To invoke a Web Service upon sending a message to a channel, there are two options: SimpleWebServiceTargetAdapter and MarshallingWebServiceTargetAdapter. The former will accept either a String or javax.xml.transform.Source as the message payload. The latter provides support for any implementation of the Marshaller and Unmarshaller interfaces. Both require the URI of the Web Service to be called.

simpleAdapter = new SimpleWebServiceTargetAdapter(uri);

marshallingAdapter = new MarshallingWebServiceTargetAdapter(uri, marshaller);

As with the other target adapters, this can then be referenced from a MessageEndpoint that is subscribed to a channel. The endpoint is then responsible for passing the response to the proper channel. It will first check for a returnAddress on the original message's header, and it will fallback to the endpoint's own default output channel.

For more detail on the inner workings, see the Spring Web Services reference guide's chapter covering client access as well as the chapter covering Object/XML mapping.