ΗΛΕΚΤΡΟΝΙΚΟ ΕΜΠΟΡΙΟ Web Services Overview Mary Grammatikou 9/06/2009

What are Web Services? Identified by a URI Interfaces defined using XML Can be discovered by other systems Interact using XML based messages conveyed by Internet protocols

The components DISCOVERING –To discover where you can get web services and what businesses have to offer – UDDI DESCRIPTION –To describe a web service and how to interact with it WSDL PACKAGING –To package your interaction with the Web Service – SOAP TRANSPORT –To carry the data envelope across the internet – HTTP Post –To fragment and deliver the http post request to the end point = TCP/IP

Transport HTTP –HTTP POST –HTTP GET

Packaging – Soap Used to mean –Simple –Object –Access –Protocol From SOAP 1.2 > SOAP is no longer an acronym Two Types of SOAP

Packaging – Soap SOAP RPC (Remote Procedure Call): –encode and bind data structures into xml –encode an RPC call SOAP ‘document style’ –packages xml in an envelope

Packaging – Soap 1234

Packaging – Soap socks 1

Description –WSDL Web Services Description Language “Web Services Description Language (WSDL) provides a model and an XML format for describing Web services.” w3c.org

Types XML schema can be used to represent constraints on the content model of the elements in an XML document Elements that contain child elements and / or attributes are defined in a schema document using complex types Elements that don’t contain child elements and attributes are defined using simple types <schema targetNamespace=" IMessageService.xsd" xmlns="…/XMLSchema" xmlns:SOAPENC="…/soap/encoding/"/>

Messages The message element gives information about the data that travels from one endpoint to another The message element depicts an one way message

Operations The operation element is the action that we call in a WSDL file It can be used instead of a method <input name="setMessageRequest“ message="tns:setMessageRequest"/> <output name="setMessageResponse“ message="tns:setMessageResponse"/>

Encoding Encoding in the web services is based on SOAP <soap:body use="encoded" namespace="MessageService" encodingStyle="…/soap/encoding/"/>

Endpoint Endpoint is the final URL of any web service <port name="MessageServicePort" binding="tns:MessageServiceBinding">

Discovery – UDDI Universal Description, Discovery and Integration A UDDI Server acts as a registry for Web Services and makes them searchable Demonstration:

Design Recommendations Create a local class Create a method with the same name

Examples (Java Client) URL endpointURL = new URL(endpoint); Call call = new Call(); call.setSOAPTransport(m_httpconn); call.setTargetObjectURI("MessageService"); call.setMethodName("setMessage"); call.setEncodingStyleURI(Constants.NS_UR I_SOAP_ENC);

Examples (Java Server) A Web service Server is simple: –New class with method Then: –Register class with soap engine (e.g. axis server)

Security WS Security Standardisation W3C - –XML Encryption –XML Digital Signatures WS-I - –WS Security Profile OASIS - –WS-Security –SAML - Security Assertion Markup Language –XACML - Extensible Access Control Markup Language –XKMS - XML Key Management Specification

Security Firewall ‘transparency’ Double-edged sword –Simplifies deployment –Opens up potential holes in enterprise security Similar to CGI, etc.

Real Examples Amazon Web Services API –Infrastructure Services –Payments and Billing –On demand Work force –Merchant Services Google Web API –… Ebay Web services –… HP & IBM online stores –…

GoogleAPI Search Requests –Search requests submit a query string and a set of parameters to the Google Web APIs service and receive in return a set of search results Cache Requests –Cache requests submit a URL to the Google Web APIs service and receive in return the contents of the URL when Google's crawlers last visited the page (if available) Spelling Requests –Spelling requests submit a query to the Google Web APIs service and receive in return a suggested spell correction for the query (if available)