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

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Introduction to Web Services

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