code: @Override
      public void validateProcessOutput(FaxClientSpi faxClientSpi,ProcessOutput processOutput,FaxActionType faxActionType)
      {
          //call exit code validation
          super.validateProcessOutput(faxClientSpi,processOutput,faxActionType);
  
          //get output
          String output=processOutput.getOutputText();
  
          if((output!=null)&&(output.length()>0))
          {
              //if no valid done output was found
              if(output.indexOf(Fax4jExeConstants.OPERATION_OUTPUT_DONE.toString())==-1)
              {
                  //get error message
                  String prefix=Fax4jExeConstants.FAX_ERROR_OUTPUT_PREFIX.toString();
                  int index=output.indexOf(prefix);
                  int prefixLenght=prefix.length();
                  String errorMessage=null;
                  if(index!=-1)
                  {
                      //get index
                      index=index+prefixLenght;
  
                      if(output.length()>index)
                      {
                          //get output
                          errorMessage=output.substring(index);
                          
                          errorMessage=errorMessage.trim();
                          index=errorMessage.indexOf("\n");
                          if(index!=-1)
                          {
                              errorMessage=errorMessage.substring(0,index);
                              errorMessage=errorMessage.trim();
                          }
                          
                          //ignore empty message
                          if(errorMessage.length()==0)
                          {
                              errorMessage=null;
                          }
                      }
                  }
                  
                  if(errorMessage==null)
                  {
                      throw new FaxException("Error while invoking fax4j.exe, no error message detected.\nNative Output:\n"+output);
                  }
                  throw new FaxException("Error while invoking fax4j.exe, error: "+errorMessage+"\nNative Output:\n"+output);
              }
          }
          else
          {
              throw new FaxException("Error while invoking fax4j.exe, no output detected.");
          }
      }
docs: This function validates the process output for errors.<br>
  If not valid, an exception should be thrown.
  
  @param   faxClientSpi
  The fax client SPI
  @param   processOutput
  The process output to validate
  @param   faxActionType
  The fax action type