1. 1 An Introduction to Web Services

2. 2 Outline What is a Web service Background Standards –XML & XML Namespaces, XML Schema,WSDL, SOAP Tools & APIs –DOM/SAX,JAX-RPC/JAX-M –Apache SOAP/Axis, MS.NET, Python, C, C++ Run time Environments –App Server/Web Server/Servlet, Client/Server, Standalone/Embedded

3. 3 What is a Web service? A service on the Web? An IBM MS Collaboration? SOAP? HTTP? XML? W3C: ”A Web service is a software system identified by a URI [RFC 2396], whose public interfaces and bindings are defined and described using XML. Its definition can be discovered by other software systems. These systems may then interact with the Web service in a manner prescribed by its definition, using XML based messages conveyed by Internet protocols.”[RFC 2396]

4. 4 Background HTTP GETs, POSTs HTML no good interface for machines Code Reuse, Component Reuse, Service Reuse IBM and MS with separate Specifications. Joined forces under W3C umbrella WSDL, SOAP, BPEL4WS

5. 5 Standards: XML & XML Namespaces Well Formed vs Valid Well Formed = Bracket matches, single document element Valid = complies to XML Schema or DTD Namespaces – Globally unique Scoping based on URIs, Imports – schema reuse QName = NamespaceURI:LocalName

6. 6 Standards: XML Schema Schema definition language based on XML Defined using its own constructs Constructs: simpleType, complexType Types: string, integer, float Check out Primer: http://www.w3.org/TR/xmlschema-0/ http://www.w3.org/TR/xmlschema-0/

7. 7 Standards: WSDL Web Service Description Language Abstract Types, Message, Interface Definitions Concrete Binding, Service Definitions Endpoints = URI where to send messages SOAP/HTTP/XML Schema optional!

8. 8 Standards: SOAP Simple Object Access Protocol No Object refs, No state assumptions Envelope, Headers (optional), Bodies (mandatory payload) Message Exchange Patterns Feature Markup/Roles Document/Literal, RPC/Encoded All WS- specs targeted towards SOAP (WS- Security, WS-Routing)

9. 9 Tools &APIs: XML APIs DOM/SAX JAX- family: RPC, M, R, P, B www.jcp.org J2EE, JAX-Pack

10. 10 Tools &APIs: Apache SOAP, Axis Apache SOAP: First Open Source SOAP Implementation Axis next generation Apache SOAP, New Code base – lessons learned from Apache SOAP development, JAX-RPC compliant GT3 based on Axis

11. 11 Tools &APIs: Microsoft.NET.NET Framework –WSDL, XML Schema tools, SOAP, WSDL, XML APIs IIS, ASP.NET, Visual Studio –Web server, IDE, Web service Wizards CLR, Visual Basic, C#

12. 12 Tools &APIs: Python, C, C++ Python –SOAPpy –WSDL and SOAP support C/C++ –gSOAP (SOAP, WSDL) –Apache Axis C++

13. 13 Run Time Environments HTTP Web Server (Tomcat), SOAP Servlet (Axis) Application Server (JBOSS, WebSphere, IIS) Client side only toolkits, Client/Server Standalone/Embedded

14. 14 Further Reading http://www.w3.org/TR/ http://www.webservices.org/