1. INTRODUCTION TO STRUTS
Presentation by
NEELIMA MULAMPAKA
2008 Spring Class – CSI668

2. STRUTS - Agenda History Application Framework
Model-View-Controller Design Pattern
Struts Architecture
How Struts Works
Major Struts Components
The Big Picture
Strengths And Weaknesses
A Simple Application
References
Assignment

3. History
Struts is hosted by the Apache Software Foundation (ASF) as part of its Jakarta Project.
The primary architect and developer of the Struts framework is Craig R.McClanahan.
MVC-based (Model-View-Controller) open source software Used for constructing web applications using Servlets and JSPs
Why is it called Struts ?

4. Framework
Is a reusable, semi-complete application that can be specialized to produce custom applications .
Application frameworks build on a common ground to provide developers with a reusable structure that can serve as the foundation for their own products.
Provides developers with a set of backbone components .

5. Common Framework Strategies
Java web application frameworks use several common techniques to help make products easier to design, write, and maintain.
Some common components:
External configuration files.
A central controller
External presentation systems

6. Framework Components

7. Model-View-Controller

8. MVC-based Architecture
3 Major Components in Struts
Servlet controller (Controller)
Java Server Pages or any other presentation technology (View)
Application Business Logic in the form of whatever suits the application (Model)
The centerpiece of Struts is MVC style controller.
Struts is focused on Controller
Struts is Model and View independent

9. Controller Is the switch board of MVC architecture
Every request goes through the controller
Responsible for flow control (action mapping) of the request handling
Reads configuration file to determine the flow control

10. Controller Components in Struts Framework
Major Struts classes as they relate to MVC
ActionServlet - The part of the Controller that receives user gestures and state changes and issues view selections
ActionMapping - The state change event
ActionForm - The data for a state change
ActionClass - The part of the Controller that interacts with the model to execute a state change or query and advises the ActionServlet of the next view to select
ActionForward - A user gesture or view selection

11. How Struts Works

12. Struts Flow (Struts 1.0)

13. Struts View Helpers Tag Library Descriptor Purpose
struts-html.tld JSP tag extension for HTML forms
struts-bean.tld JSP tag extension for handling JavaBeans
struts-logic.tld JSP tag extension for testing the values of properties

14. The Big Picture Struts request-response process
A client requests a path that matches the Action URI pattern .
The container passes the request to the ActionServlet.
If this is a modular application, the ActionServlet selects the appropriate module.
The ActionServlet looks up the mapping for the path.
If the mapping specifies a form bean, the ActionServlet sees if there is one already or creates one .
If a form bean is in play, the ActionServlet resets and populates it from the HTTP request.
If the mapping has the validate property set to true, it calls validate on the form bean .
If it fails, the servlet forwards to the path specified by the input property and this control flow ends.

15. The Big Picture(contd)
If the mapping specifies an Action type, it is reused if it already exists or instantiated .
The Action’s perform or execute method is called and passed the instantiated form bean (or null).
The Action may populate the form bean, call business objects, and do whatever else is needed .
The Action returns an ActionForward to the ActionServlet.
If the ActionForward is to another Action URI, we begin again; otherwise,
It’s off to a display page or some other resource. Most often, it is a JSP.

16. The Big Picture

17. What Does ActionServlet Do?
Performs the role of Controller
Process user requests
Determine what the user is trying to achieve according to the request
Pull data from the model (if necessary) to be given to the appropriate view, and Select the proper view to respond to the user
Delegates most of this grunt work to Action classes

18. ActionServlet(contd)
Invoking ActionServlet
One of the standard servlet settings is the servlet mapping. The container uses this setting to decide which requests are sent to which servlet:
<servlet-mapping>
<servlet-name>action</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>

19. ActionServlet(contd)
ActionServlet is configured in the web.xml
<servlet>
<servlet-name>action</servlet-name>
<servlet-class>
org.apache.struts.action.ActionServlet
</servlet-class>
</servlet>

20. ActionMapping (You provide it)
Action Mapping is configured in Struts Config File
Each action element has requires the following attributes to be defined:
path: The application context-relative path to the action
type: The fully qualified java classname of your Action class
name: The name of your <form-bean> element to use with this action

21. ActionMapping(contd)
<action-mappings>
<action path="/submit"
type="hansen.playground.SubmitAction"
name="submitForm"
input="/submit.jsp"
scope="request"
validate="true">
<forward name="success" path="/submit.jsp"/>
<forward name="failure" path="/submit.jsp"/>
</action>
</action-mappings>

22. ActionForm (You provide it)
Provided by developer
Define an ActionForm bean (that is, a Java class extending the ActionForm class) for the input form
Extend Struts-provided ActionForm class
Define it in servlet-config.xml file
<form-bean>
name attribute of <Action> class
Contains only property getter and property
setter methods for each field-no business logic
Provides standard validation mechnism

23. ActionForm(contd) <form-beans> <form-bean name="submitForm"
type="hansen.playground.SubmitForm"/>
</form-beans>

24. How to write ActionForm Bean
Add just getter and setter methods for each property of a input form
Do not include any business logic code
Add a standard validation method
Controller will call this validation
Define a property (with associated getXxx and setXxx methods) for each field that is present in the form

