Exercise 11: Enhance the BO Behavior with Business Events

Introduction

In the previous exercise, you've implemented a function for the booking BO entity (see Exercise 10).

In this exercise, you will enhance the behavior defintion of the Travel BO entity ZRAP110_R_TRAVELTP_### with business events. Your RAP BO will act as an event provider. The events will be used to send a message when the overall status of the Travel BO node is changed to accepted or rejected to inform possible consumers about the change.

In this exercise your RAP BO acts as an event provider. For the local event consumption, you will implement a local event handler that acts as an event consumer, listening to and processing events raised by your Travel RAP BO in the same system.

Exercises:

11.1 - Define the Business Event Parameter
11.2 - Define the Business Event in the Travel BO
11.3 - Raise the Event in the Travel BOl
11.4 - Create a Local Event Handler
11.5 - Test the Enhanced Travel App
Summary

Reminder: Do not forget to replace the suffix placeholder ### with your assigned suffix in the exercise steps below.

About Business Events in RAP

Click to expand the details!

Developers can now define and raise business events in a RAP BO or in a RAP BO behavior extension.

RAP supports event-driven architecture natively on SAP BTP ABAP environment and SAP S/4HANA in the cloud and on-prem as of release 2022. Event-driven architecture enables asynchronous communication between an event provider and an event consumer in use cases where no direct response from the event consumer is required.

Business events provide the opportunity of light-weight, decoupled process integration based on standardized and stable APIs and they are now a native part of the SAP - ABAP RESTful Application Programming Model. With the RAP Business Event Bindings Editor, you can create RAP Event Bindings which are needed to provide a mapping between the definition of RAP Events via behavior definition (BDEF) and the external representation of Business Events.

A RAP BO can act as event consumer or event provider.

RAP Business events can be consumed in other systems (remote consumption), or in the same system as they are raised (local consumption).

ℹ Further reading: About RAP Business Events | Develop RAP Business Events | Business Event Consumption |

Exercise 11.1: Define the Business Event Parameter

^Top of page

A RAP Business event can be defined with or without an output parameter. An output parameter is used to transfer values that are not inherently part of the BO data model.

Parameters in RAP are modelled using CDS abtract entity.

In this exercise, you will use the CDS abstract entity ZRAP110_A_TRAVEL_### available in your exercise package ZRAP110_###, where ### is your assigned suffix.

🔵 Click to expand!

Go to the Project Explorer, open the CDS abtract view ZRAP110_A_TRAVEL_### in your package and have a look at its data definition.

Source code

  @EndUserText.label: 'Abtract Entity for Travel'
  define abstract entity ZRAP110_A_TRAVEL_###
  {
    travel_id      : /dmo/travel_id;
    agency_id      : /dmo/agency_id;
    customer_id    : /dmo/customer_id;
    overall_status : /dmo/overall_status;
    description    : /dmo/description;
    @Semantics.amount.currencyCode: 'currency_code'
    total_price    : /dmo/total_price;
    currency_code  : /dmo/currency_code;
    begin_date     : /dmo/begin_date;
    end_date       : /dmo/end_date;
    email_address  : /dmo/email_address;
  }

Beside attributes - such as travel_id, customer_id, and total_price - that can be retrieved from the Travel BO entity, the variable email_address can contains the e-mail address of an Agency which needs to be informed. The variable travel_id contains the information about the travel that triggered the event.

Close the abstract entity and go ahead with the next step.

Exercise 11.2: Define the Business Event in the Travel BO

^Top of page

Define the events travel_accepted (with output parameter) and travel_rejected (without output parameter).

The event travel_accepted will be defined with the abstract entity ZRAP110_A_TRAVEL_### as output parameter.

🔵 Click to expand!

Open the behavior definition of the travel BO entitiy ZRAP110_R_TravelTP_### in your package.
Define the event travel_accepted using the keyword event in the behavior definition of the Travel BO node, just after the Side Effects as shown on the screenshot below. Replace the placeholder ### with your assigned suffix.

Insert the code snippet provided below for the purpose after the side effects definition.
```
  //business events
  event travel_accepted parameter ZRAP110_A_Travel_###; 
  event travel_rejected;   
```
Business events must be raised in the save sequence, therefore, we have to enable the additional save for our managed BO by specifying the statement with additional save.

We will add the keywords with full data to always have access to all the data of the travel entity instances without having to read them.

For that, insert the code snippet provided below after the late numbering statement,
```
  with additional save with full data
```
Save (Ctrl+S) and activate (Ctrl+F3) the changes.

