Grails and Rails: Domain Classes and Web Services

Let's take a brief look at the differences between Grails and Rails in term of persisting domain classes and creating web services. Both Grails and Rails are MVC frameworks and are very similar in terms of code syntax.

1. Domain Class Persistence

In Grails:

class Person {
    String firstName
    String lastName
    String email
    Date birthDate
    Address address

    static constraint = {
        firstName(blank:false)
        lastName(blank:false)
        email(blank:false, email:true) // check if it's really e-mail
    }
}

class Address {
     String street
     String city
     String country
     Person person

     static belongsTo = Person
}

In Rails, attributes can be inferred from the database table's structure:

class Person <>
    # Expects database schema to have a table "person" 
    # with columns first_name, last_name, email, birth_date

  validates_presence_of :first_name, :last_name, :email 
end

class Address <> has_one :address 
   belongs_to :person
end

2. Making a service class available as a web service

In Grails, inside a controller closure:

def listAllPeople = {
    def pplList = Person.list() // or by query Person.findByLastName("Hewitts") 
    render pplList as XML 
    // render pplList as JSON
}

In Rails, inside a controller block:

def listAllPeople 
   @pplList = Person.all # or by query Person.find_by_last_name("Hewitts") 
   render :xml => @pplList
  # render :json => pplList 
end

Note:
1. Grails will auto-generate the database schema and update the schema when more domain fields are added to the class. It's also possible to go in the reverse direction if you prefer starting with an existing schema.
2. Rails expects the database schema to be pre-created and to conform to camel case naming conventions.
3. Grails has the notion of service classes which are commonly used for business logic and can be use in a controller as a web service end point.