Transcript J2Pres - University of Connecticut

J2EE - ENTERPRISE DEVELOPMENT AND
INTEROPERABILITY WITH NON-J2EE CLIENTS
presented by
Sudha Balla, Betsy Cherian and Lance Fiondella
Semester Project
CSE333 – Distributed Component Systems (FALL 2002)
Instructor
Prof. Steven A. Demurjian
Department of Computer Science and Engineering
University of Connecticut
[email protected]
[email protected]
[email protected]
J2EE--1
Organization of presentation
1.
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8.
Introduction and Motivation(Lance)
Server-side component architectures(Sudha)
J2EE Platform overview(Lance)
J2EE Standardized Services(Betsy)
EJB/CORBA(Sudha)
J2EE Patterns(Betsy)
The Department of Motor Vehicles Prototype(Sudha)
Conclusion(Sudha)
J2EE--2
Introduction - Assessment
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Java has been around for over 7 years now.
Server-side component architectures
Microsoft’s .NET product
Sun Microsystems’ Java2 Platform Enterprise
Edition (J2EE) standard
Object Management Group’s CORBA standard
J2EE--3
Introduction - Benefits
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Enterprise JavaBeans includes both Java/RMI and
RMI – IIOP as middleware options.
Sun and OMG support EJB/CORBA interoperability
and have produced standards for the same.
The EJB/CORBA mapping specification and RMIIIOP relieve EJB from being restricted to the Java
platform, enabling EJB components to be exposed as
CORBA objects making them well suited for crosslanguage interoperability.
J2EE--4
J2EE--5
Motivation – SE to EE
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Large organizations utilize J2EE.
J2EE--6
Motivation - …
J2EE--7
Motivation – Academic perspective
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Maintain an objective research perspective on the
state of development of Java2 Enterprise Edition
and Java technologies in general.
Determine the role Java plays as an educational
language, problem-solving skill for the workplace,
and research tool for academia.
Focus on the classical facilities provides insight
into the true maturation of Java.
J2EE--8
Server-side Component Architectures
(Overview)
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Issues surrounding server-side development
The need for standardized architecture
Popular server-side architecture standards
Similarities and differences between J2EE and
other competing technologies
Enterprise Application Development and these
technologies
J2EE--9
Server-side Component Architectures
(Software Components)
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What are software components?
What is a component architecture?
Divide-and-conquer approach and its advantages
 Saves development and deployment time
 Services could be simply outsourced
 Users save time by buying instead of building
 Deployment is strengthened as the common
products are developed by domain experts
J2EE--10
Server-side Component Architectures
(Server-side Components)
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What is a server-side deployment?
Logical layers in the deployment
 Presentation Layer
 Business logic Layer
 Data Layer
Layers are pure abstractions and may or may not
correspond to physical distribution
a N-tier architecture deployment is one where there
is a physical separation between each of the layers
Each of the layers could further be decomposed to
allow various parts of the system to scale
independently
J2EE--11
Server-side Component Architectures
(Three-tier Web-based Application Architecture)
Presentation
layer
WEB SERVER
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Firewall + tier boundary
APPLICATION SERVER
WITH COMPONENT
CONTAINER
Business logic
Layer
tier boundary
Data layer
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Database
J2EE--12
Server-side Component Architectures
(N-Tier Architectures)
PRO:
 Deployment costs are low
 Database switching costs are low
 Low costs in business logic migration
 Securing deployments using firewalls is possible
 Resource pooling is possible
 Performance slowdown is localized
 Errors are localized
CON:
 Communication performance suffers
 Maintenance costs are high
J2EE--13
Server-side Component Architectures
(Demands of a multi-tier deployment)
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Handle lifecycle of the components
Perform resource pooling
Broker method requests
Handle the logic to load-balance communications
between each tier
Deal with ramifications of two or more clients
concurrently accessing the same component
Reroute client requests to other machines in case of
failure
Provide secure environment and deal with
unauthorized accesses
APPLICATION SERVERS WERE BORN AS A
SOLUTION TO THESE ISSUES
J2EE--14
Server-side Component Architectures
(Role of Application Servers)
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provide the middleware services
allow enterprises buy the services
aid in rapid the application development
Anomalies and problems:
 Vendor specific middleware services
 Once an application sever is chosen the code is
locked to that particular vendor’s solution
 Reduces portability
 Hampers commerce of components
J2EE--15
Server-side Component Architectures
(Need for a standard)
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The standard would describe a well-formed
interface between the application server and the
components themselves
Components could be managed in a portable way
Components could be switched between various
application servers
Component vendors could be relieved of issues
about external overhead such as resource pooling,
networking, security etc.
