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1. Explain J2EE architecture.
The JEE platform provides the environment to develop enterprise applications / services using
multitier architecture. The highly intensified technology made the need for scalable, efficient, faster
solutions for information management. The JEE technology is rightly apt for meeting these
requirements. JEE provides a programming development environment which improves the
productivity of development, standards for hosting / deploying enterprise applications.
The following are the tiers in JEE application
Client Tier: The client tier includes the web components such as Servlets, JSP or standalone Java
Desktop applications. This tier provides dynamic interfaces to the middle tier.
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Middle Tier: This also called as the server tier. In the middle tier enterprise beans and web
services encapsulate distributable business logic for the applications which are reusable. The
JEE application server contains the server-tier components which provides the platform for
these web components for actions to be performed and data to be stored / persisted.
Enterprise data tier: The enterprise level data is stored / persisted preferably or typically in
a relational database, in this tier.
The JEE applications comprises of components, containers and services. All the web components
(Servlets, JSP) provide dynamic requests and responses from a web page. The EJB components
contain the server-side business logic for enterprise applications.
2. J2EE is a container centric architecture. Explain.
A container acts as an interface between a platform-specific functionality and a component. The
component must be assembled before a web or enterprise bean or application client component
execution, into a JEE application and deployed into its container.
The settings of a container can be customized for underlying support provided by the JEE server.
These include security, transaction management, and Java Naming and Directory Interface lookups.
The management of non-configurable services such as servlet life cycle, enterprise bean life cycle,
database connection, data persistence, database connection pooling also can be done by the
container.
3. Explain the four types of container that the J2EE specification defines.
A container is a runtime support of a system level entity [Applet, Servlet/JSP, EJB]
The four types of container that the J2EE specification defines are applet container, application-client
container, web container and EJB container.
Applet Container : An applet is a java program that can be embedded into a web page.
Most of the web pages are authored in HTML. To use an applet in HTML document , the
tags <APPLET> and </APPLET> are used. They are used to indicate to the browser that a java
applet should be loaded. “These tags act as a container for the java applet definition. “ Applet
container manages the execution of applet, and contains the web browser.
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Application-client Container : The Application Client Container (ACC) is a combination of Java
classes, libraries, and other files. They are used to distribute along with Java client programs that
execute on their own JVM. The execution of the application client components is managed by the
application-client container. The ACC can take the responsibility to collect user name and password
which is treated as authentication data.
Web Container : A web container is a part of web server. It provides the run time environment to
execute a web application such as a servlet, JSP. A servlet container translates the URL requests into
servlet requests. The JSP implicit objects such as request, response, out, page, pageContext etc., are
exposed by JSP container.
EJB Container : The EJB container, like other containers provides run-time environment to execute
EJB components such as enterprise beans. An EJB Container manages transactions, state
management details, multi-threading, connection pooling. The applications are provided with
security using EJB container. All database access required by the entity bean will be handled by the
EJB container.
4. Explain the J2EE container architecture.
J2EE Container Architecture:
The J2EE application component needs support at runtime. This support is provided by J2EE
containers. They use protocols, methods of the containers to access other application components.
The containers of J2EE are 1) Web container 2) EJB container.
1) The web container is used to host web applications. It provides the run time environment to
execute Servlet and JSP component types.
2) The business logic is dealt by the server components called EJB components. The access to local
and remote enterprise beans is provided by the EJB container. The operations of the three beans
namely Entity Bean, Session Bean and Message-driven bean are handled by the EJB Container.
5. Explain the technologies that J2EE platform provides for developing components.
1) Servlet Technology: It is considered as the foundation of web technologies. It overcomes the
limitations of CGI technology. It is a server side component to serve the clients and to generate
dynamic content. Servlets interacts with web clients using the paradigm ‘request-response’. All client
requests are sent through web servers to the servlet container. The servelt then process the request
and sends the response back to the client. Servlets are reliable, scalable, efficient and reusable server
side components.
2) JSP Technology: It is the extension of servlet technology. It is easy to author JSP without much
knowledge of the supporting API. JSP can be used to work with HTTP requests and HTTP
responses, session management and so on. It is easy to combine both static and dynamic content with
JSP. The factor to develop JSP technology is to use regular HTML tags. The JSP author can place
servlet or simple java code in the page by using special designated tags. The entire JSP will be
translated into Servlet and the servlet related code is communicated to container to run.
