Struts interview questions 7

31.What is DynaActionForm?

A specialized subclass of ActionForm that allows the creation of form beans with dynamic sets of properties (configured in configuration file), without requiring the developer to create a Java class for each type of form bean.

32.What are the steps need to use DynaActionForm?

Using a DynaActionForm instead of a custom subclass of ActionForm is relatively straightforward. You need to make changes in two places:

• In struts-config.xml: change your <form-bean> to be an org.apache.struts.action.DynaActionForm instead of some subclass of ActionForm

<form-bean name="loginForm"type="org.apache.struts.action.DynaActionForm" >
    <form-property name="userName" type="java.lang.String"/>
    <form-property name="password" type="java.lang.String" />
</form-bean>

In your Action subclass that uses your form bean:

• import org.apache.struts.action.DynaActionForm
• downcast the ActionForm parameter in execute() to a DynaActionForm
• access the form fields with get(field) rather than getField()

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.ActionMessage;
import org.apache.struts.action.ActionMessages;


import org.apache.struts.action.DynaActionForm;

public class DynaActionFormExample extends Action {
 public ActionForward execute(ActionMapping mapping, ActionForm form,
   HttpServletRequest request, HttpServletResponse response)
            throws Exception {            
  DynaActionForm loginForm = (DynaActionForm) form;
                ActionMessages errors = new ActionMessages();       
        if (((String) loginForm.get("userName")).equals("")) {
            errors.add("userName", new ActionMessage(
                            "error.userName.required"));
        }
        if (((String) loginForm.get("password")).equals("")) {
            errors.add("password", new ActionMessage(
                            "error.password.required"));
        }
        ...........

33.How to display validation errors on jsp page?

<html:errors/> tag displays all the errors. <html:errors/> iterates over ActionErrors request attribute.

34.What are the various Struts tag libraries?

The various Struts tag libraries are:

• HTML Tags
• Bean Tags
• Logic Tags
• Template Tags
• Nested Tags
• Tiles Tags

35.What is the use of <logic:iterate>?

<logic:iterate> repeats the nested body content of this tag over a specified collection.

<table border=1>
  <logic:iterate id="customer" name="customers">
    <tr>
      <td><bean:write name="customer" property="firstName"/></td>
      <td><bean:write name="customer" property="lastName"/></td>
      <td><bean:write name="customer" property="address"/></td>
   </tr>
  </logic:iterate>
</table>