Parse the Metadata from an SAP OData V2 Service

Parses the metadata XML describing an SAP OData V2 service and generates two Rust modules: one for the Service Document and one for the metadata document.

The code generated by this crate is designed to work in conjunction with the crate parse-sap-atom-feed.

Table of Contents

• Usage
• EntitySets Enum
• Metadata Module
• Limitations and Issues

Generated Modules

OData Service Document Module

• The metadata description of the OData service is used to declare all the structs and enums needed to interact with your chosen OData service.

• For each OData Collection, a Rust struct is generated to represent a row of that collection, then the entire collection is represented as a Vec of that generated struct.

  • Edm.DateTime fields are transformed into chrono::NaiveDateTime using a custom deserializer.

  • Edm.Decimal fields transformed into rust_decimal::Decimal

    However, this transformation can only account for the declared number of decimal places (defined by the Scale property). The number of decimal digits (defined by the Precision property) is ignored as rust_decimal::Decimal values use a hard-coded precision of 64.

• The generated module declares external crate dependencies on quick_xml and serde and possibly also on chrono, rust_decimal and uuid depending on whether Edm.DateTime, Edm.Decimal or Edm.Guid properties are encountered.

OData Service Metadata Module

Version 1.6.0 introduces a potentially breaking change. In the metadata module, Property.edm_type used to be of type String which had the consequence that the same String value was repeatedly defined in the generated code: such as Edm.String, Edm.Decimal or Edm.DateTime. These redundant declarations have been replcaed by the use of the types EdmType and EdmPrimitive — both of which implement std::fmt::Display.

Property.edm_typ is now of type EdmType:

pub enum EdmType {
    Primitive(EdmPrimitive),
    Complex(String),
    Unknown(String),
}

Where the EdmPrimitive enum holds each of the declared EDM datatypes, plus an Unknown(String) member for error handling.

• For each EntityType occurring in the metadata:

  • A struct is created using the EntityType's name followed by Metadata. E.G. <EntityType Name="BusinessPartner"> generates pub struct BusinessPartnerMetadata
  • An implementation is created containing a key() function and getter function for each struct property that returns an instance of a Property object.

• The Name property of each <Association> metadata tag is stripped of the Assoc_ prefix and added as a member to the Associations enum.

• The Name property of each <AssociationSet> metadata tag is stripped of the Assoc_ prefix and the _AssocSet suffix and added as a member to the AssociationSets enum.

• For each <Association> or <AssociationSet> enum, there is an implementation containing a getter function for each Association(Set).

• The generated module declares an external crate dependency on parse_sap_atom_feed.

Change Log