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3) EJB Technology: EJB is a server-side web component. It depends on other Java technologies for
proper functionality such as Remote Method Invocation. RMI is used as a protocol between 2
enterprise beans and between an enterprise bean and its client. EJB encapsulates the business logic.
All EJBs are developed, deployed and run only in an EJB container. This is similar to servlets and
JSP run in a web container.
EJB applications are easy to develop because the applications developer can concentrate on business
logic. The developer can utilize the services provided by the EJB container, like connection pooling
and transactions.
6. Explain the J2EE APIs, i.e. RMI/IIOP, JNDI, JDBC, Java Mail and JMS.
RMI/IIOP: RMI stands for Remote Method Invocation. IIOP stands for Inter Internet-ORB
Protocol. ORB
RMI/IIOP API is used to write distributed objects using Java technology, which enables
communication between objects in the memory, across JVM and also physical devices.
RMI/IIOP yields the benefits of OOP such as inheritance, polymorphism and encapsulation and is
platform independent. In RMI/IIOP, the code related to network is written by applying the interface
but not the implementations. The operation can solely on the interface that object’s class.
RMI-IIOP relies on object serialization for passing parameters via remote method invocations.
JNDI ( Java Naming and Directory Interface) API : To enable java programs to access the
naming and directory services, the JNDI API is utilized. Naming services emphasizes on the services
that are to associate names with objects.
We are familiar with naming systems such as the file system which has a directory or path associated
it. Surfing web is associated a name that is the URL called Domain Naming System. EJB
components of a J2EE application server, user profiles are associated in LDAP (Lightweight
Directory Access Protocol) directory.
For example, JNDI is the best API to write a java application that is used for search utility over
network-enabled desktop, class-browser or an address book search utility.
JDBC (Java Database Connectivity) API:Many java applications use a database and database
accessing and programming is a significant role in web application development. JDBC is an API
that enables the accessibility to a database in order to manipulate the database.
The JDBC API supports both two-tier and three-tier models for database access.
Two-tier model -- a Java application interacts directly with the database.
Three-tier model -- introduces a middle-level server for execution of business logic: the middle tier
to maintain control over data access.
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The application that uses the JDBC implements the following sequence.
1. Importing Packages
2. Registering the JDBC Drivers
3.Opening a Connection to a Database
4.Creating a Statement Object
5. Executing a query and Returning a Result Set Object
6. Processing the Result Set
7. Closing the Result Set and Statement Objects
8. Closing the Connection
Java Mail API: Mailing and Messaging applications can be modeled or developed using Java Mail.
The e-mail messaging applications can be developed for both high-level implementation and lowlevel implementation. That is, a small company which is heading towards growth can develop
solutions which ensure the accessing to their mail server in an efficient manner. A blue-chip
company can focus on providing the access to industry-level access which is a wider reach and
provides vast support.
JMS: Java Message Services is an API that enables the components of an application, could it be
JSE or JEE component to provide messaging services such as create, send, receive and read
messages. Using the loosely coupled, reliable and asynchronous communications are enabled by
JMS.
The JMS application contains the following parts:
1.JMS Provider : It implements the JMS interface and provides the administration and control
services for the messages. J2EE 1.3 includes the JMS Provider service.
2.JMS Clients : These are the java applications that produces or consumes the messages.
3. Messages : These are the objects that communicate the messages between clients.
4. Administered Objects : They are the JMS objects created by the administrator that can be used by
the clients. They are namely destinations and connection factories.
5. Native Clients :These are the applications that use message client’s native client API instead of
JMS API.
7. What are the 3 different Java platform editions? Explain them.
Java 2 Platform, Standard Edition (J2SE)
Java 2 Platform, Enterprise Edition (J2EE)
Java 2 Platform, MicroEdition (J2ME)
Java 2 Platform, Standard Edition (JSE): J2SE is used to develop stand alone / desktop portable
java applications. J2SE consists of two components. Core component and desktop component. Core
component provides back end functionality. Desktop component provides GUI functionality. J2SE
consists of Java Development Kit and Java Runtime Environment. JDK consists of java compiler and
other related tools to enable the users to create Java Applications. Java Runtime Environment
consists of java virtual machine, libraries and all other components that are necessary to run a java
application.
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Java 2 Platform, Enterprise Edition (JEE): J2EE is a platform to develop multi-tier enterprise
applications. JEE includes Servlets API, Java Server Pages and Enterprise Java Beans. It was built on
J2SE technology.
