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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.

Create a Project ​

sh
cds init hello-world --add tiny-sample
cd hello-world
npm install
sh
cds init hello-world --add java,samples
cd hello-world

With the cds init command above you also created a sample schema and service. It's not relevant and can be ignored for now, but a CAP Java service currently needs persistence in order to startup correctly.

Define a Service ​

... using CDS:

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

Implement it ​

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

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

... or Node.js ES6 classes style.

js
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:

java
package customer.hello_world.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":

sh
cds watch
sh
cd srv
mvn cds:watch

Consume it ​

... for example, from your browser:

http://localhost:4004/odata/v4/say/hello(to='world')

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

You should see the value "Hello world!" being returned.