SAP Cloud Application Programming Model Getting Started (CAP)
This article describes how to get started with building Cloud Application Programming Model (CAP) projects and according artefacts with Core Data Services (CDS).
For local native development see SAP HANA Local Native Development
Sources and Further Reading
| Description | URL | Comment |
|---|---|---|
| All-in-one Quick Start | https://github.com/SAP-samples/cloud-cap-walkthroughs/blob/master/exercises-node/intro/README.md | |
| Back to basics SAP Cloud Application Programming Model (CAP) | https://www.youtube.com/playlist?list=PL6RpkC85SLQBHPdfHQ0Ry2TMdsT-muECxhttps://github.com/qmacro/capb2b | SAP Developers YouTube Playlist and GitHub Repository |
| Qmacro / DJ Adams | https://qmacro.org/tags/cap/ | |
| Qmacro @ SAP Community | https://community.sap.com/t5/user/viewprofilepage/user-id/53 | |
| SAP CAP Documentation | https://cap.cloud.sap/ | |
| SAP CAP Sample Repositories | https://github.com/SAP-samples/cloud-cap-samples | Use opensap*-Branches |
| GitHub Repositories of CAP and Fiori Showcases | https://github.com/SAP-samples/cap-sflighthttps://github.com/SAP-samples/fiori-elements-feature-showcase | |
| ABAP Freak Show Ep. 1 - HANA Cloud and the Business Application Studio | https://www.youtube.com/watch?v=a3WPQwmpbvI&list=PLoc6uc3ML1JR38-V46qhmGIKG07nXwO6X&index=71 |
Installation of Prerequisites
Relevant Tools from SAP
npm i -g @sap/cds npm i -g @sap/cds-dk
Additional 3rd Party Tools1
npm i -g hana-cli
Create CDS Project
cds init bookshop
or
cds init MyCDSProject --add hana, mta
Download and install dependencies:
npm install
Start Service
cds watch
This also monitors changes to the underlying files and restarts when a file has changed.
Add Persistency to CDS
In case of SQLite first install SQLite3 packages by executing in the root of the project folder:
npm i sqlite3 -D
Deploy data model to different database types:
cds deploy
This deploys the cds entity models and csv files to the database specified in package.json in section cds.requires.db. This should look like this:
{ "cds":
{ "requires": {
"db": {
"kind": "sqlite",
"credentials": { "url": "db.sqlite" }
}
}
}
}
For more explainations see for SQLite see https://cap.cloud.sap/docs/guides/databases-sqlite
cds deploy --to sqlite # Deploys to sqlite.db
cds deploy --to sqlite:my.db # Deploys to my.db
cds deploy --to hana # Deploys to HDI container on HANA
# (Requires Cloud Foundry login)
This does not update the package.json secion cds.requires.db any more as opposed to older cds versions.
In order to see the actual created SQL statements:
cds compile srv/cat-service.cds --to sql # Creates SQL statements cds compile srv/cat-service.cds --to hana # Creates hdbcds or hdbtable/hdbview artefacts
When deployed to SQLite database use this statement to view the database:
sqlite3 my.db -cmd .dump
Create CSV header files in db location (by default db/data) for modeled entities:
cds add data
Deployment to SAP Business Technology Platform (BTP)
Login to CF space:
cf login
Build Deployment Package
cds add hana
package.json needs to contain "kind": "hana". (really? - for which CF / HANA Cloud Version?)
Also when deploying to BTP which is internally HANA 4.0 "deploy-format": "hdbtable" has to be set and hdi-deploy should be at least version 4. Example:
{
...
"devDependencies": {
"@sap/hdi-deploy": "^4"
},
...
"cds": {
"hana": {
"deploy-format": "hdbtable"
},
"requires": {
"db": {
"model": [
"db",
"srv"
],
"kind": "hana"
}
}
}
}
Deploy via Cloud Foundry CLI
Build the deployment artifacts:
cds build/all cds build --production # Only production profile?
