Class: SPARQL::Client

Inherits:
Object
  • Object
show all
Defined in:
lib/sparql/client.rb,
lib/sparql/client/query.rb,
lib/sparql/client/update.rb,
lib/sparql/client/version.rb,
lib/sparql/client/repository.rb

Overview

A SPARQL 1.0/1.1 client for RDF.rb.

See Also:

Defined Under Namespace

Modules: Update, VERSION Classes: ClientError, MalformedQuery, Query, QueryElement, Repository, ServerError

Constant Summary collapse

RESULT_JSON = 
'application/sparql-results+json'.freeze
RESULT_XML = 
'application/sparql-results+xml'.freeze
RESULT_CSV = 
'text/csv'.freeze
RESULT_TSV = 
'text/tab-separated-values'.freeze
RESULT_BOOL =

Sesame-specific

'text/boolean'.freeze
RESULT_BRTR =

Sesame-specific

'application/x-binary-rdf-results-table'.freeze
RESULT_ALL = 
[
  RESULT_JSON,
  RESULT_XML,
  RESULT_BOOL,
  "#{RESULT_TSV};q=0.8",
  "#{RESULT_CSV};q=0.2",
  '*/*;q=0.1'
].join(', ').freeze
GRAPH_ALL = 
(
  RDF::Format.content_types.keys +
  ['*/*;q=0.1']
).join(', ').freeze
ACCEPT_JSON = 
{'Accept' => RESULT_JSON}.freeze
ACCEPT_XML = 
{'Accept' => RESULT_XML}.freeze
ACCEPT_CSV = 
{'Accept' => RESULT_CSV}.freeze
ACCEPT_TSV = 
{'Accept' => RESULT_TSV}.freeze
ACCEPT_BRTR = 
{'Accept' => RESULT_BRTR}.freeze
ACCEPT_RESULTS = 
{'Accept' => RESULT_ALL}.freeze
ACCEPT_GRAPH = 
{'Accept' => GRAPH_ALL}.freeze
DEFAULT_PROTOCOL = 
1.0
DEFAULT_METHOD = 
:post
XMLNS = 
{'sparql' => 'http://www.w3.org/2005/sparql-results#'}.freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(url, **options, &block) ⇒ Client

Initialize a new sparql client, either using the URL of a SPARQL endpoint or an RDF::Queryable instance to use the native SPARQL gem.

Parameters:

  • url (String, RDF::Queryable, #to_s) —

    URL of endpoint, or queryable object.

  • options (Hash{Symbol => Object})

Options Hash (**options):

  • :method (Symbol) — default: DEFAULT_METHOD
  • :protocol (Number) — default: DEFAULT_PROTOCOL
  • :headers (Hash) —

    HTTP Request headers

    Defaults Accept header based on available reader content types if triples are expected and to SPARQL result types otherwise, to allow for content negotiation based on available readers.

    Defaults User-Agent header, unless one is specified.

  • :read_timeout (Hash) 


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# File 'lib/sparql/client.rb', line 95

def initialize(url, **options, &block)
  case url
  when RDF::Queryable
    @url, @options = url, options.dup
  else
    @url, @options = RDF::URI.new(url.to_s), options.dup
    @headers = @options.delete(:headers) || {}
    @http = http_klass(@url.scheme)

    # Close the http connection when object is deallocated
    ObjectSpace.define_finalizer(self, self.class.finalize(@http))
  end

  if block_given?
    case block.arity
      when 1 then block.call(self)
      else instance_eval(&block)
    end
  end
end

Instance Attribute Details

#headers ⇒ Hash{String => String} (readonly)

The HTTP headers that will be sent in requests to the endpoint.

Returns:

  • (Hash{String => String}) 


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# File 'lib/sparql/client.rb', line 70

def headers
  @headers
end

#options ⇒ Hash{Symbol => Object} (readonly)

Any miscellaneous configuration.

Returns:

  • (Hash{Symbol => Object}) 


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# File 'lib/sparql/client.rb', line 76

def options
  @options
end

#url ⇒ RDF::URI, RDF::Queryable (readonly)

The SPARQL endpoint URL, or an RDF::Queryable instance, to use the native SPARQL engine.

