What is Struts?
Struts is a web page development framework and an open source software that
helps developers build web applications quickly and easily. Struts
combines Java Servlets, Java Server Pages, custom
tags, and message resources into a unified framework. It is a cooperative,
synergistic platform, suitable for development teams, independent developers,
and everyone between.
How is the MVC design pattern used in Struts framework?
In the MVC design pattern, application flow is mediated by a central
Controller. The Controller delegates requests to an appropriate handler. The
handlers are tied to a Model, and each handler acts as an adapter between the
request and the Model. The Model represents, or encapsulates, an application's
business logic or state. Control is usually then forwarded back through the
Controller to the appropriate View. The forwarding can be determined by
consulting a set of mappings, usually loaded from a database or configuration
file. This provides a loose coupling between the View and Model, which can make
an application significantly easier to create and maintain.
Controller--Servlet controller which supplied by
Struts itself; View --- what you can see on the screen, a JSP page and
presentation components; Model --- System state and a
business logic JavaBeans.
Who makes the Struts?
Struts is hosted by the Apache Software Foundation(ASF)
as part of its Jakarta project, like Tomcat, Ant and Velocity.
Why it called Struts?
Because the designers want to remind us of the invisible
underpinnings that hold up our houses, buildings, bridges, and ourselves when
we are on stilts. This excellent description of Struts reflect
the role the Struts plays in developing web applications.
Do we need to pay the Struts if being used in commercial purpose?
No. Struts is available for commercial use at no
charge under the Apache Software License. You can also integrate the Struts
components into your own framework just as if they were written in house
without any red tape, fees, or other hassles.
What are the core classes of Struts?
Action, ActionForm, ActionServlet,
ActionMapping, ActionForward
are basic classes of Structs.
What is the design role played by Struts?
The role played by Structs is controller in
Model/View/Controller(MVC) style. The View is played
by JSP and Model is played by JDBC or generic data source classes. The Struts
controller is a set of programmable components that allow developers to define
exactly how the application interacts with the user.
How Struts control data flow?
Struts implements the MVC/Layers pattern through the
use of ActionForwards and ActionMappings
to keep control-flow decisions out of presentation layer.
What configuration files are used in Struts?
ApplicationResources.properties
struts-config.xml
These two files are used to bridge the gap between the
Controller and the Model.
What helpers in the form of JSP pages are provided in
Struts framework?
--struts-html.tld
--struts-bean.tld
--struts-logic.tld
Is Struts efficient?
The Struts is not only thread-safe but thread-dependent(instantiates
each Action once and allows other requests to be threaded through the original
object.
ActionForm beans minimize subclass code and shorten
subclass hierarchies
The Struts tag libraries provide general-purpose functionality
The Struts components are reusable by the application
The Struts localization strategies reduce the need for redundant JSPs
The Struts is designed with an open architecture--subclass available
The Struts is lightweight (5 core packages, 5 tag libraries)
The Struts is open source and well documented (code to be examined
easily)
The Struts is model neutral
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.
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.
How you will make available any Message Resources Definitions file to the Struts Framework Environment?
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 / >
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.
Write
code of any Action Class?
Here is the code of Action Class that returns the ActionForward
object.
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
public class TestAction extends Action
{
public ActionForward execute(
ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response) throws Exception
{
return mapping.findForward(\"testAction\");
}
}
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