Java 2 Platform, Micro Edition (JME): JME is the technology for micro electronic devices like
PDAs, Mobile phones etc. JME supports the flexibility for user interfaces, provides the security and
uses the built-in network protocols for networked applications.JME applications can be ported across
different devices.
8. Provide an overview of web container.
The web container is used to implement the web components functionality. The functionality
specifies an environment, called as runtime environment which the web components security,
deployment, life-cycle management transaction management, request-response services. A container
manages the servlet / JSP/ EJB functionality. J2EE server runs the components and the containers. A
web container will also manage the database connection pooling, data persistence and access to the
J2EE API.
9. Explain the Java Servlet programming model.
The servlets are server side components in a web application. These components platform
independent and on any server as the java technology is platform independence. The servlets are
dynamically loaded by the JRE of servlets. When a request is received from a client the web
container / web server will ignite the servlet. The servlet processes the request the sends the response
back to the container / web server which in turn sends the response back to the client.
10. Describe in brief about deployment descriptors.
A deployment descriptor describes the configuration information to deploy a web application. For a
web application, it directs the deployment tool that is to deploy a module for a specific container
such as ejb container / servlet/jsp container. For web applications the deployment descriptor is
web.xml and must be placed in a WEB-INF directory of a web application root directory. For EE
deployment descriptor the name should be application.xml and must be placed in a META-INF
directory at the top level of the application .ear file.
11. Explain the J2EE container architecture.
J2EE Container Architecture:
The J2EE application components needs support at runtime. This support is provided by J2EE
containers. They use protocols, methods of the containers to access other application components.
The containers of J2EE are 1) Web container 2) EJB container.
1) The web container is used to host web applications. It provides the run time environment to
execute Servlet and JSP component types.
2) The business logic is dealt by the server components called EJB components. The access to local
and remote enterprise beans is provided by the EJB container. The operations of the three beans
namely Entity Bean, Session Bean and Message-driven bean are handled by the EJB Container.
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12. Explain the components of J2EE architecture, i.e. Application components, containers
and J2EE APIs
J2EE Components:
Application components:
Every JEE application is made up of different components. A component can be defined as software
that is self-contained functionality that is a part of JEE application related in terms of classes, files
and perform communication with other components. The JEE components are
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Applets, Application clients are client components
Servlets and JSP technologies are referred as web components
The EJB components that comprise enterprise beans are referred as business components.
JEE components are authored using java programming language and compiled just like a simple java
desktop applications. JEE components are deployed according to the production requirement and
managed by the JEE server.
JEE containers:
All JEE components are installed in the respective containers while deploying the web applications.
All the components are supposed to be assembled into a JEE application and then deployed in the
respective container, before the execution of a web, an enterprise bean or even application client
component execution.
Container Types
The deployment process is container specific.
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An EJB container manages the execution of all enterprise beans for a specific JEE
application. The enterprise beans and their container will be run on JEE server.
A web container is responsible for the execution of all servlets components and JSP for a
specific JEE web application. These web components and the corresponding container will be
run on JEE server.
The execution of all application client components for a JEE applications is managed /
executed by an application client container. The application clients and their applications run
on the client machines.
A container by name applet container is a web browser. The applet container along with Java
plug-in combination runs on the client machine.
JEE API:
In order to run all the JEE SDK for web applications, the JSE SDK is needed. The JSE SDK
provides the entire required core API for writing JEE components and the JVM. The following are
the JEE APIs that are to be used in JEE applications.
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EJB API - This API enables the fast, simplified distributed application development at
enterprise level.
JDBC API – Enables the relational database accessibility for java applications
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Servlet API – Provides simple consistent mechanism to manage the application at web server
level.
JSP API - Provides simple and fastest dynamic web page development
JMS API – Provides the mechanism for simple messaging services
Java Transaction API – An interface between transaction manager and the others involved in
distributed transaction system.
Java Mail API – Provides platform and protocol independent mailing services
13. Explain the Java Servlets. Explain its lifecycle.
A servlet is a java class that provides a powerful mechanism for developing server side application
programs. It provides the component-based, platform-independent methods for building any web
based applications by overcoming the performance limitations of CGI programs. A servlet
application can run on any servlet enabled web container. It runs completely in a JVM. Browser
compatibility is not an issue as the servlet run at the server side. The set of HTML-based calls can
also be accessed by the servlets. For interactive web applications, servlets is the right choice.
