Lecture5 Web Services

7/31/2019 Lecture5 Web Services

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Web Services Technology

COMP3150/7700 E-technology

Architectures, Tools and Applications(Semester 1, 2010/11)


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COMP3150/COMP7700 E-technology Architectures, Tools and Applications (Web Services) 2

Some software functional block

Location, platform, code are irrelevant

Loosely coupled software components that encapsulatediscrete functionality and that are accessible over standardInternet protocols.The Stencil Group

Web Services are a new breed of web application. They areself-contained, self-describing, modular applications that can bepublished, located, and invoked across the Web. IBM

Web services are a form of distributed information systemGustavo Alonso

Web services: concepts, architectures and applications


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Outline

Client-Server to 3-Tier

Middleware Technology

Web services


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Outline



Web Services


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Different Layers of an

Information System

Client

Presentation Layer

Application Logic Layer

Res. Management LayerInformation

System


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Different Layers of an

Information System Conceptual Layers of an IS

Presentation Layer

For interacting with external entities (clients) for receivingrequests & sending responses.

Application logic Layer

For system/process integration, business rule/logicexecution,

References for business rules:

http://www.businessrulesgroup.org/

Resource Management Layer

Data sources from databases or other informationsystems, specialized computing services,

Client

Presentation Layer


Res. Management Layer

Information

System


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From 1-tier to 3-tier

UI

Presentation Layer



UI

Presentation Layer



UI

Presentation Layer



1-tier 2-tier 3-tier

Middleware

Client Client

Server



Application Framework

Computer and Communication Facility

System Service

Data Repository

Control Integration

Task Management

Presentation Interface

User Interface

Hardware

Enterpriseware

Middleware

Userware

APPLICATI

ON



Integration: 2-tier Approach(data-oriented)

UI

PresentationLayer 1



Rice A

Rice B

Rice B

Drink C

Drink C

Food D

Food D

Food E

combined catalog

e.g., html or xml

e.g., html or xml

All logics are embedded

in your web programs

(e.g., *.asp, *.php, )
http://www.answers.com/topic/wellcome-new-gifhttp://www1.parknshop.com/WebShop/Home.do;jsessionid=G0m15HQ006Do0LjY9RzVxycOM87NUzp2ODC77WiV5e1Sv41O6oLW!-666216154http://www1.parknshop.com/WebShop/Home.do;jsessionid=G0m15HQ006Do0LjY9RzVxycOM87NUzp2ODC77WiV5e1Sv41O6oLW!-666216154http://www1.parknshop.com/WebShop/Home.do;jsessionid=G0m15HQ006Do0LjY9RzVxycOM87NUzp2ODC77WiV5e1Sv41O6oLW!-666216154http://www1.parknshop.com/WebShop/Home.do;jsessionid=G0m15HQ006Do0LjY9RzVxycOM87NUzp2ODC77WiV5e1Sv41O6oLW!-666216154http://www1.parknshop.com/WebShop/Home.do;jsessionid=G0m15HQ006Do0LjY9RzVxycOM87NUzp2ODC77WiV5e1Sv41O6oLW!-666216154



Integration: 3-tier Approach(data-oriented)

Client

Presentation Layer

Rice A

Rice B

Rice B

Drink C

Drink C

. . .



html or xml

e.g., html or xml

Eg., integration rules &

exception handling rules

(declarative)

e.g., The rule can be:

If a source is not

responding, showservice not available

and send a notification

e-mail to Manager A

and .

e.g., ODBC/Vendor_Specific_Protocol

Eg., database

management systemOracle, DB2
http://www.answers.com/topic/wellcome-new-gifhttp://www1.parknshop.com/WebShop/Home.do;jsessionid=G0m15HQ006Do0LjY9RzVxycOM87NUzp2ODC77WiV5e1Sv41O6oLW!-666216154http://www1.parknshop.com/WebShop/Home.do;jsessionid=G0m15HQ006Do0LjY9RzVxycOM87NUzp2ODC77WiV5e1Sv41O6oLW!-666216154http://www1.parknshop.com/WebShop/Home.do;jsessionid=G0m15HQ006Do0LjY9RzVxycOM87NUzp2ODC77WiV5e1Sv41O6oLW!-666216154http://www1.parknshop.com/WebShop/Home.do;jsessionid=G0m15HQ006Do0LjY9RzVxycOM87NUzp2ODC77WiV5e1Sv41O6oLW!-666216154



Integration: 2-tier Approach(computation-oriented)

UI

PresentationLayer 1



e.g., student essays

(*.doc)e.g., analysis results

in html/xml

Logics for analysis are

embedded in the web

programs.

e.g., html or xml



Integration: 3-tier Approach(computation-oriented)

UI

Presentation Layer



Eg., integration via

message queues

Eg., database

management systemOracle, DB2

e.g., JMS/Vendor-Specific-Protocol

e.g., student essays

(*.doc)e.g., html or xml

Products that support

Java Message Service:

Apache ActiveMQ,

Oracle AQ, IBM MQ,

etc.



