chamikaramj commented on a change in pull request #15484:
URL: https://github.com/apache/beam/pull/15484#discussion_r709677951
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File path: sdks/python/apache_beam/transforms/external.py
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@@ -144,6 +147,101 @@ def _get_named_tuple_instance(self):
return self._tuple_instance
+class JavaClassLookupPayloadBuilder(PayloadBuilder):
+ """
+ Builds a payload for directly instantiating a Java transform using a
+ constructor and builder methods.
+ """
+ def __init__(self, class_name):
+ """
+ :param class_name: fully qualified name of the transform class.
+ """
+ if not class_name:
+ raise ValueError('Class name must not be empty')
+
+ self._class_name = class_name
+ self._constructor_method = None
+ self._constructor_params = None
+ self._builder_methods_and_params = OrderedDict()
+
+ def _get_schema_proto_and_payload(self, **kwargs):
+ named_fields = []
+ for key, value in kwargs.items():
+ if not key:
+ raise ValueError('Parameter name cannot be empty')
+ if value is None:
+ raise ValueError(
+ 'Received value None for key %s. None values are currently not '
+ 'supported' % key)
+ named_fields.append(
+ (key, convert_to_typing_type(instance_to_type(value))))
+
+ schema_proto = named_fields_to_schema(named_fields)
+ row = named_tuple_from_schema(schema_proto)(**kwargs)
+ schema = named_tuple_to_schema(type(row))
+
+ payload = RowCoder(schema).encode(row)
+ return (schema_proto, payload)
+
+ def build(self):
+ constructor_params = self._constructor_params or {}
+ constructor_schema, constructor_payload = (
+ self._get_schema_proto_and_payload(**constructor_params))
+ payload = JavaClassLookupPayload(
+ class_name=self._class_name,
+ constructor_schema=constructor_schema,
+ constructor_payload=constructor_payload)
+ if self._constructor_method:
+ payload.constructor_method = self._constructor_method
+
+ for builder_method_name, params in
self._builder_methods_and_params.items():
+ builder_method_schema, builder_method_payload = (
+ self._get_schema_proto_and_payload(**params))
+ builder_method = BuilderMethod(
+ name=builder_method_name,
+ schema=builder_method_schema,
+ payload=builder_method_payload)
+ builder_method.name = builder_method_name
+ payload.builder_methods.append(builder_method)
+ return payload
+
+ def add_constructor(self, **kwargs):
+ """
+ Specifies the Java constructor to use.
+
+ :param kwargs: parameter names and values of the constructor.
+ """
+ if self._constructor_method or self._constructor_params:
+ raise ValueError(
+ 'Constructor or constructor method can only be specified once')
+
+ self._constructor_params = kwargs
+
+ def add_constructor_method(self, method_name, **kwargs):
+ """
+ Specifies the Java constructor method to use.
+
+ :param method_name: name of the constructor method.
+ :param kwargs: parameter names and values of the constructor method.
+ """
+ if self._constructor_method or self._constructor_params:
+ raise ValueError(
+ 'Constructor or constructor method can only be specified once')
+
+ self._constructor_method = method_name
+ self._constructor_params = kwargs
+
+ def add_builder_method(self, method_name, **kwargs):
Review comment:
> Ordering
Right. The issue goes away if we always use *args before *kwargs (in the
order they are specified).
> One issue is that the java argument names are not part of the signature's
spec
This should be fine. We ignore argument names at Java side when the are not
available through reflection.
> As for defining names, a simple scheme that uses "illegal" parameter names
(e.g. #N) should be sufficient.
Sounds good I can add that and update the spec. I assume you meant that
certain parameter names that will be ignored by the expansion service and will
not be used for validation.
> Do we correctly handle builderMethod(a=1, b=2) vs. builderMethod(b=2, a=1)
or otherwise enforce the names today?
We cannot reorder args since that could lead to ambiguities in Java side.
Hence we send the args exactly in the order they are specified. May be we can
clarify this in the documentation ?
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