Necessary elements of enterprise-class
deployments are externalized to application server
vendors, providing common services to all
component developers
J2EE--16
Server-side Component Architectures
(Standards)
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OMG’s CORBA Standard
Sun Microsystem’s J2EE Standard
Microsoft’s .NET Architecture
J2EE--17
Server-side Component Architectures
(Standards – J2EE vs .NET)
Java Client Application
Business System
Web Client
Container
Servlets and JSPs
EJBs
Connectors
Legacy Systems or Databases or Other Business Systems
The J2EE Server-side Architecture
J2EE--18
Server-side Component Architectures
(Standards – J2EE vs .NET)
Business System
Rich Client Application
Web Client
Container
ASP.NET
.Net Managed Components
Host
Integration
Server 2000
Legacy Systems or Databases or Other Business Systems
The .NET Server-side Architecture
J2EE--19
Server-side Component Architectures
(Standards – J2EE vs .NET)
J2EE was found advantageous over .NET:
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a proven platform while .NET is a rewrite of Microsoft’s previous
technologies and introduces risk as with any first-generation
technology
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lets enterprises take advantage of existing hardware they may
have
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gives platform neutrality, including Windows and good portability
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has a better legacy integration through the Java Connector
Architecture (JCA)
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lets the use of any operating system enterprises prefer, such as
Windows, UNIX, or mainframe
J2EE--20
J2EE Platform Overview - Environment
J2EE--21
J2EE Platform Overview Components and Containers
J2EE--22
J2EE--23
J2EE Platform Overview –
Java Servlet Technology(1)
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Mechanism for generating dynamic web content.
They may be thought of as Java applets for
servers.
platform independent, pleasant user interfaces,
better performance due to persistent well-defined
API for flexibility.
J2EE--24
J2EE Platform Overview –
Java Servlet Technology(2)
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Web browser  HTTP request  web server
Web server  gives request to servlet container
gives request to specific servlet
Servlet receives request object.
Servlet processes. (may return a response object)
During process, servlet may use a context object to
save information usable by other servlets, and
read a session object to determine a client state.
J2EE--25
J2EE Platform Overview –
JavaServer Pages(1)
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Utilize Java Servlet technology to simplify well
organized dynamic web content.
JSP pages define the static HTML template, and
embeds invocations to Java code.
Useful and routine operations like embedding
dynamic distributed database queries and
generation of their associated reports.
Hides the complexity of programming in Java
from the page designer
J2EE--26
Enterprise JavaBean Components(1)
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A server-side technology for developing and
deploying components containing the business
logic of an enterprise application.
Allows encapsulation of legacy technologies.
EJB is a client-neutral standard.
J2EE--27
Enterprise JavaBean Components –
Entity Beans
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Represent persistent objects like database entries.
EJB specification indicates that a bean and its
references survive a crash of its container.
(achieved by storing the state in the database or
through serialization)
Container provides a class in order to provide
meta-data to the client.
J2EE--28
Enterprise JavaBean Components Message-Driven Beans
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A basis for constructing loosely coupled
applications capable of communicating indirectly
using the queuing and subscription models
supported by JMS.
More flexible and realistic for heavily congested
networks.
J2EE--29
Enterprise JavaBean Components Session Beans
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Limited lifetime as the name suggests
If stateless won’t preserve state between calls
Saving and restoring state are properties of stateful
session beans
J2EE--30
J2EE Technology Suite
J2EE--31
J2EE Standardized Services
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The containers supporting the J2EE components provide
three types of services :
 Communication
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Enterprise
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RMI-IIOP
Java IDL
JMS
Java Mail
JDBC
JTA
JNDI
JCA
Internet
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HTTP
TCP/IP
SSL
XML
J2EE--32
Communication Services
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JavaIDL, RMI-IIOP
 Allows objects written in Java to to invoke
CORBA objects using IIOP. Provides
interoperability with CORBA objects.
