Introduction to Web Services

Topic 2

Introduction to Web Service

Dr.Thanachart Numnonda
Sun Microsystems (Thailand)
Asst.Prof.Thanisa Kruawaisayawan
KMITL

Agenda
 What is Service?
 What/Why Web Services?
 Web Services Specifications:
 Web Services Demo

2

What is Service?
 Primary goal of a service is to represent a “natural”
step of business functionality
 Technically, a service is a software component
 a service is an interface for (multiple) messages that
return information and/or change the state of an
associate entity (backend)
 The operations defines in the interface carry out
business functions
 Service is available across a network.

4

Services in SOA
• SOA is focused on business process
• Services can be implemented by any technology on
any platform (NOT only web services)
• In fact, SOA has been around for quite a while
• Other service components
– EJB (Enterprise Java Bean), COM+, .NET Enterprise
services, CCM (CORBA Component Models)

5

Characteristics of Service

6

Characteristics of Service (cont.)

7

Types of Services
• Entity Service
– Represent one or more business entity
– Features CRUD operations
• Functional Service
– Is a technology oriented service
– Perform a given function; eg: sending mail, deposit
• Process Service
– Represents a series of related tasks
– Can be represented as an orchestration invoked by ESB;
eg: loan process
8

What/Why Web Service?

9

What is Web Service?
 A Web service is a software module that has a URL
or an Internet address so they can be called upon to
perform a operation via the Internet.
 One Web service makes a request of another Web
service to perform its task or tasks and pass back an
answer creating a highly distributed system.
 using XML based messages via internet-based
protocols
 Web Services are latest distributed technology

10

Web Services Conceptual Model

11

Web Services Conceptual Model (cont.)

12


13


14

Characteristics of Web Services

XML based everywhere

Message-based

Programming language independent

Could be dynamically located

Could be dynamically assembled or aggregated

Accessed over the internet

Loosely coupled

Based on industry standards

15

How Web Services differ from Others?
• Supported by all major software vendors; so fulfills
the promose of universal interoperability
• Operations of Web Services are based on the
exchanged of XML format
• Web Services utilize standard Internet protocols such
as HTTP, SMTP, FTP

16

Distributed Computing Evolution
Servers Servers

Clients PDA Cell
Internet
Phone

Client-Server(C/S)
silos
Clients Workstation Server
Web-based computing
Kiosk Laptop

Web Services/Peer-to-Peer
17

Traditional C/S vs. Web Services

Traditional C/S Web Service

Within enterprise 
Between enterprises

Tied to a set of 
Program language
programming languages independent

Procedural 
Message-driven

Usually bound to a 
Easily bound to different
particular transport transports

Tightly-coupled 
Loosely-coupled

Efficient processing 
Relatively not efficient
(space/time) processing

Web Application vs. Web Services

Web Application Web Service

User-to-program 
Program-to-program
interaction interaction

Static integration of 
Possibility of dynamic
components integration of

Monolithic service components (in the
future)

Possibility of service
aggregation (in the
future)

Why Web Services?

Web Services:

Are platform neutral

Are accessible in a standard way

Are accessible in an interoperable
way

Use simple and ubiquitous
plumbing

Are relatively cheap

Simplify enterprise integration

20

Why Web Services are a Hot Topic:
 Interoperable – Connect across heterogeneous networks using
ubiquitous web-based standards
 Economical – Recycle components, no installation and tight
integration of software
 Automatic – No human intervention required even for highly
complex transactions
 Accessible – Legacy assets & internal apps are exposed and
accessible on the web
 Available – Services on any device, anywhere, anytime
 Scalable – No limits on scope of applications and amount of
heterogeneous applications

Web Services Usage Example
Distributor

XML

XML
Manufacturing
Supplier Internet Facility
XML

XML

Logistics

“Growing need for a standard lightweight infrastructure
for data exchange in e-business applications.”
22

Myth: Web Services is a New Concept

Web services is distributed computing all over
again – only now it is based on the web
Distributed Computing via
Concept CORBA /Java Basic Web Services
Interface Description CORBA IDL, Java interface WSDL
RPC support ORBs, Idl2java compilers, rmic SOAP
Service Registry CORBA naming service, JNDI UDDI
Messaging support CORBA Event/Notification service, JMS WS-Reliable Messaging?
Transaction support CORBA Transaction service, JTS WS-AtomicTransaction ?
Secuity support CORBA Security service, Java security WS-Security ?

