Gregor Wolf

OData Services
with SAP

REST

Stands for Representational State Transfer

Client-Server
Statless
Caching
Multi-Level systemes
Uniform interface

Uniform interface

Resource identification in requests
Resource manipulation through representations
Self-descriptive messages
Hypermedia as the engine of application state (HATEOAS)

Resource identification in requests
Individual resources are identified in requests, for example using URIs in Web-based REST systems. The resources themselves are conceptually separate from the representations that are returned to the client. For example, the server could send data from its database as HTML, XML or as JSON—none of which are the server's internal representation.

Resource manipulation through representations
When a client holds a representation of a resource, including any metadata attached, it has enough information to modify or delete the resource.

Self-descriptive messages
Each message includes enough information to describe how to process the message. For example, which parser to invoke can be specified by a media type.

Hypermedia as the engine of application state (HATEOAS)
Having accessed an initial URI for the REST application—analogous to a human Web user accessing the home page of a website—a REST client should then be able to use server-provided links dynamically to discover all the available actions and resources it needs. As access proceeds, the server responds with text that includes hyperlinks to other actions that are currently available. There is no need for the client to be hard-coded with information regarding the structure or dynamics of the REST service.

OData - Open Data Protocol

OData

V4 ia a OASIS Standard since March 2014
Based on Standards like REST, RSS, Atom, XML and JSON
Provides a uniform interface to data sources (Query + CRUD + Actions)
Allows application integration using Internet technologies
Available for SAP since May 2011 as SAP NetWeaver Gateway (today SAP Gateway)

SAP Gateway

SAP Gateway is part of SAP NetWeaver ABAP since 7.40
Allows to connect from Browser, Devices and Plattforms to SAP Systemen
Implements OData v2 and starting with 7.50 also v4)
Can run as a Hub system or embedded i.e. with SAP ERP as an Add-on

SAP Gateway - service implementation

ABAP OO
Core Data Services (CDS, minimum 7.50, AnyDB)

SAP Gateway - Architecture

SAP Gateway

Steps to an OData Service with SAP Gateway

Activate SAP Gateway in STC01
(Tasklist SAP_GATEWAY_BASIC_CONFIG)
Define interface in SEGW
(Entities, Entity Sets, Function Import)
Implement Model- and Data-Provider classes
Activate Services in /IWFND/MAINT_SERVICE

Comparison with other SAP Technologies

iDoc
mass data, asynchronous processing
RFC
SAP to SAP connections (also used in SAP Gateway)
OData
Easy to understand HTTP(S) API, synchronous processing

Benefits of OData (1 of 2)

SAP is basing S/4HANA on it
Humans can understand the interface
Tight integration to SAPUI5

Benefits of OData (2 of 2)

Push and Pull (Queue) for Backend changes
Access SAP Data from non SAP programming languages
Various uses of the data provided

Drawbacks of OData

Backend must be reachable
Only synchronous processing

OData Services with SAP

REST

Uniform interface

OData - Open Data Protocol

OData

SAP Gateway

SAP Gateway - service implementation

SAP Gateway - Architecture

Steps to an OData Service with SAP Gateway

Comparison with other SAP Technologies

Benefits of OData (1 of 2)

Benefits of OData (2 of 2)

Drawbacks of OData

OData Services
with SAP