resourcebundle.properties file is used to define specific error messages in key value pairs for any possible errors that may occur in the code. This approach helps to keep the code clean as developer doesn’t need to embed all error messages inside code.
This tag is used whenever the requested variable has a value which is present in the sub string. To evaluate the contents present in the nested tag, logic match is used. This tag is used when the requested value is present in the tag of the variable in which this value is present.
In Struts framework, actionServlet acts as a controller and all the requests made by users are controlled by this controller. ActionServlet is based on singleton design patter as only one object needs to be created for this controller class. Multiple threads are created later for each user request.
Struts.xml file is one the key configuration files of Struts framework which is used to define mapping between URL and action. When a user’s request is received by the controller, controller uses mapping information from this file to select appropriate action class.
When logic for exception handling is defined in struts-config.xml or within the action tag, it’s known as declarative exception handling in Struts. In the following example, we have defined exception in struts-config.xml file for NullPointerException:
Execute method of action class is responsible for execution of business logic. If any processing is required on the user’s request, it’s performed in this method. This method returns actionForward object which routes the application to appropriate page.
Tiles help the developer to create a template and a validator framework. If a developer is planning to develop a website where there would be almost 500 pages of static content and additional dynamic content then it is recommended for him to use template designed with the help of Tiles because it would help him in making necessary changes.
Tiles allow template mechanism to be present in your components. You can compose a presentation layer from different components such as footer, header and content components. This form of composition helps in validating web forms much easier.
Library tag is a very powerful tag which is used to write code for Java beans programs. This tag gives a special permission to read and write the content of beans without any special form of embedded java code in the application.
Basically Dispatch action is used when you have multiple submit buttons in a single form.The Dispatch action is a class which extends the Struts DispatchAction , and encpsulates all the action methods (similar to execute method in Action class)in one single class.These actions methods will get executed based on the parameter that you pass in a jsp page.In the Struts-Config.xml you need to define the DispatchAction class and the parameter name that you passing in the URL.Based on the parameter the Controller will invoke the action method.
struts-config.xml
parameter –attribute is used to delegate the request to corresponding method of the BookAction class. So define this value with appropriate name.
BookAction.java
It eliminates theexecutemethod entirely. Because it directly implements the desired methods, those custom methods have same signature asexecutemethod.
The class BookAction extends org.apache.struts.actions.DispatchAction
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.action.ActionForward;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.actions.DispatchAction;
public class BookAction extends DispatchAction
{
public ActionForward addBook(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) {
System.out.println("Add Book Page");
return mapping.findForward("addBook");
}
public ActionForward editBook(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) {
System.out.println("Edit Book Page");
return mapping.findForward("editBook");
}
public ActionForward saveBook(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) {
System.out.println("Save Book Page");
return mapping.findForward("saveBook");
}
public ActionForward deleteBook(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) {
System.out.println("Delete Book Page");
return mapping.findForward("deleteBook");
}
}
bookdetails.jsp
This page has four different links for doing different actions say Add/Edit/Save/Delete books. Every individual action has to be uniquely represented by the request parameteractionMethod.
An Action that includes the context-relative URI specified by the parameter property of our associated ActionMapping. This can be used to integrate Struts with other business logic components that are implemented as servlets (or JSP pages), but still take advantage of the Struts controller servlet's functionality
The struts framework ForwardAction class provides a mechanism for forwarding to a specified URL. In an MVC Web application, all requests to the application are supposed to flow through the Controller servlet.
This will ensure that the Controller layer of the application has an opportunity to prepare any resources that may be needed to handle the request meaning selecting the correct module and so on. The struts framework ForwardAction is provided as a simple utility action that can be used for scenarios in which you simply want to link to a JSP page. Example:
Mutli-click prevention using struts tokens- Prevent Duplicate Submission : saveToken() : generate the token key and save to request/session attribute. isTokenValid() : validate submitted token key against the 1 store in request/session. resetToken() : reset the token key
Follow the steps to setup Mutli-click prevention using struts tokens.
Step 1: Action Class where saveToken() before JSP Page
First saveToken() then forward to your jsp.
Upon loading the form, invokes saveToken() on the action class to create and store the token key.
Struts will store the generated key in request/session.
public class LoadAction extends Action
{
public ActionForward execute(ActionMapping mapping,ActionForm form,
HttpServletRequest request,HttpServletResponse response)
{ ActionForward forward;
saveToken(request);
forward=mapping.findForward("empformpage");
// this is the jsp page where you want to struts tokens.
return forward;
}
}
Step 2:Store Token key as a hidden field ( empform.jsp)
In the browser if you type :
http://localhost:8080/testApp/loadActio.do
This will call execute() method of LoadAction.
Then saveToken(request);//create and store the token key
and mapping.findForward("empformpage"); forward to empform.jsp (below code is for empform.jsp)
Step 3. Check Token is Valid ?
Once the form submitted, invokes isTokenValid() on the action class,
it will validate the submitted token key(hidden field) with the token key stored previously on request/session.
If match, it will return true.
public class SubmitAction extends Action
{
public ActionForward execute(ActionMapping mapping ,ActionForm form ,HttpServletRequest request,
HttpServletResponse response)
{
EmpForm frm=(EmpForm)form;
if(isTokenValid(request))
{ // This is Not Duplicate Submission of the form
// You can add your logic here
resetToken(request);
return mapping.findForward("sucess");
}
else
{ // This is Duplicate Submission of the form
// Return to the JSP to display the error message ( This is Duplicate Submission);
return mapping.findForward("duplicatesubmitpage");
}
}
}
Posted in: Struts FAQs