Free OData V4.0 Library for Ruby
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README.md

FrOData - Free OData V4.0 library for Ruby

Happy Little Entities

Bob Ross

The FrOData gem provides a simple wrapper around the OData Version 4.0 API protocol. It has the ability to automatically inspect compliant APIs and expose the relevant Ruby objects dynamically. It also provides a set of code generation tools for quickly bootstrapping more custom service libraries.

This gem supports OData Version 4.0. Support for older versions is not a goal.

If you need a gem to integration with OData Version 3, you can use James Thompson's original OData gem, upon which this gem is based.

Gem Version Build Status Maintainability Test Coverage Documentation

Installation

Add this line to your application's Gemfile:

gem 'frodata'

And then execute:

$ bundle

Or install it yourself as:

$ gem install frodata

Usage

Services & the Service Registry

The FrOData gem provides a number of core classes, the two most basic ones are the FrOData::Service and the FrOData::ServiceRegistry. The only time you will need to worry about the FrOData::ServiceRegistry is when you have multiple FrOData services you are interacting with that you want to keep straight easily. The nice thing about FrOData::Service is that it automatically registers with the registry on creation, so there is no manual interaction with the registry necessary.

To create an FrOData::Service simply provide the location of a service endpoint to it like this:

  FrOData::Service.new('http://services.odata.org/V4/OData/OData.svc')

You may also provide an options hash after the URL. It is suggested that you supply a name for the service via this hash like so:

  FrOData::Service.new('http://services.odata.org/V4/OData/OData.svc', name: 'ODataDemo')

For more information regarding available options and how to configure a service instance, refer to Service Configuration below.

This one call will setup the service and allow for the discovery of everything the other parts of the FrOData gem need to function. The two methods you will want to remember from FrOData::Service are #service_url and #name. Both of these methods are available on instances and will allow for lookup in the FrOData::ServiceRegistry, should you need it.

Using either the service URL or the name provided as an option when creating an FrOData::Service will allow for quick lookup in the FrOData::ServiceRegistry like such:

  FrOData::ServiceRegistry['http://services.odata.org/V4/OData/OData.svc']
  FrOData::ServiceRegistry['ODataDemo']

Both of the above calls would retrieve the same service from the registry. At the moment there is no protection against name collisions provided in FrOData::ServiceRegistry. So, looking up services by their service URL is the most exact method, but lookup by name is provided for convenience.

Service Configuration

Metadata File

Typically the metadata file of a service can be quite large. You can speed your load time by forcing the service to load the metadata from a file rather than a URL. This is only recommended for testing purposes, as the metadata file can change.

  service = FrOData::Service.new('http://services.odata.org/V4/OData/OData.svc', {
    name: 'ODataDemo',
    metadata_file: "metadata.xml",
  })

Headers & Authorization

The OData protocol does not deal with authentication and authorization at all, nor does it need to, since HTTP already provides many different options for this, such as HTTP Basic or token authorization. Hence, this gem does not implement any special authentication mechanisms either, and relies on the underlying HTTP library (Faraday) to take care of this.

Setting Custom Headers

You can customize request headers with the :connection option key. This allows you to e.g. set custom headers (such as Authorization) that may be required by your service.

  service = FrOData::Service.new('http://services.odata.org/V4/OData/OData.svc', {
    name: 'ODataDemo',
    connection: {
      headers: {
        "Authorization" => "Bearer #{access_token}"
      }
    }
  })
Using Authentication Helpers

You may also set up authorization by directly accessing the underlying Faraday::Connection object yielded to the constructor (as explained in Advanced Customization below). This allows you to make use of Faraday's authentication helpers, such as basic_auth or token_auth.

For instance, if your service requires HTTP basic authentication:

  service = FrOData::Service.new('http://services.odata.org/V4/OData/OData.svc', {
    name: 'ODataDemo'
  }) do |conn|
    conn.basic_auth('username', 'password')
  end

Advanced Connection Customization

Under the hood, the gem uses the Faraday HTTP library to provide flexible integration of various Ruby HTTP backends.

There are several ways to access the underlying Faraday::Connection:

As a service option

If you already have a Faraday::Connection instance that you want the service to use, you can simply pass it to the constructor instead of the service URL as first parameter. In this case, you'll be setting the service URL on the connection object, as shown below:

  conn = Faraday.new('http://services.odata.org/V4/OData/OData.svc') do |conn|
    # ... customize connection ...
  end

  service = FrOData::Service.new(conn, name: 'ODataDemo')

NOTE: if you use this method, any options set via the :connection options key will be ignored.

Passing a block to the constructor

Alternatively, the connection object is also yielded by the constructor, so you may customize it by passing a block argument. For instance, if you wanted to use Typhoeus as your HTTP library:

  service = FrOData::Service.new('http://services.odata.org/V4/OData/OData.svc', {
    name: 'ODataDemo'
  }) do |conn|
    conn.adapter :typhoeus
  end

Exploring a Service

Once instantiated, you can request various information about the service, such as the names and types of entity sets it exposes, or the names of the entity types (and custom datatypes) it defines.

