Programming PDF – Java EE

Java EE

Web Applications / Web Systems

Juan Pavón Mestras
Dep. Software Engineering and Artificial Intelligence
School of Computing
Universidad Complutense Madrid

Creative Commons

Java EE

 Java Platform, Enterprise Edition (Java EE)

 Web Applications built based on components:

 Application clients and applets (on the client)
 Java Servlet, JavaServer Faces (JSF), and JavaServer Pages (JSP) (on

the server)

 Enterprise JavaBeans (EJB) (or enterprise beans) (on the server)

 Components are deployed and executed in specialized containers

 Container examples:

• Applet container in a browser Web
• Tomcat Web Container
• EJB Container

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Java EE – Component Containers

Figure from The Java EE 6 Tutorial (2013). Java EE Containers
http://bit.ly/2SiDaU8

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Components vs. objects

 A component is characterized by:

 Being an independent deployment unit

• Encapsulates its constituent characteristics with respect to its environment
• Third parties can not access the construction details of [19659002] component

• Not partially implanted

 Be a composition unit

• With components possibly developed by others
• Must be sufficiently self-contained
• Clear specifications of what is required and of what it provides

• Interacts with its environment through well-defined interfaces

 Not having persistent status

• A component is indistinguishable from other copies of it

• Except non-functional attributes such as the serial number

• Therefore, in a process we can say whether or not there is a component,

but not several instances of it

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Components vs. objects

 An object is characterized by:

 Being an instantiation unit; they have a unique identity

• They are not partially instantiated
• The identity is unique and does not change during the life of the object

 Having a state

• It is created with an initial state that evolves during execution

 Encapsulate its state and behavior

• Which is defined either by a class or by a prototype object

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Interfaces

 Points Access to components

 Allows clients to access services provided by a

component

 One component can have multiple interfaces

 One for each access point: use, administration, configuration , …
 But it is not convenient to have several similar or redundant interfaces

 The specification of the interfaces is a contract

 The respect of this contract per client and component ensures the success

of the interaction ion

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Containers

 A container is a process where the components are executed

 Manages the components of the application

• Lifecycle

 Provides access to platform services

• Security, transactions, persistence, connectivity, etc.

 The developer has to specify

 The components of the application

• Servlets
• JSPs (JavaServer Pages)
• JSFs (JavaServer Faces)
• EJBs (Enterprise Java Beans)

 Deployment descriptors (19659002) • Files XML describing the application components

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Architecture of a container

Contract of the component

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Components
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] Descriptor of
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Application components

Descriptor of
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Application components

Descriptor of
display

APIs Services container

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Container of applets

class java.applet.Applet

MiApplet

Descriptor of
display

Methods to access other APIs, eg play (url)

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Java EE – Multi-level architecture (multi-tier)

 This model promotes web applications in 4 levels:

machine
client

Level
client

Pages (X) HTML,
applets, JS, CSS

server
Java EE

Level
web

Level
business

JSP or
] servlets

EJBs

server

BD

Level

system of
information

Database

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Web Components in Java EE

 Java Servlets

 Classes written in Java that process HTTP requests and build

responses



JavaServer Pages (JSP)
 Documents text-based containing two types of text

• a static data template that can be expressed in a format

as (X) HTML or XML

• elements JSP that determine how the page builds

dynamic content

 JavaServer Faces (JSF)

 UI components for web applications

 Clients in Java EE are

 Web Clients : web browsers, web pages, applets
 Client applications

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Web container

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Java Servlet APIs and JSPs

MiServlet

Descriptor of
deployment

MiJSP

Descriptor of
deployment

Access to remote services

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Business components in Java EE

 Logic that solves the needs of a certain domain

of application

 Enterprise beans (EJBs)

 They can process data received from the client side and send them to the level of [19659002] information system for storage

 Can retrieve information from the information system, process it and

send it to the customer

 Types of EJBs

 Session bean

• A conversation with a client

 Message driven Bean

• Allows a business component to receive messages

asynchronously, usually with the Java Message Service (JMS) [19659002] Juan Pavón – UCM 2012-13

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EJBs container

javax.ejb.EJBHome, javax.ejb.EJBObject
javax.ejb.SessionBean or javax.ejb. EntityBean

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MiEntityBean

Descriptor of
deployment

MiMessageBean

Descriptor of
deployment

MiSessionBean

Descriptor of
deployment

Access to remote services

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Java EE Services

 Each Java EE container provides services to the

components
 Java Naming Direct Interface (JNDI)
 Java Persistence API (JPA)
]  Java Database Connectivity API (JDBC)
 Java Transaction API (JTA)
 Java Message Service (JMS)
 JavaMail
 Java Beans Active Framework (JAF)
 Java EE Connector Architecture
 Java Authentication and Authorization Service (JAAS)
 Java API for XML Processing (JAXP)
 SOAP with Attachments API for Java (SAAJ)
 Web Services (JAX-WS )
 Java API for RESTful Web Service s (JAX-RS)

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Assembling and deploying Java EE components

 The components are installed in containers from which

can use the services of the platform

 The assembly process of the components requires

specify the support of the J2EE server
 Security: authorized users
 Transaction management model: relationships between methods that

constitute a transaction (treated as a unit)

 Java Naming and Directory Interface (JNDI): access to services from

names and directory

 Remote connectivity: allows clients to invoke methods in [19659002] the EJBs as if they were in the same virtual machine

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Composition of modules in applications

 A Java EE application can be delivered as files :

 Java Archive (JAR)
 Web Archive (WAR) file
 Enterprise Archive (EAR)

• Java EE Modules
• Deployment Descriptor (XML document with extension .xml )

.jar

.class files

from EJBs

.war

.class files
from servlets,
other classes
Java, HTML,
images

.rar

Resource adapter
archive: classes and
native code for

connector to EIS

.jar

Java application

Figure 1-6 EAR File Structure, of The Java EE 6 Tutorial (2013).
http://bit.ly/2SiDaU8

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Life cycle of a Java EE application

Source: Sun Microsystems, Inc., J2EE Connector Architecture Specification

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Frameworks Java EE

 Apache S truts
 Spring
 JBoss Seam
 GWT (Google Web Toolkit)

 Java applications based on Ajax

 Stripes, Tapestry, Wicket, Maverick, etc.

 See http://bit.ly/2Acnfja

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Bibliography

 Eric Jendrock et al. The Java EE 6 Tutorial (2013).

http://bit.ly/zyLQ2F

 Official documentation
 Java EE Specifications

http://bit.ly/1jYQ2rU /javaee/tech/index.html

 API specification for version 6 of Java EE

http://bit.ly/1pho3Hx

 API specification for GlassFish Server, including Java EE 6 platform

packages and nonplatform packages that are specific to the GlassFish
Server product
http://bit.ly/2AcerKi

 J2EE is more efficient than PHP:
http://bit.ly/2SmWekt

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