Outline



Web Services



Middleware Technologies 101

RPC -> Workflow



Middleware Technologies:

RPC -> Workflow Middleware to handle the execution complexity fordistributed

applications

Remote Procedure Call (RPC) a process in a computer invokes a process in another

synchronous (wait until the response is ready)

Going beyond simple RPC Transactional

with commit and rollback handling (error handling)

Message-oriented (e.g., Oracle AQ) asynchronous, enabled by message queue

Message-brokering (e.g., Oracle Message Broker) from O(nxn) to O(n) communication

support logic-dependent routing

Workflow Management System (e.g., Oracle Workflow) process flow status control

Workflow --The automation of a business process, in whole or part,during which documents, information or tasks are passed from oneparticipant (resource or human or machine) to another for action,according to a set of procedural rules.


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Web ProcessesWorkflows Distributed

Workflows

GlobalEnterprise Inter-Enterprise

B2B E-Services

Globalization of Processes

Processes driving the Networked Economy

EAI
http://lsdis.cs.uga.edu/lib/download/SAA99.pdfhttp://lsdis.cs.uga.edu/lib/download/SAA99.pdf


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Outline


Middleware Technology 101

Web Services


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Software as Services?

Examples?

S i O i t d A hit t


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Service-Oriented Architecture

(SOA)

3 fundamental operations:

publish

find bind


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Web Services (1) What is

Web Services

Software systems designed to support interoperablemachine-to-machine interaction over a network.(W3C)

Messages in-between are XML-based Internet based Remote Procedure Call (RPC)

Request/Response (so, synchronous essentially)

Web Service Description Language (WSDL)

A XML-based markup language for specifying interfaces

for consuming services over the network.


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Web Services (2) What is

UDDI

Universal Description, Discovery and Integration

A platform-independent XML-based registry for

businesses worldwide to list themselves on the Internet. SOAP

Simply Object Access Protocol

A protocol forexchanging XML-based messages over

computer networks by HTTP/HTTPS.


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How can UDDI be Used

industry published an UDDI standard forflightrate checking and reservation;

airlines register their services into an UDDIdirectory.

Travel agencies search the UDDI directory to

find the airline's reservation interface. Thetravel agency can communicate with the

service immediately because it uses a well-

defined reservation interface.


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Who is Supporting UDDI?

UDDI is supported by all major platform and

software providers, like Dell, Fujitsu, HP,

Hitachi, IBM, Intel, Microsoft, Oracle, SAP,and Sun.

Over 220 companies are members of theUDDI community.

S i O i t d A hit t


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Service-Oriented Architecture

(SOA)

3 fundamental operations:

publish

find bind

Implement a web service

Define its WSDL

1. Look up service broker for web services

2. Develop a client program that can

communicate with the web service (basedon the WSDL description) and then

consume the web service.

Store the meta data of web services,

including where to locate the WSDLdescriptions and support search.

1

2 3


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Web Services Roles

Service provider Implements the services

Makes the services available on the web

Service requestor Consumes the web services

Service registry Logically centralized registry provides a central place

where allows developers to publish new services orsearch (or discover) existing ones


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Web Services Procedures (1)

Service

Requester

Service

RegistryUDDI

Service

Provider

Register

WS Search &Discovery

SOAP Request

Retrieve WSDL Documents

SOAP Response


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Web Services Procedures (2)

1. Web services providers register in UDDI Registry.

2. Web service consumers discoverthe desiredweb services in UDDI server.

3. Consumers retrieve the WSDL documents fromdesired web service providers.

4. Consumers sendSOAP request messages toservice providers.

5. Providers receive the requests, process themrequest, and return SOAP responses.

W b S i D i ti


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Web Services Description

Language (WSDL)

4 critical pieces of information

: describes a web service, the operations

performed by the web service (the most important).

: defines the data elements of an

operation.

: defines the data type used by the web

service.

: defines the message format and protocol

details for each port.

WSDL S pport 4 Basic


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WSDL Support 4 Basic

Operation Types


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Binding to SOAP


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Binding Element

The binding element has twoattributesname, type

Name: defines the name of the

binding (you can use any name youwant).

Type: points to the port for thebinding, in this case the"glossaryTerms" port.


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SOAP: Binding

The soap:binding element has twoattributes - style, transport

Style: could be "rpc" or "document". Transport defines the SOAP

protocol to use. In this case we use

HTTP.


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Operation

The operation element defines eachoperation that the port exposes.

--For each operation the corresponding

SOAP action has to be defined. Youmust also specify how the input and

output are encoded. In this case we use

"literal".


