1Struts DynaActionForm

In this tutorial you will learn how to create Struts DynaActionForm. We will recreate our address form with Struts DynaActionForm. DynaActionForm is specialized subclass of ActionForm that allows the creation of form beans with dynamic sets of properties, without requiring the developer to create a Java class for each type of form bean. DynaActionForm eliminates the need of FormBean class and now the form bean definition can be written into the struts-config.xml file. So, it makes the FormBean declarative and this helps the programmer to reduce the development time.

In this tutorial we will recreate the add form with the help of DynaActionForm. It also shows you how you can validate use input in the action class. 

Adding DynaActionForm Entry in struts-config.xml

First we will add the necessary entry in the struts-config.xml file.  Add the following entry in the struts-config.xml file. The form bean is of org.apache.struts.action.DynaActionForm type. The <form-property/> tag is used to define the property for the form bean. We have defined three properties for our dynamic form bean.

Adding action mapping

Add the following action mapping in the struts-config.xml file:

Creating Action Class

Code for action class is as follows:

 package roseindia.net;                        

                        /**

                        * @author Deepak Kumar

                        * @Web http://www.roseindia.net

                        * @Email [email protected]

                        */                        

                        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;

                        import org.apache.struts.action.DynaActionForm;

                        import org.apache.struts.action.ActionMessages;

                        import org.apache.struts.action.ActionMessage;                        

                        public class AddressDynaAction extends Action

                        {

                          public ActionForward execute(

                          ActionMapping mapping,

                          ActionForm form,

                          HttpServletRequest request,

                          HttpServletResponse response) throws Exception{      

                          DynaActionForm addressForm = (DynaActionForm)form;

                        
                         //Create object of ActionMesssages

                          ActionMessages errors = new ActionMessages();

                          //Check and collect errors

                          if(((String)addressForm.get("name")).equals("")) {

                         errors.add("name",new ActionMessage("error.name.required"));

                          }                        

                          if(((String)addressForm.get("address")).equals("")) {

                         errors.add("address",new ActionMessage("error.address.required"));

                          }                       

                          if(((String)addressForm.get("email")).equals("")) {

                         errors.add("email",new ActionMessage("error.emailaddress.required"));

                          }

                          //Saves the error

                          saveErrors(request,errors);

                          //Forward the page

                          if(errors.isEmpty()){

                          return mapping.findForward("success");

                          }else{

                          return mapping.findForward("invalid");

                          }

                          }
 
                        

Creating the JSP file

We will use the Dyna Form DynaAddressForm created above in the jsp file. Here is the code of the jsp(DynaAddress.jsp) file.

Add the following line in the index.jsp to call the form.

<li>
<html:link page="/pages/DynaAddress.jsp">Dyna Action Form Example</html:link>
<br>
Example shows you how to use DynaActionForm.
</li>

Building Example and Testing

To build and deploy the application go to Struts\strutstutorial directory and type ant on the command prompt. This will deploy the application. Open the browser and navigate to the DynaAddress.jsp page. Without entering anything in the form and submitting the submit button, your browser should show the following out put.