Servlet life cycle:
The servlet life cycle includes four stages:
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Loading and Instantiation : The servlet container loads the servlet during and startup of a
web application and or when the first request is made. The container creates the servlet
instances after loading the servlet .
Initialization: Soon after the creation of the instance of a servlet, the container invokes the
init() method and passes the servelt’s the initialization information to the init() method. The
init() must be called by the servelt container before performing any requests by the servlet.
Responding for the requests: Once the initialization is properly done, the servlet is ready to
service the requests. The servlet creates separate threads for each and every request. The
servlet container invokes the service() method which in turn invokes the appropriate doGet()
or doPost() methods for handling the requests and sending responses to the client using
response objects.
Destroying the servlet: If the servlet is not needed for processing the requests, the destroy()
method will be invoked by the container. This method also invoked only once through out the
life cycle of a servlet. Invoking the destroy() method indicates the servlet container not to
send any requests for the service and the servlet will release the resources that are associated
with it. JVM will claim the memory with the resources for garbage collections.
14. Explain JSP. Describe JSP lifecycle.
Java Server Pages (JSP): A JSP is used for the development of dynamic web pages. JSP provides the
server side scripting support for creating web applications that uses database. JSP encourages the
developers to directly insert the java code into .jsp file. This process is very simple to develop and
maintain.
JSP are loaded into the web servers’ memory as soon as receiving the request in the very first time.
The subsequent calls are served within a very short span of time. The usage of JSP in combination
with JDBC is very easy to efficient to develop the database specific applications. JSP are platform
independence as java is and any JSPage can be ported to any platform.
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JSP Life Cycle:
JSP services the requests from clients as that of a servlet. At the time of the JSP request mapping, the
request is handled by a special servlet. This servlet first checks whether the first JSP servlet is older
than the JSP. If it is so, the translation of JSP into servlet class and compilation of this class is done.
And then the request is handled by the servlet like an ordinary servlet.
15. Explain the following java graphical interface framework.
Abstract windows toolkit (AWT)
Swing
Standard widget toolkit (SWT)
Abstract Windows Toolkit (AWT):
AWT provides the interface between the user and different windowing toolkits, such as buttons,
checkboxes, radio buttons and menus etc. AWT establishes the connection between java applications
and the Graphical User Interface. It is adequate to develop many applications. For example, the
menus on the TV sets and other remote controls were developed using AWT (may be with Swings).
AWT uses the basic GUI operating systems controls. AWT is a part of Java Foundation
Classes(JFC).
Swing:
A Swing toolkit includes much more rich set of GUI tools compared to AWT. Few more high-level
component sets are available in Swing such as (tree view, list boxes, tabbed panes, pop up windows,
tooltips, icons). To leverage cross-platform capabilities, Swing supports more similar look and feel
of the components. Swing is more flexible the all swing components are light weight, thereby
reduces the loading time.
Standard Widget Toolkit (SWT):
SWT is an open source widget tool kit for developing rich, efficient and portable GUI applications. It
was originally developed by IBM and being maintained by Eclipse Foundation along with Eclipse
IDE. It is an alternative to AWT and Swing. To display the elements, it implements the operating
system GUI libraries by using Java Native Interface. The SWT applications are portable and unique
for each platform.
The need of SWT is to provide a common API for accessing different operating system / platform
specific widgets. The goal for designing of SWT is high performance, native OS look and feel, and
platform integration. Swing on the other hand, designed to allow for a highly customizable look and
feel that is common across different platforms.
16. List out components by AWT? Explain each in brief.
•Button
•Canvas
•Choice
•Checkbox
•Container
-Panel
-Scrollpane
-Windows
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•Label
•List
•Scrollbar
•TextComponent
-TextArea
-TextField
Button: A component that is used to display the command button on the canvas. By clicking on the
button, an action is performed
Canvas: A blank rectangular area on the screen on which an application can draw other components
or on which an action can be trapped.
Choice: A component that pop ups a menu of choices and the current choice is displayed as the title
of the menu.
Checkbox: A component that represents a check box that represents either true or false state. If the
option is true, then a tick mark appears in the box.
Container: A component that can contain another set of components. All these components are
tracked in a list.
