J2EE interview questions for freshers/J2EE Interview Questions and Answers for Freshers & Experienced

What is the relationship of the Apache Tomcat open-source application server to the J2EE SDK?

Tomcat is based on the original implementation of the JavaServer Pages (JSP) and Java Servlet specifications, which was donated by Sun to the Apache Software Foundation in 1999. Sun continues to participate in the development of Tomcat at Apache, focusing on keeping Tomcat current with new versions of the specifications coming out of the Java Community Source Process.

Sun adapts and integrates the then-current Tomcat source code into new releases of the J2EE SDK. However, since Tomcat evolves rapidly at Apache, there are additional differences between the JSP and Servlet implementations in the J2EE SDK and in Tomcat between J2EE SDK releases. Tomcat source and binary code are governed by the ASF license, which freely allows deployment and redistribution.

What is the difference between being a J2EE licensee and being J2EE compatible?

A J2EE licensee has signed a commercial distribution license for J2EE. That means the licensee has the compatibility tests and has made a commitment to compatibility. It does not mean the licensees’ products are necessarily compatible yet. Look for the J2EE brand which signifies that the specific branded product has passed the Compatibility Test Suite (CTS) and is compatible.

Are there compatibility tests for the J2EE platform?

Yes. The J2EE Compatibility Test Suite (CTS) is available for the J2EE platform. The J2EE CTS contains over 5,000 tests for J2EE 1.4 and will contain more for later versions. This test suite tests compatibility by performing specific application functions and checking results. For example, to test the JDBC call to insert a row in a database, an EJB component makes a call to insert a row, and then a call is made to check that the row was inserted.

What is the Hibernate proxy?

An object proxy is just a way to avoid retrieving an object until you need it. Hibernate 2 does not proxy objects by default.

Define connection pooling?

Connection pooling is a mechanism reuse the connection which contains the number of already created object connection. So whenever it is necessary for an object, this mechanism is used to get objects without creating it.

What is the file name of hibernate configuration file?

The name of the file should be like this: hibernate.cfg.xml

What is Hashtable?

Hashtable is a collection synchronized object. It allows null value but not the duplicate values. Hashtable is like a HashMap.

What does Enterprise JavaBeans module contain?

The Enterprise JavaBeans (EJB) module contains the following:

Class files for enterprise beans
An EJB deployment descriptor
These modules are packaged as JAR files with a .jar extension.

What are some advantages of ORM?

There are several key advantages to ORM. The first is productivity, since ORM produces automatic code creation according to the defined data model. This saves time on data access coding. Maintainability is another. Codes that are generated for ORM are thoroughly tested. As long as the developer creates the correct functionality, there is little maintenance required.

Another advantage is performance. The code that the ORM generates fully manages the application’s data access needs. The code that is generated is also optimized to speed up the data access process. The last is vendor independence. The code that is generated by ORM doesn’t depend on any particular vendor. This is to increase the application’s portability.

What is the file extension used for hibernate mapping file?

The name of the file should be like this: filename.hbm.xml

Is technical support “Free” as well?

There are resources that are available for free on the Sun Solaris website that may help you resolve your issues without requiring technical support. For example, you can ask questions on the forum, search for known issues on the bug database, review the documentation, or take a look at code samples and applications to help you at no cost.

What are the JSP tags?

There are four different types of JSP tags:

Declarations
Scriplets
Expressions
Directives

Difference between load and get method?

load() can’t find the object from cache or database, an exception is thrown, and the load() method never returns null.

get() method returns null if the object can’t be found. The load() method may return a proxy instead of a real persistent instance get() never returns a proxy.

Who needs the J2EE platform?

ISVs need the J2EE platform because it gives them a blueprint for providing a complete enterprise computing solution on the Java platform. Enterprise developers J2EE Tutorial, because writing distributed business applications are hard, and they need a high-productivity solution that allows them to focus only on writing their business logic and having a full range of enterprise-class services to rely on, like transactional distributed objects, message-oriented middleware, and naming and directory services.

How are the J2EE architecture and the Sun Java Enterprise System related?

<> The J2EE architecture is the foundation of the Sun Java System Application Server, a component of the Sun Java Enterprise System. The Sun Java System Application Server in the current Sun Java Enterprise System is based on the J2EE platform v1.3, with additional support for Web services.

