamic typed. (Why would you hide important information in your code about types if you need to document it anyway.)

I’m not an expert in these frameworks. Maybe I don’t even know the existence of some basic features. So if you think I forgot to mention something important, then leave a comment 🙂

Grails and Rails, in common

  • Development, production and test modes.
  • built-in webserver
  • quick boot/startup
  • hot deploy / class reloading without restarting the server
  • ORM (Object Relational Mapping) / Active record
  • lots of plugins, that can be downloaded from the command line. a plugin manager
  • nice URLs
  • model, view, controller, and test generators
  • popular, an active community
  • easy to learn / use
  • The language supports: string interpolation, multi line strings, raw string (no Java escape hell), closures
  • Full stack frameworks
  • screencasts
  • console for additional testing
  • easy to configure
  • productive
  • Builders. Configuration can be done in Groovy/Ruby files that look like normal configuration files. Easier to read than XML.
  • Books are available
  • quick releases
  • Dare to drop features. Can be good or bad, but I like it when features are dropped in order to keep the framework good.
  • Build tasks
  • Very easy to create tags/reusable HTML components. (Something you cannot say about JSF.)
  • Convention over Configuration

Grails vs. Rails

  • Documentation. The first thing that frustrated me about Rails was documentation. How do you learn Rails? Grails has an excellent up-to-date User guide, but on the Rails doc webpage you have API, Books, some outdated not-working external third-party tutorials, and how-to’s. But no userguide….. It’s very frustrating when you are halfway your first Rails steps in a tutorial (that is directly linked from the official main Rails docpage), and find yourself having to Google for solutions/workarounds because the popular Rails tutorials are so outdated that it doesn’t work anymore. If you want good learning material, you are forced to buy a RECENT (e)book otherwise you’ll find code that doesn’t work.

    API documentation is probably better in Rails than Grails because they have examples and more info in it. Rails also has wiki pages, which can be useful when looking for specific problems. Grails on the other hand has a userguide/tutorial that is very suitable for beginners, it is also useful for a quick reference. Grails website has some pages that have duplicated info about the same subject, sometimes these pages are outdated, and thus conflicting each other. e.g. the Grails pages about validation.

  • Grails uses other solid frameworks underneath it, like Hibernate and Spring. Frameworks that are well known in Java enterprise. These frameworks have a lot of features for the Model and controller, and thus give Grails a lot of features.
  • The View layer in Rails has a lot of features; there are a lot of view helpers/functions, which can be very handy. e.g. link_to_unless_current, which creates a hyperlink to an URL unless it is already the URL of the current page. Another example is Rails’ RJS, which allows you to write Ruby code that is outputted in Javascript.

    But Grails has IMO too less helpers. On this point, Grails is very weak compared to Rails. e.g. a select html input in Grails doesn’t allow selecting more than one item. Also, implementing error textfield highlighting using default Grails tags is very cumbersome.

  • Both frameworks are popular and have an active community. Rails is more popular; it existed before Grails and has inspired other frameworks. Rails has more jobs.
  • Grails automatically adapts the DB when creating/changing model attribute names, but this feature might be a bit unstable sometimes, since updating existing model classes is not very stable in Hibernate. (It is hard to determine whether a new found attribute is a new attribute or a renamed existing attribute when no versioning is used.) (Hibernate can also generate Java classes from an existing DB.)

    Rails uses Migrations to change the DB. A migration is a Ruby file containing almost SQL-like commands; it’s like writing pure SQL, but you have to write it yourself. Every migration has a version, and commands to change versions, so Rails has a DB versioning system. This can be very useful when you need to update the Production servers’ DB in a consistent way.

    Grails has a more object oriented approach; it shields/protects you from low-level sql. Where Rails gives you more SQL control when creating tables, and Rails allows you to control db versions.

  • Grails has GORM (Grails Object Relational Mapping) for making, saving and retrieving the domain models from the database. Rails uses Active Record.

