Create simple CAP Service with Node.js using the SAP Business Application Studio

1. Open SAP Business Application Studio.

2. Choose Create Dev Space.

   

3. Use name demo for your dev space and select kind Full-Stack Application Using Productivity Tools.

   

   By selecting Full-Stack Application Using Productivity Tools, your dev space comes with several extensions out-of-the-box that you need to develop CAP services.

4. Choose Create Dev Space.

   

   The creation of the dev space takes a while. You see that the status for your dev space will change from STARTING to RUNNING.

5. Once the dev space is running, click the dev space name to open it.

   

   Opening the dev space and starting the Application Studio takes a while.

1. Use the File menu to create a New Project from Template.

   

2. Choose CAP Project from the templates and choose Start.

   

3. Enter the CAP Project Details, use name sap-build-cap-sample-library, select Cloud Foundry: MTA Deployment and choose Finish.

   Runtime Node.js is already selected.

   

4. Change the view from Project Explorer to Explorer, choose View > Explorer.

   

   The Explorer view will show all files of your project.

1. In the Explorer view you will find the file mta.yaml in the root folder of your project sap-build-cap-sample-library.

   

2. Check the file in a text editor, right-click > Open With… > Text Editor default.

   

3. In the srv folder, create a new file called service.cds.

4. In the same folder, create another new file called service.js.

5. Select the file service.cds and copy the following code into the editor.

   Contains the definition of data types and function headers. Functions and actions will make the API of your service.

   Simple functions like converting a String to an Integer, a list to a CSV String or getting the list of Todos.

   CDS Copy

   @Capabilities.BatchSupported : false
   
   service sap_build_cap_sample_library @(path : '/api/v1') {
   
   define type DataString {
       value : String;
   }
   
   define type DataInteger {
       value : Integer;
   }
   
   define type DataNumber {
       value : Double;
   }
   
   define type DataList {
       id : Integer;
       title: String;
       userId: Integer;
       completed: Boolean;
   }
   
   define type DataListArray {
       responseArray : array of DataList;
   }
   
   @Core.Description : 'toInteger'
   function toInteger(value : String) returns DataInteger;
   
   @Core.Description : 'toNumber'
   function toNumber(value : String) returns DataNumber;
   
   @Core.Description : 'toString'
   function toStr(value : Double) returns DataString;
   
   @Core.Description : 'addQuotes'
   function addQuotes(value : String) returns DataString;
   
   @Core.Description : 'listToString'
   action listToString(responseArray : array of DataList, field : String) returns DataString;
   
   @Core.Description : 'get list of dodos'
   function getListOfTodos() returns DataListArray;
   
   }

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6. Select the file service.js and copy the following code into the editor.

   The JavaScript implementation for the API of your service.

   JavaScript Copy

   module.exports = srv => {
   
       srv.on('toInteger', req => {
           const {value} = req.data;
   
           return { 'value' : parseInt(value) };
       });
   
       srv.on('toNumber', req => {
           const {value} = req.data;
   
           return { 'value' : parseFloat(value) };
       });
   
       srv.on('toStr', req => {
           const {value} = req.data;
   
           return { 'value' : value.toString() };
       });
   
       srv.on('addQuotes', req => {
           const {value} = req.data;
   
           return { 'value' : "'" + value + "'"};
       });
   
       srv.on('listToString', req => {
   
           var values = req.data.responseArray;
           var resultList = [];
           var field = req.data.field;
           if (values) {
               for (var i = 0; i < values.length; i++) {
                   resultList.push(values[i][field]);
               }
           }
   
           return { value : resultList.toString() };
       });
   
       srv.on('getListOfTodos', req => {
           return { responseArray : [            {
               "id": 1,
               "completed": false,
               "title": "delectus aut autem",
               "userId": 1
           },
           {
               "id": 2,
               "completed": false,
               "title": "quis ut nam facilis et officia qui",
               "userId": 1
           }] }; 
       });
   
   }

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This step describes how to test the service locally using a file that contains the Service Endpoints.

1. On the sap-build-cap-sample-library folder, create a new file called test.http.

2. Select the file test.http and copy the following content into the editor.

   Samples for HTTP requests for the services of your API.

   HTTP Copy

   ### call toInteger
   GET http://localhost:4004/api/v1/toInteger(value='20')
   
   ### call toNumber
   GET http://localhost:4004/api/v1/toNumber(value='20.2')
   
   ### call toString
   GET http://localhost:4004/api/v1/toStr(value=20.2)
   
   ### call addQoutes
   GET http://localhost:4004/api/v1/addQuotes(value='abcd')
   
   ### call getListOfTodods
   GET http://localhost:4004/api/v1/getListOfTodos()
   
   ### call listToString
   POST http://localhost:4004/api/v1/listToString
   Content-Type: application/json
   
   {
       "field" : "id",
       "responseArray": [
           {
               "id": 1,
               "title": "delectus aut autem",
               "userId": 1,
               "completed": false
           },
           {
               "id": 2,
               "title": "quis ut nam facilis et officia qui",
               "userId": 1,
               "completed": false
           }
       ]
   }     

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3. From the Terminal menu, select New Terminal.

   

4. On the sap-build-cap-sample-library folder, run the following command in the Terminal window:

   This will start a local server with your service that will allow you to test your API calls.

   Shell Copy

   cds watch