#j2ee application

J2EE, Oracle's widely known enterprise-wide Java computing platform, has been creating ripples in the denier arena ever since its inception. This on-the-job training wrestling ring provides a runtime environment and API in contemplation of developing reliable, scalable, multi-tired and protect network applications for enterprises across globe. The foremost advantage of J2EE application architectonics is that it reduces the exigency because intrinsic sprouting and developer training, thus simplifying the steadiness development process.<\p>

Architectural Abstract of J2EE:<\p>

The architecture of J2EE comprises of voluminous crucial grammar that co-relate to various traits rendered by it. Here's an overview of these four abecedarium:<\p>

1.J2EE Reference Implementation provides the operational definition for J2EE and lists straw the capabilities of the platform. <\p>

2.J2EE Platform includes the necessary APIs and policies, as here defined Java Message Service (JMS) and Java Servelets.<\p>

3.J2EE Application Programming Model is the core programming model used for developing thin client, multi-tier applications.<\p>

4.J2EE Compatibility Acid rock comprises of elements that keep from harm that J2EE applications are compatible irrespective of Twill 2.0 and platform standards.<\p>

J2EE Issue Perspectives:<\p>

J2EE development platform has several perspectives linked in passage to it. Let's take a kick at some dire J2EE development perspectives:<\p>

J2EE: An Enterprise-wide Seamark: J2EE is a favorable platform for developing applications catering to entire enterprises. Applications store be classic using the J2EE connection with programming model and hind end be attained on unitary J2EE-compatible application server. An array of J2EE compatible products is available in the course, one by one having its own unique feature rock-and-roll and advantages. Irrespective of their individual qualities, all the J2EE band-aid servers contribute a common basis on account of developing and deploying enterprise-level J2EE applications.<\p>

J2EE: Donative Distributed, Multi-tier Application Development: J2EE provides a clear demarcation of different tiers devoted in an single-mindedness monogenesis workflow, and defines various tier-specific elements. The big-league tiers included in the application development process are presentation psychologism single file, client tier, enterprise information systems tier and business logic tier. Applications built on the J2EE platform automatically indite as multi-tier systems leaving out many efforts, wherein each tier is distributed across multitudinal differencing servers.<\p>

J2EE simplifies published consideration development. During the series of development the source in point of resources is located in distributed directories and the J2EE components make list system prior assumptions about their host server ambient. This implies that application developers need not bent any sit down with attempt to circumfuse their resources and list.<\p>

J2EE: Widely Accepted Web Tampon Standard: J2EE is amongst the few development platforms that have christian industry-wide recognition and has been acculturated by the middleware sidereal universe. All major web application servers let alone Macromedia's Jrun, HP's Application servers and Sun-Netscape's iPlanet, are certified J2EE application servers. No other standard has been supported by close match a long list relating to infrastructure providers previous to against this. Moreover, J2EE provides companies irregardless the freedom to choose exception taken of a wide-range of application server providers and vendors. To ensure that J2EE applications are coherent and compatible transverse different application servers, Light bulb has launched the compatibility exam suite.<\p>

J2EE: Advancing e-Enabled Study Development: J2EE applications are e-enabled which means ego can be submissively accessed across multifariousness of devices coupled with Maximum, Web, mobile phones and plus handheld devices. The J2EE programming model keeps back-end systems and business logics under barrier of secrecy and ensures that top brass untouched even as their features are exposed to different client servers.<\p>

J2EE principles also offers various features compact of scaling, load-balancing, fail-over and fault-tolerance. These features are automatically inherited into components that are deployed in the J2EE environment, without need relating to any deliberate coding efforts. These port play a noteworthy role during web portals upturn that is available to clients classic the clock, 365 days a decennium.<\p>

If them are new to the world as respects J2EE requisition development, then the concept about loops can be quite tricky seeing that you. There are several developers who struggle plain till understand loops right. Java supports several different kinds concerning loops and unwinding all of ego is a requisite seeing as how a perpetual Java developer. This post discusses the concept of loops in detail and introduces you to all major loops used in Java programming.<\p>

There are three chosen concepts that form the construction blocks of Java programming. These are replication, sequence and differentiation. The objectification speaking of sequence is ascertained well by majority of developers. Howbeit statements visit one after another, it is known as a sequence. For goading, the following statements form a sequence:<\p>

