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import json
from rdflib.query import (
Result, ResultException, ResultSerializer, ResultParser)
from rdflib import Literal, URIRef, BNode, Variable
"""A Serializer for SPARQL results in JSON:
http://www.w3.org/TR/rdf-sparql-json-res/
Bits and pieces borrowed from:
http://projects.bigasterisk.com/sparqlhttp/
Authors: Drew Perttula, Gunnar Aastrand Grimnes
"""
class JSONResultParser(ResultParser):
def parse(self, source, content_type=None):
inp = source.read()
if isinstance(inp, bytes):
inp = inp.decode('utf-8')
return JSONResult(json.loads(inp))
class JSONResultSerializer(ResultSerializer):
def __init__(self, result):
ResultSerializer.__init__(self, result)
def serialize(self, stream, encoding=None):
res = {}
if self.result.type == 'ASK':
res["head"] = {}
res["boolean"] = self.result.askAnswer
else:
# select
res["results"] = {}
res["head"] = {}
res["head"]["vars"] = self.result.vars
res["results"]["bindings"] = [self._bindingToJSON(
x) for x in self.result.bindings]
r = json.dumps(res, allow_nan=False, ensure_ascii=False)
if encoding is not None:
stream.write(r.encode(encoding))
else:
stream.write(r)
def _bindingToJSON(self, b):
res = {}
for var in b:
j = termToJSON(self, b[var])
if j is not None:
res[var] = termToJSON(self, b[var])
return res
class JSONResult(Result):
def __init__(self, json):
self.json = json
if "boolean" in json:
type_ = 'ASK'
elif "results" in json:
type_ = 'SELECT'
else:
raise ResultException('No boolean or results in json!')
Result.__init__(self, type_)
if type_ == 'ASK':
self.askAnswer = bool(json['boolean'])
else:
self.bindings = self._get_bindings()
self.vars = [Variable(x) for x in json["head"]["vars"]]
def _get_bindings(self):
ret = []
for row in self.json['results']['bindings']:
outRow = {}
for k, v in row.items():
outRow[Variable(k)] = parseJsonTerm(v)
ret.append(outRow)
return ret
def parseJsonTerm(d):
"""rdflib object (Literal, URIRef, BNode) for the given json-format dict.
input is like:
{ 'type': 'uri', 'value': 'http://famegame.com/2006/01/username' }
{ 'type': 'literal', 'value': 'drewp' }
"""
t = d['type']
if t == 'uri':
return URIRef(d['value'])
elif t == 'literal':
return Literal(d['value'], datatype=d.get('datatype'), lang=d.get('xml:lang'))
elif t == 'typed-literal':
return Literal(d['value'], datatype=URIRef(d['datatype']))
elif t == 'bnode':
return BNode(d['value'])
else:
raise NotImplementedError("json term type %r" % t)
def termToJSON(self, term):
if isinstance(term, URIRef):
return {'type': 'uri', 'value': str(term)}
elif isinstance(term, Literal):
r = {'type': 'literal',
'value': str(term)}
if term.datatype is not None:
r['datatype'] = str(term.datatype)
if term.language is not None:
r['xml:lang'] = term.language
return r
elif isinstance(term, BNode):
return {'type': 'bnode', 'value': str(term)}
elif term is None:
return None
else:
raise ResultException(
'Unknown term type: %s (%s)' % (term, type(term)))
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