Examples of callback functions

In the code samples are examples of all the preprocessing and postprocessing BDL functions you can use in your REST web service module.

These samples are intended as templates for your callback functions. Copy those that you need to your REST web service module and adapt them to your needs.

Types of callback

There are two primary types of callbacks.

Preprocessing callbacks: These are functions you use to preprocess the query, header, body, and input parameter values of the REST request. They are identified with the name *PreCallback and are set with the WSPreProcessing attribute. If the content type of the body of the incoming request uses a JSON, XML, or text format, use the appropriate preprocessing function.
The HTTPPreCallback function may be used to validate the request as it is called first in the callback order. This function either returns a zero to continue to process the REST operation, or a HTTP return code to return to the client.
Postprocessing callbacks: These are functions you use to process the return header and body of the REST request. They are identified with the name *PostCallback and are set with the WSPostProcessing attribute. If the content type of the return body of your request uses JSON, XML, or text format, use the appropriate postprocessing function.
The HTTPPostCallback function may be used to validate the response as it is called first in the callback order after executing the REST operation. This function either returns a zero to continue to process the REST operation, or a HTTP return code to return to the client.

Examples of preprocessing and postprocessing BDL functions

# REST Web service module

PRIVATE # HTTP incoming request callback 
FUNCTION HTTPPreCallback() ATTRIBUTES (WSPreProcessing) RETURNS (INTEGER)
  DISPLAY "Doing HTTP Pre processing"
  DISPLAY Context["RequestOPERATION"] # Display current REST service
  RETURN 0 # HTTP ret code, or 0 to continue standard REST service processing
END FUNCTION

PRIVATE # HTTP response callback
FUNCTION HTTPPostCallback() ATTRIBUTES (WSPostProcessing) RETURNS (INTEGER)
  DISPLAY "Doing HTTP Post processing"   
  DISPLAY Context["RequestOPERATION"] # Display current REST service    
  RETURN 0 # HTTP ret code, or 0 to continue standard REST service processing
END FUNCTION

PRIVATE # REST Query string incoming callback
FUNCTION QueryPreCallback(query STRING, value STRING) ATTRIBUTES (WSPreProcessing="wsquery") RETURNS (STRING)
  DISPLAY "Query:",query
  DISPLAY "Value:",value
  RETURN value # new query value
END FUNCTION

PRIVATE # REST Parameter incoming callback
FUNCTION ParamPreCallback(param STRING, value STRING) ATTRIBUTES (WSPreProcessing="wsparam") RETURNS (STRING)
  DISPLAY "Param:",param
  DISPLAY "Value:",value
  RETURN value # new parameter value
END FUNCTION

PRIVATE # REST Header incoming callback
FUNCTION HeaderPreCallback(header STRING, value STRING) ATTRIBUTES (WSPreProcessing="wsheader") RETURNS (STRING)
  DISPLAY "Header:",HEADER
  DISPLAY "Value:",value
  RETURN value # new header value
END FUNCTION

PRIVATE # REST Header outgoing callback
FUNCTION HeaderPostCallback(header STRING, value STRING) ATTRIBUTES (WSPostProcessing="wsheader") RETURNS (STRING)
  DISPLAY "Header:",HEADER
  DISPLAY "Value:",value
  RETURN value # new header value
END FUNCTION

PRIVATE # REST JSONObject incoming callback
FUNCTION JSONObjectPreCallback(obj util.JSONObject) ATTRIBUTES (WSPreProcessing) RETURNS (util.JSONObject)
  DISPLAY "Doing JSON pre processing"
  RETURN obj# new JSONObject value
END FUNCTION

PRIVATE # REST JSONObject outgoing callback
FUNCTION JSONObjectPostCallback(obj util.JSONObject) ATTRIBUTES (WSPostProcessing) RETURNS (util.JSONObject)
  DISPLAY "Doing JSON Post processing"
  RETURN obj # modified JSONObject value
END FUNCTION

PRIVATE # REST JSONArray incoming callback
FUNCTION JSONArrayPreCallback(obj util.JSONArray) ATTRIBUTES (WSPreProcessing) RETURNS (util.JSONArray)
  RETURN obj # modified JSONArray value
END FUNCTION

PRIVATE # REST JSONArray outgoing callback
FUNCTION JSONArrayPostCallback(obj util.JSONArray) ATTRIBUTES (WSPostProcessing) RETURNS (util.JSONArray)
  RETURN obj # modified JSONArray value
END FUNCTION

PRIVATE # REST XML incoming callback
FUNCTION XMLPreCallback(xml xml.DomDocument) ATTRIBUTES (WSPreProcessing) RETURNS (xml.DomDocument)
  return xml # modified XML value
END FUNCTION

PRIVATE # REST XML outgoing callback
FUNCTION XMLPostCallback(xml xml.DomDocument) ATTRIBUTES (WSPostProcessing) RETURNS (xml.DomDocument)
  RETURN xml # modified XML value
END FUNCTION

PRIVATE # REST TXT incoming callback
FUNCTION TextPreCallback(s STRING) ATTRIBUTES (WSPreProcessing) RETURNS (STRING)
  RETURN s # modified STRING value
END FUNCTION

PRIVATE # REST TXT outgoing callback
FUNCTION TextPostCallback(s STRING) ATTRIBUTES (WSPostProcessing) RETURNS (STRING)
    RETURN s # modified STRING value
END FUNCTION