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import base64
import copy
import logging
from io import BytesIO
from typing import TYPE_CHECKING, Optional, Tuple
from urllib.error import HTTPError
from urllib.parse import urlencode
from urllib.request import Request, urlopen
from rdflib.query import Result
from rdflib.term import BNode
log = logging.getLogger(__name__)
if TYPE_CHECKING:
import typing_extensions as te
class SPARQLConnectorException(Exception): # noqa: N818
pass
# TODO: Pull in these from the result implementation plugins?
_response_mime_types = {
"xml": "application/sparql-results+xml, application/rdf+xml",
"json": "application/sparql-results+json",
"csv": "text/csv",
"tsv": "text/tab-separated-values",
"application/rdf+xml": "application/rdf+xml",
}
class SPARQLConnector:
"""
this class deals with nitty gritty details of talking to a SPARQL server
"""
def __init__(
self,
query_endpoint: Optional[str] = None,
update_endpoint: Optional[str] = None,
returnFormat: str = "xml", # noqa: N803
method: "te.Literal['GET', 'POST', 'POST_FORM']" = "GET",
auth: Optional[Tuple[str, str]] = None,
**kwargs,
):
"""
auth, if present, must be a tuple of (username, password) used for Basic Authentication
Any additional keyword arguments will be passed to to the request, and can be used to setup timesouts etc.
"""
self._method: str
self.returnFormat = returnFormat
self.query_endpoint = query_endpoint
self.update_endpoint = update_endpoint
self.kwargs = kwargs
self.method = method
if auth is not None:
if type(auth) != tuple:
raise SPARQLConnectorException("auth must be a tuple")
if len(auth) != 2:
raise SPARQLConnectorException("auth must be a tuple (user, password)")
base64string = base64.b64encode(bytes("%s:%s" % auth, "ascii"))
self.kwargs.setdefault("headers", {})
self.kwargs["headers"].update(
{"Authorization": "Basic %s" % base64string.decode("utf-8")}
)
@property
def method(self) -> str:
return self._method
@method.setter
def method(self, method: str) -> None:
if method not in ("GET", "POST", "POST_FORM"):
raise SPARQLConnectorException(
'Method must be "GET", "POST", or "POST_FORM"'
)
self._method = method
def query(
self,
query: str,
default_graph: Optional[str] = None,
named_graph: Optional[str] = None,
) -> "Result":
if not self.query_endpoint:
raise SPARQLConnectorException("Query endpoint not set!")
params = {}
# this test ensures we don't have a useless (BNode) default graph URI, which calls to Graph().query() will add
if default_graph is not None and type(default_graph) != BNode:
params["default-graph-uri"] = default_graph
headers = {"Accept": _response_mime_types[self.returnFormat]}
args = copy.deepcopy(self.kwargs)
# merge params/headers dicts
args.setdefault("params", {})
args.setdefault("headers", {})
args["headers"].update(headers)
if self.method == "GET":
params["query"] = query
args["params"].update(params)
qsa = "?" + urlencode(args["params"])
try:
res = urlopen(
Request(self.query_endpoint + qsa, headers=args["headers"])
)
except Exception as e: # noqa: F841
raise ValueError(
"You did something wrong formulating either the URI or your SPARQL query"
)
elif self.method == "POST":
args["headers"].update({"Content-Type": "application/sparql-query"})
args["params"].update(params)
qsa = "?" + urlencode(args["params"])
try:
res = urlopen(
Request(
self.query_endpoint + qsa,
data=query.encode(),
headers=args["headers"],
)
)
except HTTPError as e:
# type error: Incompatible return value type (got "Tuple[int, str, None]", expected "Result")
return e.code, str(e), None # type: ignore[return-value]
elif self.method == "POST_FORM":
params["query"] = query
args["params"].update(params)
try:
res = urlopen(
Request(
self.query_endpoint,
data=urlencode(args["params"]).encode(),
headers=args["headers"],
)
)
except HTTPError as e:
# type error: Incompatible return value type (got "Tuple[int, str, None]", expected "Result")
return e.code, str(e), None # type: ignore[return-value]
else:
raise SPARQLConnectorException("Unknown method %s" % self.method)
return Result.parse(
BytesIO(res.read()), content_type=res.headers["Content-Type"].split(";")[0]
)
def update(
self,
query: str,
default_graph: Optional[str] = None,
named_graph: Optional[str] = None,
) -> None:
if not self.update_endpoint:
raise SPARQLConnectorException("Query endpoint not set!")
params = {}
if default_graph is not None:
params["using-graph-uri"] = default_graph
if named_graph is not None:
params["using-named-graph-uri"] = named_graph
headers = {
"Accept": _response_mime_types[self.returnFormat],
"Content-Type": "application/sparql-update; charset=UTF-8",
}
args = copy.deepcopy(self.kwargs) # other QSAs
args.setdefault("params", {})
args["params"].update(params)
args.setdefault("headers", {})
args["headers"].update(headers)
qsa = "?" + urlencode(args["params"])
res = urlopen( # noqa: F841
Request(
self.update_endpoint + qsa, data=query.encode(), headers=args["headers"]
)
)
__all__ = ["SPARQLConnector", "SPARQLConnectorException"]
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