Returns:

  • (RDF::URI, RDF::Queryable) 


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# File 'lib/sparql/client.rb', line 64

def url
  @url
end

Class Method Details

.finalize(klass) ⇒ Object

Close the http connection when object is deallocated



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# File 'lib/sparql/client.rb', line 117

def self.finalize(klass)
  proc do
    klass.shutdown if klass.respond_to?(:shutdown)
  end
end

.parse_csv_bindings(csv, nodes = {}) ⇒ <RDF::Query::Solutions>

Parameters:

  • csv (String, Array<Array<String>>)

Returns:

  • (<RDF::Query::Solutions>)

See Also:



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# File 'lib/sparql/client.rb', line 453

def self.parse_csv_bindings(csv, nodes = {})
  require 'csv' unless defined?(::CSV)
  csv = CSV.parse(csv.to_s) unless csv.is_a?(Array)
  vars = csv.shift
  solutions = RDF::Query::Solutions.new
  csv.each do |row|
    solution = RDF::Query::Solution.new
    row.each_with_index do |v, i|
      term = case v
      when /^_:(.*)$/ then nodes[$1] ||= RDF::Node($1)
      when /^\w+:.*$/ then RDF::URI(v)
      else RDF::Literal(v)
      end
      solution[vars[i].to_sym] = term
    end
    solutions << solution
  end
  solutions
end

.parse_json_bindings(json, nodes = {}) ⇒ <RDF::Query::Solutions>

Parameters:

  • json (String, Hash)

Returns:

  • (<RDF::Query::Solutions>)

See Also:



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# File 'lib/sparql/client.rb', line 413

def self.parse_json_bindings(json, nodes = {})
  require 'json' unless defined?(::JSON)
  json = JSON.parse(json.to_s) unless json.is_a?(Hash)
  case
    when json.has_key?('boolean')
      json['boolean']
    when json.has_key?('results')
      solutions = json['results']['bindings'].map do |row|
        row = row.inject({}) do |cols, (name, value)|
          cols.merge(name.to_sym => parse_json_value(value, nodes))
        end
        RDF::Query::Solution.new(row)
      end
      RDF::Query::Solutions.new(solutions)
  end
end

.parse_json_value(value, nodes = {}) ⇒ RDF::Value

Parameters:

  • value (Hash{String => String})

Returns:

  • (RDF::Value)

See Also:



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# File 'lib/sparql/client.rb', line 435

def self.parse_json_value(value, nodes = {})
  case value['type'].to_sym
    when :bnode
      nodes[id = value['value']] ||= RDF::Node.new(id)
    when :uri
      RDF::URI.new(value['value'])
    when :literal
      RDF::Literal.new(value['value'], datatype: value['datatype'], language: value['xml:lang'])
    when :'typed-literal'
      RDF::Literal.new(value['value'], datatype: value['datatype'])
    else nil
  end
end

.parse_tsv_bindings(tsv, nodes = {}) ⇒ <RDF::Query::Solutions>

Parameters:

  • tsv (String, Array<Array<String>>)

Returns:

  • (<RDF::Query::Solutions>)

See Also:



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# File 'lib/sparql/client.rb', line 477

def self.parse_tsv_bindings(tsv, nodes = {})
  tsv = tsv.lines.map {|l| l.chomp.split("\t")} unless tsv.is_a?(Array)
  vars = tsv.shift.map {|h| h.sub(/^\?/, '')}
  solutions = RDF::Query::Solutions.new
  tsv.each do |row|
    solution = RDF::Query::Solution.new
    row.each_with_index do |v, i|
      if !v.empty?
        term = RDF::NTriples.unserialize(v) || case v
        when /^\d+\.\d*[eE][+-]?[0-9]+$/  then RDF::Literal::Double.new(v)
        when /^\d*\.\d+[eE][+-]?[0-9]+$/  then RDF::Literal::Double.new(v)
        when /^\d*\.\d+$/                 then RDF::Literal::Decimal.new(v)
        when /^\d+$/                      then RDF::Literal::Integer.new(v)
        else
          RDF::Literal(v)
        end
        nodes[term.id] = term if term.is_a? RDF::Node
        solution[vars[i].to_sym] = term
      end
    end
    solutions << solution
  end
  solutions
end

