In the asynchronous communication using the addressing functionality, the Web Service client sends a request message for invoking a service method that exists in a Web Service, and then ends the processing without receiving the resulting response message from the Web Service. The Web Service sends the response message to another Web Service.

The following figure shows the flow of asynchronous communication:

Figure 37-2 Flow of asynchronous communication

To use the asynchronous communication, set up the Web Service URL that sends response messages in the wsa:ReplyTo/wsa:Address and wsa:FaultTo/wsa:Address elements of the addressing header.

The following are the examples of the contents specified in the addressing header with the conditions:

• Web Service URI
  http://localhost/addressing/AddNumbersImplService
  
• Action value for invoking the Web Service
  http://sample.com/input
  
• URL for sending the response message when the Web Service terminates successfully
  http://localhost/responseserver/ResponseServerImplService
  
• URL for sending the response message when the Web Service terminates abnormally
  http://localhost/responseserver/FaultServerImplService
  
• Unique ID indicating this message
  uuid:b19439fa-7a29-4045-93d9-56d6a2183afd
  

  <To xmlns="http://www.w3.org/2005/08/addressing"> http://localhost/addressing/AddNumbersImplService </To> <Action xmlns="http://www.w3.org/2005/08/addressing"> http://sample.com/input </Action> <ReplyTo xmlns="http://www.w3.org/2005/08/addressing"> <Address> http://localhost/responseserver/ResponseServerImplService </Address> </ReplyTo> <FaultTo xmlns="http://www.w3.org/2005/08/addressing"> <Address> http://localhost/responseserver/FaultServerImplService </Address> </FaultTo> <MessageID xmlns="http://www.w3.org/2005/08/addressing"> uuid:b19439fa-7a29-4045-93d9-56d6a2183afd </MessageID>

This subsection describes the precautions for using the asynchronous communication.

• Even if the Web Service fails to send the response message, no error is returned to the Web Service client.
• In the wsa:ReplyTo/wsa:Address and wsa:FaultTo/wsa:Address elements of the addressing header, if you set up the same URL as you would set up for the Web Service specified in the wsa:To element, the sending source and destination of the response message become the same and the communication might go into an infinite loop.
• If the JAX-WS engine of the Web Service machine receives a fault message as the request message, the fault message is processed as a server error (HTTP code: 500). Therefore, you cannot create a Web Service that receives a fault message as a request message.
• You cannot use the asynchronous communication through a proxy. To use the asynchronous communication, send the response message to another Web Service without passing through a proxy.