Other Popular Myths Surrounding Web Services


Web services require only SOAP, WSDL, UDDI:
− We need more high-level semantics

Web services are based on the RPC paradigm:
− Document-driven model would be more popular
communication model

Web services must be based on HTTP:
− Other transports such as SMTP can be also used

24

Myths about Web Services

Web Services cure cancer: Not for a very very long
time!

Web Services are something completely new: Not
True!

You have to write Web Services from scratch: Not
True!

Java Platform does not support web services: Not
True!

25

State of Web Services

Technology/Standards are still evolving
− SOAP, WSDL, UDDI are not enough

Business web services is the next big thing, but more
works are needed in
− Quality of Service, management
− Security, transaction, state and user context
− Work flow, Identity management,
− Provisioning, Accounting

Will be adopted in phases
26

Web Services Adoption Phases
 1st phase (in the past)
 Concerted deployment internally within an organization
mainly for interoperability
 SOAP over HTTP/S
 2nd phase (current state)
 Selective and non-aggregate deployment with trusted
outside business partners
 Private registry deployment
 3rd phase (1 to 2 years)
 Wider, more dynamic and aggregate deployment with
outside business partners
 Public registry deployment

Web Services Adoption Phases (cont.)

 1st Phase – Simple Web Services (Past)

Consumer-focused, stateless, SOAP over HTTP/S
 2nd Phase – EAI Web Services (Now)

Deployed within organization boundaries to enable internal
integration
 3rd Phase – Business Web Services (1-2 Year)

Deployed on extranets to enable business transactions with
trading partners, suppliers, and customers, ebXML & UBL

Trends Towards Service Orientation

Evolution of EAI to web service standards

XML RPC => Asynchronous XML Messaging

Towards de-centralization

Componentized services
− Composable and composite services
− Data encapsulated within component
− Data ownership follows component ownership

Brokered web services

Flexible relationships => Adaptive businesses 29

Web Service Specifications?

30

Web Services : Fundamental Specifiations

 Service Invocation => SOAP
 Service Description => WSDL
 Service Registration (Publication) and Discovery
=> UDDI
 SOAP, WSDL and UDDI are XML based

XML Schema
• XML is the lingua franca of SOA, used for message
payloads
• XML Schema provides data definition in XML
format
• XML Schemas are not object-oriented , are intended
to capture a data model

33

Example: Book.xsd

34

SOAP

Simple Object Access Protocol

Wire protocol similar to
− IIOP for CORBA
− JRMP for RMI

XML is used for data encoding
− “text” based protocol vs. “binary” protocol

Supports XML-based RPC

36

What SOAP is Not

Not a component model
− So it will not replace objects and components, i.e. EJB,
JavaBeans

Not a programming language
− So it will not replace Java

Not a solution for all
− So it will not replace other distributed computing
technologies such as RMI

37

What does SOAP Define?

Message Envelope

Encoding Rules

RPC Convention

Binding with underlying protocols

38

SOAP Message Format
SOAP Message SOAP Envelope
SOAP Header
Primary MIME part
(text/xml) Header Entry

Header Entry
Attachment
SOAP Body
Attachment
Body Entry

Body Entry
Attachment

39

SOAP Message Envelope

Encoding information

Header
− Optional
− Could contain context knowledge

Security

Transaction

Body
− RPC methods and parameters
− Contains application data

40

SOAP Encoding
• Rules of expressing application-defined data types in
XML
• Based on W3C XML Schema
• Simple values
– Built-in types from XML Schema, Part 2 (simple types,
enumerations, arrays of bytes)
• Compound values
– Structs, arrays, complex types

41

SOAP RPC Request Example
<SOAP-ENV:Envelope
xmlns:SOAP-ENV="…"
SOAP-ENV:encodingStyle="…">
<SOAP-ENV:Header>