.parse_xml_bindings(xml, nodes = {}) ⇒ <RDF::Query::Solutions>

Parameters:

  • xml (String, IO, Nokogiri::XML::Node, REXML::Element)

Returns:

  • (<RDF::Query::Solutions>)

See Also:



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# File 'lib/sparql/client.rb', line 506

def self.parse_xml_bindings(xml, nodes = {})
  xml.force_encoding(::Encoding::UTF_8) if xml.respond_to?(:force_encoding)

  if defined?(::Nokogiri)
    xml = Nokogiri::XML(xml).root unless xml.is_a?(Nokogiri::XML::Document)
    case
      when boolean = xml.xpath("//sparql:boolean", XMLNS)[0]
        boolean.text == 'true'
      when results = xml.xpath("//sparql:results", XMLNS)[0]
        solutions = results.elements.map do |result|
          row = {}
          result.elements.each do |binding|
            name  = binding.attr('name').to_sym
            value = binding.elements.first
            row[name] = parse_xml_value(value, nodes)
          end
          RDF::Query::Solution.new(row)
        end
        RDF::Query::Solutions.new(solutions)
    end
  else
    # REXML
    xml = REXML::Document.new(xml).root unless xml.is_a?(REXML::Element)
    case
      when boolean = xml.elements['boolean']
        boolean.text == 'true'
      when results = xml.elements['results']
        solutions = results.elements.map do |result|
          row = {}
          result.elements.each do |binding|
            name  = binding.attributes['name'].to_sym
            value = binding.select { |node| node.kind_of?(::REXML::Element) }.first
            row[name] = parse_xml_value(value, nodes)
          end
          RDF::Query::Solution.new(row)
        end
        RDF::Query::Solutions.new(solutions)
    end
  end
end

.parse_xml_value(value, nodes = {}) ⇒ RDF::Value

Parameters:

  • value (Nokogiri::XML::Element, REXML::Element)

Returns:

  • (RDF::Value)

See Also:



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# File 'lib/sparql/client.rb', line 551

def self.parse_xml_value(value, nodes = {})
  case value.name.to_sym
    when :bnode
      nodes[id = value.text] ||= RDF::Node.new(id)
    when :uri
      RDF::URI.new(value.text)
    when :literal
      lang     = value.respond_to?(:attr) ? value.attr('xml:lang') : value.attributes['xml:lang']
      datatype = value.respond_to?(:attr) ? value.attr('datatype') : value.attributes['datatype']
      RDF::Literal.new(value.text, language: lang, datatype: datatype)
    else nil
  end
end

.serialize_patterns(patterns, use_vars = false) ⇒ String

Serializes a SPARQL graph

Parameters:

  • patterns (RDF::Enumerable)
  • use_vars (Boolean) (defaults to: false) —

    (false) Use variables in place of BNodes

Returns:

  • (String) 


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# File 'lib/sparql/client.rb', line 638

def self.serialize_patterns(patterns, use_vars = false)
  patterns.map do |pattern|
    serialized_pattern = case pattern
    when SPARQL::Client::QueryElement then [pattern.to_s]
    else
      RDF::Statement.from(pattern).to_triple.each_with_index.map do |v, i|
        if i == 1
          SPARQL::Client.serialize_predicate(v)
        else
          SPARQL::Client.serialize_value(v, use_vars)
        end
      end
    end
    serialized_pattern.join(' ') + ' .'
  end
end

.serialize_predicate(value, rdepth = 0) ⇒ String

Serializes a SPARQL predicate

Parameters:

  • value (RDF::Value, Array, String)
  • rdepth (Fixnum) (defaults to: 0)

Returns:

  • (String) 


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# File 'lib/sparql/client.rb', line 617

def self.serialize_predicate(value,rdepth=0)
  case value
    when nil
      RDF::Query::Variable.new.to_s
    when String then value
    when Array
      s = value.map{|v|serialize_predicate(v,rdepth+1)}.join
      rdepth > 0 ? "(#{s})" : s
    when RDF::Value
      # abbreviate RDF.type in the predicate position per SPARQL grammar
      value.equal?(RDF.type) ? 'a' : serialize_value(value)
  end
end

.serialize_uri(uri) ⇒ String

Serializes a URI or URI string into SPARQL syntax.

