1. Create SAP OData project in SAP ABAP transaction code segw

Start with this article , We step out and use the thing code SEGW Development OData The first step of service .

We will develop a library management (Book Management) Of OData service , First, create a model of the book entity , That is to say ABAP Dictionary, Things code SE11 Create a ABAP structure (Structure), named ZTS_BOOK.

The following figure shows the thing code SE11 The interface of ：

Create a new one Structure：

We first create a key That is, the primary key field , Field called BOOK_GUID, Type words , choice ABAP Self contained RAW type . In order to input this ABAP Standard type , Let's order Built-in Type, And then in turn Data Type and Length Field maintenance RAW and 16：

Maintain other fields in turn ：

• BOOK_ID: Recording books ID, The type is CHAR, The length is 4 Characters .
• BOOK_NAME: Record the name of the book , The type is SSTRING, The length is 20 Characters .
• AUTHOR_ID: The author of the book ID, The type is CHAR, The length is 4 Characters .
• AUTHOR_NAME: The name of the author of the book , The type is SSTRING, The length is 20 Characters .
• STOCK_NUMBER: The number of books in stock , integer .

Then enter the thing code SEGW, Create a new project ：

The project name is maintained as ZBOOK_MANAGE, Project Type Maintenance into Service with SAP Annotations, Click on Local Object Can be stored locally $tmp In the development package .

Then we will see these new folders under the project folder ：

We're facing Data Model Under the folder Entity Types Right click , Select... From the right-click menu Create.
The purpose of this step is to create OData The entity type of the service model , That is to say SAP What the help document says Entity Type.

because OData It's a protocol , It can be implemented based on many high-level programming languages ,ABAP Is one of them , So take ABAP Realized OData service , Its data model is also based on ABAP DDIC Data structure created in . Next steps , We will put SEGW Created in OData Model Entity Type, Same as ABAP DDIC Structure namely ZTS_BOOK Fields in , Establish a one-to-one mapping relationship .

Entity Type The name of , Maintenance into Book：

Click on * after , You can see the following interface , among ABAP Structure The column below is empty .

Manual input we just SE11 Created in ABAP Structure ZTS_BOOK after , Using shortcut keys Ctrl + S Save changes ：

Now, on the left Entity Type Under the folder , There will be one more node ：Book

double-click Book Under the folder Properties Folder , The discovery is empty . At this time, we need to maintain manually Book Every field of this entity type .

Click on this. Append Row Button , Create a new blank line ：

First of all, it needs to be Entity Type Define a primary key (key)： stay Name Manually enter book_guid, hold Is Key Of * In the play , indicate book_guid Property is primary key , And then in Edm Type Field , from F4 help Interior selection Edm.Guid This type .

Next, you need to maintain whether this attribute is supported in OData Service implementation is created , Be modified , Is sorted and whether to allow its value to be Null.

because Edm.Guid The value of type is shaped like this 16 The combination of digits and letters ：00163EA720001ED29D9420A624836ED3, So obviously , Once this data format is created , Should not be modified , therefore Updatable Of * Should not be selected . Empathy ,Sortable and Nullable Nor should it be chosen , Because of GUID The sorting is unreasonable ,GUID Nor should it be allowed Null Exists as an initial value .

Filterable Search according to this field , about GUID It's not suitable for .

But the next steps in this tutorial , our OData Service implementation , Will support direct passage OData Create new Book data , therefore Creatable Of * It should be .

Last , It needs to be for this Entity Type attribute field , Choose one from ABAP structure ZTS_BOOK Medium ABAP Field . Or from the F4 Value Help Interior selection BOOK_GUID:

Select and save , give the result as follows ：

Repeat the above steps , take ZTS_BOOK Other fields , Also manually maintain one by one until Entity Type Properties Under the folder ：

Be careful ,ABAP DDIC Inside CHAR and SSTRING type , stay OData Entity Type The corresponding type in , All for Edm.String.

After property maintenance , Choose ZBOOK_MANAGE project , From the right-click menu , choice Check Consistency, Make sure there is no Error That is, the error message is reported .

Shown above , There are two warning messages (Warning Message)：Potential loss of data: EDM type is more restriction. Map instead to the ABAP type ‘CHAR[20]’.

The main idea of these warning messages is , our book_name and author_name, Select the Edm Type The type is Edm.String, Maximum length is 20, We call these two attribute fields , Bound to ABAP structure ZTS_BOOK Of BOOK_NAME and AUTHOR_NAME Field , these two items. ABAP The data types of fields are SSTRING, Because we expect these two fields to be case sensitive . and SEGW It is suggested that we map to the type CHAR 20 Of ABAP Field .

For this warning message , We can ignore .

Check Consistency After finding no errors , From the right-click menu , choice Generate Runtime：

Pop it out Model and Service Definition The dialog . up to now , We just finished OData Model creation , These models are not yet operational , It can't be consumed by the outside world . therefore , We pass the Generate Runtime, Automatic generation OData Implementation class of metadata (MPC, Metadata Provider Class) and OData Service business data providing class (DPC,Data Provider Class)：

Click on * after ,SEGW Will be generated automatically MPC,MPC_EXT and DPC,DPC_EXT four ABAP class , On the left Runtime Artifacts You can see it under the folder .

MPC and DPC Implementation source code of , Every time we talk to SEGW The project in , After modification , Click... Again Generate Runtime after , Will be automatically overwritten , Replace it with the present SEGW The source code corresponding to the latest settings . therefore ,MPC and DPC It is not an ideal place for developers to write business logic .

So if we want to be right SEGW Created OData Metadata of the model , Must be in MPC_EXT This ABAP Class .MPC_EXT Class is MPC Subclasses of classes , stay MPC_EXT Code written in , stay Generate Runtime It will not be covered later . Empathy ,OData The business logic of services , It should also be written in DPC_EXT In class , instead of DPC In class .

So far we're done SEGW Model creation , The next step in this tutorial , We'll show you how to build a good OData Model to test .