1. Enterprise Computing: Web Services

2. Exercise What is wrong with JEE?
Why would you not use it for web-based application integration?
Why would you not use it for intranet-based application integration?

3. Web Services: Definitions
A Web service is a collection of functions that are packaged as a single entity and published to the network for use by other programs.
Web services are building blocks for creating open distributed systems, and allow companies and individuals to quickly and cheaply make their digital assets available worldwide.
Web Service standards form a platform-independent, open framework for describing services, discovering businesses, and integrating business services.

4. eXtensible Markup Language
A common data format derived from SGML
Language independent, hierarchical and self-describing
Uses tag-based structure similar to HTML to define XML documents
<?xml version="1.0" encoding="ISO " ?>
<bankaccount type=“Current”>
  <name>John Smith</name>
  <address>
<line 1>1 Grafton Street </line1>
<line 2>Dublin 2, Ireland </line2>
</address>
</bankaccount>
Supports arbitrarily complex data formats
Schema (defined in xsd files) can be used to define document formats
Fragment defining a BankAccount as a type of financial record
<xsd:element name="purchaseOrder" type="PurchaseOrderType"/>

5. eXtensible Markup Language
Independent of IT infrastructure
Separates the what from the how
Many industry based schema standards have been developed
For example, Financial Services:
ISO15022 (SWIFT, FIX, FpML)
XBRL (business reporting)
Any XML based infrastructure can handle multiple and evolving schema standards without excessive cost
Due to changes in business relationships
Due to regulatory changes (e.g. Basil II)
Due to evolution of the schemas themselves

6. The Web Services architecture
UDDI
Registry
Web Services is based on three standards
Simple Object Access Protocol (SOAP)
defines the communication mechanism
Universal Directory Discovery Interface (UDDI)
defines the registry of interface definitions
Web Service Definition Language
defines the actual interfaces
2. Request contract information
3. Retrieve WSDL definition
Service
Consumer
WSDL
WSDL
4. Exchange SOAP messages
Service
Provider
1. Register contract information

7. SOAP- Simple Object Access Protocol
SOAP1.1 Message
Structure
XML based protocol for exchange of information
Encoding rules for datatype instances
Convention for representing RPC invocations
Used with XML Schema
Normally HTTP-based
Uses Request/Response
Two different modes
RPC
Document
SOAP with Attachments allow arbitrary data to be packaged.
SOAP
Envelope
Header
Entries
Header
Body
Fault
Element

8. SOAP Example: Request Sample SOAP Message embedded in an HTTP Request
POST /StockQuote HTTP/1.1
Host:
Content-Type: text/xml; charset="utf-8"
Content-Length: 1024
SOAPAction: "
<env:Envelope xmlns:env=" >
<env:Body>
<m:GetLastTradePrice
env:encodingStyle="
xmlns:m="
<symbol>IBM</symbol>
</m:GetLastTradePrice>
</env:Body>
</env:Envelope>

9. SOAP Example: Response
SOAP message sent by the StockQuote service in the corresponding HTTP response to the request
HTTP/ OK
Content-Type: text/xml; charset="utf-8"
Content-Length: 512
<env:Envelope xmlns:env=" >
<env:Body>
<m:GetLastTradePriceResponse
env:encodingStyle="
xmlns:m="
<Price>97.5</Price>
</m:GetLastTradePriceResponse>
</env:Body>
</env:Envelope>

10. UDDI Universal Description, Discovery and Integration
Platform-independent, open framework for describing services, discovering businesses, and integrating business services.
A DNS-like model implementation of the directory
Originally intended to support global registries
Created during the .com bubble.
Includes White, Green and Yellow Pages for search purposes
Now primarily inside organisations if at all

11. Web Service Description Language (WSDL)
Interface definition language in XML
Conceptually, no different from Enterprise Java Bean or Common Gateway Interface
Based on XML Schema
Can appear to be very verbose
An interface description is a contract between the server developers and the client developers
WSDL describes the web service
Similar to Java method signatures

12. Interoperability Challenges
Interoperability remains the chief challenge of web services
Complex and imprecise standard
Tools generating SOAP, WSDL, UDDI, etc. need to be interoperable
Web Services Interoperability (WS-I) focus on creating to Interoperability
WS-I Basic Profile 1.0 defines an interoperable web services platform

13. WS-I Basic Profile V1.2 in draft form WS-I Basic Profile 1.1: SOAP 1.1
WSDL 1.1
Must use HTTP binding, should use HTTP 1.1
XML Schema Part 1, Part 2
May use HTTPS
SOAP messages should use document/literal
V1.2 in draft form

14. Web Services: Another approach to distributed computing
Builds on the legacy of CORBA, J2EE etc
It is not a new component model, programming model or programming language.
UDDI/WSDL/SOAP provide another distributed computing technology
Standards developing for the Quality of Services and other EAI-type functionality.
Exercise: Write down the standards for J2EE
Quality Of Service
Discovery
Description
Messaging
Transport

15. Web Services: Another approach to distributed computing
WS-
Reliable Messaging
WS-
Security
WS- BA
Quality Of Service
WS- Coordination
UDDI
Discovery
XSD, WSDL, WS-Policy
Description
SOAP
Messaging
XML
HTTP, MQ, SMTP
Transport

16. Web Services Strengths
Interoperability
Based on open standards, utilizes existing infrastructure
Can be accessed from any programming language/model
Ubiquity
Communicates through XML/HTTP – Any system that supports these standards, supports Web Services
Support from all major software vendors (IBM and Microsoft)
Low barrier to entry
Concepts easy to understand, easy to implement
Toolkits allow COM, JEE, and CORBA components to be exposed as Web Services

17. Web Services and XML/WS standards
Java API for XML Parsing (JAXP)
JAXP enables applications to parse and transform XML documents
Independent of XML processor implementation
JAXP includes common industry standard components/interfaces
DOM (Document Object Model and SAX (Simple API for XML Processing)
XSLT (XML Style Language Transformations)
JAXP adds additional functionality beyond these standards
Java API for XML
Remote Procedure Call (JAX-RPC)
SOAP (Simple Object Access Protocol) 1.1 specification
Java API for XML Registries (JAX-R)
APIs to access UDDI Registry