HANA XSA - Developers Handbook - Application Development - Expose Service-Need to Know

[pallab_haldar]

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Scenario when use odata and XSJS is preferable
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When required this two use oData -
1. Select data from the database and Expose as a service.

2. Do n't used to perform CRUD operations (CREATE, READ, UPDATE and DELETE).

When required this two use XSJS -

1.Crud Operation is needed.

2.Sending data to another server, one way may be by providing a web service to the second server.

XSJS can make Web Request to a configured destination so you can POST data to your server.To check for any GET or POST request & request parameters, you can use $.request. With these you can perform your CRUD operations

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************** Sample Syntax to Send data to different sever********************************************

var dest = $.net.http.readDestination("<package path to destination file>", "<destination file name>");

var client = new $.net.http.Client();

var req = new $.web.WebRequest($.net.http.POST, "/");

req.contentType = "application/json";

req.setBody("My data");

client.request(req, dest);

var response = client.getResponse(); 



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3 Scenario to expose Database table as a Service using Pure Node.JS,XSJS and OData
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1. Pure Node.JS : 

 

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Pure Node.JS

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var hana = require("@sap/hana-client");



var conn = {

  serverNode: "f5b68294-bd42-4e68-a1c9-4bfbf5a2f32d.hana.trial-us10.hanacloud.ondemand.com:443",

  encrypt: "true",

  sslValidateCertificate: "false",

  uid: "DBADMIN",

  pwd: "**********",

};



var hanaConnect = hana.createConnection();



hanaConnect.connect(conn, function (err) {

   if(err){

        console.log(err);

    }

   else{

	hanaConnect.exec("SELECT * FROM EMPLOYEE",

    function (err, result) {

      if (err) throw err;

      console.log(result[0]);

	  console.log(result[1]);

	  console.log(result[2]);

      hanaConnect.disconnect();

    }

  );

  }

});

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2. Expose as XSJS -

 

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XSJS Expose

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var employee = [];

var stmnt = null;

var rs = null;

var conn = $.db.getConnection();

var stmnt = conn.prepareStatement( "select * from "DB_PLB.OFFICE"::"CV_EMPLOYEE" );

var rs = stmnt.executeQuery();



if (!rs.next()) {

  $.response.setBody( "Unable to get result" );

  $.response.status =  $.net.http.INTERNAL_SERVER_ERROR;

} else {

	  emp = {};

	  emp.emp_id = resultSet.getString(1);

	  emp.emp_name = resultSet.getString(2);

	  emp.emp_mail_id = resultSet.getString(3);

	  emp.address = resultSet.getString(4);

	  employee.push(emp);

}

rs.close();

pstmt.close();

conn.close();



try{

		$.response.contentType = "application/json";

		$.response.setBody(JSON.stringify(employee));

}

catch(err){

		$.response.contentType = "text/plain";

		$.response.setBody("Got error : [" + err.message + "]");

		$.response.returnCode = 400;

}

 

3. Odata Expose -

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Odata Expose

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Service{

"PLB_PROJECT.DB_PLB::CV_EMPLOYEE " AS "EMPLOYEE" Key ("EMP_ID")

}

 

4.

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Web module include XSJS service and odata
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1. Add UAA-service to the dependent node.js module for dependency service
2. configuration to the xss-app.json file to change the route to xsjs -

"routes": [{

"source": "(.*)(.xsjs)",

"destination": "demo_dest",

"csrfProtection": false,

"authenticationType": "xsuaa"

}, {

"source": "(.*)(.xsodata)",

"destination": "demo_dest",

"authenticationType": "xsuaa"



}]

3. Change the Servery.js file and comment // anonymous : true to activate.
4. Change the Node version to “10.X” in the package. Json file.
5. Execute the HTML5 app and copy the url and replace the index.html file –

 

Output Url -

http://hcpeur10.hcs.cloud.sap:8000/employee. Xsodata?$format=json

http://hcpeur10.hcs.cloud.sap:8000/employee. Xsodata/$metadata
http://hcpeur10.hcs.cloud.sap:8000/employee. Xsodata?$format=json