Returning http status code 404 for exception in Integrated SOA Gateway EBS 12.1.3. as RESTful webser

I have deployed a PL/SQL RESTful web service in EBS 12.1.3 and it is working fine except for an issue I have with exception handling.

When there is an exception, I would like to return a http status code '404'. By default it is returning http 500 :

{<br/> "ISGServiceFault" : {<br/>  "Code" : "ISG_SERVICE_EXECUTION_ERROR",<br/>  "Message" : "Error while executing service",<br/>  "Resolution" : "Please check Server logs.",<br/>  "ServiceDetails" : {<br/>  "ServiceName" : "xxxwebservices",<br/>  "OperationName" : "xxxretrieve_inventory_info",<br/>  "InstanceId" : "0"<br/>  }<br/> }<br/>}

How can I return http 404 in exception handling for a PL/SQL RESTful web service?