Design Strategy - Distributed
Systems
Part 2
New Architectures
CSIS3600 Systems Analysis and
Design
New Architectures
• Module/Component Based
– Smaller applications that link to other applications and
resources to complete a task
– Model is based on ‘consuming’ resources
– Idea is that software now provides a service to other
apps as well
• Primary development platforms that support these
models are J2EE and .Net (IBM has Websphere
which is the same idea)
Component Architecture
• Component Architecture is considered one of the
most flexible architectural model.
• Component Object Model (COM) is a general
architecture for component software. COM is
associated with Microsoft. However it is not an
implementation but a standard.
• Components allow for partitioning business logic
out of the front-end and back-end applications and
into its own set of components.
Component Architecture – the Last
Rendition
• ActiveX is Microsoft’s physical
implementation of COM and DCOM.
• DCOM is a protocol that enables
applications to make object-oriented remote
procedure calls.
• Javabeans is Java’s component architecture.
Component Development
•
•
•
•
•
Middleware
COM, DCOM, ActiveX
CORBA, SOAP
XML
Sun’s Java™ 2 Platform, Enterprise
Edition
• Microsoft’s .NET
Components and Services Model
Services Model
Services Layer Architecture
• Logical way to group components. The
Services model is often referred to as a
layer approach.
• Components can request services from
fellow components in their current tier and
any tier below or above a component tier.
Services Layer Approach continued
• Requests cannot skip tiers. User services
components cannot communicate directly
with components in the data services tier
and vice versa.
• The typical use of the term layer refers to a
process in which one layer must speak to
the next layer and move from top to bottom
and then back up.
New View of Development
J2EE and .NET
• The idea is to make it easier to deploy
applications that use distributed resources
• Practical use of these platforms will be for
large application deployment
– Too expensive for small or even medium size
needs
– Not here yet but it’s coming
Intro to J2EE
• JavaTM 2 Platform, Enterprise Edition
(J2EETM) provides a component-based
approach to the design, development,
assembly, and deployment of enterprise
applications
What is J2EE
• J2EE was designed to simplify complex problems
with the development, deployment, and
management of multi-tier enterprise solutions.
J2EE is an industry standard, and is the result of a
large industry initiative led by Sun Microsystems.
• J2EE is a standard, not a product. You cannot
"download" J2EE. Rather you download a set of
files which describe agreements between
applications and the containers in which they run.
– So long as both sides obey the J2EE contracts,
applications can be deployed in a variety of container
environments.
J2EE Platform
The J2EE platform uses a multi-tiered distributed
application model.
– This means application logic is divided into
components according to function
– Various application components are combined into a
J2EE application
– Each component, its related files such as GIF and
HTML files or server-side utility classes, and a
deployment descriptor (DD), are assembled into a
module and added to the J2EE application
J2EE Applications
– J2EE applications are installed on different
machines depending on which tier the
application component belongs.
– J2EE applications are ‘served’ on a J2EE server
which is not usually maintained in-house
– The J2EE server is responsible for the software
to hardware relationship which is the most
difficult for organizations to understand,
manage and maintain
Microsoft’s .NET
Microsoft’s answer to J2EE
• The focus is to make computing easier
• Microsoft will retain all .NET servers
• .Net is a little bit of everything
– Next-generation development environment
– Based on Visual Studio
– New programming language C#
– Data exchange and messaging – XML and SOAP
What is .Net?
• Microsoft.NET is product suite that enables
organizations to build smart, enterpriseclass web services.
– Note the important difference: .NET is a
product strategy, whereas J2EE is a standard to
which products are written.
• Not revolutionary – evolution of existing
technologies (COM, etc.)
.NET BlueprintYour Internal Services
Visual
Studio.NET
Applications
Using Your
Service
Smart Clients
.NET FW
Windows
Smart
Devices
.NET FW
Simple
Browsers
Sales Data Service
Corporate Fullfilment Service
Your
application
and web
service
.NET
Framework
Windows
CE, XP, 2000, .NET
Open Internet Protocols
XML, XSLT, XSD, SOAP,
DISCO, UDDI, XHTML,
HTTP, SSL, WAP
.NET Enterprise Servers
SQL Server
BizTalk Server
Application Center
Commerce Server
Host Integration Server
Internet Security and Acceleration
Exchange Server
.NET FW
Windows
Building Block Services
Passport – Identity Service
Calendaring Service
…
[myServices]
3rd Party Web Services
Geographic Mapping Service
Credit Card Statement Service
…
[ActiveX Paradigm]
Assemblies and Manifests
• Resources are collected into Assemblies described by
Manifests (ie Application described by DD)
• Simplify Deployment And Management
– The functional unit of sharing for deployment, versioning,
and security
• Zero-impact install
– Applications and components can be shared or private
• Side-by-side execution
– Multiple versions of the same component can co-exist, even
in the same process
Microsoft Intermediate Language
(MSIL)
• CPU-independent set of instructions
– Provides machine-code abstraction
• instructions for loading, storing, initializing, arithmetic
and logical operations, control flow, direct memory
access, and exception handling
– Can be JIT compiled to native code very efficiently
– All code in Visual Studio .Net is written into MSIL
– The idea is that various programming languages can
be used because the original code will be written to
MSIL
– Converters for currently used languages are
underway
Common Language Runtime (CLR)
•
Manages running code
– The glue that binds .NET together!
