Struts – part 1
Struts is a widely used open framework for developing Jave EE web applications
•Combines Java Servlets, JSP’s, custom tags and manages resources into a reusable framework
•Based on the Model-View-Controller Design pattern.
•Originally created by Craig McClanahan and donated to the Apache Foundation
In this session -we’ll look on
Model-View-Controller (MVC) Architecture
•How struts implements MVC architecture
•Discuss different components of struts
•A Sample Struts Application
•Advantage of using Struts
Model – View – Controller
Model-view-controller (MVC) is a design pattern used to separate data (model) and user interface (view), so that changes to the user interface do not impact the data handling and vice versa.
Model
• The domain-specific representation of the information on which the application operates. i.e the data and the business logic.
•
View
• Renders the model into a form suitable for interaction, typically a user interface element. HTML pages in case of web applications
•
Controller
• Processes and responds to user actions (request in web apps), and may invoke changes on the model.
• The model has no direct knowledge of the view.
Configuring Struts
•struts.jar in /WEB-INF/lib/
< web-app >
< servlet >
< servlet-name >action< /servlet-name >
< servlet-class >org.apache.struts.action.ActionServlet< /servlet-class >
< init-param >
< param-name config< /param-name >
< param-value > /WEB-INF/struts-config.xml< /param-value >
< /init-param >
< /servlet >
< servlet-mapping >
< servlet-name >action< /servlet-name >
< url-pattern >*.do< /url-pattern >
< /servlet-mapping >
< taglib>
< !- - taglibs used in the applications – >
< /taglib >
< /web-app >
Struts controller components
ActionServlet
•Extends HttpServlet
•Configured in web.xml, all requests reach the ActionServlet
•Instantiates and passes the request to the RequestProcessor
•
RequestProcessor
•Delegates the handling of the request to a helper class(Action Class) based on the struts configuration file.
•
Struts Action Classes
•Acts as a bridge between client side user action and business operation
•Can perform other functions like authorization, logging and session validation before invoking the business operation.
•We usually extend the Action class and override the execute method
Class LoginAction extends Action{
public ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response){
//take request parameters from the form and process them
// return the next view
return mapping.findForward(“nameOfNextView”)
}
}
Struts-config.xml
< struts-config >
…
< action path=“\login” type=”com.sample.struts.action.LoginAction” scope=”request” name=”loginForm” validate=”true” input=”/login.jsp” >
< forward name=”success” path=“/homepage.jsp”/ >
< forward name=”failure” path=”/login.jsp”/ >
< exception key=”error.invalidlogin” path=”/login.jsp” scope=”request” type=”come.sample.struts.exception.InvalidLoginException”/ >
< /action >
…
< struts-config >
Dispatch Action
•Allows multiple operations normally scattered across multiple action classes to a single class.
• Related functionality can be kept in a DispatchAction subclass
< action path=“\login” type=”com.sample.struts.action.AccountAction” scope=”request” parameter=”method” name=”loginForm” >
< forward name=”success” path=“/homepage.jsp”/ >
< forward name=”failure” path=”/login.jsp”/ >
< exception key=”error.invalidlogin” path=”/login.jsp” scope=”request” type=”come.sample.struts.exception.InvalidLoginException”/ >
< /action>
class AccountAction extends DispatchAction{
public ActionForward viewAccount(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response){
//take request parameters from the form and process them
// return the next view
return mapping.findForward(“nameOfNextView”)
}
}
Struts model components
Does not directly provide components for model since this is a web framework.
The following are the commonly used models.
•Data Transfer objects
•EJBs
•Business Object.
Struts view components
The components user for view in Struts are
•HTML
•Data Transfer Objects
•Struts Action Forms
•JSP
•Custom Tags
•Resource Bundles
