Struts

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.

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.

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.

Example:

<message-resources parameter="MessageResources" />.

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.

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.

The different kinds of actions in Struts are:

► ForwardAction

► IncludeAction

► DispatchAction

► LookupDispatchAction

► SwitchAction

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.

Struts is a set of cooperating classes, servlets, and JSP tags that make up a reusable MVC 2 design.

► JavaBeans components for managing application state and behavior.

► Event-driven development (via listeners as in traditional GUI development).

► Pages that represent MVC-style views; pages reference view roots via the JSF component tree.

To use the DispatchAction, follow these steps :

► Create a class that extends DispatchAction (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 DispatchAction class itself provides execute() method.

► Add an entry to struts-config.xml

Struts components can be categorize into Model, View and Controller:

► Model: Components like business logic /business processes and data are the part of model.

► View: HTML, JSP are the view components.

► Controller: Action Servlet of Struts is part of Controller components which works as front controller to handle all the requests.

We can get the values in the action classes by using data.getParameter("variable name defined in the velocity page");

Struts framework is an open-source framework for developing the web applications in Java EE, based on MVC-2 architecture. It uses and extends the Java Servlet API. 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.

The ForwardAction class is useful when you’re trying to integrate Struts into an existing application that uses Servlets to perform business logic functions. You can use this class to take advantage of the Struts controller and its functionality, without having to rewrite the existing Servlets. 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. By using this predefined action, you don’t have to write your own Action class. You just have to set up the struts-config file properly to use ForwardAction.

A framework is made up of the set of classes which allow us to use a library in a best possible way for a specific requirement.

when the scope is request,the values of formbean would be available for the current request.

when the scope is session,the values of formbean would be available throughout the session.

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

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.