Parameters:

  • uri (RDF::URI, String)

Returns:

  • (String) 


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# File 'lib/sparql/client.rb', line 584

def self.serialize_uri(uri)
  case uri
    when String then RDF::NTriples.serialize(RDF::URI(uri))
    when RDF::URI then RDF::NTriples.serialize(uri)
    else raise ArgumentError, "expected the graph URI to be a String or RDF::URI, but got #{uri.inspect}"
  end
end

.serialize_value(value, use_vars = false) ⇒ String

Serializes an RDF::Value into SPARQL syntax.

Parameters:

  • value (RDF::Value)
  • use_vars (Boolean) (defaults to: false) —

    (false) Use variables in place of BNodes

Returns:

  • (String) 


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# File 'lib/sparql/client.rb', line 599

def self.serialize_value(value, use_vars = false)
  # SPARQL queries are UTF-8, but support ASCII-style Unicode escapes, so
  # the N-Triples serializer is fine unless it's a variable:
  case
    when value.nil?      then RDF::Query::Variable.new.to_s
    when value.variable? then value.to_s
    when value.node?     then (use_vars ? RDF::Query::Variable.new(value.id) : value)
    else RDF::NTriples.serialize(value)
  end
end

Instance Method Details

#ask(*args, **options) ⇒ Query

Executes a boolean ASK query.

Parameters:

  • options (Hash{Symbol => Object}) —

    (see #initialize)

Returns:



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# File 'lib/sparql/client.rb', line 138

def ask(*args, **options)
  call_query_method(:ask, *args, **options)
end

#call_query_method(meth, *args, **options) ⇒ Object 



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# File 'lib/sparql/client.rb', line 291

def call_query_method(meth, *args, **options)
  client = self
  result = Query.send(meth, *args, **options)
  (class << result; self; end).send(:define_method, :execute) do
    client.query(self)
  end
  result
end

#clear(what, *arguments) ⇒ void #clear(what, *arguments, **options) ⇒ void

Executes a CLEAR operation.

This requires that the endpoint support SPARQL 1.1 Update.

Examples:

‘CLEAR GRAPH <example.org/>`

client.clear(:graph, RDF::URI("http://example.org/"))

‘CLEAR DEFAULT`

client.clear(:default)

‘CLEAR NAMED`

client.clear(:named)

‘CLEAR ALL`

client.clear(:all)

Overloads:

  • #clear(what, *arguments) ⇒ void

    This method returns an undefined value.

    Returns self.

    Parameters:

  • #clear(what, *arguments, **options) ⇒ void

    This method returns an undefined value.

    Returns self.

    Parameters:

    Options Hash (**options):

    • :silent (Boolean)

See Also:



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# File 'lib/sparql/client.rb', line 285

def clear(what, *arguments)
  self.update(Update::Clear.new(what, *arguments))
end

#clear_graph(graph_uri, **options) ⇒ void

This method returns an undefined value.

Executes a ‘CLEAR GRAPH` operation.

This is a convenience wrapper for the #clear method.

Examples:

‘CLEAR GRAPH <example.org/>`

client.clear_graph("http://example.org/")

Parameters:

  • graph_uri (RDF::URI, String)
  • options (Hash{Symbol => Object})

Options Hash (**options):

  • :silent (Boolean)

See Also:



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# File 'lib/sparql/client.rb', line 250

def clear_graph(graph_uri, **options)
  self.clear(:graph, graph_uri, **options)
end

#close ⇒ void

This method returns an undefined value.

Closes a client instance by finishing the connection. The client is unavailable for any further data operations; an IOError is raised if such an attempt is made. I/O streams are automatically closed when they are claimed by the garbage collector.



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# File 'lib/sparql/client.rb', line 127

def close
  @http.shutdown if @http
  @http = nil
  self
end

#construct(*args, **options) ⇒ Query

Executes a graph CONSTRUCT query.