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HelloServices.wsdl (1)

Definition

Message

Visit this following link for more detailed specification

http://www.w3.org/TR/wsdl#_wsdl

H ll S i dl (2)


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PortType

Binding

previous

slides

matched operations

rpc - simple data types

document xml documents/data

encoded with data types based

on encodingStyleliteral no encoding


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WSDL File for HelloService

Service

previous

slides


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What is SOAP?

SOAP stands forSimple Object Access Protocol SOAP is XML-based SOAP is a protocol foraccessing a Web Service SOAP is for communication between applications

SOAP is a format forsending messages SOAP is via Internet (HTTP) SOAP is platform independent SOAP is language independent SOAP will be developed as a W3C standard


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SOAP Building Blocks

A requiredEnvelope element that identifiesthe XML document as a SOAP message

An optional Header element that containsheader information

A required Body element that contains calland response information

An optional Fault element that provides

information about errors that occurred whileprocessing the message


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Syntax Rules

A SOAP message MUST be encoded usingXML

A SOAP message MUST use the SOAPEnvelope namespace

A SOAP message MUST use the SOAPEncoding namespace

A SOAP message must NOT contain a DTDreference

A SOAP message must NOT contain XMLProcessing Instructions


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SOAP Message


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Skeleton SOAP Message


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Envelope Element

The xmlns:soap namespace The encodingStyle attribute

--soap:encodingStyle="URI"

--


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Header Element

Actor---A SOAP message may travel from a sender to a

receiver by passing different endpoints along themessage path. The SOAP actor attribute is toaddress the Header element to a particular endpoint

mustUnderstand=0/1

---It is to indicate whether a header entry is mandatoryor optional for the recipient to process.

encodingStyle


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Header Element

234soap:actor="http://www.w3schools.com/appml/

...

...


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Body Element


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Fault Element

Fault element has the following sub elements:

Value of faultcode

Error Description

VersionMismatch Found an invalid namespace for the SOAP Envelope element

MustUnderstand An immediate child element of the Header element, with the

mustUnderstand attribute set to "1", was not understood

Client The message was incorrectly formed or contained incorrect

information

Server There was a problem with the server so the message could not

proceed


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SOAP Hand-shaking

Example: weather services (refer to thelink provided on course home page)


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SOAP Hand-shaking (Request)

10016

Envelope

Body

Envelope contains namespaces which directsto the external schema

Body contains the request getTemp


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SOAP Hand-shaking (Response)

71.0

Envelope

Body

Envelope contains the same namespaces

Body contains the payload type(getTempResponse), corresponding to ourinitial request


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SOAP over HTTP

SOAP Request Sent via HTTP GET or POST

HTTP POST requests specifies at least two

HTTP headers: Content-Type and Content-Length.

SOAP Response

Delivered by HTTP with corresponding statuscode


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SOAP Request


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SOAP Response


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Universal Description, Discovery and

Integration (UDDI) UDDI stores the web services providers

and their web services provided in a

common XML format, acted as a

registry and database of web services Web-based applications interact with a

UDDI registry using SOAP messages


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UDDI Registry CategoriesWhite Yellow Green

High-level businessinformation

Company name

Description Contact info

Known Identifiers

(Thomas, DUNS, tax

ID, etc.)

Classification ofbusiness andservices

Uses widely knownclassification schemes

such as NAICS,

UN/SPSC (ECMA),

SIC, and geographic

taxonomies

Technical info for

consuming the service

Called a Type Model

(tModel)Defines the services

API, binding

requirements, and so

on

Usually a pointer to aWSDL document

http://www.uddi.org/schema/uddi_v2.xsd

Wh t i th l f W b
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What is the role of Web

Services for middleware?

UI

Presentation Layer



UI

Presentation Layer



2-tier 3-tier

Client Client

Server


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More on Web Services

We are only talking about Web services as RPC so far(stone age concept)!!!

Asynchronous request/response

Production and transmission of a request by a client.

Consumption of the request by service provider.

Production and transmission of a response by service provider.

Consumption of the response by the client.

* Can you see a collaboration activity?

* Can you define several web services to support that? Study whichweb services should be made known to client and which should bemade known to service provider.


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More on Web Services

WS-Coordination (a step towards asynchronous WS) describes how services can make use of pre-defined coordination

contexts to subscribe to a particular role in a collaborative activity.

WS-Transaction (a step towards transactional WS)

provides a framework for incorporating transactional semantics into

coordinated activities.

Business Process Execution Language - BPEL (a step

towards workflow)

describe how Web services are connected to create reliable and

dependable business solutions


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References

http://www.w3schools.com/ Darren Barefoot, Web Services Primer, Sept 2002,http://www.capescience.com/education/primer/index.shtml

New to Web Services, http://www-

106.ibm.com/developerworks/webservices/newto E Cerami, Web Services Essentials, OReilly, Feb 2002

David S. Linthisum, B2B Application Integration,Addison Wesley, 2001


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Lecture5 Web Services

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