</SOAP-ENV:Header>

<SOAP-ENV:Body>
   <m:GetLastTradePrice xmlns:m=“some_URI">
     <tickerSymbol>SUNW</tickerSymbol>
   </m:GetLastTradePrice>
</SOAP-ENV:Body>

</SOAP-ENV:Envelope>

42

SOAP RPC Response Example
<SOAP-ENV:Envelope
xmlns:SOAP-ENV="…"
SOAP-ENV:encodingStyle="…">
<SOAP-ENV:Header>

</SOAP-ENV:Header>

<SOAP-ENV:Body>
  <m:GetLastTradePriceResponse xmlns:m=“some_URI">
     <price>30.5</price>
  </m:GetLastTradePriceResponse>
</SOAP-ENV:Body>

</SOAP-ENV:Envelope>

43

SOAP RPC

Information needed for a method call:
− The URI of the target object

<SOAP-ENV:Body>
<m:GetLastTradePrice
xmlns:m=“http://stocks.com/StockQuotes">
</SOAP-ENV:Body>

44

SOAP RPC (cont.)

− Method name

<SOAP-ENV:Body>
</SOAP-ENV:Body>

45

SOAP RPC (cont.)

− Method name
− Parameters

<SOAP-ENV:Body>
</SOAP-ENV:Body>

46

What is WSDL?
• XML language for describing web services
• Web service is described as
– A set of communication endpoints (ports)
• Endpoint is made of two parts
– Abstract definitions of operations and messages
– Concrete binding to networking protocol (and corresponding
endpoint address) and message format
• Why this separation?
– Enhance reusability (as we will see in UDDI reference to
WSDL document)
48

Why WSDL?
• Enables automation of communication details between
communicating partners
– Machines can read WSDL
– Machines can invoke a service defined in WSDL
• Discoverable through registry
• Arbitration
– 3rd party can verify if communication conforms to WSDL

49

WSDL Document Example

Simple service providing stock quotes

A single operation called GetLastTradePrice

Deployed using SOAP 1.1 over HTTP

Request takes a ticker symbol of type string

Response returns price as a float

50

WSDL Elements

Types

Message

Operation

Port Type

Binding

Port

Service

51

WSDL Elements (cont.)

Types
− Data type definitions
− Used to describe exchanged messages
− Uses W3C XML Schema as canonical type system

52

WSDL Example: Types
<definitions name="StockQuote"
targetNamespace="http://example.com/stockquote.wsdl"
xmlns:tns="http://example.com/stockquote.wsdl"
xmlns:xsd1="http://example.com/stockquote.xsd"
xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns="http://schemas.xmlsoap.org/wsdl/”>
<types>
<schema targetNamespace="http://example.com/stockquote.xsd"
xmlns="http://www.w3.org/2000/10/XMLSchema">
<element name="TradePriceRequest">
<complexType>
<all>
<element name=”tickerSymbol" type="string"/>
</all>
</complexType>
</element>
<element name="TradePrice">
<complexType>
<all>
<element name="price" type="float"/>
</all>
</complexType>
</element>
</schema>
</types>

53

WSDL Elements

Messages
− Abstract, typed definitions of data being exchanged

Operations
− Abstract description of an action
− Refers to an input and/or output messages

Port type
− Collection of operations
− Abstract definition of a service

54

Example:
Messages, Operation, Port type
<message name="GetLastTradePriceInput">
<part name="body" element="xsd1:TradePriceRequest"/>
</message>

<message name="GetLastTradePriceOutput">
<part name="body" element="xsd1:TradePrice"/>
</message>

<portType name="StockQuotePortType">
<operation name="GetLastTradePrice">
<input message="tns:GetLastTradePriceInput"/>
<output message="tns:GetLastTradePriceOutput"/>
</operation>

</portType>

55

WSDL Elements

Binding
− Concrete protocol and data format for a particular Port type
− Protocol example: SOAP 1.1 over HTTP or SOAP 1.1 over
SMTP

Port
− Defines a single communication endpoint
− Endpoint address for binding
− URL for HTTP, email address for SMTP

