Integration of SAP OnDemand Products with Business Suite via REST/OData Services

In my article “SAP Business Suite BO List” Solution Template, I described the integration with an SAP OnDemand solution (ByDesign, Customer OD) with SAP Business Suite via SOAP-based enterprise services using the ByDesign studio / Cloud Developer studio. In this article, I will show how to implement the same use case using REST / OData / SAP Gateway communication.

Background
In a SAP Business Suite system, you can expose REST/OData services via SAP Gateway. The article SAP Gateway Demo System provides a jump start into the world of SAP NetWeaver Gateway services. So, if you want to learn more about SAP NetWeaver Gateway and OData service, have a look at this article and the references in this article. In the section “Sales Order Example” you find a Sales Orders Query service, which I extended for the purpose of this article:
http://gw.esworkplace.sap.com/sap/opu/odata/sap/SALESORDERS/SOHeaders?&$filter=CustomerId eq ‘0000001390’&$top=2

The response contains the sales orders for the customer with customer number ‘0000001390’, the list is restricted to 2 entries ($top=2). The XML file looks like (excerpt):

<?xml version="1.0" encoding="utf-8" ?>
<feed xml:base="http://GW.ESWORKPLACE.SAP.COM:80/sap/opu/odata/sap/SALESORDERS/" xmlns="http://www.w3.org/2005/Atom" xmlns:m="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata" xmlns:d="http://schemas.microsoft.com/ado/2007/08/dataservices">
<entry>
<id>http://GW.ESWORKPLACE.SAP.COM:80/sap/opu/odata/sap/SALESORDERS/SOHeaders('0000008078')</id>
<m:properties>
  <d:OrderId>0000008078</d:OrderId>
  <d:DocumentType>TA</d:DocumentType>
  <d:DocumentDate>2002-10-17T00:00:00</d:DocumentDate>
  <d:CustomerId>0000001390</d:CustomerId>
  <d:OrderValue>35000.00</d:OrderValue>
  <d:Currency>EUR</d:Currency>
  </m:properties>
  </content>
  </entry>
  </feed>

We want to consume this service in our SAP OnDemand solution.

Solution
Let us revisit the solution described in the article “SAP Business Suite BO List” Solution Template . This solution contains an embedded component BusinessObjectList.EC.uicomponent (EC). This EC invokes a custom BO BusinessObjectList and triggers the GetResult action of the BO. The GetResult action calls a web service that reads a list of SAP business suite BOs. The list is displayed in the EC. In the mentioned solution, the service call is a SOAP-based service call. In the solution described here, we will work with the same UI and business object and just replace the implementation of the SOAP-based web service call in the GetResults action with a REST-based service call.
Before we start the implementation, we have to configure the REST web service in the ByDesign or Customer OD system.

1. To do so, create a new Mashup Web Service of type REST. You can do this from the studio (Add New Item dialog) or from the Application and User Management. You user must be enabled as key user in the studio.  See the screenshot below.
2. Set the authentication method to “basic” and enter name and password (This will be done by the key user in the production system.)
3. Enter the URL mentioned above and click “Extract Parameters”. The system shortens the URL and extracts the parameters “$filter” and “$top”.
4. Delete the values in column “Constant”. See the result in the following figure.
5. Save the service configuration.

Figure: Mashup Web Service Configuration

As a second step, we do the implementation of the GetResults action. The first part of the implementation is:

var parameter : NameAndValue;
var parameters : collectionof NameAndValue;
var response;
var xml;
parameter.Name = "$filter";
parameter.Value = "CustomerId eq '0000001390'";
parameters.Add(parameter);
parameter.Name = "$top";
parameter.Value = "10";
parameters.Add(parameter);
response = WebServiceUtilities.ExecuteWebService("PW00008", parameters);
// for test purpose only – remove later
raise WebServiceContentError.Create("I", "Returncode: " + response.ReturnCode);
xml = response.ResponseContent;

The first part of the code fills the parameters; in our example the customer ID is hard-coded. The following line executes the web service. The ID of the web service “PW00008” is the ID that you can see in of the web service configuration screenshot. The final line fills the response content into the xml variable.
In case of the SOAP-based web services, you can generate a proxy from the WSDL file that does the parsing of the web service message. For REST-based web services, there is no proxy generation available; so the parsing of the message must happen in the code. The following code snippet shows the parsing for some selected elements:

var s1;
var l1;
var f1;
var pos = 0;
var pos1 = 0;
var i = 0;
var newDocData : elementsof BusinessObjectList.List;
while (i < 100) {
      pos = xml.Find("<entry>", pos1);
      if (pos < 0) { break; }

      pos1 = pos + 7;

     f1 = "<d:OrderId>"; l1 = 10;
     pos = xml.Find(f1, pos1);
      if (pos > 0) {  s1 = xml.Substring(pos + f1.Length(), l1); }
      newDocData.ID.content = s1;
      f1 = "<d:CustomerId>"; l1 = 10;
      pos = xml.Find(f1, pos1);
      if (pos > 0) {  s1 = xml.Substring(pos + f1.Length(), l1); }
      newDocData.Name = s1;
      this.List.Create(newDocData);
 
      i = i + 1;
}