A warning ⚠ will be displayed about the need for a redefinition of the local saver method save_modified. You will tackle this in the next step.

Exercise 11.3: Raise the Event in the Travel BO

^Top of page

The business events travel_accepted and travel_rejected must be respectively raised each time a travel BO entity is accepted or rejected. This can be used, for example, to trigger an email 📤 to be sent out to whomever it may concern.

Business events are raised in the additional save of the BO entity for which you want to raise the event, i.e. in the local saver class method save_modified of the behavior pool ZRAP110_BP_TRAVELTP_### of Travel BO entity in the present scenario.

🔵 Click to expand!

Go to the behavior pool ZRAP110_BP_TRAVELTP_### and navigate to the local saver class lsc_zrap110_r_traveltp_### located on the Local Types tab.

Define the constant travel_status for the different overall travel status and redefine the method save_modified in the local saver class definition.

Insert the code snippet provided below in the PROTECTED SECTION for the purpose.

  CONSTANTS:
    BEGIN OF travel_status,
      open     TYPE c LENGTH 1 VALUE 'O', "Open
      accepted TYPE c LENGTH 1 VALUE 'A', "Accepted
      rejected TYPE c LENGTH 1 VALUE 'X', "Rejected
    END OF travel_status.

   METHODS save_modified REDEFINITION.

Add the method implementation using the ADT Quick Fix (Ctrl+1).
Select the appropriate entry for the method implementation to be added to the class implementation.

Now go to the class implementation section and raise the event with the appropriate information. The appropriate events should be raised only when the overall status of a travel instance is set to accepted or rejected.

For that, replace the empty method implementation of save_modified with the source code provided below and replace all occurences of the placeholder ### with your assigned suffix using Ctrl+F.

 METHOD save_modified.
   "send notification for all accepted and rejected travel instances
   IF update IS NOT INITIAL.

     "raise event
     RAISE ENTITY EVENT ZRAP110_R_TravelTP_###~travel_accepted
      FROM VALUE #(
        FOR travel IN update-travel
        WHERE ( %control-OverallStatus EQ if_abap_behv=>mk-on AND
                OverallStatus          EQ travel_status-accepted )
          "transferred information      
          ( %key           = travel-%key
            travel_id      = travel-TravelID
            agency_id      = travel-AgencyID
            customer_id    = travel-CustomerID
            overall_status = travel-OverallStatus
            description    = travel-Description
            total_price    = travel-TotalPrice
            currency_code  = travel-CurrencyCode
            begin_date     = travel-BeginDate
            end_date       = travel-EndDate
          )
        ).

     "raise event
     RAISE ENTITY EVENT ZRAP110_R_TravelTP_###~travel_rejected
      FROM VALUE #(
        FOR travel IN update-travel
        WHERE ( %control-OverallStatus EQ if_abap_behv=>mk-on AND
                OverallStatus          EQ travel_status-rejected )
          "transferred information                       
           ( %key = travel-%key )
        ).  

   ENDIF.

 ENDMETHOD.

Save (Ctrl+S) and activate (Ctrl+F3) the changes.

Exercise 11.4: Create a Local Event Handler

^Top of page

As mentioned in the introduction, RAP business events can be consumed locally in the same system where they are raised (local consumption) or remotely in a separate system using SAP Event Mesh (remote consumption) for the a cross-system communication. The events will be consumed locally in this exercise.

For that, you will create an event handler class to locally consume the RAP business events raised by your application, ie. by your RAP BO: ZRAP110_TRAVEL_EVENT_HANDL_###, where ### is your assigned suffix. In this exercise, the event handling will simply consist of persisting the received information to a database table.

🔵 Click to expand!

First create a database table with a UUID-based primary key to store the received event information.

For that, right-click the folder Database Tables and select New Database Table from the context menu to launch the creation wizard.

Maintain the required information and click Next >.
- Name: ZRAP110_ETRAV###, where ### is your assigned suffix
- Description: Travel event data
Select a transport request, and click Finish to create the database table.

Replace the default code with the code snippet provided below and replace all occurences of the placeholder ### with your assigned suffix.

   @EndUserText.label : 'Travel data'
   @AbapCatalog.enhancement.category : #NOT_EXTENSIBLE
   @AbapCatalog.tableCategory : #TRANSPARENT
   @AbapCatalog.deliveryClass : #A
   @AbapCatalog.dataMaintenance : #RESTRICTED
   define table zrap110_etrav### {

     key client     : abap.clnt not null;
     key uuid       : sysuuid_x16 not null;
     travel_id      : /dmo/travel_id not null;
     agency_id      : /dmo/agency_id;
     customer_id    : /dmo/customer_id;
     event_name     : /dmo/description;
     overall_status : /dmo/overall_status;
     created_at     : abap.utclong;
   }

Save (Ctrl+S) and activate (Ctrl+F3) the changes.
Now go ahead, create, and implement the event handler class for the local event consumption.