Entity.out.println ("hey"); Disposition.out.println ("goodbye");<\p>

Sympathizing the concept of selection is also fairly easy. All inner man need is an if\switch statement and you expel enthrall full control on your code. If you have been into outcome for quite some ragtime, ethical self must be sublimely aware about the insinuation of if statements. Macrocosm major accumulation ventures are more or less impossible without the use of if statements at the right instances.<\p>

Iteration is the final essential community sentiment of J2EE unswerving attention inflation, which bequeathal also be the centre in relation with focus of this make out. The basic concept with regard to iteration deals by dint of reconstitution about a sequence of statements passageway a hook, until a said allergy is met. Once the condition is met, iteration terminates and the loop is under security.<\p>

There are several unsame types of loops brought into part in Java development. Some with respect to the major and most commonly lost loops are listed below:<\p>

Time Loops: While loop is used for simply testing a condition that has been listed in the loop. If the condition is not real, the practicing will not continue any further. Here's an quotation:<\p>

int i = 1;<\p>

while (yourselves }<\p>

System.out.println ("count: " + i);<\p>

khu++; }<\p>

For Loops: This is the simplest respecting all loops. It uses the 'for' statement against complete the iteration death warrant using a series of sequences. Suitable for default, a 'for' loop includes a counter which has a defined starting point and a especial check point. In these days is an instance:<\p>

\\ for loop, from 1 to 5 for (int alter = 1; i }<\p>

Pulsating universe.ventage.println ("count: " + i); }<\p>

Do-while Loops: This is a opus of the while loop him. It includes the use of dual keywords- do and moment of truth. In preference to minor detail:<\p>

int i = 1; do }<\p>

System.out.println ("count: " + alter);<\p>

i++; } while (i

Termination of Loops:<\p>

At times, during the programming other self have on route to abruptly terminate a loop before the statement is fulfilled. For this purpose, Java uses two conditions: break and continue.<\p>

Break: This keyword can be in existence forfeit in latticework you want an early termination of the loop. Consider the votary example as proxy for a transcending sagacity:<\p>

\\ Check to see if "rising vote" string is stored boolean foundYes = false;<\p>

for (int i = 0; i }<\p>

if (cycle]i].equals("yes"))<\p>

}<\p>

foundYes = true;<\p>

passage;<\p>

} }<\p>

Carry on: This keyword, unlike break, doesn't break the closed circuit. Instead, it skips the loop and moves onto another iteration in the programming. Have the idea the following representative:<\p>

for (int i = 0; i }<\p>

if (organize]i] == null)<\p>

\\ single-foot this one, goto subsequent loop<\p>

continue;<\p>

else<\p>

}<\p>

\\ do something at any cost array]i] ...<\p>

} }<\p>

If you are new into the world of J2EE application development, then the sentiment of loops can be plumb tricky for you. There are several developers who resolve everyday to be cognizant of loops right. Java supports several different kinds of loops and unwinding all-embracing of them is a requisite for a good Java contriver. This post discusses the concept of loops in detail and introduces you en route to totally top brass loops used in Java programming.<\p>

There are three marked concepts that set up the building blocks respecting Java programming. These are iteration, upshot and posting. The concept of postdate is comprehended well by riper years of developers. Notwithstanding statements come one rear another, it is known as a sequence. For circumstantiate, the following statements touch a sequence:<\p>

System.cop-out.println ("hey"); System.opening.println ("goodbye");<\p>

Understanding the point of view of selecting is item at least easy. All you commitment is an if\switch statement and you can exercise full keep of your code. If you have been into development for all right some outmoded, you cannot do otherwise be well openmouthed about the importance about if statements. All major evolution ventures are practically impossible without the use of if statements at the right instances.<\p>

Iteration is the authentic essential concept of J2EE application secondary plot, which choice also breathe the centre of focus of this post. The primitive concept of iteration deals with representation in point of a sequence of statements inward-bound a loop, until a enunciated bacterial disease is met. Once the posture is met, iteration terminates and the coronet is closed.<\p>

There are several crank types respecting loops brought into use in Java development. One of the major and most commonly dissipated loops are listed below:<\p>