Parameters:

  • patterns (Array<RDF::Query::Pattern, Array>)

Returns:



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# File 'lib/sparql/client.rb', line 165

def construct(*args, **options)
  call_query_method(:construct, *args, **options)
end

#delete_data(data, **options) ⇒ void

This method returns an undefined value.

Executes a ‘DELETE DATA` operation.

This requires that the endpoint support SPARQL 1.1 Update.

Examples:

Deleting data sourced from a file or URL

data = RDF::Graph.load("https://raw.githubusercontent.com/ruby-rdf/rdf/develop/etc/doap.nt")
client.delete_data(data)

Deleting data from a named graph

client.delete_data(data, graph: "http://example.org/")

Parameters:

  • data (RDF::Enumerable)
  • options (Hash{Symbol => Object})

Options Hash (**options):

  • :graph (RDF::URI, String)

See Also:



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# File 'lib/sparql/client.rb', line 217

def delete_data(data, **options)
  self.update(Update::DeleteData.new(data, **options))
end

#delete_insert(delete_graph, insert_graph = nil, where_graph = nil, **options) ⇒ void

This method returns an undefined value.

Executes a DELETE/INSERT operation.

This requires that the endpoint support SPARQL 1.1 Update.

Parameters:

  • delete_graph (RDF::Enumerable)
  • insert_graph (RDF::Enumerable) (defaults to: nil)
  • where_graph (RDF::Enumerable) (defaults to: nil)
  • options (Hash{Symbol => Object})

Options Hash (**options):

  • :graph (RDF::URI, String)

See Also:



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# File 'lib/sparql/client.rb', line 233

def delete_insert(delete_graph, insert_graph = nil, where_graph = nil, **options)
  self.update(Update::DeleteInsert.new(delete_graph, insert_graph, where_graph, **options))
end

#describe(*args, **options) ⇒ Query

Executes a DESCRIBE query.

Parameters:

  • variables (Array<Symbol, RDF::URI>)

Returns:



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# File 'lib/sparql/client.rb', line 156

def describe(*args, **options)
  call_query_method(:describe, *args, **options)
end

#insert_data(data, **options) ⇒ void

This method returns an undefined value.

Executes an ‘INSERT DATA` operation.

This requires that the endpoint support SPARQL 1.1 Update.

Note that for inserting non-trivial amounts of data, you probably ought to consider using the RDF store’s native bulk-loading facilities or APIs, as ‘INSERT DATA` operations entail comparably higher parsing overhead.

Examples:

Inserting data constructed ad-hoc

client.insert_data(RDF::Graph.new { |graph|
  graph << [:jhacker, RDF::Vocab::FOAF.name, "J. Random Hacker"]
})

Inserting data sourced from a file or URL

data = RDF::Graph.load("https://raw.githubusercontent.com/ruby-rdf/rdf/develop/etc/doap.nt")
client.insert_data(data)

Inserting data into a named graph

client.insert_data(data, graph: "http://example.org/")

Parameters:

  • data (RDF::Enumerable)
  • options (Hash{Symbol => Object})

Options Hash (**options):

  • :graph (RDF::URI, String)

See Also:



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# File 'lib/sparql/client.rb', line 196

def insert_data(data, **options)
  self.update(Update::InsertData.new(data, **options))
end

#inspect ⇒ String

Returns a developer-friendly representation of this object.

Returns:

  • (String) 


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# File 'lib/sparql/client.rb', line 667

def inspect
  sprintf("#<%s:%#0x(%s)>", self.class.name, __id__, url.to_s)
end

#inspect! ⇒ void

This method returns an undefined value.

Outputs a developer-friendly representation of this object to stderr.



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# File 'lib/sparql/client.rb', line 659

def inspect!
  warn(inspect)
end

#nodes ⇒ Object

Returns a mapping of blank node results for this client.