For that, go to the Project Explorer, right-click the folder Classes in your package, and select New ABAP Classes from the context menu to launch the creation wizard.

Maintain the required information and press Finish.
- Name: ZRAP110_TRAVEL_EVENT_HANDL_###, where ### is your assigned suffix
- Description: Travel event handler for local consumption
Select a transport request, and click Finish to create the ABAP class.
Specify the class as event handler class pool for your RAP BO by adding the statement FOR EVENTS OF entity_name of the class definition section, directly after the keyword FINAL as shown on the screenshot. Do not forget to replace all occurence of ### with your assigned suffix.
```
     FOR EVENTS OF ZRAP110_R_TRAVELTP_###
```
You can now go ahead with the event handler implementation.
Now go to the Local Types tab to define and implement the local handler class lhe_travel for the travel BO entity.

For that, simply replace the skeleton code with the source code provided in the document below. You can access the ABAP Kexword documentation (F1) for more details on the classes cl_abap_behavior_event_handler and cl_abap_tx used in the implementation.

Do not forget to replace all occurences of the placeholder ### with your assigned suffix.

▶📄 Source code document: Local Types of ABAP Class ZRAP110_TRAVEL_EVENT_HANDLER_###

Brief explanation of the local RAP event handler class lhe_travel
Click to expand!
1. A local event handler class must inherit from the superclass cl_abap_behavior_event_handler.
2. Our current local event handler contains a RAP event handler method for each event we whant to handle:
  - i.e. on_travel_accept() and on_travel_reject() for the events travel_accepted and travel_rejected respectively, in this exercise.
  - In the method signature, the importing parameter, the entity, as well as the event to be consumed are specified.
  Note: An event can only be handled by one method within an event handler class. However, method handling across multiple handler classes is possible.
3. In this exercise, the method get_uuid() is used for convenience to centrally generate UUIDs for the new database records to be persisted.
4. About the implementation of the RAP event handler methods: on_travel_accept() and on_travel_reject()
  - Because we are doing an insert on a database, we must first close the active modify phase of the RAP LUW by calling the method cl_abap_tx=>save().
  - Loop over the transfered event instances and do the needful 🙂
Save (Ctrl+S) and activate (Ctrl+F3) the changes.

Exercise 11.5: Test the Enhanced Travel App

^Top of page

Now play aroud with your Travel app and check out whether the raised events were process by the event handler class and the respective information persisted in the database table ZRAP110_ETRAV###.

🔵 Click to expand!

First, start the Data Preview (F8) of the new database table ZRAP110_ETRAV_###. No data should be shown as it is empty.
Now, go to your Travel app, and, for example, set a Travel record to accepted and another one to rejected.
Go back to the ABAP Development Tools and refresh the Data Preview of the database table ZRAP110_ETRAV_###.

Entires of the raised events should now appear on the screen.
You can repeat the test: Play around in the Travel app and check the new entries in the database table ZRAP110_ETRAV_###.

Summary

^Top of page

Now that you've...

Defined and raised an event in your BO behavior definition,
Created and implemented an event handler class for the local event consumption, and
Test the enhanced Travel App,

you can continue with the next exercise – Exercise 12: Implement the Base BO Behavior - Dynamic Feature Control

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

README.md

README.md

Exercise 11: Enhance the BO Behavior with Business Events

Introduction

Exercises:

About Business Events in RAP

Exercise 11.1: Define the Business Event Parameter

Exercise 11.2: Define the Business Event in the Travel BO

Exercise 11.3: Raise the Event in the Travel BO

Exercise 11.4: Create a Local Event Handler

Exercise 11.5: Test the Enhanced Travel App

Summary

Files

README.md

Latest commit

History

README.md

File metadata and controls

Exercise 11: Enhance the BO Behavior with Business Events

Introduction

Exercises:

About Business Events in RAP

Exercise 11.1: Define the Business Event Parameter

Exercise 11.2: Define the Business Event in the Travel BO

Exercise 11.3: Raise the Event in the Travel BO

Exercise 11.4: Create a Local Event Handler

Exercise 11.5: Test the Enhanced Travel App

Summary