Source code for rdflib.plugins.sparql.results.jsonresults

import json
from typing import IO, Any, Dict

from rdflib import BNode, Literal, URIRef, Variable
from rdflib.query import Result, ResultException, ResultParser, ResultSerializer

"""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

"""


[docs]class JSONResultParser(ResultParser):
[docs]    def parse(self, source, content_type=None):
        inp = source.read()
        if isinstance(inp, bytes):
            inp = inp.decode("utf-8")
        return JSONResult(json.loads(inp))


[docs]class JSONResultSerializer(ResultSerializer):
[docs]    def __init__(self, result):
        ResultSerializer.__init__(self, result)

[docs]    def serialize(self, stream: IO, encoding: str = None):  # type: ignore[override]

        res: Dict[str, Any] = {}
        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


[docs]class JSONResult(Result):
[docs]    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


[docs]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)


[docs]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)))