ArticlesTutorialsInterview Questions & AnswersCertificationsFree Books & Sample ChaptersTechnical Discussions  Your Account | Advertise with us | Feedback |
Few pages of this site are under construction and we are constantly trying to improve it. If you have any suggestions or ideas about how to improve the site, please Let us know.
Struts Interview Questions

« Previous | 1 2 3 |Next »

add to:
Del.icio.us
Digg
Google
Spurl
Slashdot
Y! MyWeb
Blink
Furl
 
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>

36.What are differences between <bean:message> and <bean:write>

<bean:message>: is used to retrive keyed values from resource bundle. It also supports the ability to include parameters that can be substituted for defined placeholders in the retrieved string.

<bean:message key="prompt.customer.firstname"/>

<bean:write>: is used to retrieve and print the value of the bean property. <bean:write> has no body.

<bean:write name="customer" property="firstName"/>

37.How the exceptions are handled in struts?

Exceptions in Struts are handled in two ways:

  • Programmatic exception handling :
  • Explicit try/catch blocks in any code that can throw exception. It works well when custom value (i.e., of variable) needed when error occurs.

  • Declarative exception handling :You can either define <global-exceptions> handling tags in your struts-config.xml or define the exception handling tags within <action></action> tag. It works well when custom page needed when error occurs. This approach applies only to exceptions thrown by Actions.
<global-exceptions>
<exception key="some.key"
type="java.lang.NullPointerException"
path="/WEB-INF/errors/null.jsp"/>
</global-exceptions>

or

<exception key="some.key" 
type="package.SomeException"
path="/WEB-INF/somepage.jsp"/>

38.What is difference between ActionForm and DynaActionForm?
  • An ActionForm represents an HTML form that the user interacts with over one or more pages. You will provide properties to hold the state of the form with getters and setters to access them. Whereas, using DynaActionForm there is no need of providing properties to hold the state. Instead these properties and their type are declared in the struts-config.xml
  • The DynaActionForm bloats up the Struts config file with the xml based definition. This gets annoying as the Struts Config file grow larger.
  • The DynaActionForm is not strongly typed as the ActionForm. This means there is no compile time checking for the form fields. Detecting them at runtime is painful and makes you go through redeployment.
  • ActionForm can be cleanly organized in packages as against the flat organization in the Struts Config file.
  • ActionForm were designed to act as a Firewall between HTTP and the Action classes, i.e. isolate and encapsulate the HTTP request parameters from direct use in Actions. With DynaActionForm, the property access is no different than using request.getParameter( .. ).
  • DynaActionForm construction at runtime requires a lot of Java Reflection (Introspection) machinery that can be avoided.

39.How can we make message resources definitions file available to the Struts framework environment?

We can make message resources definitions file (properties file) available to Struts framework environment by adding this file to struts-config.xml.

<message-resources parameter="com.login.struts.ApplicationResources"/>

40.What is the life cycle of ActionForm?

The lifecycle of ActionForm invoked by the RequestProcessor is as follows:

  • Retrieve or Create Form Bean associated with Action
  • "Store" FormBean in appropriate scope (request or session)
  • Reset the properties of the FormBean
  • Populate the properties of the FormBean
  • Validate the properties of the FormBean
  • Pass FormBean to Action


Back to top

« Previous | 1 2 3 |Next »
Test

Add this FAQs to :
Del.icio.us
Digg
Google
Spurl Slashdot
Y! MyWeb
Blink
Furl
 

  ALSO SEE :

About Us | Our Mission | Terms of use | Author Terms |    Search        | Contact Us | Advertise With Us | Link to Us | Sitemap
Copyright © 2016 developersBOOK.COM. All rights reserved.