Create a CAP Project with SAP Business Application Studio

Your project is auto-configured by the @cap-js/sqlite plugin. The benefit of this auto-wired configuration is, that it works out of the box. Until now you used the in-memory database automatically when you ran the application. It reflects all changes you do to your data model and sample data on the fly. But it also means that data is reset to the initial .csv content with every restart.

The next step is to have a file-based persistence of your data. And it’s just some configuration you need to add and your application is configured to use a database. That gives you persistent data even though you’re restarting your application. To use persistence also means you explicitly deploy the changes you make, to see them in your application.

1. First let’s make sure that you know the current state of effective database configuration.

   Open a terminal by going to Terminal > New Terminal and execute the following:

   Shell/Bash Copy

   cds env requires.db

   The response should look as follows:

   Shell/Bash Copy

   {
     impl: '@cap-js/sqlite',
     credentials: { url: ':memory:' },
     kind: 'sqlite'
   }

   You see, that the current configuration uses an in-memory database. Let’s change that.

2. Add the needed configuration for a file-based SQLite database to your package.json.

   JSON Copy

   "cds": { "requires": {
       "db": {
       "kind": "sqlite",
       "credentials": { "url": "db.sqlite" }
       }
   }}

3. Go to your terminal and deploy your data to a file-based SQLite3 database.

   Shell/Bash Copy

   cds deploy

   This creates a file called db.sqlite and deploys the data into this file.

4. Stop and then start your application in debug mode by going to View > Debug.

   

5. Refresh the browser tab of your application and navigate to the Books entity in the CatalogService.

The data you see is now served from the file db.sqlite and is located in the root of your folder. The next step includes a proof that the file-based persistence is used.

To have some sample data for the data model you’ve just created, you create the needed files and then copy csv content over.

cds add data

This adds csv files with a single header line for all entities to the db/data/ folder. The name of the files matches the entities’ namespace and name, separated by -.

1. Open my.bookshop-Books.csv in the db/data folder and replace the content.

   The filename is important to make use of a default to pick up sample data.

   CSV Copy

   ID,title,descr,stock,price,currency_code,authors_ID
   201,Wuthering Heights,"Wuthering Heights, Emily Brontë's only novel, was published in 1847 under the pseudonym ""Ellis Bell"". It was written between October 1845 and June 1846. Wuthering Heights and Anne Brontë's Agnes Grey were accepted by publisher Thomas Newby before the success of their sister Charlotte's novel Jane Eyre. After Emily's death, Charlotte edited the manuscript of Wuthering Heights and arranged for the edited version to be published as a posthumous second edition in 1850.",12,11.11,GBP,101
   207,Jane Eyre,"Jane Eyre /ɛər/ (originally published as Jane Eyre: An Autobiography) is a novel by English writer Charlotte Brontë, published under the pen name ""Currer Bell"", on 16 October 1847, by Smith, Elder & Co. of London. The first American edition was published the following year by Harper & Brothers of New York. Primarily a bildungsroman, Jane Eyre follows the experiences of its eponymous heroine, including her growth to adulthood and her love for Mr. Rochester, the brooding master of Thornfield Hall. The novel revolutionised prose fiction in that the focus on Jane's moral and spiritual development is told through an intimate, first-person narrative, where actions and events are coloured by a psychological intensity. The book contains elements of social criticism, with a strong sense of Christian morality at its core and is considered by many to be ahead of its time because of Jane's individualistic character and how the novel approaches the topics of class, sexuality, religion and feminism.",11,12.34,GBP,107
   251,The Raven,"""The Raven"" is a narrative poem by American writer Edgar Allan Poe. First published in January 1845, the poem is often noted for its musicality, stylized language, and supernatural atmosphere. It tells of a talking raven's mysterious visit to a distraught lover, tracing the man's slow fall into madness. The lover, often identified as being a student, is lamenting the loss of his love, Lenore. Sitting on a bust of Pallas, the raven seems to further distress the protagonist with its constant repetition of the word ""Nevermore"". The poem makes use of folk, mythological, religious, and classical references.",333,13.13,USD,150
   252,Eleonora,"""Eleonora"" is a short story by Edgar Allan Poe, first published in 1842 in Philadelphia in the literary annual The Gift. It is often regarded as somewhat autobiographical and has a relatively ""happy"" ending.",555,14,USD,150
   271,Catweazle,"Catweazle is a British fantasy television series, starring Geoffrey Bayldon in the title role, and created by Richard Carpenter for London Weekend Television. The first series, produced and directed by Quentin Lawrence, was screened in the UK on ITV in 1970. The second series, directed by David Reid and David Lane, was shown in 1971. Each series had thirteen episodes, most but not all written by Carpenter, who also published two books based on the scripts.",22,150,JPY,170

2. Open my.bookshop-Authors.csv file in the db/data folder and replace the content.

   CSV Copy

   ID,name
   101,Emily Brontë
   107,Charlotte Brontë
   150,Edgar Allen Poe
   170,Richard Carpenter

   In the previous step we switched to a file-based persistence. That means you can’t see your sample data in your application without deployment. And as we didn’t deploy the sample data until now, you can restart your running application and still see the initial sample data.

   To see your recent changes, you need to deploy your data using cds deploy.

3. Go to the debug panel with View > Debug and restart the app.

   

   There is a convenient shortcut that removes the need to restart the app with every change: Execute cds watch in the terminal. Call cds help watch in the terminal for more information.

4. Open the application and refresh or select Open in New Tab from the prompt in the bottom right corner of the UI.

5. Select Books and see that the newly changed model and its sample data is served as part of your CatalogService service.

   

   The JSON displayed here, is formatted by a browser extension.

   The CatalogService defined in the cat-service.cds file in the srv folder remains unchanged.

You’re set up with a basic CAP project showing some important features that make the CAP model so valuable. And you got in touch on some of the nice SAP Business Application Studio features. The next tutorial of this series gives you more details and encourages you to play around with those CAP and studio features.