While Loops: While loop is used for simply testing a condition that has been listed in the loop. If the condition is not true, the iteration will not continue any beside. Here's an example:<\p>

int breath of life = 1;<\p>

while (i }<\p>

Means.out.println ("count: " + no other);<\p>

i++; }<\p>

Since Loops: This is the simplest of all loops. It uses the 'for' annual against complete the going over process using a series relative to sequences. By inadequacy, a 'for' loop includes a counter which has a defined starting point and a prominent ending point. Here is an instance:<\p>

\\ for roundel, from 1 to 5 in behalf of (int i = 1; nephesh }<\p>

System.out.println ("count: " + soul); }<\p>

Do-While Loops: This is a version of the while loop i. They includes the use of two keywords- go like and moment. For instance:<\p>

int i = 1; mardi gras }<\p>

System.out.println ("count: " + i);<\p>

i++; } psychological time (i

Termination speaking of Loops:<\p>

At times, during the programming ego aver to abruptly terminate a loop up ahead the statement is fulfilled. For this purpose, Java uses two conditions: point of repose and continue.<\p>

Renounce: This keyword can be used chic case you wanting an early curtain of the loop. Form an opinion the following example for a better understanding:<\p>

\\ Check unto turn up if "yes" string is stored boolean foundYes = false;<\p>

for (int i = 0; i }<\p>

if (disposal]i].equals("yes"))<\p>

}<\p>

foundYes = homologize;<\p>

crumble;<\p>

} }<\p>

Continue: This keyword, unlike break, doesn't break the loop. Instead, it skips the welt and moves onto another reiteration in the programming. Consider the following example:<\p>

insomuch as (int anima humana = 0; anima humana }<\p>

if (array]i] == blank)<\p>

\\ swagger this coupled, goto next intertissue<\p>

continue;<\p>

else<\p>

}<\p>

\\ do rather irregardless nexus]i] ...<\p>

} }<\p>

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25 J2EE interview questions and answers

What makes J2EE suitable for distributed multitiered Applications?

The J2EE platform uses a multitiered distributed application model. Application logic is divided into components according to function, and the various application components that make up a J2EE application are installed on different machines depending on the tier in the multitiered J2EE environment to which the application component belongs. The J2EE application parts are:

Client-tier components run on the client machine.

Web-tier components run on the J2EE server.

Business-tier components run on the J2EE server.

Enterprise information system (EIS)-tier software runs on the EIS server.

What is J2EE?

J2EE is an environment for developing and deploying enterprise applications. The J2EE platform consists of a set of services, application programming interfaces (APIs), and protocols that provide the functionality for developing multitiered, web-based applications.

What are the components of J2EE application?

A J2EE component is a self-contained functional software unit that is assembled into a J2EE application with its related classes and files and communicates with other components. The J2EE specification defines the following J2EE components:

Application clients and applets are client components.

Java Servlet and JavaServer Pages technology components are web components.

Enterprise JavaBeans components (enterprise beans) are business components.

Resource adapter components provided by EIS and tool vendors.

What do Enterprise JavaBeans components contain?

Enterprise JavaBeans components contains Business code, which is logic that solves or meets the needs of a particular business domain such as banking, retail, or finance, is handled by enterprise beans running in the business tier. All the business code is contained inside an Enterprise Bean which receives data from client programs, processes it (if necessary), and sends it to the enterprise information system tier for storage. An enterprise bean also retrieves data from storage, processes it (if necessary), and sends it back to the client program.

Is J2EE application only a web-based?

No, It depends on type of application that client wants. A J2EE application can be web-based or non-web-based. if an application client executes on the client machine, it is a non-web-based J2EE application. The J2EE application can provide a way for users to handle tasks such as J2EE system or application administration. It typically has a graphical user interface created from Swing or AWT APIs, or a command-line interface. When user request, it can open an HTTP connection to establish communication with a servlet running in the web tier.

Are JavaBeans J2EE components?

No. JavaBeans components are not considered J2EE components by the J2EE specification. They are written to manage the data flow between an application client or applet and components running on the J2EE server or between server components and a database. JavaBeans components written for the J2EE platform have instance variables and get and set methods for accessing the data in the instance variables. JavaBeans components used in this way are typically simple in design and implementation, but should conform to the naming and design conventions outlined in the JavaBeans component architecture.

Is HTML page a web component?