    Grails (GORM) uses Hibernate (one of the best ORM frameworks) underneath its layers. When making a model class in Grails, you make a plain basic class with the attributes defined in it. When making relations between model classes, you’ll have to use special variable names that define the relations. Like belongsTo, hasMany, mappedBy and embedded. Maybe this can be done with Groovy annotations in the future? Grails automatically saves adaptions you make to a model class, to the db. Although, as mentioned previously, it uses Hibernates hbm2ddl, so for safety, you have to check manually that the DB table is what you expected when changing/renaming existing attributes. Validation of attributes is also put in the model class.

    Rails Active Record differs a lot from Grails GORM. A Rails domain class/entity is composed of two files, a migration file and a Rails model class file. All model attributes and datatypes are defined in the migration file and/or database, using an SQL wrapper. So that the migration files can be directly translated to pure SQL; writing a migration file is like writing SQL DDL (CREATE statements). At this point the associated Rails model class file is empty. From an Object Oriented point of view, this is an ugly approach; the attributes are defined in SQL/db instead of the domain model class itself. It also makes IDE autocompletion and refactoring hard. It also makes it cumbersome for yourself to lookup the attributes for a domain model class; you have to look in multiple files for it! Making relations is done both using SQL foreign keys and is similar to Grails, putting special variable names or methods in the model class: belongs_to, has_many etc. Validation is also done in the model class. When you add new attributes to a model, you can use a new Rails Migrations to propagate it to the DB. Which basically is a SQL change table add column command.

    So the Domain model in Rails is database based, instead of OOP based like Grails. I know OOP and Hibernate, so I like starting with OOP for the domain model and generate the DB from it. Btw Hibernate can do both; it can reverse engineer/generate Java classes from an existing DB, and it can generate the DB from domain model classes.

  • Both have books available. Rails has more books.
  • Grails has Implicit Dynamic Scaffolding (optional), you don’t have to write the view. The view (html) is generated, and changes automatically when you add new properties to the model. This can be useful when learning the framework. But when coding a webapp, you probably write the view yourself. Rails had Implicit Dynamic Scaffolding in the past, but they removed it because it’s only useful for beginners. Both frameworks also have explicit scaffolding.

    I prefer the scaffold generated by Rails, but Grails has column sorting.

  • Grails uses Groovy, so you can use new or existing Java classes/libraries, and thus have both dynamic and static typed. You can even code pure Java in Groovy classes, or mix them. Rails uses Ruby, but Rails also has third party JRuby, which allows you to call Ruby classes from Java classes and back. JRuby is less integrated with Java than Groovy. Like Grails, with JRuby you can run a web-app in a Java EE environment. JRuby is probably only interesting for those who want to use existing Java classes.
  • Grails is faster than Rails, but with JRuby, Rails can increase its speed. The ruby Merb framework (similar to Rails) will be merged with Rails in the future. Merb is faster than Rails.
  • In Rails, it’s very easy to pass objects from the controller to the view, because of Ruby. For example in Rails:
    		*** ProductController ***
    		@product = Product.find(1)
    		@category = Category.find(1)

    In Grails you have an extra step with duplicated names.

    		*** ProductController ***
    		product = Product.find(1)
    		category = Category.find(1)
    		['product' : product, 'category' : category] // last line in controller action. It defines an identifier twice.
  • Rails has a lot of different names for the same thing, which can be confusing. This is caused by Rails pluralization; controller names and db tables are automatically named in plural from a singular name. For example, when you have a domain class for a shipping address. In Rails you’ll find names:
    • ShippingAddress (model classname)
    • shipping_address (model filename, attribute name)
    • shipping_addresses (controller filename, attribute list name, db table and migration name)
    • ShippinAdresses (controller classname)
    • Pluralization can be turned off, but is enabled by default, it’s the Rails way of naming.

