Wednesday, 23 May 2012

Struts Interview Questions with answers

Struts Interview Questions

1) What is Struts?
The core of the Struts framework is a flexible control layer based on standard technologies
like Java Servlets, JavaBeans, ResourceBundles, and XML, as well as various Jakarta
Commons packages. Struts encourages application architectures based on the Model 2
approach, a variation of the classic Model-View-Controller (MVC) design paradigm.
Struts provides its own Controller component and integrates with other technologies to
provide the Model and the View. For the Model, Struts can interact with standard data
access technologies, like JDBC and EJB, as well as most any third-party packages, like
Hibernate, iBATIS, or Object Relational Bridge. For the View, Struts works well with
JavaServer Pages, including JSTL and JSF, as well as Velocity Templates, XSLT, and other
presentation systems.
The Struts framework provides the invisible underpinnings every professional web
application needs to survive. Struts helps you create an extensible development
environment for your application, based on published standards and proven design patterns.

2) What is Jakarta Struts Framework?
Jakarta Struts is open source implementation of MVC (Model-View-Controller) pattern for
the development of web based applications. Jakarta Struts is robust architecture and can be
used for the development of application of any size. Struts framework makes it much easier
to design scalable, reliable Web applications with Java.

3) What is ActionServlet?
The class org.apache.struts.action.ActionServlet is the called the ActionServlet. In the the
Jakarta Struts Framework this class plays the role of controller. All the requests to the
server goes through the controller. Controller is responsible for handling all the requests.

4) How you will make available any Message Resources
Definitions file to the Struts Framework Environment?
T Message Resources Definitions file are simple .properties files and these files contains the
messages that can be used in the struts project. Message Resources Definitions files can be
added to the struts-config.xml file through <message-resources /> tag.
<message-resources parameter=\"MessageResources\" />.

5) What is Action Class?
The Action Class is part of the Model and is a wrapper around the business logic. The
purpose of Action Class is to translate the HttpServletRequest to the business logic. To use
the Action, we need to Subclass and overwrite the execute() method. In the Action Class allthe database/business processing are done. It is advisable to perform all the database
related stuffs in the Action Class. The ActionServlet (commad) passes the parameterized
class to Action Form using the execute() method. The return type of the execute method is
ActionForward which is used by the Struts Framework to forward the request to the file as
per the value of the returned ActionForward object.

6) What is ActionForm?
An ActionForm is a JavaBean that extends org.apache.struts.action.ActionForm. ActionForm
maintains the session state for web application and the ActionForm object is automatically
populated on the server side with data entered from a form on the client side.

7) What is Struts Validator Framework?
Struts Framework provides the functionality to validate the form data. It can be use to
validate the data on the users browser as well as on the server side. Struts Framework
emits the java scripts and it can be used validate the form data on the client browser.
Server side validation of form can be accomplished by sub classing your From Bean with
DynaValidatorForm class.
The Validator framework was developed by David Winterfeldt as third-party add-on to
Struts. Now the Validator framework is a part of Jakarta Commons project and it can be
used with or without Struts. The Validator framework comes integrated with the Struts
Framework and can be used without doing any extra settings.

8) Give the Details of XML files used in Validator
The Validator Framework uses two XML configuration files validator-rules.xml and
validation.xml. The validator-rules.xml defines the standard validation routines, these are
reusable and used in validation.xml. to define the form specific validations. The
validation.xml defines the validations applied to a form bean.

9) How you will display validation fail errors on jsp page?
Following tag displays all the errors:

10) How you will enable front-end validation based on the
xml in validation.xml?
The <html:javascript> tag to allow front-end validation based on the xml in validation.xml.
For example the code: <html:javascript formName=\"logonForm\"
dynamicJavascript=\"true\" staticJavascript=\"true\" /> generates the client side java script
for the form \"logonForm\" as defined in the validation.xml file. The <html:javascript>
when added in the jsp file generates the client site validation script.

11) How to get data from the velocity page in a action
We can get the values in the action classes by using data.getParameter(\"variable name
defined in the velocity page\");

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