25. Action Class Focus on control flow
Process client request by calling other objects (BusinessLogic beans) inside its execute() method
Returns an ActionForward object that identifies where control should be forwarded
JSP
Another Action

26. execute(..) method of Actionclass (Struts 1.1 only)
Invoked by controller
Function Signature
public ActionForward execute(
ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception;

27. ActionForward - View
ActionForward object tells Servlet controller which JSP page is to be dispatched to
JSP pages use ActionForm beans to get output Model data to display
Struts contains a series of tag libraries
Facilitates communication between HTML designers and developers
Facilitates dynamic Web content

28. Struts Configuration (strut-config.xml)
It is like a Blueprint of your Application.
Lot of information collected in one place.
Every component in the struts configuration is a java object

29. Struts Configuration(contd)
A very simple application could create all of these informational objects in an initialization method and then set each object to the default values needed.
For example:
ActionForward logoff = new ActionForward();
logoff.setName("logoff");
logoff.setPath("/Logoff.do");
ActionForward logon = new ActionForward();
logoff.setName("logon");
logoff.setPath("/Logon.do");

30. Struts-config.xml <?xml version="1.0" encoding="ISO-8859-1" ?>
<!DOCTYPE struts-config PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 1.1//EN“ "
<struts-config>
<!-- == Form Bean Definitions == -->
<form-beans>
<form-bean name="submitForm"
type="hansen.playground.SubmitForm"/>
</form-beans>

31. Struts-config.xml(Contd)
<!-- == Action Mapping Definitions == -->
<action-mappings>
<action path="/submit"
type="hansen.playground.SubmitAction"
name="submitForm" input="/submit.jsp"
scope="request“ validate="true">
<forward name="success“path="/submit.jsp"/>
<forward name="failure" path="/submit.jsp"/>
</action>
</action-mappings>
</struts-config>

32. Validation
Indicate you want input validation as attributes of <action> element under
<action-mapping> in strut-config.xml file – validate=”true”
Specify the JSP page that needs to be
displayed when validation fails
input=”/errorpage.jsp”
Override validate() method within
ActionForm class – optional

33. struts-config.xml:Validation
Example
<action-mappings>
<action path="/submit"
type="hansen.playground.SubmitAction"
name="submitForm"
input="/submit.jsp"
scope="request"
validate="true">
<forward name="success" path="/submit.jsp"/>
<forward name="failure" path="/submit.jsp"/>
</action>
</action-mappings>
</struts-config>

34. Strengths HTTP-centric Standard logging Lightweight Open source
Strongly founded in design patterns

35. Weaknesses Logging Loads a single configuration file per application
Single ActionServlet
Requires understanding of Struts components

36. A Simple Application Simple user registration application.
Registration screen
Three Fields -username,password, and confirmation password.
A successful registration requires that the two passwords match.
If the registration is successful, control flows to a page that says successful!. If the two passwords do not match, control flows to a page that says failure.

37. Create The ActionForm package app; import org.apache.struts.action.*;
public class RegisterForm extends ActionForm {
protected String username;
protected String password1;
protected String password2;
public String getUsername () {return username;}
public String getPassword1() {return password1;}
public String getPassword2() {return password2;}
public void setUsername (String username) {this.username = username;}
public void setPassword1(String password) {this.password1 = password;}
public void setPassword2(String password) {this.password2 = password;} }

38. Creating the RegisterAction
package app;
import org.apache.struts.action.*;
import javax.servlet.http.*;
import java.io.*;
public class RegisterAction extends Action {
public ActionForward perform (ActionMapping mapping,
ActionForm form,
HttpServletRequest req,
HttpServletResponse res) {
// b Cast the form to the RegisterForm
RegisterForm rf = (RegisterForm) form;
String username = rf.getUsername();
String password1 = rf.getPassword1();
String password2 = rf.getPassword2();

39. Creating the RegisterAction(contd)
// c Apply business logic
if (password1.equals(password2)) {
try {
// d Return ActionForward for success
UserDirectory.getInstance().setUser(username,password1);
return mapping.findForward("success");
} catch (UserDirectoryException e) {
return mapping.findForward("failure"); }
// E Return ActionForward for failure

40. Creating the Struts configuration file (struts-config.xml)
<?xml version="1.0" encoding="ISO " ?>
<!DOCTYPE struts-config PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 1.0//EN"
"
<struts-config>
<form-beans>
<form-bean name="registerForm" type="app.RegisterForm"/>
</form-beans>
<action-mappings

41. Creating the Struts configuration file (struts-config.xml)(contd)
<action path="/register"
type="app.RegisterAction"
name="registerForm"
input="/register.jsp">
<forward name="success" path="/success.html"/>
<forward name="failure" path="/failure.html"/>
</action>
</action-mappings>
</struts-config>

42. References
Struts In Action By Ted Husted
Jakarta Struts By O’Reilly

43. Assignment
The application you are going to create mimics entering an employee into a database. The user will be required to enter an employee's name and age.

44. NEELIMA MULAMPAKA nm121262@albany.edu
QUESTIONS ??
NEELIMA MULAMPAKA