Exploring Diverse Approaches of OData Services creation in SAP

Introduction

OData (Open Data Protocol) is a standardized protocol for building and consuming RESTful APIs (Application Programming Interfaces) that expose data resources over the web. It was developed by Microsoft and has gained widespread adoption as an open industry standard for data exchange and integration.

Creating OData services in SAP offers various approaches to cater to different development scenarios and requirements. These methods provide flexibility and allow developers to leverage existing data models, applications, and frameworks. Let's explore some of the key ways to create OData services in SAP.

In this article , we would be talking about below approaches.

1. SEGW : Manual Approach
2. SEGW: Import
3. SADL
4. SEGW: RFC
5. Annotation based

1. SEGW : Manual Approach

Go to T-code SEGW and create new project.

Create Entity

Enter Entity and Entity set name.

Expand Entity and double click on property to add field .

project should look like below.

Save project and generate service.

Runtime objects would get generated.

Add service through T-code /n/iwfnd/maint_service

Go to T-code /n/iwfnd/maint_service , select service and click on SAP Gateway client.

We can go to below screen via /n/iwfnd/gw_client as well.

2.SEGW : Import

We will create Odata project through DDIC table.

DDIC table .

Go to SEGW project , right click on data model > import > DDIC Structure

Give Entity name and DDIC structure.

select desired field and finish.

After save , project would look like below.

Generate runtime object and Go to T-code /n/iwfnd/GW_CLIENT to check the service .

We can see there is another entity has been added (imported from DDIC ).

3. SEGW : SADL Approach

We will use below CDS to create OData service. We can leverage benefits of CDS annotations in service.

Go to SEGW project , Right Click on data model >> Reference >> Data source.

Provide CDS name and proceed further.

Project would look like below.

Generate service and check service in /N/IWFND/GW_CLIENT. There is another entity set has been generated from CDS view.

4. SEGW : RFC

We can create OData service on RFC enabled Function module and make use of the FM functionality through service.

We have created a custom RFC FM which has importing parameter VBELN and returns VBELN,AUART and LIFSK .

Create SEGW project.

Right click on data model ,Import >>RFC/BOR Interface.

Provide entity name and RFC enabled FM to proceed.

Select required parameters.

Mark suitable field as key and finish.

Project would look like below.

Now we need to map the service to the FM to get the data. Expand Service implementation and right click on getEntity(Since we are reading data from FM) and click map data source .

Provide FM details.

Propose mapping ,framework will auto map the importing and exporting fields.

As of now we have generated design time objects , lets Generate runtime objects.

Since we have mapped the data source to GET_ENTITY method , framework has generated code accordingly. Lets check DPC_EXT class.

Next step is to register the service and test .

Go to T-code /N/IWFND/MAINT_SERVICE

Service has been generated . OData is a complete framework , we can create and test OData service within SAP system itself .

We can go to SAP gateway system to test the service (/N/IWFND/GW_CLIENT).

We have pass VBELN through URI and service has executed FM and return the data.

5. Annotation Based

We can create Odata service directly from CDS view with the help of annotation 'Odata.publish:true' .

If we notice ADT is showing warning that service is not active.

Go to T-code /N/IWFND/MAINT_SERVICE and add the service .

Odata service is activated now.

Important URIs

A URL used by an OData service has at most three significant parts: the service root URL, resource path and query options. Additional URL constructs (such as a fragment) MAY be present in a URL used by an OData service; however, this specification applies no further meaning to such additional constructs.

• To get the Metadata information

/sap/opu/odata/sap/ZGW_PO_SRV/$metadata        

• URI to READ

/sap/opu/odata/sap/ZGW_PO_SRV/POHeaderSet(‘4500002012’).        

• How to pass multiple fields of the Composite Primary Key?

/sap/opu/odata/sap/ZWM_ODATA_SRV/ZZCALIBRATE_JSON_Set(CMSASSET=’CMS456788879′,LAST_CAL_DATE=’20160923′,CAL_DUE_DATE=’20230923′)        

• Filter Option (look for IV_FILTER_STRING in the GET_ENTITYSET method).

/sap/opu/odata/sap/ZWM_ODATA_SRV/ZZCALIBRATE_JSON_Set?&$filter=CMSASSET eq ‘CMS45678887        

• READ one particular field or property of the Entity Type (/Field1) (Reading plant of specific material)

/sap/opu/odata/sap/ZGW_PO_SRV/POHeaderSet(‘4500002013’)/Lifnr.        

• Count the number of entries in the system ($count)

/sap/opu/odata/sap/ZGW_PO_SRV/POHeaderSet/$count
 /sap/opu/odata/sap/ZGW_PO_SRV/POHeaderSet(‘4500002012’)/$count        

• Extract only some fields of the Entity Type ($select=Field1,Field2,Field3) (Projection)

/sap/opu/odata/sap/ZGW_PO_SRV/POHeaderSet?$select=Ernam,Bukrs,Ebeln.        

/sap/opu/odata/sap/ZGW_PO_SRV/POItemSet?$select=Ebeln,Ebelp,Werks&$format=json        

• URI to send non-Key Filters in the OData Service – ?&$filter=Xblnr eq ‘RON MILLS 2’

 /sap/opu/odata/sap/ZGW_VIM_APP_SRV/DocDetailSet?&$filter=Xblnr eq ‘RON MILLS 2’        

• URI to send multiple Filters in the OData Service 

?$filter=Erdat gt datetime’2015-01-01T00:00:00’and Ekgrp eq ’17’and Werks eq ‘4030’
        

/sap/opu/odata/sap/ZGW_PREQ_SRV/PReqSet?$filter=Erdat gt datetime’2015-01-01T00:00:00’and Ekgrp eq ’17’and Werks eq ‘4030’        

Association specifies the cardinality between Entity Types. When an Association is created, a Navigation Property of the Entity Type is also generated. 

if we execute below query to get one data set , system will show us (link href ) that we can make use of navigation property as well.

it will show the code as well.

/sap/opu/odata/sap/ZGW_PO_SRV/POHeaderSet(‘4500002012’
<link href=POHeaderSet(‘4500002012’)/HeadtoItemNav)        

• $Expand : will fetch both item and header details using navigation property

/sap/opu/odata/sap/ZGW_PO_SRV/POHeaderSet(‘4500001729’)?$expand=HeadToItemNav        

whereas below URL will fetch only item details

/sap/opu/odata/sap/ZGW_PO_SRV/POHeaderSet(‘4500001729’)/HeadToItemNav        

Conclusion and further resources

This guide has given an overview of OData services and walked you through the step-by-step process of creating a service using SAP.

If you're looking for more information, check out the official SAP documentation on OData service creation, the OData official website, and the OData community resources. Thanks for reading!