Bài giảng Web technologies and e-Services - Bài 9, Phần 2: Service-oriented architecture

5/13/21

IT4409: Web Technologies and e-Services

2020-2

Service-Oriented Architecture (SOA)

Instructor: Dr. Thanh-Chung Dao

Slides by Dr. Binh Minh Nguyen

Department of Information Systems

School of Information and Communication Technology

Hanoi University of Science and Technology

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TOPICS

Introduction to SOA

§ Service

§ Service Oriented Architecture

Web services

Web services programming

§ SOAP Web services

§ REST Web services

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History of creating application

Programming with

§ 0 and 1

§ Assembly

§ Procedural programming language

§ OOP programming

§Service-Oriented Architecture

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What is a service?

Restaurant provides food: a service

After the order is taken, food is produced, served,

…: service may consist of other services

The menu indicates the service provided: a

service description

The order is written down, or yelled at, the cook:

services communicate through messages

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What is a service in IT?

An entity that provides some capability to its clients by exchanging

messages (request - response)

Request

Response

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Service characteristics

n Services are autonomous

n Services hide their logic

n Services are reusable

§ Services can (must) be

discovered

§ Services can be composed to

form larger services

§ Services adhere to a service

n Services use open standards

description/contract

§ Services are loosely coupled

§ Services are stateless

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Loosely coupled, stateless, autonomous & hide logic

§ Loosely coupled: system is one in which each of its components has, or makes

use of, little or no knowledge of the definitions of other separate components

§ Stateless: Rental agencies come and go, the agencies cannot retain information:

it doesn’t know if and when it will be invoked again, and by whom

§ Autonomous: Its logic does not depend on the tenants

§ Hide logic: Rental agency has its own rules on how to structure its process

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What is SOA?

SOA is a software architecture model in which business functionality are logically

grouped and encapsulated into self contained, distinct and reusable units called

services

represent a high level business concept

can be distributed over a network

can be reused to create new business applications

contain contract with specification of the purpose, functionality, interfaces, usage

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SOA from different views

A set of business services

composed to capture the business

design that an enterprise wants to

expose to its customers and clients

Business

An architectural style that requires

a service provider, requester and a

service description

Architecture

A programming model complete

with standards, tools, methods and

technologies such as Web services

Programming

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Application centric

Business scope

Narrow Consumers

Limited Business Processes

Finance

Application

Integration

Supply

Application

Architecture

Redundancy

Distribution

Manufacturing

Overlapped resources

Overlapped providers

Business functionality is

duplicated in each application that

requires it.

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Service centric

Business scope

Multiple Service Consumers

Multiple Business Processes

Finance

Service

Supply

Service Architecture

Shared

Services

Service

Distribution

Manufacturing

Multiple Discrete Resources

Multiple Service Providers

Service virtualizes how that capability is performed,

and where and by whom the resources are provided,

enabling multiple providers and consumers to

participate together in shared business activities.

SOA structures the business and its systems as a set of

capabilities that are offered

as Services, organized into a Service Architecture

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Application centric vs Service centric

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Why SOA?

Enabling alternative

implementations

Enabling a virtual federation of

participants to collaborate in an

end-to-end business process

Enabling reuse of

Services

Service

Identification

Ticket Collection

Service

Ordering

Ticket Sales

Service

Inventory

Service

Logistics

Service

Availability

Manufacturing

Enabling aggregation from multiple

providers

Enabling virtualization of business resources

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SOA is an evolutionary step

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SOA layered architecture

Example Layers

Reasons for Layering

Presentation

& workflow

1.

Flexible composition.

Reuse.

2.

Composed Services

3.

4.

5.

Functional standardization in lower levels

Customization in higher layers

Separation of Concerns.

Basic Services

6.

Policies may vary by Layer

Underlying

API

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TOPICS

Introduction to SOA

§ Service

§ Service Oriented Architecture

Web services

Web services programming

§ SOAP Web services

§ REST Web services

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Web services & SOA

Web services is chosen for SOA because:

§ Loose coupling

Service requesters depend only the interface described in WSDL and not

on the implementation of the service provide

§ Interoperability

Service interactions are based on the exchange of XML-based SOAP

messages over standards based transport protocols

§ Wide industry support

Wide industry support for adoption of Web services standards promotes

interoperability of various vendor platforms that support Web services

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What is web service?

Implementation means to realize services

Based on open standards:

§ XML

§ SOAP: Simple Object Access Protocol

§ WSDL: Web Services Description Language

§ UDDI: Universal Description, Discovery and Integration

§ BPEL4WS: Business Process Execution Language for Web Services

Main standardization bodies: OASIS, W3C

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One for all …

Browser

GUI

Browser

Client

Web

Server

WSDL

HTTP GET/POST

SOAP

WSDL

Web

Server

Web

Server

SOAP

JDBC

DB

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OSI and Web service

Application

Presentation

Session

Application

Web Services

Others

TCP

UDP

Transport

Network

TCP

Ipv4, IPv6

Device Driver

&

Hardware

Datalink

Device Driver

&

Hardware

Physical

OSI Model

Internet Protocol

Suite

Web Services

Model

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Example

Web Services Based Travel Web Site

Web Services

Client

Application

Airlines -- Delta

RDMS

Web Browser

Hotels -- Marriot

Automobiles -- Hertz

Web Browser

Travel

Customers

Travel Services -- Sabre

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Open standard technologies for web service

