Import parameter is empty after an RFC call from BW to JCo

Question

I am calling a Java function (implemented using JCO and deployed on J2EE stack of the Portal box) from within a user-exit in BW (on a separate box) using RFC. The code in BW looks like:
CALL FUNCTION 'Z_BW_VALIDATE_PROXY' DESTINATION 'ACF2PROXY'
    EXPORTING
        IREQUESTOR = 'AE012345'
        IREQUESTED = '012345'
    IMPORTING
        ERESULT = lv_result
    EXCEPTIONS
        SYSTEM_FAILURE = 1 message lv_rfc_mess
        COMMUNICATION_FAILURE = 2 message lv_rfc_mess.
The following are working/setup correctly:
1. RFC destination ACF2PROXY, in BW using transaction SM59;
2. Java function 'Z_BW_VALIDATE_PROXY' , as the server log on the Portal(J2EE) shows the correct IMPORT and EXPORT parameters after processing a call from BW;
The data types of the parameters in the function call above matches with those of the formal parameters in Java function where they are defined using JCO data types (export parameter is defined at CHAR 1 at both places).
The problem is that I am not getting any value back in the IMPORT parameter 'lv_result'. I am expecting either '0' or '1' which is populated correctly in the Java function.
Any insight is appreciated.

Answer 1

The following is the code of the method in the class that inherits from JCO.Server. In this method the export parameter ERESULT is set with the value of variable 'result'. I thought it may be helpful to reporduce it here.
protected void handleRequest(JCO.Function function) throws MMException
          if (function == null) {
              LOGGER.logInfo("handleRequest - JCO.Function object is null.");
               return;
          LOGGER.logDebug("handleRequest(" + function.getName() + ")");
          //process this function only, although I don't know what else would fall to this
          //server request method...
          if (function.getName().equalsIgnoreCase(ACF2Listener.ABAP_RFC_PROXY_FUNCTION)) {
               //get input & output definitions from RFC. These are defined in the repository interface definition
               JCO.ParameterList input = function.getImportParameterList();
              JCO.ParameterList output = function.getExportParameterList();
              LOGGER.logDebug("Received the following from ABAP: " + input.toString());
              String requestor = input.getString("IREQUESTOR");
              String requested = input.getString("IREQUESTED");
              //call DAO to read ACF2 for these values
              String result = null;
              try {
                   ACF2DAO acf2 = ACF2DAO.getInstance();
                   if (acf2 != null) {
                        result = acf2.getACF2Delegation(requestor,requested);
              catch (MMException e) {
                  LOGGER.logError("Exception occured during ACF2 DAO lookup: " + e.getMessage());
                  throw e;
             output.setValue(result, "ERESULT");
             LOGGER.logDebug("ACF2 Service Call returning: " + output.toString());
          else {
               throw new JCO.AbapException("NOT_SUPPORTED","This service is not implemented by the ACF2 Proxy external server.");
Thanks
Sanjeev