JMS
 API for asynchronous messaging
JavaMail:
 Provides an API for electronic mail
J2EE--33
Enterprise Services
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JDBC
 API for DB independent connectivity between
J2EE and other datasources
JTA
 The transaction API for J2EE which guarantees
transactional integrity
JNDI
 Provides a naming environment, & facilitates
directory operations
JCA
 Mandatory with v.1.3 of J2EE. Helps to
integrate different EJB containers with
different EIS.
J2EE--34
Internet Services
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For access to Internet services, J2EE supports the
following protocols:
 TCP/IP
 HTTP
 SSL
XML
 J2EE v.1.3. supports XML functionality.
J2EE--35
EJB – CORBA INTEROPERABILITY
(Overview)
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how EJB and CORBA complement each other
where EJB gets its edge over CORBA
where CORBA would be still depended on
benefits of EJB / CORBA interoperability
interoperability scenarios
J2EE--36
EJB – CORBA INTEROPERABILITY
(CORBA Overview)
CLIENT
CORBA Object
Implementation
CORBA Object Interface
CORBA Stub
CORBA Skeleton
ORB
ORB
Network via IIOP
CORBA Architecture
J2EE--37
EJB – CORBA INTEROPERABILITY
(CORBA Services)
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COS Naming
CORBA Event Service
Object Transaction Service (OTS)
Concurrency Control Service
Security Service
J2EE--38
EJB – CORBA INTEROPERABILITY
(CORBA)
Advantages:
 not controlled by one organization
 language-independent
Disadvantages:
 Slow-moving
 Steep learning curve
J2EE--39
EJB – CORBA INTEROPERABILITY
(OMG’s CCM Specification)
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adds component features to CORBA objects
similar to EJBs
intention that CORBA components and EJBs
can reside together
a CORBA component could appear as if it
were an EJB
an EJB could appear as if it were a CORBA
component
J2EE--40
EJB – CORBA INTEROPERABILITY
(Why is CORBA important for EJBs?)
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Legacy Integration
Advanced middleware services
EJBs exposed to CORBA clients (the
highlight of this interoperability section)
J2EE--41
EJB – CORBA INTEROPERABILITY
(RMI and IIOP)
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Remote Method Invocation(RMI) is a
communications package for performing
distributed computing in Java
default protocol layer for communication used
by RMI is Java Remote Method
Protocol(JRMP)
CORBA uses Internet Inter-ORB
Protocol(IIOP) as its default protocol layer for
communications
RMI and CORBA are very similar
technologies
J2EE--42
EJB – CORBA INTEROPERABILITY
(RMI and CORBA)
Problems:
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RMI - built specifically for Java and CORBA – built to
allow language interoperability
two technologies are highly incompatible
major portion of a program coded for the RMI API
needs to be rewritten if there is a need to switch to
CORBA and vice versa
prohibits code reuse
Ideal Scenarios:
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Combine client-side Java RMI with server-side
CORBA
Combine client-side CORBA with server-side Java
RMI
Need: bridge between RMI and CORBA
Solution: RMI over IIOP
J2EE--43
EJB – CORBA INTEROPERABILITY
(RMI and CORBA – Ideal Scenarios)
RMI CLIENT
CORBA Object
Implementation
CORBA CLIENT
RMI Remote
CORBA Object
Object Interface
Interface
RMI Object
Implementation
RMI Stub
CORBA Skeleton
CORBA Stub
RMI Skeleton
ORB
ORB
ORB
ORB
Network via IIOP
Scenario #1
Network via IIOP
Scenario #2
J2EE--44
EJB – CORBA INTEROPERABILITY
(RMI over IIOP)
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unification of RMI and CORBA
RMI run over IIOP (instead of JRMP)
delivers CORBA distributed computing capabilities to the
Java2 platform
speeds distributed application development completely in
Java
code reusability of programs coded with the RMI API and
the CORBA API
lessens the impact of switching between the two
technologies
IIOP eases legacy application and platform integration
IIOP makes RMI more robust
J2EE--45
EJB – CORBA INTEROPERABILITY
(RMI over IIOP : Combinations)
CLIENT
SERVER
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RMI client with RMI-IIOP
Stub
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RMI Server with RMI-IIOP
skeleton
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RMI client with RMI-IIOP
Stub
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CORBA object implementation
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CORBA client
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RMI Server with RMI-IIOP
skeleton
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CORBA client
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CORBA object implementation
J2EE--46
EJB – CORBA INTEROPERABILITY
(EJB Specification)
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EJB components must be able to run over both
RMI and RMI-IIOP
RMI-IIOP as an on-the-wire protocol for EJB
components
Advantages to J2EE:
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greatly assist the integration of the J2EE environment into
existing corporate infrastructures, most of which are quite
CORBA intensive
EJBs could be exposed as CORBA components that could
be accessed by non-Java Clients
relieves EJBs off the constraint that they could be only Java
based
J2EE--47
EJB – CORBA INTEROPERABILITY
(Scenarios)
RMI-IIOP
CLIENT
EJB Object
Implementation
CORBA CLIENT
EJB Remote
EJB Remote
Object Interface
Object Interface
EJB Object
Implementation
RMI – IIOP
Stub
RMI-IIOP
Skeleton
CORBA Stub
RMI-IIOP
Skeleton
ORB
ORB
ORB
ORB
Network via IIOP
Scenario #1
Network via IIOP
Scenario #2
J2EE--48
Patterns - Definition
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Definition
 “.. are a collection of J2EE based solutions to
common problems... They extract the core
issues of each problem, offering solutions that
represent an applicable distillation of theory
and practice”.
