In previous blog, we discussed Introduction to OData and how
to create an OData service in SAP NetWeaver Gateway. We have also shown how to
test an OData if it is working fine or not. Now, we need to learn how to perform
operations like Insert, Update and Delete. In this article we will also learn
basic queries of reading data.
How it works
In case of OData, there are three phases of data transfer. These are:
1. Sending Data
from Frontend
Data is sent from UI (Client) to
OData (Server)
in form of query
2. Taking Data
from Frontend
At OData we receive data from Frontend using data provider (Code
implemented in CRUD Operation section)
io_data_provider->read_entry_data(IMPORTING es_data= ls_entity).
3. Sending Data
to Frontend
From OData we send data to UI using et_entityset or er_entity after data manipulation (Code implemented in CRUD Operation section).
Operations in ODATA
In this section, we will explore all the methods generated automatically,
once you generate an OData. In last article, we have already instructed to
write all your CRUD operations related code in DPC_EXT class. Hence, we will
follow the same concept here.
SAP ABAP OData provides different methods for CRUD operations, these are:
|
Method |
SQL
Operation |
Description |
|
GET_ENTITY |
Select |
This method is used to read a
single data based on table keys |
|
GET_ENTITYSET |
Select |
This method is used to read
entire data of a table |
|
CREATE_ENTITY |
Insert |
This method is used to
create/insert a new data in table |
|
UPDATE_ENTITY |
Update/Modify |
This method is used to update
an existing data in table |
|
DELETE_ENTITY |
Delete |
This method is used to delete
an existing data in table |
Query in SAP OData
In this section, we will explore all the Query we can perform while
reading data from OData. In above section, we have learnt how to do read calls
using GET_ENTITY and GET_ENTITYSET. Sometimes, we need to filter out data
according to our requirement, or to get total number of data counts or to get
data in specific order. These all SAP OData Queries are explained below:
Here, let us suppose <your service name> =
https://isd.sap.com/<OData Service Name>
|
Query |
Description |
Example |
|
$metadata |
It gives the metadata detail
of your service. By metadata we mean it will provide information about all
the entity sets with their field names and their attributes |
<your service
name>/$metadata |
|
$FILTER |
It is mainly used during Read
Entity Set call. During Read, we can send some filter value in backend that
can be later used in where condition of Select queries |
<your service
name>/$FILTER |
|
$top and $skip |
It is mainly used to get
limited data in the UI, in case you are reading all the data, and the table
is having a very large data |
<your service name>/$top
and $skip |
|
$orderby |
This is used to order the data
in ascending or descending order for a specific key |
<your service
name>/$orderby |
|
$format=json |
This returns the data in form
of JSON format. By default, the result is in XML format. |
<your service
name>/$format=json |
|
$inlinecount |
This returns the number of
data of a table that will appear in the UI |
<your service
name>/$inlinecount |
|
$expand |
This is used to bind the
association and navigation data together |
<your service
name>/$expand |
|
$value |
This is used to return the
media data |
<your service
name>/$value |
In the following steps, I will list down steps to create an
entry through OData service. Similar steps are required for other CRUD
operations.
To configure a well-defined SAP
Gateway OData service, complete the following steps in your SAP system. These
steps cover the general procedure, but need some consideration for your own SAP
OData system and your preferred techniques for configuring SAP.
Display
the SAP Gateway Service Builder (transaction SEGW)
Create a project
Figure 1. Select Create Project
Configure details for the
project
Chose a project name, give your
project a description, select Standard generation strategy, and specify the
package. The project will be saved as a local object (Package: $TMP, or click Local Object.)
Create the Entity type by
importing a pre-defined DDIC Structure for the Order header.
Right-click Data Model, and then
select Import > DDIC
Structure.
Choose the required structure.
If the Sales order structure is
not available in your SAP system, select the ABAP structure ZST_VBAK. Click Next.
Choose the required fields, and
then click Next.
Select the key field, VBELN,
and then click Finish.
Repeat the same sequence of
steps from 4 to 7 to import the next structure, OrderStatus.
This may be an Item structure.
The following example shows the import of another custom structure called
ZST_SO_STATUS.
Second
Import from DDIC Structure, step 1 of 3
Second Import from DDIC
Structure, step 2 of 3
Second Import from DDIC
Structure, step 3 of 3
When you have completed the
preceding steps, you should see the two newly-created Entity Types: OrderStatus
and SalesOrder:
Figure 7. Result of Import from
DDIC Structures – The two newly-created Entity Types: OrderStatus and SalesOrder
Create the Entity Sets for the
entity types that you have just created.
Right-click
the folder Entity Sets, and then select Create.
Figure 8. Create Entity Sets
Create an Entity Set
SalesOrderSet for the entity type SalesOrder.
(A naming convention is to make
the Entity Set name by appending ‘_Set’ to the Entity Type name.)
Create an Entity Set
OrderStatusSet for the entity type OrderStatus:
You should now see the newly-created entity sets:
Create the Associations which
sets the cardinal rules, and then click Next.
Set the Dependent Property,
Vbeln, and then click Next.
Figure 13. Create Association, step 2 of 3
Click Finish.
Click Save.
Check Consistency. Right-click
ZORDER_MAINTAIN and then select Check Consistency:
Generate runtime objects
To use the service with the changes that you have made, you need to generate the runtime objects. This creates the underlying ABAP classes that contain all the information that you've specified in the service builder. Click the Generate Runtime Objects icon or right-click ZORDER_MAINTAIN and then select Generate Runtime:
While generating the runtime
objects, the class and service details are generated as shown below.
Choose the package for the
objects.
Now, you should see that the runtime objects were created successfully:
This completes the design stage.
Next, you need to develop the code as part of the implementation.
Expand
the Runtime Artifacts folder.
Double-click the Data Provider
Class Extension (DPC_EXT)
Implement the insert method
Because more than one structure
or table is involved, you need to implement the method
'/IWBEP/IF_MGW_APPL_SRV_RUNTIME~CREATE_DEEP_ENTITY' for implementing CREATE
(POST) functionality for deep insert. However, for single insert, you can use
the CREATE_ENTITY method.
To
implement the method, first click the Change Mode icon:
Select the method:
Deep
Insert (Nested)
Independent Insert Implement separate CREATE ENTITY methods as shown
below:
After selecting the method,
click the Redefine icon.
The method has been redefined
and is available to code the business logic.
Add
the business logic for your requirements.
After completing the logic
development, the CREATE functionality is complete.
Register
the service Use Service Registration: Transaction: /IWFND/MAINT_SERVICE
In
the Activate and Maintain Service window, click Add Service
Get the Technical service name from the transaction SEGW.
The Runtime artifact which ends with 'SRV' in SEGW refers to the Technical Service; for example:
In the next screen, specify the
System Alias (created by Basis) and the new service which has been created.
After that, click the Get Services icon. The result is displayed:
Click Add
Selected Services.
Our service is now registered
and ready to be exposed in Fiori application. In the above steps, we saw how to
create an entry in table using create OData service. Similarly, if we are to read,
update or delete entries we can redefine respective methods and add appropriate
code.
In the next blog, we will look
deeply into how to register service SAP OData service through /iwfnd/maint_service
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