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# File 'lib/sparql/client.rb', line 304

def nodes
  @nodes ||= {}
end

#parse_rdf_serialization(response, **options) ⇒ RDF::Enumerable

Parameters:

  • response (Net::HTTPSuccess)
  • options (Hash{Symbol => Object})

Returns:

  • (RDF::Enumerable) 


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# File 'lib/sparql/client.rb', line 569

def parse_rdf_serialization(response, **options)
  options = {content_type: response.content_type} unless options[:content_type]
  if reader = RDF::Reader.for(options)
    reader.new(response.body)
  else
    raise RDF::ReaderError, "no RDF reader was found for #{options}."
  end
end

#parse_response(response, **options) ⇒ Object

Parameters:

  • response (Net::HTTPSuccess)
  • options (Hash{Symbol => Object})

Returns:

  • (Object) 


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# File 'lib/sparql/client.rb', line 390

def parse_response(response, **options)
  case options[:content_type] || response.content_type
    when NilClass
      response.body
    when RESULT_BOOL # Sesame-specific
      response.body == 'true'
    when RESULT_JSON
      self.class.parse_json_bindings(response.body, nodes)
    when RESULT_XML
      self.class.parse_xml_bindings(response.body, nodes)
    when RESULT_CSV
      self.class.parse_csv_bindings(response.body, nodes)
    when RESULT_TSV
      self.class.parse_tsv_bindings(response.body, nodes)
    else
      parse_rdf_serialization(response, **options)
  end
end

#query(query, **options) ⇒ Array<RDF::Query::Solution>

Executes a SPARQL query and returns the parsed results.

Parameters:

  • query (String, #to_s)
  • options (Hash{Symbol => Object})

Options Hash (**options):

  • :content_type (String)
  • :headers (Hash)

Returns:

  • (Array<RDF::Query::Solution>)

Raises:

  • (IOError) —

    if connection is closed

See Also:



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# File 'lib/sparql/client.rb', line 318

def query(query, **options)
  @op = :query
  @alt_endpoint = options[:endpoint]
  case @url
  when RDF::Queryable
    require 'sparql' unless defined?(::SPARQL::Grammar)
    begin
      SPARQL.execute(query, @url, optimize: true, **options)
    rescue SPARQL::MalformedQuery
      $stderr.puts "error running #{query}: #{$!}"
      raise
    end
  else
    parse_response(response(query, **options), **options)
  end
end

#response(query, **options) ⇒ String

Executes a SPARQL query and returns the Net::HTTP::Response of the result.

Parameters:

  • query (String, #to_s)
  • options (Hash{Symbol => Object})

Options Hash (**options):

  • :content_type (String)
  • :headers (Hash)

Returns:

  • (String)

Raises:

  • (IOError) —

    if connection is closed



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# File 'lib/sparql/client.rb', line 369

def response(query, **options)
  headers = options[:headers] || @headers
  headers['Accept'] = options[:content_type] if options[:content_type]
  request(query, headers) do |response|
    case response
      when Net::HTTPBadRequest  # 400 Bad Request
        raise MalformedQuery.new(response.body + " Processing query #{query}")
      when Net::HTTPClientError # 4xx
        raise ClientError.new(response.body + " Processing query #{query}")
      when Net::HTTPServerError # 5xx
        raise ServerError.new(response.body + " Processing query #{query}")
      when Net::HTTPSuccess     # 2xx
        response
    end
  end
end

#select(*args, **options) ⇒ Query

Executes a tuple SELECT query.

Parameters:

  • variables (Array<Symbol>)

Returns:



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# File 'lib/sparql/client.rb', line 147

def select(*args, **options)
  call_query_method(:select, *args, **options)
end

#update(query, **options) ⇒ void

This method returns an undefined value.

Executes a SPARQL update operation.

Parameters:

  • query (String, #to_s)
  • options (Hash{Symbol => Object})

Options Hash (**options):

  • :endpoint (String)
  • :content_type (String)
  • :headers (Hash)

Raises:

  • (IOError) —

    if connection is closed

See Also:



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# File 'lib/sparql/client.rb', line 346

def update(query, **options)
  @op = :update
  @alt_endpoint = options[:endpoint]
  case @url
  when RDF::Queryable
    require 'sparql' unless defined?(::SPARQL::Grammar)
    SPARQL.execute(query, @url, update: true, optimize: true, **options)
  else
    response(query, **options)
  end
  self
end