<> Developers familiar with J2EE technology can easily apply their skills to building applications, including Web services applications, using the Sun Java Enterprise System. For more information, see the Sun Java Enterprise System Web site.

Can applications are written for the J2EE platform v1.3 run in a J2EE platform v1.4 implementation?

J2EE applications that are written to the J2EE 1.3 specification will run in a J2EE 1.4 implementation. Backward compatibility is a requirement of the specification.

Name the different phases of servlet lifecycle?

Class Loading Phase, Instantiation Phase, Initialize Phase, Removal Phase, and the Request Handling Phase.

Define the servlet?

Servlet is a server-side component that offers full functionalities to create a server-side program. The different servlets are available with a specific design for a variety of protocols. Most popular type of protocol for the servlet is HTTP.

What is a thin client?

A program that doesn’t have any complex operations like connection, business rules or database queries is termed as the thin client.

What is Spring Framework and discuss its benefits?

To reduce the overall complexity of an enterprise application, the open source Spring Framework is used. The major benefits of any spring Framework include –

* The middle tier objects can be managed more efficiently.
* The properties can be initialized quickly.
* The testability of application is made easier with injection dependencies.
* The containers are lightweight and components are defined clearly.
* The Spring services are managed or configured in runtime environment instead of
focusing on its architectural layer.

Define the concept of connection pooling?

Connection Pooling is a simple concept that is popular to reuse the existing connections. In other words, if object connections are already well defined and connected then they can be reused whenever there is a requirement instead of generating the new one.

Define ORM and how it works in J2EE?

ORM is abbreviated as Object-relational mapping in J2EE. The objects are mapped to tables in the relational databases by transforming data from one form to another.

Define the web components and how are they helpful?

Java Servlets or Java Server Pages are the web components that dynamically receive requests from users and respond accordingly. JSP pages are further executed in the form of servlets to generate more static content for the web pages.

What are the advantages of object relational mapping?

>> Code reuse
>> Application maintainability
>> Productivity
>> Application design

Difference between public, private and protected?

Private: It has the data accessible to the class to which they belong

Protected: It has the data accessible to the class to which they belong and any subclass

Public: It has the data accessible to all the classes

What are the benefits of Hibernate?

<> Built-in connection pool implementation
<> Standard ORM
<> Mapping of domain object to relational database
<> Layered architecture

Define Hibernate and HQL?

Hibernate is an open-source query and object-relational mapping service. Here, you can write HQL (Hibernate Query Language) scripts instead of using SQL that saves a lot of time and efforts. Hibernate is closely related to composition, polymorphism, inheritance, and collections. With the help of this framework, you can process queries beautifully by using simple Java objects.

How to design interactive UI for J2EE apps?

To design interactive User Interface in J2EE, you must opt for JSF (Java Server Faces). The framework has a wider set of reusable UI components that is based on MVC architecture and design concepts. Further, the automated data that is created at server side and displayed ay client side is also managed by the JSF.

What is the J2EE 1.4 SDK?

The Java 2 SDK, Enterprise Edition 1.4 (J2EE 1.4 SDK) is a complete package for developing and deploying J2EE 1.4 applications. The J2EE 1.4 SDK contains the Sun Java System Application Server Platform Edition 8, the J2SE 1.4.2 SDK, J2EE 1.4 platform API documentation, and a slew of samples to help developers learn about the J2EE platform and technologies and prototype J2EE applications. The J2EE 1.4 SDK is for both development and deployment.

What technologies are included in the J2EE platform?

The primary technologies in the J2EE platform are Java API for XML-Based RPC (JAX-RPC), JavaServer Pages, Java Servlets, Enterprise Java Beans components, J2EE Connector Architecture, J2EE Management Model, J2EE Deployment API, Java Management Extensions (JMX), J2EE Authorization Contract for Containers, Java API for XML Registries (JAXR), Java Message Service (JMS), Java Naming and Directory Interface (JNDI), Java Transaction API (JTA), CORBA, and JDBC data access API.

What technologies are included in the J2EE platform?

The primary technologies in the J2EE platform are Java API for XML-Based RPC (JAX-RPC), JavaServer Pages, Java Servlets, Enterprise Java Beans components, J2EE Connector Architecture, J2EE Management Model, J2EE Deployment API, Java Management Extensions (JMX), J2EE Authorization Contract for Containers, Java API for XML Registries (JAXR), Java Message Service (JMS), Java Naming and Directory Interface (JNDI), Java Transaction API (JTA), CORBA, and JDBC data access API.

