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.

What are the four components of J2EE application?

1. Application client’s components
2. Servlet and JSP technology are web components
3. Business components (JavaBeans)
4. Resource adapter components

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 considered as a web component?

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

What is JSF?

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

Define Hash table

Hash Table is just like Hash Map, Collection having key (Unique), value pairs. Hash table is a collection Synchronized object .It does not allow duplicate values but it allows null values.

What is Hibernate?

Hibernate is an open source object-relational mapping and query service. In hibernate we can write HQL instead of SQL which save developers to spend more time on writing the native SQL. Hibernate has more powerful association, inheritance, polymorphism, composition, and collections. It is a beautiful approach for persisting into database using the java objects. Hibernate also allows you to express queries using java-based criteria.

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

What are the advantage of hibernate?

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

What is DispatchAction?

The DispatchAction class is used to group related actions into one class. Using this class, you can have a method for each logical action compared than a single execute method. The DispatchAction dispatches to one of the logical actions represented by the methods. It picks a method to invoke based on an incoming request parameter. The value of the incoming parameter is the name of the method that the DispatchAction will invoke.

How to use DispatchAction?

To use the Dispatch Action, follow these steps:

Create a class that extends Dispatch Action (instead of Action)

In a new class, add a method for every function you need to perform on the service – The method has the same signature as the execute() method of an Action class.

Do not override execute() method – Because Dispatch Action class itself provides execute() method.

Add an entry to struts-config.xml

What is Include Action?

Include Action class is useful when you want to integrate Struts into an application that uses Servlets. Use the Include Action class to include another resource in the response to the request being processed.

What is the difference between ForwardAction and IncludeAction?

The difference is that you need to use the IncludeAction only if the action is going to be included by another action or jsp. Use ForwardAction to forward a request to another resource in your application, such as a Servlet that already does business logic processing or even another JSP page.

What is ORM?

ORM stands for Object-Relational mapping. The objects in a Java class which is mapped in to 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.

Difference between save and saveorupdate

save() – This method in hibernate is used to stores an object into the database. It insert 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.

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.

How to invoke stored procedure in hibernate?

{ ? = call thisISTheProcedure() }

What are the benefits of ORM?

• Productivity
• Maintainability
• Performance
• Vendor independence

What the Core interfaces are of hibernate framework?

• Session Interface
• Session Factory Interface
• Configuration Interface
• Transaction Interface
• Query and Criteria Interface

What is the file extension used for hibernate mapping file?

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

What is the file name of hibernate configuration file?

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

How to add hibernate mapping file in hibernate configuration file?

By <mapping resource=” filename.hbm.xml”/>

Define connection pooling?

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

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.

What is HQL?

HQL stands for Hibernate Query Language. Hibernate allows to the user to express queries in its own portable SQL extension and this is called as HQL. It also allows the user to express in native SQL.

What are the Collection types in Hibernate?

Set, List, Array, Map, Bag

What is a thin client?

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

Differentiate between .ear, .jar and .war files

.ear files: The .ear file contains the EJB modules of the application.

.jar files: These files are with the .jar extension. The .jar files contains the libraries, resources and accessories files like property files.

.war files: These files are with the .war extension. The .war file contains jsp, html, JavaScript and other files for necessary for the development of web applications.

What are the various Struts tag libraries?

• HTML Tags
• Bean Tags
• Logic Tags
• Template Tags
• Nested Tags
• Tiles Tags

What are the JSP tag?

JSP tags can be divided into 4 different types.

• Directives
• Declarations
• Scriplets
• Expressions

What are JSP Directives?

page Directives <%@page language=”java” %>

include Directives: <%@ include file=”/header.jsp” %>

taglib Directives <%@ taglib uri=”tlds/taglib.tld” prefix=”html” %>

What is the EAR file?

An EAR file is a JAR file with an .ear extension. A J2EE application with all of its modules is delivered in EAR file.

What is Struts?