Create a hana service for the hdi-container. The stated hdi-container name must correlate to the services-name in /gen/db/src/manifest.yaml.
cf create-service hana hdi-shared <app-db-hdi-container>
Now push the DB deployer application and also the actual service application:
cf push -f gen/db cf push -f gen/srv --random-route
Deploy via MTA
Install MTA Build Tool
npm install -g mbt
Generate MTA project descriptor file mta.yaml and build MTA archive:
cds add mta mbt build
Deploy MTA archive to CF space:
cf deploy mta_archives/<buildmta>.mtar
Troubleshooting
Real-time output of CF services can be displayed in BAS terminal with
cf logs <appname>
CDS Commands Cheatsheet
Noteworthy Commands
| Command | Description |
|---|---|
| cds env | Displays the effective configuration... |
| cds env ls | ... in .properties format |
| cds compile services.cds | Compile JSON-like database structure |
| cds compile services.cds | jq | dto, but in actual JSON |
| cds compile services.cds --to sql | Compile SQL statements from CDS |
| cds compile services.cds --to edmx | Compile EDMX file (metadata) from CDS |
| cds compile services.cds --to csn | Output CSN = Internal CDS Schema Notation... |
| cds compile services.cds --to csn | jq '.definitions | keys' | ... and process output with JSON processor by extracting keys of definition nodes |
| cds compile schema.cds --to yaml | Output Yaml of database schema |
| cds compile services.cds --to yaml | Output Yaml of all services including their db schema |
| cds add data | Create CSV header files in db location (by default db/data) for modeled entities |
Using CDS REPL & JavaScript APIs
cds r cds repl
This launches an read-eval-print-loop which can be used as an interactive playground to experiment with CDS' JavaScript APIs.
| API | Description |
|---|---|
| cds.utils.uuid() | Returns an UUID |
Accessing Services from Command Line
Reading from Services
Read output of services via curl and pipe it through jq for nicer formatting:
curl -s 'localhost:4004/odata/v4/bookshop/Orders' | jq
Output (example for Bookshop repo):
{
"@odata.context": "$metadata#Orders",
"value": [
{
"ID": "6091d4ab-650e-4afa-90bb-163305e473a2",
"comment": "second order"
},
{
"ID": "ac5aeb9f-c7cd-4f52-ab4a-9c0313ded402",
"comment": "first order"
}
]
}
Deep Insert into Service
For performing a deep insert we first need a at least two level deep structure.
The following neworder.json file with a two-level deep structure is given:
{
"comment": "New Order",
"Items": [
{
"pos": 1,
"quantity": 10
},
{
"pos": 2,
"quantity": 20
}
]
}
To perform the deep insert put the json file into the service by utilizing curl. The filename needs to be prefixed with a @. As we are connecting to a web service we also need to add a header and specify the content type, in this case application/json:
curl --verbose --data @neworder.json --header 'content-type: application/json' --url 'localhost:4004/odata/v4/bookshop/Orders'
We should receive an answer that is similar to the following one in that we are connected to localhost, and we posted to odata service and that the HTTP status was 201 Created:
* Trying 127.0.0.1:4004...
* Connected to localhost (127.0.0.1) port 4004 (#0)
> POST /odata/v4/bookshop/Orders HTTP/1.1
> Host: localhost:4004
> User-Agent: curl/7.74.0
> Accept: */*
> content-type: application/json
> Content-Length: 193
>
* upload completely sent off: 193 out of 193 bytes
* Mark bundle as not supporting multiuse
< HTTP/1.1 201 Created
< X-Powered-By: Express
< X-Correlation-ID: a5b9998a-103c-4c45-bb26-dff71aeadb69
< OData-Version: 4.0
< content-type: application/json;odata.metadata=minimal
< Location: Orders(173239cc-a256-4cc3-a323-947883622e29)
< Date: Sat, 20 Apr 2024 11:35:34 GMT
< Connection: keep-alive
< Keep-Alive: timeout=5
< Content-Length: 280
<
* Connection #0 to host localhost left intact
{"@odata.context":"$metadata#Orders(Items())/$entity","ID":"173239cc-a256-4cc3-a323-947883622e29","comment":"New Order","Items":[{"parent_ID":"173239cc-a256-4cc3-a323-947883622e29","pos":1,"quantity":10},{"parent_ID":"173239cc-a256-4cc3-a323-947883622e29","pos":2,"quantity":20}]}
