Module: OAI::Provider
- Included in:
- Base
- Defined in:
- lib/oai/provider.rb,
lib/oai/provider/model.rb,
lib/oai/provider/response.rb,
lib/oai/provider/partial_result.rb,
lib/oai/provider/resumption_token.rb,
lib/oai/provider/model/activerecord_wrapper.rb,
lib/oai/provider/model/activerecord_caching_wrapper.rb
Overview
# OAI::Provider
Open Archives Initiative - Protocol for Metadata Harvesting see <www.openarchives.org/>
## Features
-
Easily setup a simple repository
-
Simple integration with ActiveRecord
-
Dublin Core metadata format included
-
Easily add addition metadata formats
-
Adaptable to any data source
-
Simple resumption token support
## Usage
To create a functional provider either subclass Base, or reconfigure the defaults.
### Sub classing a provider
“‘ruby
class MyProvider < Oai::Provider
repository_name 'My little OAI provider'
repository_url 'http://localhost/provider'
record_prefix 'oai:localhost'
admin_email 'root@localhost' # String or Array
source_model MyModel.new # Subclass of OAI::Provider::Model
end
“‘
### Configuring the default provider
“‘ruby
class Oai::Provider::Base
repository_name 'My little OAI Provider'
repository_url 'http://localhost/provider'
record_prefix 'oai:localhost'
admin_email 'root@localhost'
sample_identifier 'oai:pubmedcentral.gov:13900'
source_model MyModel.new
end
“‘
The provider does allow a URL to be passed in at request processing time in case the repository URL cannot be determined ahead of time.
## Integrating with frameworks
### Camping
In the Models module of your camping application post model definition:
“‘ruby
class CampingProvider < OAI::Provider::Base
repository_name 'Camping Test OAI Repository'
source_model ActiveRecordWrapper.new(YOUR_ACTIVE_RECORD_MODEL)
end
“‘
In the Controllers module:
“‘ruby
class Oai
def get
@headers['Content-Type'] = 'text/xml'
provider = Models::CampingProvider.new
provider.process_request(@input.merge(:url => "http:"+URL(Oai).to_s))
end
end
“‘
The provider will be available at “/oai”
### Rails
At the bottom of environment.rb create a OAI Provider:
“‘ruby
# forgive the standard blog example.
require 'oai'
class BlogProvider < OAI::Provider::Base
repository_name 'My little OAI Provider'
repository_url 'http://localhost:3000/provider'
record_prefix 'oai:blog'
admin_email 'root@localhost'
source_model OAI::Provider::ActiveRecordWrapper.new(Post)
sample_identifier 'oai:pubmedcentral.gov:13900'
end
“‘
Create a custom controller:
“‘ruby
class OaiController < ApplicationController
def index
# Remove controller and action from the options. Rails adds them automatically.
= params.delete_if { |k,v| %w{controller action}.include?(k) }
provider = BlogProvider.new
response = provider.process_request()
render :text => response, :content_type => 'text/xml'
end
end
“‘
Special thanks to Jose Hales-Garcia for this solution.
## Supporting custom metadata formats
See MetadataFormat for details.
## ActiveRecord Integration
ActiveRecord integration is provided by the ‘ActiveRecordWrapper` class. It takes one required paramater, the class name of the AR class to wrap, and optional hash of options.
Valid options include:
-
‘timestamp_field` - Specifies the model field to use as the update filter. Defaults to `updated_at`.
-
‘limit` - Maximum number of records to return in each page/set. Defaults to 100. The wrapper will paginate the result via resumption tokens. _Caution: specifying too large a limit will adversely affect performance._
Mapping from a ActiveRecord object to a specific metadata format follows this set of rules:
-
Does ‘Model#to_metadata_prefix` exist? If so just return the result.
-
Does the model provide a map via ‘Model.map_metadata_prefix`? If so use the map to generate the xml document.
-
Loop thru the fields of the metadata format and check to see if the model responds to either the plural, or singular of the field.
For maximum control of the xml metadata generated, it’s usually best to provide a ‘to_metadata_prefix` in the model. If using Builder be sure not to include any `instruct!` in the xml object.
### Explicit creation example
“‘ruby
class Post < ActiveRecord::Base
def to_oai_dc
xml = Builder::XmlMarkup.new
xml.tag!("oai_dc:dc",
'xmlns:oai_dc' => "http://www.openarchives.org/OAI/2.0/oai_dc/",
'xmlns:dc' => "http://purl.org/dc/elements/1.1/",
'xmlns:xsi' => "http://www.w3.org/2001/XMLSchema-instance",
'xsi:schemaLocation' =>
%{http://www.openarchives.org/OAI/2.0/oai_dc/
http://www.openarchives.org/OAI/2.0/oai_dc.xsd}) do
xml.tag!('oai_dc:title', title)
xml.tag!('oai_dc:description', text)
xml.tag!('oai_dc:creator', user)
.each do |tag|
xml.tag!('oai_dc:subject', tag)
end
end
xml.target!
end
end
“‘
### Mapping Example
“‘ruby
# Extremely contrived mapping
class Post < ActiveRecord::Base
def self.map_oai_dc
{:subject => :tags,
:description => :text,
:creator => :user,
:contibutor => :comments}
end
end
“‘
Defined Under Namespace
Modules: Metadata, Response Classes: ActiveRecordCachingWrapper, ActiveRecordWrapper, Base, Model, OaiEntry, OaiToken, PartialResult, ResumptionToken