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Panel: It is one of the simplest container classes. A panel provides space to place other
components including other panels.
Scrollpane: A container which implements the scrolling that can be horizontal or vertical for
a child component.
Windows: Represents a top level window that has no borders and no menubar. A window
must have a frame, a dialog box or another window as its owner window.
Label: A component to place text in a container that is displayed as read only text containing a single
line
List: A component that specifies a list of items of text with a provision for the user to select a single
or multiple items.
Scrollbar: A component that is used basically for moving the visible area, where the components /
contents are not enough to appear in a single screen page.
Text Components:
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TextArea: A component where multiple lines of text can be typed / visible. It can make to
appear as read-only area or to appear for editing.
TextField: A component where a single line of text can be typed / visible.
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17. Packaging J2EE Components
J2EE components are packaged separately and bundled into a J2EE application for deployment. Each
component, its related files such as GIF and HTML files or server-side utility classes, and a
deployment descriptor are assembled into a module and added to the J2EE application.
A J2EE application is composed of one or more enterprise bean, Web, or application client
component modules. The final enterprise solution can use one J2EE application or be made up of
two or more J2EE applications, depending on design requirements.
A J2EE application and each of its modules has its own deployment descriptor. A deployment
descriptor is an XML document with an .xml extension that describes a component's deployment
settings. An enterprise bean module deployment descriptor, for example, declares transaction
attributes and security authorizations for an enterprise bean. Because deployment descriptor
information is declarative, it can be changed without modifying the bean source code. At run time,
the J2EE server reads the deployment descriptor and acts upon the component accordingly.
A J2EE application with all of its modules is delivered in an Enterprise Archive (EAR) file. An EAR
file is a standard Java Archive (JAR) file with an .ear extension. In the GUI version of the J2EE
SDK application deployment tool, you create an EAR file first and add JAR and Web Archive
(WAR) files to the EAR. If you use the command line packager tools, however, you create the JAR
and WAR files first and then creates the EAR.
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Each EJB JAR file contains a deployment descriptor, the enterprise bean files, and
related files.
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Each application client JAR file contains a deployment descriptor, the class files for
the application client, and related files.
·
Each WAR file contains a deployment descriptor, the Web component files, and
related resources.
Using modules and EAR files makes it possible to assemble a number of different J2EE applications
using some of the same components. No extra coding is needed; it is just a matter of assembling
various J2EE modules into J2EE EAR files.
18. Overview of Assembly (Packaging) and Deployment
Application assembly (also known as packaging) is the process of combining discrete components of
an application into a single unit that can be deployed to a J2EE-compliant application server. A
package can be classified either as a module or as a full-fledged application.
Modules
A J2EE module is a collection of one or more J2EE components of the same container type (for
example, web or EJB) with deployment descriptors of that type. One descriptor is J2EE standard, the
other is Sun Java System Application Server specific. Types of J2EE modules are as follows:
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
Web Application Archive (WAR): A web application is a collection of servlets, HTML
pages, classes, and other resources that can be bundled and deployed to several J2EE
application servers. A WAR file can consist of the following items: servlets, JSPs, JSP tag
libraries, utility classes, static pages, client-side applets, beans, bean classes, and deployment
descriptors (web.xml and optionally sun-web.xml).

EJB JAR File: The EJB JAR file is the standard format for assembling enterprise beans. This
file contains the bean classes (home, remote, local, and implementation), all of the utility
classes, and the deployment descriptors (ejb-jar.xml and sun-ejb-jar.xml). If the EJB
component is an entity bean with container managed persistence, a .dbschema file and a CMP
mapping descriptor, sun-cmp-mapping.xml, must be included as well.

Application Client Container JAR File: An ACC client is a Sun Java System Application
Server specific type of J2EE client. An ACC client supports the standard J2EE Application
Client specifications, and in addition, supports direct access to the Sun Java System
Application Server. Its deployment descriptors are application-client.xml and sunapplication-client.xml.

Resource RAR File: RAR files apply to J2EE CA connectors. A connector module is like a
device driver. It is a portable way of allowing EJB components to access a foreign enterprise
system. Each Sun Java System Application Server connector has a J2EE XML file, ra.xml.
Figure Module Assembly and Deployment
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Applications
A J2EE application is a logical collection of one or more J2EE modules tied together by application
deployment descriptors. Components can be assembled at either the module or the application level.
Components can also be deployed at either the module or the application level.
