Class: Rack::SPARQL::ContentNegotiation
- Defined in:
- vendor/bundler/ruby/3.3.0/bundler/gems/sparql-796d3be4aa08/lib/rack/sparql/conneg.rb
Overview
Rack middleware for SPARQL content negotiation.
Uses HTTP Content Negotiation to find an appropriate RDF
format to serialize any result with a body being RDF::Enumerable
.
Override content negotiation by setting the :format option to #initialize.
This endpoint also serves the fuction of Rack::LinkedData, as it will serialize SPARQL results, which may be RDF Graphs
Constant Summary collapse
- VARY =
{'Vary' => 'Accept'}.freeze
Instance Attribute Summary collapse
- #app ⇒ #call readonly
- #options ⇒ Hash{Symbol => Object} readonly
Instance Method Summary collapse
- #accept_entry(entry) ⇒ Object protected
-
#call(env) ⇒ Array(Integer, Hash, #each)
Handles a Rack protocol request.
-
#http_error(code, message = nil, headers = {}) ⇒ Array(Integer, Hash, #each)
protected
Outputs an HTTP
4xx
or5xx
response. -
#http_status(code) ⇒ String
protected
Returns the standard HTTP status message for the given status
code
. -
#initialize(app, options = {}) ⇒ ContentNegotiation
constructor
A new instance of ContentNegotiation.
-
#not_acceptable(message = nil) ⇒ Array(Integer, Hash, #each)
protected
Outputs an HTTP
406 Not Acceptable
response. -
#parse_accept_header(header) ⇒ Array<String>
protected
Parses an HTTP
Accept
header, returning an array of MIME content types ordered by the precedence rules defined in HTTP/1.1 Section 14.1. -
#serialize(env, status, headers, body) ⇒ Array(Integer, Hash, #each)
Serializes a SPARQL query result into a Rack protocol response using HTTP content negotiation rules or a specified Content-Type.
Constructor Details
#initialize(app, options = {}) ⇒ ContentNegotiation
Returns a new instance of ContentNegotiation.
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# File 'vendor/bundler/ruby/3.3.0/bundler/gems/sparql-796d3be4aa08/lib/rack/sparql/conneg.rb', line 32 def initialize(app, = {}) @app, @options = app, end |
Instance Attribute Details
#app ⇒ #call (readonly)
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# File 'vendor/bundler/ruby/3.3.0/bundler/gems/sparql-796d3be4aa08/lib/rack/sparql/conneg.rb', line 21 def app @app end |
Instance Method Details
#accept_entry(entry) ⇒ Object (protected)
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# File 'vendor/bundler/ruby/3.3.0/bundler/gems/sparql-796d3be4aa08/lib/rack/sparql/conneg.rb', line 119 def accept_entry(entry) type, * = entry.delete(' ').split(';') quality = 0 # we sort smallest first .delete_if { |e| quality = 1 - e[2..-1].to_f if e.start_with? 'q=' } [type, [quality, type.count('*'), 1 - .size]] end |
#call(env) ⇒ Array(Integer, Hash, #each)
Handles a Rack protocol request. Parses Accept header to find appropriate mime-type and sets content_type accordingly.
If result is RDF::Literal::Boolean
, RDF::Query::Results
, or RDF::Enumerable
The result is serialized using SPARQL::Results
Inserts ordered content types into the environment as ORDERED_CONTENT_TYPES
if an Accept header is present.
Normalizes application/x-www-form-urlencoded
to either application/sparql-query
or application/sparql-update
forms.
