Django 에서 graphQL library 의 동작(graphene_django)
아래와 같은 graphQL 이 client --> server 로 날라가면
query{
user{
id
}
}
서버에서 개발자가 미리 정해놓은 schema 에 맞춰서 response 를 보내주게 된다. 보통 django 에서는 이것을 schema.py 에 만들어 놓는다.
위의 query 에 대한 응답은 아래와 같다.
{
"data": {
"users": [
{
"id": "1"
}
]
}
}
대략적은 동작은 아래글을 통해 파악하자.
Source flow
위와 같은 response 가 오기 위해서 django 의 graphQL library 는 어떤 과정을 거치는지 source 를 살펴보자.# my_django_project/api/schema.py import graphene from graphene_django import DjangoObjectType from api.models import UserModel class User(DjangoObjectType): class Meta: model = UserModel class Query(graphene.ObjectType): users = graphene.List(User) @graphene.resolve_only_args def resolve_users(self): return UserModel.objects.all() schema = graphene.Schema(query=Query)
# my_django_project/api/urls.py ... from graphene_django.views import GraphQLView urlpatterns = [ url(r'^graphql', GraphQLView.as_view(graphiql=True)), ]
---- libraries
# django/views/generic/base.py class View(object): ... @classonlymethod def as_view(cls, **initkwargs): ... def view(request, *args, **kwargs): self = cls(**initkwargs) if hasattr(self, 'get') and not hasattr(self, 'head'): self.head = self.get self.request = request self.args = args self.kwargs = kwargs return self.dispatch(request, *args, **kwargs)
# graphene_django/views.py class GraphQLView(View): graphiql_version = '0.7.8' graphiql_template = 'graphene/graphiql.html' schema = None graphiql = False executor = None middleware = None root_value = None pretty = False def __init__(self, schema=None, executor=None, middleware=None, root_value=None, graphiql=False, pretty=False): if not schema: schema = graphene_settings.SCHEMA if middleware is None: middleware = graphene_settings.MIDDLEWARE self.schema = schema if middleware is not None: self.middleware = list(instantiate_middleware(middleware)) self.executor = executor self.root_value = root_value self.pretty = pretty self.graphiql = graphiql assert isinstance(self.schema, GraphQLSchema), 'A Schema is required to be provided to GraphQLView.' ... @method_decorator(ensure_csrf_cookie) def dispatch(self, request, *args, **kwargs): try: if request.method.lower() not in ('get', 'post'): raise HttpError(HttpResponseNotAllowed(['GET', 'POST'], 'GraphQL only supports GET and POST requests.')) data = self.parse_body(request) show_graphiql = self.graphiql and self.can_display_graphiql(request, data) query, variables, operation_name = self.get_graphql_params(request, data) execution_result = self.execute_graphql_request( request, data, query, # 'query{ user {id }}' variables, operation_name, show_graphiql ) if execution_result: ... result = self.json_encode(request, response, pretty=show_graphiql) else: result = None if show_graphiql: return self.render_graphiql( request, graphiql_version=self.graphiql_version, query=query or '', variables=variables or '', operation_name=operation_name or '', result=result or '' ) return HttpResponse( status=status_code, content=result, content_type='application/json' ) except HttpError as e: ... return response def execute_graphql_request(self, request, data, query, variables, operation_name, show_graphiql=False): ... source = Source(query, name='GraphQL request') try: document_ast = parse(source) validation_errors = validate(self.schema, document_ast) if validation_errors: return ExecutionResult( errors=validation_errors, invalid=True, ) except Exception as e: return ExecutionResult(errors=[e], invalid=True) ... try: return self.execute( document_ast, root_value=self.get_root_value(request), variable_values=variables, operation_name=operation_name, context_value=self.get_context(request), middleware=self.get_middleware(request), executor=self.executor, ) except Exception as e: return ExecutionResult(errors=[e], invalid=True) def execute(self, *args, **kwargs): return execute(self.schema, *args, **kwargs) # graphql/execution/executor.py def execute(schema, document_ast, root_value=None, context_value=None, variable_values=None, operation_name=None, executor=None, return_promise=False, middleware=None): assert schema, 'Must provide schema' assert isinstance(schema, GraphQLSchema), ( 'Schema must be an instance of GraphQLSchema. Also ensure that there are ' + 'not multiple versions of GraphQL installed in your node_modules directory.' ) if middleware: if not isinstance(middleware, MiddlewareManager): middleware = MiddlewareManager(*middleware) ... if executor is None: executor = SyncExecutor() context = ExecutionContext( schema, document_ast, root_value, context_value, variable_values, operation_name, executor, middleware ) def executor(resolve, reject): return resolve(execute_operation(context, context.operation, root_value)) def on_rejected(error): context.errors.append(error) return None def on_resolve(data): return ExecutionResult(data=data, errors=context.errors) promise = Promise(executor).catch(on_rejected).then(on_resolve) ... def execute_operation(exe_context, operation, root_value): type = get_operation_root_type(exe_context.schema, operation) fields = collect_fields( exe_context, type, operation.selection_set, DefaultOrderedDict(list), set() ) if operation.operation == 'mutation': return execute_fields_serially(exe_context, type, root_value, fields) return execute_fields(exe_context, type, root_value, fields) def execute_fields(exe_context, parent_type, source_value, fields): contains_promise = False final_results = OrderedDict() for response_name, field_asts in fields.items(): result = resolve_field(exe_context, parent_type, source_value, field_asts) if result is Undefined: continue final_results[response_name] = result if is_promise(result): contains_promise = True def resolve_field(exe_context, parent_type, source, field_asts): field_ast = field_asts[0] # at this example, field_name is 'users' field_name = field_ast.name.value field_def = get_field_def(exe_context.schema, parent_type, field_name) if not field_def: return Undefined # field_def is GraphQLField type return_type = field_def.type # field_def.resolver is api.schema.Query.resolve_users resolve_fn = field_def.resolver or default_resolve_fn # We wrap the resolve_fn from the middleware resolve_fn_middleware = exe_context.get_field_resolver(resolve_fn) # Build a dict of arguments from the field.arguments AST, using the variables scope to # fulfill any variable references. args = exe_context.get_argument_values(field_def, field_ast) # The resolve function's optional third argument is a context value that # is provided to every resolve function within an execution. It is commonly # used to represent an authenticated user, or request-specific caches. context = exe_context.context_value # The resolve function's optional third argument is a collection of # information about the current execution state. info = ResolveInfo( field_name, field_asts, return_type, parent_type, schema=exe_context.schema, fragments=exe_context.fragments, root_value=exe_context.root_value, operation=exe_context.operation, variable_values=exe_context.variable_values, ) executor = exe_context.executor result = resolve_or_error(resolve_fn_middleware, source, args, context, info, executor) ...
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