Struts Interview Questions
1. 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.
2. 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.
3. How you will make available any Message Resources Definitions file to the
Struts Framework Environment?
The 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.
Example: <message-resources parameter=\"MessageResources\" />.
4. 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 all the 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.
5. 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.
6. 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.
7. Give the Details of XML files used in Validator Framework?
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.
8. How you will display validation fail errors on jsp page?
Following tag displays all the errors:
<html:errors/>
9. 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.
10. What is the Difference between DispatchAction and LookupDispatchAction ?
A DispatchAction contains a number of different methods other than the standard execute(). These methods are executed based on some request parameter. Your action mapping in struts-config specifies the request parameter to examine. Then whatever the value of that parameter is for a given request Struts will
try to execute the method in the action whose name matches the value of the
parameter.
A LookupDispatchAction by contrast determines which method to call not based directly on a request parameter's value but by doing a lookup to determine the method based on the value of the parameter. You provide a method that accepts the value of the request parameter and returns the method to execute. How you actually implement the lookup is of course up to you but a simple Map is
probably most typical.