– It’s the .NET Execution Engine
•
Completely replaces COM plumbing
– No registration, GUIDs, .IDL files, HRESULTs,
IUnknown, AddRef/Release, CoCreateInstance,
etc.
•
Object/Component Oriented to the core
– Even across languages!
•
Seamless integration with COM
CLR Execution Model
VB
C#
Install time
Code Gen
Script
...
Assembly:
MSIL + Metadata
Development
Deployment
Common
Language
Runtime
JIT
Code Gen
Native
Code
J2EE vs .NET
.NET
J2EE
Programming
language
Dynamic Internet
access
Interoperability with
different programming
platforms
C# (Preferred)
ASP .Net
Java (basically
necessary)
JSP
MSIL Common
Language Routine
Java Virtual Machine
and CORBA
Application
Development
Environment
Visual Studio .Net
Forte
System and
component integration
ADO.Net, SOAP and
XML
JDBC, EJB, XML,
SOAP
Web Services
• Web services are now defined as interoperable
service components that can be accessed as
necessary
• Frequently cited examples include third-party
services for instant messaging, auctions, electronic
payments and online purchasing systems. Existing
credit card authorization and content-syndication
systems also fall within the Web services realm
Definition of Web Services
• Web services are characterized by the ability to
dynamically create and discover services and the
delivery of those services over the Internet
• Web services are software components that are created
by wrapping a traditional service inside a Web service
interface eliminating the need for translation
• They communicate over Internet standard
technologies (private or public) and are invoked or
delivered through Web service interfaces
The Technologies
• Web services encompass a wide array of
technology standards.
• Simply put they are defined using WSDL (Web
Services Description Language), are accessible
using SOAP (Simple Object Access Protocol) and
are registered using UDDI (Universal Description,
Discovery and Integration)
• XML is the foundational technology of Web
Services
XML
• XML is an extensible language for describing
other languages so businesses can design their
own customized markup language
• XML is far more flexible and extensible than
traditional messaging and middleware
communications. With XML, applications can
send information across the Internet using HTTP
and support much "looser" connections
How Web Services Work
• Discovery
– How an application finds a web service
• Description
– Explains nature of the service and the company that
offers it
• Invocation
– Calling procedure or method provided by a software
component
Discovery - UDDI
• Universal Description, Discovery and
Integration is an XML-based registry that
lets businesses locate one another on the
Internet
• The UDDI standard outlines a framework
for a registry of companies and a warehouse
of their Web services
• http://www-3.ibm.com/services/uddi/find
Description
• WDSL
• WSDL is the de facto description
mechanism in the current Web Services
SOAP/WSDL/UDDI trinity (or quaternity if
you assume HTTP as the default transport
mechanism)
WSDL
• Web Services Description Language describes an
organization's services and lets other organizations
access them
• WSDL is becoming the de facto standard for
describing Web services in XML format
• WSDL is extensible to allow the description of
end points and their messages, regardless of what
message formats or network protocols are used to
communicate
Sample WDSL Code
http://www.capescience.com/tutorials/#
SOAP
• Simple Object Access Protocol is a way for programs
to communicate regardless of operating system
• SOAP defines a protocol for Remote Procedure Call,
an application-to-application communication that
hides underlying network complexities, across the
Internet using HTTP and XML.
• It is a relatively simple way to exchange information
in a decentralized, distributed environment because it
allows end points to connect via the Web and request
the use of services
Try Some Out
• Adobe Systems Inc. has a Web service that translates
HTML, graphics and Microsoft Office files into Portable
Document Format files. It can be found at
https://createpdf.adobe.com
• Another Web service
(http://webservices.eraserver.net/zipcoderesolver/) will
look up the ZIP code of any U.S. address
• Global Weather
http://live.capescience.com/AirportWeather/index.html