  • Grails uses Jetty as default webserver in development mode. Rails uses Mongrel by default, and Webrick in the past.
  • When generating a Grails project, the project will still use some script files from the Grails_home dir. Rails copies these files, which makes it easier to adapt Rails projects without influencing other projects.
  • Grails uses Java underneath it; it uses more memory than Rails. This probably makes hosting a Rails app cheaper than a Grails (Java) app. (Hosting can be cheap when you use a Virtual Private Server.)
  • Grails has an expression language, like JSP. In a Grails view, you can use:
    • <%= product.getPrice() %>, or
    • ${product.price}

    Rails doesn’t have an expression language, so you can only use <%= product.price %>. I prefer using expression language when possible; it keeps the view cleaner.

  • Grails uses Groovy, which IMO is easier to learn than Ruby, especially is you already know Java. Groovy uses a syntax that is found in other languages, like C++, Javascript and PHP. Ruby however differs from that. Also, in Ruby, there are often multiple ways to do something. Sometimes the language remove one way, while leaving the other. This can be confusing. Ruby, also has no method overloading.
  • Rails feels more matured than Grails because of it’s better View layer. It also is already at version 2.2 where Grails is at 1.0.
  • Rails has a built-in benchmark, profiler. Grails has it using third party plugins.
  • Both Grails and Rails configuration files are easy to read. Grails probably has an easier syntax.
  • Rails inspired other frameworks, like Grails.
  • Rails seems to be released/updated more often. This might be because Graeme Rocher (a Grails developer) was working a Grails book the last couple of months.

Specific for Rails:

  • Easy to change from a single Rails version on a system shared by multiple projects, to a single Rails per project config. So that you can run multiple Rails versions if needed.
  • Very REST by default. nested url resources like /articles/1/comments/5/edit
  • security, authenticity_token against cross site request forgery.
  • You need to restart the webserver when you add a scaffold for a model, because routes.rb gets changed.
  • Rails’ Active Record uses a lot more SQL in code than Grails (Hibernate).
  • Changes in routes.rb requires a restart. Thus adding new resources (like REST controller for a model) requires a server restart.
  • The DB drives the Model. E.g. default model values have to be specified in the DB.
  • Cumbersom to find how you can code in Model classes as Plain Old Ruby Objects. For example you can’t use the initialize method?
  • Rails with Capistrano and Mongrel make it easy to implement load balancing. Not sure if this is also possible with Grails.
  • Rails has special url_path variables/methods, which makes writing urls easier. For example, it automatically has variable/methods names like edit_article_url(article) that translate to the correct URL.

Specific for Grails

  • Grails: Sitemesh breaks the OSIV (Open Session In View) pattern. So you cannot use full GORM in layouts. Something that really needs to be fixed.
  • No Java annotations in Groovy?
  • (Groovy) console/shell tool cannot work with def keyword?
  • Hard to debug errors messages
  • doesn’t work out of the box with all third party servlet based software. For example, UrlRewriteFilter doesn’t work.
  • less secure? Via a html form POST hackers can set properties for new objects even is those properties aren’t defined in the form itself. (This happens when the new MyDomain(params) is used.) FIX: use command objects or bindData method. Not sure if Rails has a better solution.
  • Jsession id’s are sometimes visible in the url. e.g. when using the flash for messages.
  • Grails: Looking up a pretty url given a controller and action and id, isn’t possible? Only the default url scheme is used?

Summary and my preferences:

  • I like both Grails and Rails.
  • I prefer the Groovy language over Ruby, especially because Groovy supports static typed and Java. Although writing in Ruby is also cool.
  • Grails really has to do something about the view layer. Rails is a lot better at this point.
  • I dislike that Rails domain model is database centered. I doesn’t feel object oriented. You cannot use plain Ruby classes, you have to look in the migrations for model attributes. You cannot simply use an initialiser/constructor of the model in Rails, for example when you want to set default values. How do you make a constructor that receives parameters? Ruby also doesn’t support method overloading. The Rails domain model feels limited in a OOP way.
  • Rails feels more matured.
  • Grails is more enterprise and Java EE focussed, using Spring and Hibernate.
  • Grails focusses on the use and incorporation of other well known frameworks using plugins, making it possible to use other webframeworks if needed. For example: Struts, Wicket, Flex, GWT and Echo.
  • Rails project configuration is more flexible.
  • I should have a better look at JRuby.