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SAP Cap app in 10 steps
 

1. Set up local development environment

npm i -g @sap/cds-dk
Install VS Code extension SAP CDS Language Support
 

2. Start Project

cds init my-bookshop
cd my-bookshop
code .
npm install
 
4. Add data model schema.cds under /db
 
Example:
namespace my.bookshop;
using { Country, managed } from ‘@sap/cds/common’;
 
entity Books {
  key ID : Integer;
  title  : localized String;
  author : Association to Authors;
  stock  : Integer;
}
 
entity Authors {
  key ID : Integer;
  name   : String;
  books  : Association to many Books on books.author = $self;
}
 
entity Orders : managed {
  key ID  : UUID;
  book    : Association to Books;
  country : Country;
  amount  : Integer;
}
 
5.  Define the service cat-service.cds under /srv
 
Example:
using my.bookshop as my from ‘../db/schema’;
 
service CatalogService {
  entity Books @readonly as projection on my.Books;
  entity Authors @readonly as projection on my.Authors;
  entity Orders @insertonly as projection on my.Orders;
}
 
6. Add initial data
cds add data
 
db/data/my.bookshop-Authors.csv
 
101,Emily Brontë
107,Charlote Brontë
150,Edgar Allen Poe
170,Richard Carpenter
 
db/data/my.bookshop-Books.csv
 
201,Wuthering Heights,101,12
207,Jane Eyre,107,11
251,The Raven,150,333
252,Eleonora,150,555
271,Catweazle,170,22
 
Add persistent database in package.json
 
{
  “name”: “my-bookshop”,
  “version”: “1.0.0”,
  “description”: “A simple CAP project.”,
  “repository”: “<Add your repository here>”,
  “license”: “UNLICENSED”,
  “private”: true,
  “dependencies”: {
    “@sap/cds”: “^7”,
    “express”: “^4”
  },
  “devDependencies”: {
    “@cap-js/sqlite”: “^1”
  },
  “scripts”: {
    “start”: “cds-serve”
  },
  “cds”: { “requires”: {
   “db”: {
      “kind”: “sqlite”,
      “credentials”: { “url”: “db/my-bookshop.sqlite” }
   }
}}
}
 
Deploy the data model to an SQLite database
cds deploy
 
Open SQLite and view the newly created database
sqlite3 db/my-bookshop.sqlite -cmd .dump
 
7. Run service
cds watch
 
8. Test generic handlers
Create a file test.http under root
 
###
#
# Browse Books
#
GET http://localhost:4004/odata/v4/catalog/Books?
  # &$select=title,stock
  # &$expand=currency
  # &sap-language=de
 
###
#
# Get Author wit ID 101
#
GET http://localhost:4004/odata/v4/catalog/Authors(101)
 
###
#
# Update Author with ID 101
#
POST http://localhost:4004/odata/v4/catalog/Authors
Content-Type: application/json
 
{“ID”: 101, “name”: “Some Author”}
 
###
#
# Order a Book
#
POST http://localhost:4004/odata/v4/catalog/Orders
Content-Type: application/json;IEEE754Compatible=true
 
{“book_ID”: 201, “amount”: 5}
 
9. Add custom logic
 
Create a file cat-service.js under folder /srv
 
  module.exports = (srv) => {
 
  const {Books} = cds.entities (‘my.bookshop’)
 
  // Reduce stock of ordered books
  srv.before (‘CREATE’, ‘Orders’, async (req) => {
    const order = req.data
    if (!order.amount || order.amount <= 0)  return req.error (400, ‘Order at least 1 book’)
    const tx = cds.transaction(req)
    const affectedRows = await tx.run (
      UPDATE (Books)
        .set   ({ stock: {‘-=’: order.amount}})
        .where ({ stock: {‘>=’: order.amount},/*and*/ ID: order.book_ID})
    )
    if (affectedRows === 0)  req.error (409, “Sold out, sorry”)
  })
 
  // Add some discount for overstocked books
  srv.after (‘READ’, ‘Books’, each => {
    if (each.stock > 111)  each.title += ‘ — 11% discount!’
  })
 
}
 
10. Enhance configuration and deploy project for production
 
cds add hana,mta,xsuaa,approuter –for production
npm update –package-lock-only
 
“cds”: {
  “fiori”: {
    “preview”: true
  },
  “server”: {
    “index”: true
  },
}
 
Log in cf
cf login
 
Add the following configuration to xs-security.json
“oauth2-configuration”: {
    “redirect-uris”: [“https://*.us10-001.hana.ondemand.com/**”]
}
 
mbt build -t gen –mtar mta.tar
cf deploy gen/mta.tar
 
Application “my-bookshop” started and available at “[org]-[space]-my-bookshop.cfapps.[region].hana.ondemand.com”