Struts framework is a Model-View-Controller (MVC) architecture for designing large scale applications. Which is combines of Java Servlets, JSP, Custom tags, and message. Struts helps you to create an extensible development environment for your application, based on published standards and proven design patterns. Model in many applications represent the internal state of the system as a set of one or more JavaBeans. The View is most often constructed using Java Server Pages (JSP) technology. The Controller is focused on receiving requests from the client and producing the next phase of the user interface to an appropriate View component. The primary component of the Controller in the framework is a servlet of class Action Servlet. This servlet is configured by defining a set of Action Mappings.

What is Action Errors?

Action Errors object that encapsulates any validation errors that have been found. If no errors are found, return null or an Action Errors object with no recorded error messages. The default implementation attempts to forward to the HTTP version of this method. Holding request parameters mapping and request and returns set of validation errors, if validation failed; an empty set or null.

What is Action Form?

Action Form is a Java bean that associates one or more Action Mappings. A java bean become Form Bean when extend org.apache.struts.action.ActionForm class. ActionForm object is automatically populated on the server side which data has been entered by the client from UI. ActionForm maintains the session state for web application.

What is Action Mapping?

Action Mapping we specify action class for particular url i.e. path and different target view i.e. forwards on to which request response will be forwarded. The Action Mapping represents the information that the Action Servlet knows about the mapping of a particular request to an instance of a particular Action class. The mapping is passed to the execute() method of the Action class, enabling access to this information directly.

What is the MVC on struts?

MVC stands Model-View-Controller.

Model: Model in many applications represent the internal state of the system as a set of one or more JavaBeans.

View: The View is most often constructed using Java Server Pages (JSP) technology.

Controller: The Controller is focused on receiving requests from the client and producing the next phase of the user interface to an appropriate View component. The primary component of the Controller in the framework is a servlet of class Action Servlet. This servlet is configured by defining a set of ActionMappings.

What are different modules in spring?

There are seven core modules in spring

1. The Core container module
2. O/R mapping module (Object/Relational)
3. DAO module
4. Application context module
5. Aspect Oriented Programming
6. Web module
7. MVC module

What is spring?

Spring is a light weight open source framework for the development of enterprise application that resolves the complexity of enterprise application development also providing a cohesive framework for J2EE application development. Which is primarily based on IOC (inversion of control) or DI (dependency injection) design pattern.

Functionality of Action Servlet and Request Processor?

• Receiving the Http Servlet Request
• Populating JavaBean from the request parameters
• Displaying response on the web page Issues
• Content type issues handling
• Provide extension points

What is default scope in spring?

Singleton

What are advantages of spring usage?

• Pojo based programming enables reuse component.
• Improve productivity and subsequently reduce development cost.
• Dependency Injection can be used to improve testability.
• Spring required enterprise services without a need of expensive application server.
• It reduces coupling in code and improves maintainability.

What are the Benefits Spring Framework?

• Light weight container
• Spring can effectively organize your middle tier objects
• Initialization of properties is easy no need to read from properties file
• Application code is much easier to unit test
• Objects are created Lazily, Singleton – configuration
• Spring’s configuration management services can be used in any architectural layer, in whatever runtime environment

How to Create Object without using the keyword “new” in java?

Without new the Factory methods are used to create objects for a class.

For example Calender c=Calender.getInstance();

Here Calender is a class and the method getInstance() is a Factory method which can create object for Calender class.

What is servlet?

Servlets is a server side components that provide a powerful mechanism for developing server side programs. Servlets is a server as well as platform-independent and Servlets are designed for a various protocols. Most commonly used HTTP protocols. Servlets uses the classes in the java packages javax.servlet, javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse, javax.servlet.http.HttpSession;. All servlets must implement the Servlet interface, which defines life-cycle methods.

Servlet is pure java object or not?

Yes, pure java object

What are the phases of the servlet life cycle?

The life cycle of a servlet consists of the following phases:

• Servlet class loading
• Servlet instantiation
• The init method
• Request handling (call the service method)
• Removal from service (call the destroy method)

What must be implemented by all Servlets?

The Servlet Interface must be implemented by all servlets