Service
− Aggregate set of related ports

56

Example: Binding, Port, Service
<binding name="StockQuoteSoapBinding" type="tns:StockQuotePortType">
<soap:binding style="document"
transport="http://schemas.xmlsoap.org/soap/http"/>
<operation name="GetLastTradePrice">
<soap:operation
soapAction="http://example.com/GetLastTradePrice"/>
<input> <soap:body use="literal" />
</input>
<output> <soap:body use="literal" />
</output>
</operation>
</binding>

<service name="StockQuoteService">
<documentation>My first service</documentation>
<port name="StockQuotePort" binding="tns:StockQuoteBinding">
<soap:address location="http://example.com/stockquote"/>
</port>
</service>

57

UDDI (Universal Description,
Discovery and Integration)

“White pages”
– address, contact, and known identifiers

“Yellow pages”
– industrial categorizations

Industry: NAICS (Industry codes - US Govt.)

Product/Services: UN/SPSC (ECMA)

Location: Geographical taxonomy

“Green pages”
– technical information about services

59

Additional WS Specifications
• WS-Security: Address transport of security context
• WS-Coordination: Framework for achieving
coordination between partners
• WS Transaction Specifications: Standard for creating
distributed transaction involving multiple Web
Services
– WS-AtomicTransaction
– WS-BusinessActivity
• WS-Realiable Messaging: Standards for reliable
delivery of messages between partners
60

Additional WS Specifications (cont.)
• WS-Addressing: Defines end point communication
• WS-Inspection: Specification uses for dynamic
discovery of service documents
• WS Policy: Specifics the policy of a web service
provider
• WS-Eventing: Defines event sources and consumers
in the event model.

61

Web Services and Standards

62

RESTful Web Services
• REST => REpresentational State Transfer
• Resources (nouns) ->Identified by a URI, For example:
• http://www.parts-depot.com/parts
• Methods (verbs) to manipulate the nouns
– Create, Read, Update, Delete
• Representation is how you view the State
– data and state transferred between client and server
– XML, JSON...
• Use verbs to exchange application state and representation
63

Characteristics of REST
• RESTful services are stateless
– Each request from client to server must contain all the
information necessary to understand the request
• RESTful services have a uniform interface
– GET, POST, PUT, and DELETE.
• REST-based architectures are built from resources
(pieces of information) that are uniquely identified by
URIs
– In a RESTful purchasing system, each purchase order has a
unique URI

REST vs “Traditional” Web Services
• “Traditional” web service
– Few URIs (nouns), many custom methods (verbs)
• musicPort.getRecordings(“beatles”)
– Uses HTTP as transport for SOAP messages
• RESTful web service
– Many resources (nouns), few fixed methods(verbs)
• GET /music/artists/beatles/recordings
– HTTP is the protocol

SOAP Service and REST Resource
• SOAP based web services is about services SOA
– Stock quote service
quoteService.purchas e(“sunw”, 2000, 6.0f);

• Resource-Oriented Architecture (ROA)
– Stock quote resource
– Resources are manipulated by exchanging representations
– Eg. purchasing stock
• Manipulate my portfolio resource
• Handle a POST in a stock resource that I own
• POST /mystocks/sunw

From http://www.prescod.net/rest/mistakes/

Web Services : Demo

67

Public Web Services
• Web Service X (http://www.webservicex.net)
• StrikeIron.com
• Xmethods.com
• FedEx.com
• Amazon Web Service
• Google

68

soapUI
• Open source tool for web service testing
• Iinspecting, invoking, monitoring,
simulating/mocking and functional/load
/compliance/surveillance testing
• REST/WADL and SOAP/WSDL-based Web
Services over HTTP.
• www.soupui.org

69

Resources
 Some contents are borrowed from the presentation
slides of Sang Shin, Java™ Technology Evangelist,
Sun Microsystems, Inc.
 Business Process Execution Language for Web
Services, Matjaz B. Juric
 Java SOA Cookbook, Eben Hewitt
 SOA in Practice, Nicolai M. Josuttis

71

Thank you
thanachart.numnonda@sun.com
twitter.com/thanachart
www.facebook.com/thanachart

72

Introduction to Web Services

More Related Content

What's hot (20)

Viewers also liked (9)

Similar to Introduction to Web Services (20)

More from Thanachart Numnonda (20)

Introduction to Web Services