The following diagram illustrates how components are assembled into modules and then assembled
into a Sun Java System Application Server application EAR file ready for deployment.
Figure: Application Assembly and Deployment
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Each module has a Sun Java System Application Server deployment descriptor and a J2EE
deployment descriptor. The Sun Java System Application Server Administration Console uses the
deployment descriptors to deploy the application components and to register the resources with the
Sun Java System Application Server.
An application consists of one or more modules, an optional Sun Java System Application Server
deployment descriptor, and a required J2EE application deployment descriptor. All items are
assembled, using the Java ARchive (.jar) file format, into one file with an extension of .ear.
J2EE Standard Descriptors
The J2EE platform provides assembly and deployment facilities. These facilities use WAR, JAR, and
EAR files as standard packages for components and applications, and XML-based deployment
descriptors for customizing parameters.
J2EE standard deployment descriptors are described in the J2EE specification, v1.4.
The following table shows where to find more information about J2EE standard deployment
descriptors.
Table : J2EE Standard Descriptors
Deployment
Descriptor
Where to Find More Information
application.xml
Java 2 Platform Enterprise Edition Specification, v1.4, “Application Assembly
and Deployment - J2EE:application XML DTD”
web.xml
Java Servlet Specification, v2.3 , “Deployment Descriptor,” and JavaServer
Pages Specification, v1.2, “JSP Pages as XML Documents,” and “Tag
Extensions”
ejb-jar.xml
Enterprise JavaBeans Specification, v2.1, “Deployment Descriptor”
applicationclient.xml
Java 2 Platform Enterprise Edition Specification, v1.4, “Application Clients J2EE:application-client XML DTD”
ra.xml
Java 2 Enterprise Edition, J2EE Connector Architecture Specification, v1.0,
“Packaging and Deployment.”
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Runtime Environments
Whether you deploy an individual module or an application, deployment affects both the file system
and the server configuration. See the following Module runtime environment and Application
runtime environment figures.
Module Runtime Environment
The following figure illustrates the environment for individually deployed module-based
deployment.
Figure: Module runtime environment
For file system entries, modules are extracted as follows:
domain_dir/applications/j2ee-modules/module_name
domain_dir/generated/ejb/j2ee-modules/module_name
domain_dir/generated/jsp/j2ee-modules/module_name
The applications directory contains the directory structures described in Directory Structure. The
generated/ejb directory contains the stubs and ties that an ACC client needs to access the module; the
generated/jsp directory contains compiled JSPs.
Lifecycle modules (see Chapter 10, "Developing Lifecycle Listeners") are extracted as follows:
domain_dir/applications/lifecycle-modules/module_name
Configuration entries are added in the domain.xml file as follows:
<server>
<applications>
<type-module>
...module configuration...
</type-module>
</applications>
</server>
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The type of the module in domain.xml can be lifecycle, ejb, web, or connector. For details about
domain.xml, see the Sun Java System Application Server Reference.
Application Runtime Environment
The following figure illustrates the environment for application-based deployment.
Figure: Application runtime environment
For file system entries, applications are extracted as follows:
domain_dir/applications/j2ee-apps/app_name
domain_dir/generated/ejb/j2ee-apps/app_name
domain_dir/generated/jsp/j2ee-apps/app_name
The applications directory contains the directory structures described in Directory Structure. The
generated/ejb directory contains the stubs and ties that an ACC client needs to access the module; the
generated/jsp directory contains compiled JSPs.
Configuration entries are added in the domain.xml file as follows:
<server>
<applications>
<j2ee-application>
...application configuration...
</j2ee-application>
</applications>
</server>
For details about domain.xml, see the Sun Java System Application Server Reference.
Classloaders
Understanding Sun Java System Application Server classloaders can help you determine where and
how you can position supporting JAR and resource files for your modules and applications.
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7133-SNSCE
MC7501 WEB APPLICATION DEVELOPMENT2&6 MARK’S QUESTION BANK
In a Java Virtual Machine (JVM), the classloaders dynamically load a specific java class file needed
for resolving a dependency. For example, when an instance of java.util.Enumeration needs to be
created, one of the classloaders loads the relevant class into the environment.
The Classloader Hierarchy
Classloaders in the Sun Java System Application Server runtime follow a hierarchy that is illustrated
in the following figure.
Figure: Classloader runtime hierarchy
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7133-SNSCE