XML – tagging data such that it can be exchanged between applications and

platforms

SOAP – messaging protocol for transporting information and instructions between

applications (uses XML)

WSDL – a standard method of describing web services and their specific capabilities

(XML)

UDDI – defines XML-based rules for building directories in which companies

advertise themselves and their web services

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XML

Developed from Standard Generalized Markup Method (SGML)

XML widely supported by W3C

Essential characteristic is the separation of content from presentation

XML describes only data

Any application that understands XML can exchange data

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XML

XML parser checks syntax

If syntax is good the document is well-formed

XML document can optionally reference a Document Type Definition (DTD), also

called a Schema

If an XML document adheres to the structure of the schema it is valid

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SOAP

SOAP enables between distributed systems

SOAP message has three parts

§ envelope – wraps entire message and contains header and body

§ header – optional element with additional info such as security or routing

§ body – application-specific data being commuicated

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TOPICS

Introduction to SOA

§ Service

§ Service Oriented Architecture

Web services

Web services programming

§ SOAP Web services

§ REST Web services

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Three Most Common Styles of Use

RPC (Remote Procedure Calls)

§ A distributed function call interface

SOAP (Simple Object Access Protocol)

§ The basic unit of communication is a message, rather than an operation

REST (Representational State Transfer)

§ Standard operations in HTTP: GET, POST, PUT, DELETE

§ Interacting with stateful resources, rather than messages or operations

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RPC Web Services

Basic unit: WSDL operation

Widely deployed and supported, but not loosely coupled

Other approaches: CORBA, DCE/RPC, Java RMI

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SOAP Web Services

Basic unit: message

Envelope

Header

Supported by most major vendors, loose

coupling

Body

Message

Payload

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Representational State Transfer (REST)

Interacting with stateful resources, rather than messages or operations

Using HTTP standard operations such as GET, POST, PUT, DELETE

WSDL 2.0 offers support for binding to all HTTP request methods

§ WSDL 1.1 only GET and POST

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SOAP web service

§ HTTP-XML-based protocol

§ Enables application to communicate over Internet

§ Uses XML documents called messages

§ SOAP message contains an envelope

§ Describes message’s content and intended recipient

§ Ability to make a Remote Procedure Call (RPC)

§ Request to another machine to run a task

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SOAP

Using Web Services and SOAP, the request would look something like

this:

<?xml version="1.0"?>

<soap:Envelope

xmlns:soap="http://www.w3.org/2001/12/soap-envelope"

soap:encodingStyle="http://www.w3.org/2001/12/soap-encoding">

<soap:body pb="http://www.acme.com/phonebook">

<pb:GetUserDetails>

<pb:UserID>12345</pb:UserID>

</pb:GetUserDetails>

</soap:Body>

</soap:Envelope>

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Pros & cons

n Disadvantages

Advantages

§ Human readable XML

n S-L-O………………..-W

§ Easy to debug

§ SOAP runs over HTTP

§ Firewalls not affected

§ Services can be written in any

language, platform or operating

system

n XML produces a lot of overhead for

small messages

n Web Services speed relies on Internet

traffic conditions

n Not strictly-typed XML

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SOAP web service by Java

Java Client

Environment

Java Enterprise

Environment

Internet

WSDL

Java

RDBMS

WS Endpoint

Interface

WS Attribute

Classes

wsimport

Application

Web Service Server

Web Service

Client

Application

Framework

•Java

•.Net

WS Endpoint

Publisher

RDBS

JSE 6 .jar

• Java Web Services Development Environment

• Fully Integrated Framework and Utilities

• End to End Enterprise/Client Communications

javax.jws

javax.xml.ws

javax.xml.rpc

javax.xml.soap

javax.xml.bind

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Android Web Services Development Environment

Web Service

Missing Tool

Components

Java

RDBMS

Application

WS Endpoint

Interface

Proc beans

xml Abst

WSDL

kSOAP2

wsimport

Framework

•Java

•.Net

WS Endpoint

Publisher

Android

Java WS

Client

RDBS

Java .jars

javax.jws

javax.xml

othes...

Missing Library

Components

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SOAP vs REST

SOAP

REST

Meaning

Simple Object Access Protocol

Representational State Transfer

Design

Standardized protocol with pre-defined rules Architectural style with loose guidelines and

to follow. recommendations.

Approach

Function-driven (data available as services, e.g.: Data-driven (data available as resources, e.g.

“getUser”) “user”).

Statefulness

Stateless by default, but it’s possible to make Stateless (no server-side sessions).

a SOAP API stateful.

Caching

API calls cannot be cached.

API calls can be cached.

Security

WS-Security with SSL support. Built-in ACID Supports HTTPS and SSL.

compliance.

Performance

Requires more bandwidth and computing power. Requires fewer resources.

Message format

Transfer protocol(s)

Recommended for

Only XML.

Plain text, HTML, XML, JSON, YAML, and

others.

HTTP, SMTP, UDP, and others.

Enterprise apps, high-security apps,

distributed environment, financial services,

payment gateways, telecommunication

Only HTTP

Public APIs for web services, mobile services,

social networks.

services.

Advantages

High security, standardized, extensibility.

Scalability, better performance, browser-

friendliness, flexibility.

Disadvantages

Poorer performance, more complexity, less

flexibility.

Less security, not suitable for distributed

environments.

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email: chungdt@soict.hust.edu.vn

Q&A

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Bài giảng Web technologies and e-Services - Bài 9, Phần 2: Service-oriented architecture - Nguyễn Bình Minh