Component-Based Software Engineering

ECE493-Topic 5Winter 2007

Lecture 23– Java Enterprise(Part A)

Ladan TahvildariLadan TahvildariAssistant ProfessorAssistant Professor

Dept. of Elect. & Comp. Eng.Dept. of Elect. & Comp. Eng.University of WaterlooUniversity of Waterloo

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Abstract views(PIM,Written in UML)

Domain-specific Models(PSM,Written in UML with extra notation)

Implementations

From Abstractions to Implementations

Abstract systemarchitecture

EnterpriseMiddlewareArchitecture

OO:simple

Java: EJB,

JMS, JSP

.NET: COM+,ASP

Safety CriticalArchitecture

C

EmbeddedSystem

Architecture

CORBA

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Java Enterprise Services

Sun Microsystems provides specifications for a comprehensive suite of technologies to solve large scale distributed system problems

This suite is the Java 2 Enterprise Edition, commonly known as J2EE which offers a suite of software specification to:– Design, develop, assemble and deploy enterprise applications

Discuss the architecture of J2EE and how it can be used to develop distributed multi-tiered applications

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J2EE Technology Architecture

Serverplatform JTS JMAPI JNDI JMS JDBCJAXP JAAS …

Enterprise Java Beans Components

Java Serverpages Servlets

Application clients Web clients

IIOP,others

html

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J2EE SuiteXML Technology– The Java API for XML Processing (JAXP)– The Java API for XML-based RPC (JAX-RPC)– SOAP with Attachments API for Java (JAAS)– The Java API for XML Registries (JAXR)

Web Technology– Java Servlets– JavaServer Pages (JSP)

Enterprise Java Bean (EJB) Technology– Session beans– Entity beans– Message-driven beans

Platform Services– Transactions– Java Message Service

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J2EE-Based Application

The J2EE APIs enable distributed systems and applications through the following: – Unified application model across tiers with enterprise beans

– Simplified response and request mechanism with JSP pages and servlets

– Reliable security model with JAAS

– XML-based data interchange integration with JAXP

– Simplified interoperability with the J2EE Connector Architecture

– Easy database connectivity with the JDBC API

– Enterprise application integration with message-driven beans and JMS, JTA, and JNDI

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Enterprise Application Model

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Distributed Multi-tiered ApplicationsServices, clients (people and application) and data are distributed geographically across many platforms and many machines.

Multiple tiers:– Client-tier (browser or client-application)– Web-tier (web-server: Java Server Pages)– Business-tier (logic; Examples: Enterprise Java Beans)– Enterprise-Information-System (EIS) tier (database)

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J2EE Clients

Web Clients– Dynamic web pages with HTML, rendered by web browsers– Can include applets– Communicates with server typically using HTTP

Application Clients– User interface using GUI components such as Swing – Directly accesses the business logic tier

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Web-tier ComponentsClient can communicate with the business tier either directly or through servlets of JSP that are located in the web-tier

Web-tier can help in pre-processing and allows distribution of the functionality

Servlets are special classes to realize the request-response model (get, post of HTTP)

JSP is a developer-friendly wrapper over the servlet classes

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Business-tier Components

This is defined by the logic that pertains to the (business) application that is being developed

Enterprise Java Beans (EJB) can be used to implement this tier

This tier receives the data from the web-tier and processes the data and sends it to the EIS-tier and takes the data from the EIS and sends it to the web-tier

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Enterprise Information System Tier

In general this corresponds to the database (relational database) and other information management system

The other information management systems may include Enterprise Resource Planning (ERP) and legacy system connected through open database connectivity

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Enterprise Java Beans

Enterprise Java Beans ( EJB ) is – a middleware component model for Java – a specification for creating server-side, scalable,

transactional, multi-user and secure enterprise-level applications

Presented by Sun in the 1999, they are easier than other technologies as RMI or CORBA

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Application Server - Architecture

Presentation• HTML Application • Java Application

Business Logic

Data Access

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J2EE Application ServerJava 2 Enterprise Edition standardizes interfaces for Application Server components

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Java versus .NET for the Enterprise

Activation/Passivate (on stateful beans)JIT ActivationJava Server Page (JSP) ASP.NET

Instance PoolingObject Pooling

Can be implemented through JMSQueued Components

Java Message Service (JMS)Loosely Coupled Events

Java Transaction Service (JTS)Transactions

EJBSession Beans (Stateless, Stateful)Entity Beans Message-Driven Beans

COM+ ComponentsJava.NET