Use SAP HANA as the Database for a CAP Java Application

First you need to create and initialize an SAP HANA database schema in SAP BTP. As you’ll deploy your application to SAP BTP, Cloud Foundry Environment, you’ll also create the SAP HANA service there.

Log into the Cloud Foundry Environment using the Cloud Foundry CLI, as follows.

1. In SAP Business Application Studio, open a terminal by choosing Terminal > New Terminal from the main menu.

2. Run the following command to configure which Cloud Foundry environment you want to connect to in the terminal. Replace <CF_API_ENDPOINT> with the actual value you obtained in the previous step.

   cf api <CF_API_ENDPOINT>
   

3. Authenticate using your login credentials using the following command in the terminal:

   cf login
   

1. Make sure that you are in the root of the bookstore project:

   cd ~/projects/bookstore
   

2. Run the following command to install the necessary node packages:

   npm install --save-dev @sap/hdi-deploy
   

3. Add the following configuration in the file .cdsrc.json in the root folder of your bookstore project:

   { "hana" : { "deploy-format": "hdbtable" } }
   

4. Create an SAP HANA service instance and implicitly push all artifacts to the database using:

   cds deploy --to hana:bookstore-hana
   

   As an effect, .hdbtable and .hdbview files are generated in the (gen/)db/src/gen/ folder.

   In addition, the command initialized the database schemas inside the SAP HANA HDI container.

Aside from initializing the SAP HANA database, the cds deploy command created a file with the name default-env.json in your bookstore root folder. This file contains a set of credentials to connect to the SAP HANA HDI container, that was created by the command. CAP Java is able to automatically pick up the SAP HANA credentials from this file and configure the application running locally to use the SAP HANA HDI container as the database.

When deploying the application to the cloud, Cloud Foundry will provide the credentials as a service binding to the application through the Open Service Broker API. Also in this case, CAP Java will automatically pick up the SAP HANA credentials and configures the application for you as you’ll see in the next tutorial.

The described features are available as a plugin in CAP Java. Therefore, we’ll add an additional Maven dependency to your project. The dependency will bring the ability to read SAP HANA service bindings from the default-env.json to automatically configure the SAP HANA connectivity. In addition, it includes the SAP HANA JDBC driver.

1. Navigate back to the File Explorer by clicking on the corresponding icon.

2. Edit the pom.xml in the srv directory (not the pom.xml file located in the root project folder) and add the following dependency under the <dependencies> tag and make sure you Save the file:

   <dependency>
     <groupId>com.sap.cds</groupId>
     <artifactId>cds-feature-hana</artifactId>
   </dependency>
   

   

3. Before starting your application, make sure that you stop any running instances in the terminal or debug side panel.

4. Make sure that you are in the root of the bookstore project. Therefore, run the following command in the terminal:

   cd ~/projects/bookstore
   

5. Let’s test the SAP HANA connectivity. Start your application by running:

   mvn spring-boot:run -Dspring-boot.run.profiles=cloud
   

   The Java system property -Dspring-boot.run.profiles=cloud ensures that the default configuration using SQLite as the database, which is still defined in the application.yaml, doesn’t get activated.

   You can observe the log lines Loaded default-env.json from directory '/home/user/projects/bookstore' and Registered primary 'DataSource' bean definition for connected service 'bookstore-hana', which indicate that the SAP HANA configuration was picked up.

   

6. Try the following example request, which creates an order together with its items through a deep insert. Open a new terminal by choosing Terminal > New Terminal from the main menu.

7. Create a new order together with items:

   curl -X POST http://localhost:8080/odata/v4/OrdersService/Orders \
   -H "Content-Type: application/json" \
   -d '{ "currency_code": "USD", "items": [ { "book_ID": "b7bca6dd-0497-465e-9a5a-56f244174c8c", "amount": 1 } ] }'
   

   The expected output should be the created database record similar to the one below:

   {"@context":"$metadata#Orders(items())/$entity","ID":"67213f57-0b4c-43fc-8ed9-44f87ffb8967","createdAt":"2020-03-30T13:22:37Z","createdBy":"anonymous","modifiedAt":"2020-03-30T13:22:37Z","modifiedBy":"anonymous","total":14.14,"currency_code":"USD","items":[{"ID":"6352853e-f8e0-43b0-9c38-e15eb56a57ae","book_ID":"b7bca6dd-0497-465e-9a5a-56f244174c8c","amount":1,"netAmount":14.14,"parent_ID":"67213f57-0b4c-43fc-8ed9-44f87ffb8967"}]}