 “ a recurring solution to a problem in a
context”
Repository of patterns is called the Design Pattern
Catalog
Documented according to a template
Organized in tiers
J2EE--49
Patterns - Tiers
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Presentation Tier
 Contains the patterns related to Servlets and
JSP technology.
Business Tier
 Contains the patterns related to the enterprise
beans technology
Integration Tier
 Contains the patterns related to JMS and JDBC
J2EE--50
J2EE Pattern Relationships
J2EE--51
Presentation Tier
Pattern Name
Brief Synopsis
Decorating Filter
Facilitates pre and post-processing of a request
Front Controller
Provides a centralized controller for managing the
handling of a request
View Helper
Encapsulates logic that is not related to presentation
formatting into Helper components
Composite View
Creates an aggregate View from atomic sub-components
Service to Worker
Combines a Dispatcher component in coordination with
the FrontController and View Helper Patterns.
Dispatcher View
Combines a Dispatcher component in coordination with
the FrontController and View Helper Patterns,
deferring many activities to View processing.
J2EE--52
Business Tier
Business Delegate
Decouples presentation and service tiers, and provides a façade
and proxy interface to the services.
Value Object
Exchanges data between tiers.
Session Facade
Hides business object complexity, centralizes workflow handling.
Aggregate Entity
Represents a best practice for designing coarse-grained entity
beans.
Value Object
Assembler
Builds composite value object from multiple data sources.
Value List Handler
Manages query execution, results caching and result processing.
Service Locater
Hides complexity of business service lookup and creation, locates
business service factories.
J2EE--53
Integration Tier
Data Access Object
Abstracts data sources, provides transparent access to data.
Service Activator
Facilitates asynchronous processing for EJB components.
J2EE--54
Use of Patterns in DMV App
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The following patterns were used in the DMV
Application:
 Front Controller
 View Helper
 Session Façade
 Transfer Object
 Transfer Object Assembler
 Data Access Object
J2EE--55
Application Prototype
(Overview)
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JBuilder7 Enterprise
JDataStore
BES 5
MS VC++ 5.0 (for non-Java Client)
MVC architecture
CONTROLLER
(SERVLET & HANDLER)
VIEW
(JSPs & HELPER)
MODEL
(EJBs & Domain classes)
J2EE--56
Application Prototype
Use Case Diagram
J2EE--57
Application Prototype
Deployment Diagram
J2EE--58
Application Prototype
EJBs in the DMV Application
J2EE--59
Application Prototype
Class Diagram
J2EE--60
Application Prototype
Application Flow and Patterns(1)
This flow is followed by the Login, Registration
and License Modules
J2EE--61
Application Prototype
Application Flow and Patterns(2)
This flow is followed by the Report Module
J2EE--62
Application Prototype
EJB exposed to non-Java Clients
Non-Java Client
(C++ Application)
TrafficViolation Application
Looks up the SB as a CORBA component
TrafficViolationSB
(Session Bean)
DMV Application
Finds the License and increments its points
LicenseEB
(Entity Bean)
Updates the database
DMV Database
J2EE--63
Application Prototype
EJB exposed to non-Java Clients
J2EE--64
Application Prototype
Screen shots(1)
J2EE--65
Application Prototype
Screen shots(2)
J2EE--66