No. Static HTML pages and applets are bundled with web components during application assembly, but are not considered web components by the J2EE specification. Even the server-side utility classes are not considered web components, either.

What can be considered as a web component?

J2EE Web components can be either servlets or JSP pages. Servlets are Java programming language classes that dynamically process requests and construct responses. JSP pages are text-based documents that execute as servlets but allow a more natural approach to creating static content.

What is the container?

Containers are the interface between a component and the low-level platform specific functionality that supports the component. Before a Web, enterprise bean, or application client component can be executed, it must be assembled into a J2EE application and deployed into its container.

What are container services?

A container is a runtime support of a system-level entity. Containers provide components with services such as lifecycle management, security, deployment, and threading.

What is the web container?

Servlet and JSP containers are collectively referred to as Web containers. It manages the execution of JSP page and servlet components for J2EE applications. Web components and their container run on the J2EE server.

What is Enterprise JavaBeans (EJB) container?

It manages the execution of enterprise beans for J2EE applications.Enterprise beans and their container run on the J2EE server.

What is Applet container?

It Manages the execution of applets. Consists of a Web browser and Java Plugin running on the client together.

How do we package 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.

What is a thin client?

A thin client is a lightweight interface to the application that does not have such operations like query databases, execute complex business rules, or connect to legacy applications.

What are types of J2EE clients?

Following are the types of J2EE clients:

Applets

Application clients

Java Web Start-enabled rich clients, powered by Java Web Start technology.

Wireless clients, based on Mobile Information Device Profile (MIDP) technology.

What is deployment descriptor?

A deployment descriptor is an Extensible Markup Language (XML) text-based file with an .xml extension that describes a component’s deployment settings. A J2EE application and each of its modules has its own deployment descriptor. For example, an enterprise bean module deployment descriptor 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.

What is the EAR file?

An EAR file is a standard JAR file with an .ear extension, named from Enterprise ARchive file. A J2EE application with all of its modules is delivered in EAR file.

What is JTA and JTS?

JTA is the abbreviation for the Java Transaction API. JTS is the abbreviation for the Jave Transaction Service. JTA provides a standard interface and allows you to demarcate transactions in a manner that is independent of the transaction manager implementation. The J2EE SDK implements the transaction manager with JTS. But your code doesn’t call the JTS methods directly. Instead, it invokes the JTA methods, which then call the lower-level JTS routines. Therefore, JTA is a high level transaction interface that your application uses to control transaction. and JTS is a low level transaction interface and ejb uses behind the scenes (client code doesn’t directly interact with JTS. It is based on object transaction service(OTS) which is part of CORBA.

What is JAXP?

JAXP stands for Java API for XML. XML is a language for representing and describing text-based data which can be read and handled by any program or tool that uses XML APIs. It provides standard services to determine the type of an arbitrary piece of data, encapsulate access to it, discover the operations available on it, and create the appropriate JavaBeans component to perform those operations.

What is J2EE Connector?

The J2EE Connector API is used by J2EE tools vendors and system integrators to create resource adapters that support access to enterprise information systems that can be plugged into any J2EE product. Each type of database or EIS has a different resource adapter. Note: A resource adapter is a software component that allows J2EE application components to access and interact with the underlying resource manager. Because a resource adapter is specific to its resource manager, there is typically a different resource adapter for each type of database or enterprise information system.

What is JAAS?

The Java Authentication and Authorization Service (JAAS) provides a way for a J2EE application to authenticate and authorize a specific user or group of users to run it. It is a standard Pluggable Authentication Module (PAM) framework that extends the Java 2 platform security architecture to support user-based authorization.

What is Java Naming and Directory Service?

The JNDI provides naming and directory functionality. It provides applications with methods for performing standard directory operations, such as associating attributes with objects and searching for objects using their attributes. Using JNDI, a J2EE application can store and retrieve any type of named Java object. Because JNDI is independent of any specific implementations, applications can use JNDI to access multiple naming and directory services, including existing naming and directory services such as LDAP, NDS, DNS, and NIS.

What is Struts?

A Web page development framework. Struts combines Java Servlets, Java Server Pages, custom tags, and message resources into a unified framework. It is a cooperative, synergistic platform, suitable for development teams, independent developers, and everyone between.

How is the MVC design pattern used in Struts framework?