Can the J2EE platform interoperate with other WS-I implementations?

Yes, if the other implementations are WS-I compliant.

What does MVC stand for?

MVC means model view controller. It is a software architectural pattern for implementing user interfaces on PCs.

What do you mean by JSF?

JSF stands for JavaServer Faces. It provides a set of reusable UI components for web applications.

What are web components?

Java server pages technology and java servlet are web components.

Define J2ee module?

A collection of one or more J2ee components of the same container along with one descriptor of that type is known as J2ee module.

Difference between save and saveorupdate

save() – This method in Hibernate is used to stores an object in the database. It inserts an entry if the record doesn’t exist, otherwise not.

saveorupdate () -This method in the hibernate is used for updating the object using identifier. If the identifier is missing this method calls save(). If the identifier exists, it will call update method.

What is ORM?

ORM stands for Object-Relational mapping. The objects in a Java class which is mapped into the tables of a relational database using the metadata that describes the mapping between the objects and the database. It works by transforming the data from one representation to another.

Describe the MVC on struts?

MVC stands for Model View Controller. Each section in the Model View Controller can be described as follows:

<> Model: Model represents the internal state of the system as a set of single or many Java Beans.
<> View: Most often the view is constructed using Java Server Pages (JSP) technology.
<> Controller: The controller is the process that focuses on receiving client requests and produce the next level of a user interface according to the request. The primary component of the controller in the framework is the “ActionServlet” servlet class.

What are the advantages of hibernate?

* Hibernate is portable i mean database independent, Vendor independence.
* Standard ORM also supports JPA
* Mapping of the Domain object to the relational database.
* Hibernate is better than plain JDBC.
* JPA provider in JPA based applications.

What are defined as web components?

Java Servlets and Java server pages technology components are identified as web components. Servlets dynamically receive requests and make responses. JSP server pages also behave as Java Servlets but facilitate to create more static content.

What is the limitation of hibernate?

Slower in executing the queries than queries are used directly.
Only query language support for composite keys.
No shared references to value types.

Define Hibernate, and give some examples of its limitations and advantages.

Hibernate is an open-source object-relational mapping and query service. Hibernate allows us to write HQL (hibernate query language) scripts through an SQL extension, a much faster process than writing scripts in native SQL (structured query language).

There are some key advantages of using hibernate. It is database-independent, and its standard ORM also supports JPA (Java Persistence API). It also features domain object mapping to the regional database. Plus, the database connectivity is better in Hibernate compared to JDBC.

There are also some disadvantages of using hibernate. Its use of HQL makes it slower to execute queries. It only has HQL support available for composite keys, which limits advanced query options. Also, it doesn’t have shared value type references available.

What is a J2EE container?

A container is the server platform used to run the J2EE application. A Java component can be run on the J2EE container by using APIs supplied through the Web container and the EJB container.

To be more specific about each sub-containers function, the web container is a server platform that is used to execute JSPs and servlets. The EJB container is a server platform that is used to control the execution of the Enterprise Bean.

Define Hash table

HashTable is just like Hash Map, Collection having a key(Unique), value pairs. Hashtable is a collection Synchronized object. It does not allow duplicate values or null values.

What is JSF?

JavaServer Faces (JSF) is a user interface (UI) designing framework for Java web applications. JSF provides a set of reusable UI components, a standard for web applications. JSF is based on MVC design pattern. It automatically saves the form data to the server and populates the form date when display on the client side.


What is considered as a web component?

Java Servlet and Java Server Pages technology components are web components. Servlets are Java programming language that dynamically receives requests and makes responses. JSP pages execute as servlets but allow a more natural approach to creating static content.

What are types of J2EE clients?

* Applets
* Application clients
* Java Web Start-enabled clients, by Java Web Start technology.
* Wireless clients, based on MIDP technology.

What are the four components of J2EE application?

* Application clients components.
* Servlet and JSP technology are web components.
* Business components (JavaBeans).
* Resource adapter components

What is J2EE?

J2EE means Java 2 Enterprise Edition. The functionality of J2EE is developing multitier web-based applications. The J2EE platform is consists of a set of services, application programming interfaces (APIs), and protocols.

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