A message gateway apparatus is provided for use in a web service system to process a message containing a request for a destination web service application, in which the message includes a plurality of events within a structured document conforming to a web service protocol and each event of the plurality of events has a name and a content thereof. The message gateway apparatus comprises a message parsing module configured to sequentially identify the events of the plurality of events of the message, an input object creation module configured to sequentially extract the events of the plurality of events from the message parsing module, and a message filtering module configured to sequentially access the events of the plurality of events as the events are extracted from the message parsing module by the input object creation module to analyze the name of each event and perform security processing on the content of each event for which the corresponding name indicates that security measures have been applied according to a security protocol. The input object creation module is configured to construct an input object including input parameters for the destination web service application based on the message. The input object creation module constructing the input object by adding a representation of each event of the plurality of events to the input object after each event is accessed by the message filtering module.