For example:

Get a list of available entity types

  service.entity_types
  # => [
  #   "ODataDemo.Product",
  #   "ODataDemo.FeaturedProduct",
  #   "ODataDemo.ProductDetail",
  #   "ODataDemo.Category",
  #   "ODataDemo.Supplier",
  #   "ODataDemo.Person",
  #   "ODataDemo.Customer",
  #   "ODataDemo.Employee",
  #   "ODataDemo.PersonDetail",
  #   "ODataDemo.Advertisement"
  # ]

Get a list of entity sets

  service.entity_sets
  # => {
  #   "Products"       => "ODataDemo.Product",
  #   "ProductDetails" => "ODataDemo.ProductDetail",
  #   "Categories"     => "ODataDemo.Category",
  #   "Suppliers"      => "ODataDemo.Supplier",
  #   "Persons"        => "ODataDemo.Person",
  #   "PersonDetails"  => "ODataDemo.PersonDetail",
  #   "Advertisements" => "ODataDemo.Advertisement"
  # }

Get a list of complex types

  service.complex_types
  # => ["ODataDemo.Address"]

Get a list of enum types

  service.enum_types
  # => ["ODataDemo.ProductStatus"]

For more examples, refer to usage_example_specs.rb.

Entity Sets

When it comes to reading data from an OData service the most typical way will be via FrOData::EntitySet instances. Under normal circumstances you should never need to worry about an FrOData::EntitySet directly. For example, to get an FrOData::EntitySet for the products in the ODataDemo service simply access the entity set through the service like this:

  service = FrOData::Service.new('http://services.odata.org/V4/OData/OData.svc')
  products = service['ProductsSet'] # => FrOData::EntitySet

FrOData::EntitySet instances implement the Enumerable module, meaning you can work with them very naturally, like this:

  products.each do |entity|
    entity # => FrOData::Entity for type Product
  end

You can get a list of all your entity sets like this:

  service.entity_sets

Count

Some versions of Microsoft CRM do not support count.

  products.count

Collections

You can you the following methods to grab a collection of Entities:

  products.each do |entity|
    ...
  end

The first entity object returns a single entity object.

  products.first

first(x) returns an array of entity objects.

  products.first(x)

Find a certain Entity

  service['ProductsSet']['<primary key of entity>']

With certain navigation properties expanded (i.e. eagerly loaded):

  # Eagerly load a single navigation property
  service['ProductsSet', expand: 'Categories']

  # Eagerly load multiple navigation properties
  service['ProductsSet', expand: ['Categories', 'Supplier']]

  # Eagerly load ALL navigation properties
  service['ProductsSet', expand: :all]

Entities

FrOData::Entity instances represent individual entities, or records, in a given service. They are returned primarily through interaction with instances of FrOData::EntitySet. You can access individual properties on an FrOData::Entity like so:

  product = products.first # => FrOData::Entity
  product['Name']  # => 'Bread'
  product['Price'] # => 2.5 (Float)

Individual properties on an FrOData::Entity are automatically typecast by the gem, so you don't have to worry about too much when working with entities. The way this is implemented internally guarantees that an FrOData::Entity is always ready to save back to the service or FrOData::EntitySet, which you do like so:

  service['Products'] << product # Write back to the service
  products << product        # Write back to the Entity Set

You can get a list of all your entities like this:

  service.entity_types

Entity Properties

Reading, parsing and instantiating all properties of an entity can add up to a significant amount of time, particularly for those entities with a large number of properties. To speed this process up all properties are lazy loaded. Which means it will store the name of the property, but will not parse and instantiate the property until you want to use it.

You can find all the property names of your entity with

  product.property_names

You can grab the parsed value of the property as follows:

  product["Name"]

or, you can get a hold of the property class instance using

  product.get_property("Name")

This will parse and instantiate the property if it hasn't done so yet.

Lenient Property Validation

By default, we use strict property validation, meaning that any property validation errors in the data will raise an exception. However, you may encounter OData implementations in the wild that break the specs in strange and surprising ways (shocking, I know!).

Since it's often better to get some data instead of nothing at all, you can optionally make the property validation lenient. Simply add strict: false to the service constructor options. In this mode, any property validation error will log a warning instead of raising an exception. The corresponding property value will be nil (even if the property is declared as not allowing NULL values).

  service = FrOData::Service.new('http://services.odata.org/V4/OData/OData.svc', strict: false)
  # -- alternatively, for an existing service instance --
  service.options[:strict] = false

Queries

FrOData::Query instances form the base for finding specific entities within an FrOData::EntitySet. A query object exposes a number of capabilities based on the System Query Options provided for in the OData V4.0 specification. Below is just a partial example of what is possible:

  query = service['Products'].query
  query.where(query[:Price].lt(15))
  query.where(query[:Rating].gt(3))
  query.limit(3)
  query.skip(2)
  query.order_by("Name")
  query.select("Name,CreatedBy")
  query.inline_count
  results = query.execute
  results.each {|product| puts product['Name']}

The process of querying is kept purposely verbose to allow for lazy behavior to be implemented at higher layers. Internally, FrOData::Query relies on the FrOData::Query::Criteria for the way the where method works. You should refer to the published RubyDocs for full details on the various capabilities:

Contributing

  1. Fork it (https://github.com/[my-github-username]/odata/fork)
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create a new Pull Request

Credits

Many thanks go to James Thompson, who wrote the original OData (Version 3.0) gem.

Also, I would like to thank W+R Studios for generously allowing me to work on Open Source software like this. If you want to work on interesting challenges with an awesome team, check out our open positions.