Hello World!

Let’s create a simple Hello World OData service using the SAP Cloud Application Programming Model in six lines of code and in under 2 minutes.

You can also download the sample from github.com.

Let’s create a simple Hello World OData service using the SAP Cloud Application Programming Model with a few lines of code and in under 2 minutes.

• Initialize the project
• Define a Service
• Implement it
• Run it
• Consume it

Initialize the project

cds init hello-world --add java,samples
cd hello-world

Define a Service

… using CDS.

File srv/world.cds, content:

service say {
  function hello (to:String) returns String;
}

Implement it

… for example, using Node.js express.js handlers style.

File srv/world.js, content:

module.exports = (say)=>{
  say.on ('hello', req => `Hello ${req.data.to}!`)
}

… or Node.js ES6 classes style.

File srv/world.js, content:

module.exports = class say {
  hello(req) { return `Hello ${req.data.to}!` }
}

That has limited flexibility, for example, you can register only one handler per event.

… for example, using a CAP Java custom handler like this:

File srv/src/main/java/customer/hello_world_java/handlers/HelloWorld.java, content:

package customer.hello_world_java.handlers;

import org.springframework.stereotype.Component;

import com.sap.cds.services.handler.EventHandler;
import com.sap.cds.services.handler.annotations.On;
import com.sap.cds.services.handler.annotations.ServiceName;

import cds.gen.say.HelloContext;
import cds.gen.say.Say_;

@Component
@ServiceName(Say_.CDS_NAME)
public class HelloHandler implements EventHandler {

	@On
	public void onHello(HelloContext ctx) {
		ctx.setResult("Hello " + ctx.getTo());
		ctx.setCompleted();
	}

}

Run it

… for example, from your command line in the root directory of your “Hello World”:

cds watch

cd srv
mvn cds:watch

Consume it

… for example, from your browser:

http://localhost:4004/say/hello(to='world')

http://localhost:8080/odata/v4/say/hello(to=’world’)