CAPM First Project: Bookshop App Step by Step

05:52:00

Why the bookshop

Every CAP tutorial starts with the bookshop, and for good reason: books, authors, and orders exercise entities, associations, compositions, and services in one small domain. Twenty minutes here teaches you the whole development loop.

Goal: a running OData V4 service with sample data, built from scratch with the cds CLI.

Step 1: Scaffold the project

With Node.js 20+ and the CDS development kit installed:

cds init bookshop --add sample
cd bookshop
npm install

The --add sample flag pulls in the classic bookshop domain model so you can focus on the mechanics first.

Step 2: Look at the data model

Open db/schema.cds. You'll see the essentials of CDS modeling:

entity Books {
  key ID   : Integer;
  title    : String;
  author   : Association to Authors;
  price    : Decimal;
}

Associations like author become navigable OData relationships automatically. No join code, no DTOs.

Step 3: Expose it as a service

Check srv/cat-service.cds:

service CatalogService {
  entity Books   as projection on my.Books;
  entity Authors as projection on my.Authors;
}

Each entity in a service becomes an OData entity set. Projections let you reshape without touching the database model.

Step 4: Run it

cds watch

This starts the server with an in-memory SQLite database, loads the sample CSV data, and restarts on every file change. Open the printed URL — /catalog/Books returns your books as OData JSON.

cds watch is your development inner loop: edit CDS, save, refresh the browser. No build step.

Step 5: Add your own entity

Now make it yours. Add to db/schema.cds:

entity Reviews : cuid, managed {
  book    : Association to Books;
  rating  : Integer;
  comment : String;
}

cuid adds a UUID key, managed adds created/modified audit fields. Expose it in the service, save, and watch it appear — schema, table, and OData endpoint generated for you.

Explore the generated API

With the server running, open /odata/v4/catalog/$metadata — the full machine-readable contract of your API. Then try query options directly in the browser:

/odata/v4/catalog/Books?$select=title,price&$top=5
/odata/v4/catalog/Books?$filter=price gt 20&$orderby=title

Filtering, sorting, paging, and selecting work out of the box — no handler code. This is the moment CAP clicks for most developers: the framework did all of it from your three-line service definition.

Where to go next

You now have the full loop: model → service → data → running API. Natural next steps: custom event handlers, Fiori Elements UI generation, and deploying to HANA Cloud.

Stuck on the setup? Paste your error in the comments and I'll help.