Friday, 23 June 2017

How does annotation @OData.publish work Part 4

In part1 of this tutorial, the old way to create OData service on top of CDS view is introduced.

@OData.publish: true


Just add this annotation to your CDS view and the odata service is automatically created, no need for you to go to code SEGW any more.

SAP ABAP Development, SAP ABAP CDS

Once activated, the odata service with naming convention “<your CDS view name>_CDS” is available for registration in tcode /IWFND/MAINT_SERVICE:

SAP ABAP Development, SAP ABAP CDS

Metadata retrieval test ok:

SAP ABAP Development, SAP ABAP CDS

So the question here is: How does this annotation work? How can we research the service generation process through debugging?

Here below is how I figure it out.

First check what objects have been generated: three additional artifacts are highlighted below.

IWMO: SAP Gateway Business Suite Enablement – Model
IWSV: SAP Gateway Business Suite Enablement – Service
CLAS: provider class ZCL_ZJERRYTEST20160311 is generated

SAP ABAP Development, SAP ABAP CDS

If I remove the annotation, or change the annotation to @OData.publish: false, and the two are gone:

SAP ABAP Development, SAP ABAP CDS

So it means the annotation @OData.publish: true will trigger table entry insertion for type IWMO, IWSV and CLAS during view activation. Then again I switch on ST05 trace and easily find the ABAP code where the table insertion is done.

SAP ABAP Development, SAP ABAP CDS

Set breakpoint on the code and observe the callstack in the runtime.

SAP ABAP Development, SAP ABAP CDS

The highlighted callstack frames are essential for odata service generation.

SAP ABAP Development, SAP ABAP CDS

Let’s have a deep look at stack frame 21:

CL_WB_DDLS_SECOBJ_HNDLR_SINGLE->IF_DDIC_WB_DDLS_SECOBJ_HANDLER~ON_ACTIVATION

It will first identify which objects must be created based on delta state.

SAP ABAP Development, SAP ABAP CDS

For example, if I add @OData.publish: true to an existing CDS view and activate it, the corresponding entry will have flag N ( New ) while other existing annotation has type “U” ( Unchanged ).

SAP ABAP Development, SAP ABAP CDS

Inside this method, if annotation ODATA.PUBLISH is found,

SAP ABAP Development, SAP ABAP CDS

and the annotation value is true, then it is considered that the odata service must be created.

SAP ABAP Development, SAP ABAP CDS

SAP ABAP Development, SAP ABAP CDS

SAP ABAP Development, SAP ABAP CDS

The odata service creation is implemented in CL_SADL_GTK_ODATA_SERVICE_GEN~CREATE_VIA_EXPOSURE below.

SAP ABAP Development, SAP ABAP CDS

Complete callstack:

SAP ABAP Development, SAP ABAP CDS

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