Misra’s blog

Struts interview questions

Posted by mtwinkle on May 18, 2006

Q. What is struts?
Q. What is Model-View-Controller (MVC) Architecture?
Ans. Model-View-Controller architecture is all about dividing application components into three different categories Model,View and the Controller.
Model: Model is responsible for providing the data from the database and saving the data into the data store. All the business logic are implemented in the Model. Data entered by the user through View are check in the model before saving into the database. Data access, Data validation and the data saving logic are part of Model.
View: View represents the user view of the application and is responsible for taking the input from the user, dispatching the request to the controller and then receiving response from the controller and displaying the result to the user. HTML, JSPs are the part of view component.
Controller: Controller is responsible for receiving the request from client. Once request is received from client it executes the appropriate business logic from the Model and then produce the output to the user using the View component.
ActionServlet, Action, ActionForm and struts-config.xml org.apache.struts.action.ActionServlet is the Controller part of the Struts.
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.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.

public ActionForward execute(ActionMapping mapping, ActionForm form, javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws java.lang.Exception

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.

Validator 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 to validate the form data on the client browser. Server side validation of the form can be accomplished by sub classing your From Bean with DynaValidatorForm class.
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.

Q. What is Struts Tiles?
Tiles uses the concept of reuse and enables the developers to define a template for the web site and then use this layout to populate the content of the web site. For example, if you have to develop a web site having more that 500 page of static content and many dynamically generated pages. The layout of the web site often changes according to the business requirement. In this case you can use the Tiles framework to design the template for the web site and use this template to populate the contents. In future if there is any requirement of site layout change then you have to change the layout in one page. This will change the layout of you whole web site.


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