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# File 'vendor/bundler/ruby/3.3.0/bundler/gems/sparql-796d3be4aa08/lib/rack/sparql/conneg.rb', line 49 def call(env) env['ORDERED_CONTENT_TYPES'] = parse_accept_header(env['HTTP_ACCEPT']) if env.has_key?('HTTP_ACCEPT') # Normalize application/x-www-form-urlencoded to application/sparql-query or application/sparql-update if env['REQUEST_METHOD'] == 'POST' && env.fetch('CONTENT_TYPE', 'application/x-www-form-urlencoded').to_s.start_with?('application/x-www-form-urlencoded') content = env['rack.input'].read params = Rack::Utils.parse_query(content) if query = params.delete('query') return [406, {"Content-Type" => "text/plain"}, ["Multiple query parameters"]] unless query.is_a?(String) env['rack.input'] = StringIO.new(query) env['CONTENT_TYPE'] = 'application/sparql-query' env['QUERY_STRING'] = Rack::Utils.build_query(params) elsif update = params.delete('update') return [406, {"Content-Type" => "text/plain"}, ["Multiple update parameters"]] unless update.is_a?(String) env['rack.input'] = StringIO.new(update) env['CONTENT_TYPE'] = 'application/sparql-update' env['QUERY_STRING'] = Rack::Utils.build_query(params) else env['rack.input'].rewind # never mind end end response = app.call(env) body = response[2].respond_to?(:body) ? response[2].body : response[2] body = body.first if body.is_a?(Array) && body.length == 1 && body.first.is_a?(RDF::Literal::Boolean) case body when RDF::Enumerable, RDF::Query::Solutions, RDF::Literal::Boolean response[2] = body # Put it back in the response, it might have been a proxy serialize(env, *response) else response end end |
#http_error(code, message = nil, headers = {}) ⇒ Array(Integer, Hash, #each) (protected)
Outputs an HTTP 4xx
or 5xx
response.
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# File 'vendor/bundler/ruby/3.3.0/bundler/gems/sparql-796d3be4aa08/lib/rack/sparql/conneg.rb', line 142 def http_error(code, = nil, headers = {}) = http_status(code) + (.nil? ? "\n" : " (#{})\n") [code, {'Content-Type' => 'text/plain; charset=utf-8'}.merge(headers), []] end |
#http_status(code) ⇒ String (protected)
Returns the standard HTTP status message for the given status code
.
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# File 'vendor/bundler/ruby/3.3.0/bundler/gems/sparql-796d3be4aa08/lib/rack/sparql/conneg.rb', line 152 def http_status(code) [code, Rack::Utils::HTTP_STATUS_CODES[code]].join(' ') end |
#not_acceptable(message = nil) ⇒ Array(Integer, Hash, #each) (protected)
Outputs an HTTP 406 Not Acceptable
response.
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# File 'vendor/bundler/ruby/3.3.0/bundler/gems/sparql-796d3be4aa08/lib/rack/sparql/conneg.rb', line 131 def not_acceptable( = nil) http_error(406, , VARY) end |
#parse_accept_header(header) ⇒ Array<String> (protected)
Parses an HTTP Accept
header, returning an array of MIME content
types ordered by the precedence rules defined in HTTP/1.1 Section 14.1.
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# File 'vendor/bundler/ruby/3.3.0/bundler/gems/sparql-796d3be4aa08/lib/rack/sparql/conneg.rb', line 114 def parse_accept_header(header) entries = header.to_s.split(',') entries.map { |e| accept_entry(e) }.sort_by(&:last).map(&:first) end |
#serialize(env, status, headers, body) ⇒ Array(Integer, Hash, #each)
Serializes a SPARQL query result into a Rack protocol response using HTTP content negotiation rules or a specified Content-Type.
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# File 'vendor/bundler/ruby/3.3.0/bundler/gems/sparql-796d3be4aa08/lib/rack/sparql/conneg.rb', line 90 def serialize(env, status, headers, body) begin = {} [:content_types] = env['ORDERED_CONTENT_TYPES'] if env['ORDERED_CONTENT_TYPES'] .merge!(@options) results = ::SPARQL.serialize_results(body, **) raise RDF::WriterError, "can't serialize results" unless results headers = headers.merge(VARY).merge('Content-Type' => results.content_type) # FIXME: don't overwrite existing Vary headers [status, headers, [results]] rescue RDF::WriterError => e # Use this instead of not_acceptable so that headers are not lost. http_error(406, e., headers.merge(VARY)) end end |