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G52IWS: XML Messaging (briefly)

G52IWS: XML Messaging (briefly). Chris Greenhalgh 2007-11-30. Contents. Introduction to message-based communication SOAP with Attachment API for Java Provider-less messaging Messaging with a JAXM provider. See “Developing Java Web Services”, Chapter 9. Message-based communication.

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G52IWS: XML Messaging (briefly)

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  1. G52IWS: XML Messaging (briefly) Chris Greenhalgh 2007-11-30

  2. Contents • Introduction to message-based communication • SOAP with Attachment API for Java • Provider-less messaging • Messaging with a JAXM provider See “Developing Java Web Services”, Chapter 9

  3. Message-based communication • Send an XML document, not parameters • No necessary response • But a later message may be a response :-) “Developing Java Web Services”, figure 3.4

  4. SOAP with Attachment API for Java • Defined by Java Community Process JSR-67 • Allows explicit construction and unpacking of SOAP messages using Java • See example client in src/sample/client/SaajClient.java • Can be used • to implement SOAP clients and servers directly over HTTP (as in example) • With JAXM to support indirect and asynchronous communication (see later)

  5. Recap: SOAP Message structure “Developing Java Web Services”, figure 4.1

  6. SOAP: main classes & interfaces • javax.xml.soap.SOAPMessageFactory • Source of new SOAPMessages • javax.xml.soap.SOAPMessage • An entire SOAP message, including attachments (not XML) • javax.xml.soap.SOAPPart, javax.xml.soap.AttachmentPart.  • SOAP and Attachment Part(s) of a SOAPMessage • SOAP Part has SOAPEnvelope & MIMEHeaders • javax.xml.soap.SOAPEnvelope • Contains SOAPHeader &SOAPBody

  7. javax.xml.soap.SOAPHeader & javax.xml.soap.SOAPHeaderElement • javax.xml.soap.SOAPBody & javax.xml.soap.SOAPBodyElement • The body and body elements  • javax.xml.soap.SOAPElement • (Interface) Any SOAP-related XML element in a SOAP message • javax.xml.soap.Node • Any XML element in a SOAP message (compare XML Document Object Model) • javax.xml.soap.SOAPFault • Representation of a SOAP Fault

  8. Using SAAJ with HTTP: client • javax.xml.soap.SOAPConnection.    • obtained from SOAPConnectionFactory • Supports request/response over HTTP • E.g. from sample client:SOAPMessage rp = conn.call(msg, urlval);

  9. Using SAAJ/JAXM with no JAXM Provider: server • Extend javax.xml.messaging.JAXMServlet and implement javax.xml.messaging.ReqRespListener • E.g.public class ReqRespServlet extends JAXMServlet implements ReqRespListener { public SOAPMessage onMessage(SOAPMessage msg) { //Implement your business logic here return respMsg; }}

  10. Servlet runs in container which handles HTTP • JAXMServlet handles • converting the POSTed SOAP message (MIME-encoded) into a javax.xml.soap.SOAPMessage • calling onMessage() • Converting the returned SOAPMessage into the HTTP response

  11. Main JAXM classes & interfaces • javax.xml.messaging.OneWayListener • Interface for receiving a SOAPMessagepublic void onMessage(SOAPMessage msg); • javax.xml.messaging.ReqRespListener • Interface for receiving a SOAPMessage and replyingpublic SOAPMessage onMessage(SOAPMessage msg); • javax.xml.messaging.JAXMServlet • Utility servlet for doing JAXM HTTP-based message receivers • javax.xml.messaging.ProviderConnection • Interface for communicating with JAXM “Provider” (see later) • javax.xml.messaging.Endpoint • Endpoint (client or service) identifier; URI

  12. Recap: Message-Oriented Middleware (MOM)‏ MOM infrastructure Application A Application B Adapter API Adapter API Messages sent & received (& transactions contexts)‏ Persistence After “Developing Java Web Services” figure 1.6

  13. JAXM-based application architecture “Developing Java Web Services”, figure 9.1

  14. JAXM-based application architecture details OneWayListener or ReqRespListener interface to receive message(s). Identified by an Endpoint (URI) Message bean or JAXMServlet ProviderConntection: allows message sending and registering of receivers Logical distributed JAXM provider Local API/client for provider “Developing Java Web Services”, figure 9.1

  15. Simple JAXM provider realisation Provider Connection w. Endpoint Provider Infrastructure Including persistence Local API/client for provider Messages to/from external services Messages between client and provider

  16. JAXM Provider • C.f. MOM infrastructure • Handles message transmission and routing • Including message reliability (through retransmission) • Uses “Profiles” to specify the underlying messaging protocol • E.g. SOAP-RP (SOAP Routing Protocol) or ebXML • Handles synchronous vs asynchronous interactions • E.g. mapping asynchronous client request to synchronous server handling

  17. Conclusion • SAAJ allows direct construction/consumption of SOAP messages • No mapping to programming language types or paradigms (such as RPC) • JAXM supports messaging-style use of SOAP, in particular asynchronous interactions • E.g. extended business processes

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