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JEE Interview Questions

1 . 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 multi tiered, and web-based applications.

2 . What is the J2EE module?

  • A J2EE module consists of one or more J2EE components for the same container type and one component deployment descriptor of that type.

3 . 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:

4 . Application clients and applets are client components.

  • Java Servlets and Java Server PagesTM (JSPTM) technology components are web components.
    Enterprise JavaBeansTM (EJBTM) components (enterprise beans) are business components.
    Resource adapter components provided by EIS and tool vendors.

5 . What are the four types of J2EE modules?

    • Application client module
    • Web module
    • Enterprise JavaBeans module
    • Resource adapter module

6 . What does application client module contain?

  • The application client module contains:
    class files,
    an application client deployment descriptor.
    Application client modules are packaged as JAR files with a .jar extension.

7 . What does Enterprise JavaBeans module contain?

  • The Enterprise JavaBeans module contains: class files for enterprise beans An EJB deployment descriptor. EJB modules are packaged as JAR files with a .jar extension.

8 . What does resource adapt module contain?

  • The resource adapt module contains:
    • all Java interfaces, classes,
    • native libraries,
    • other documentation,
    • A resource adapter deployment descriptor.
    • Resource adapter modules are packages as JAR files with a .rar (Resource adapter Archive) extension.

9 . What are the differences between Ear, Jar and War files? Under what circumstances should we use each one?

  • There are no structural differences between the files;
    they are all archived using zip-jar compression. However, they are intended for different purposes.
    • Jar files (files with a .jar extension) arre intended to hold generic libraries of Java classes, resources, auxiliary files, etc.
    • War files (files with a .war extension) arre intended to contain complete Web applications. In this context, a Web application is defined as a single group of files, classes, resources, .jar files that can be packaged and accessed as one servlet context.
    • Ear files (files with a .ear extension) arre intended to contain complete enterprise applications. In this context, an enterprise application is defined as a collection of .jar files, resources, classes, and multiple Web applications.
    • Each type of file (.jar, .war, .ear) is processed uniquely by application servers, servlet containers, EJB containers, etc.

10 . What is the difference between Session bean and Entity bean?one?The Session bean and Entity bean are two main parts of EJB container.

    • Session Bean
      • represents a workflow on behalf of a client
      • one-to-one logical mapping to a client.
      • created and destroyed by a client
      • not permanent objects
      • lives its EJB container(generally) does noot survive system shut down
      • two types: stateless and stateful beans
    • Entity Bean
      • represents persistent data and behavior off this data
      • can be shared among multiple clients
      • persists across multiple invocations
      • findable permanent objects
      • outlives its EJB container, survives systeem shutdown
      • two types: container managed persistence(CCMP) and bean managed persistence(BMP)

11 . What is "applet" ?

  • A J2EE component that typically executes in a Web browser but can execute in a variety of other applications or devices that support the applet programming model.

12 . What is "applet container" ?

  • A container that includes support for the applet programming model.

13 . What is "application assembler" ?

  • A person who combines J2EE components and modules into deployable application units.

14 . What is "application client" ?

  • A first-tier J2EE client component that executes in its own Java virtual machine. Application clients have access to some J2EE platform APIs.

15 . What is "application client container" ?

  • A container that supports application client components.

16 . What is "application client module" ?

  • A software unit that consists of one or more classes and an application client deployment descriptor.

17 . What is "application component provider" ?

  • A vendor that provides the Java classes that implement components' methods, JSP page definitions, and any required deployment descriptors.

18 . What is "application configuration resource file" ?

  • An XML file used to configure resources for a JavaServer Faces application, to define navigation rules for the application, and to register converters, validators, listeners, renderers, and components with the application.

19 . What is "archiving" ?

  • The process of saving the state of an object and restoring it.

20 . What is "asant" ?

  • A Java-based build tool that can be extended using Java classes. The configuration files are XML-based, calling out a target tree where various tasks get executed.

21 . What is "attribute"What is "asant" ?

  • A qualifier on an XML tag that provides additional information.

22 . What is authentication ?

  • The process that verifies the identity of a user, device, or other entity in a computer system, usually as a prerequisite to allowing access to resources in a system. The Java servlet specification requires three types of authentication-basic, form-based, and mutual-and supports digest authentication.

23 . What is authorization?

  • The process by which access to a method or resource is determined. Authorization depends on the determination of whether the principal associated with a request through authentication is in a given security role. A security role is a logical grouping of users defined by the person who assembles the application. A deployer maps security roles to security identities. Security identities may be principals or groups in the operational environment.

24 . Is J2EE application only a web-based?

  • NO. 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.