[DSBW Spring 2009] Unit 07: WebApp Design Patterns & Frameworks (3/3)

Unit 7: Design Patterns and Frameworks
 “A framework is a defined support structure in which another
software project can be organized and developed. A framework may
include support programs, code libraries, a scripting language, or
other software to help develop and glue together the different
components of a software project” (from Wikipedia)

 Here we are going to consider 3 MVC-based Web frameworks for
Java:
Struts 1


Spring MVC


JavaServer Faces


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Struts 1: Overview

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Struts 1: Terminology wrt. J2EE Core Patterns

Struts 1 J2EE Core Patterns
Implementation Concept

ActionServlet Front Controller

RequestProcessor Application Controller

UserAction Businesss Helper

ActionMapping View Mapper

ActionForward View Handle

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Struts 1: Example - Wall’s New User

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Struts 1: Example – wall_register.vm (Velocity template)
<html><head> .... </head>
<body>
…
<form action = “register.doquot; method=quot;postquot;>
User’s Nickname:
<input name=“usernamequot; value=quot;$!registrationForm.usernamequot;
size=40> $!errors.wrongUsername.get(0)
Password :
<input name=“userpassword“ size=40> $!errors.wrongPassword.get(0)

<!–- CAPTCHA CODE -->

<input type=quot;submitquot; name=quot;insertquot; value=“insertquot;>
</form>

<center>$!errors.regDuplicate.get(0)</center>

</body></html>

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Struts 1: Example – Form validation

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Struts 1: Example - RegistrationForm
public class RegistrationForm extends ActionForm
{
protected String username;
// ... The remaining form attributes + getter & setter methods

public void reset(ActionMapping mapping,
HttpServletRequest request) {
/* ... Attribute initialization */ }

public ActionErrors validate(ActionMapping mapping,
HttpServletRequest request) {
ActionErrors errors = new ActionErrors();
if (username== null || username.equals(quot;quot;)) {
errors.add(“wrongUsernamequot;,
new ActionMessage(quot;errors.username”));
}
// .... Remaining validations
return errors; }
}

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Struts 1: Example – Error Messages (Message.properties file)

errors.username=(*) Username required

errors.password=(*) Password required

errors.regCAPTCHA=(*) Invalid CAPTCHA values

errors.duplicateUser = Username '{0}' is already taken by
another user

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Struts 1: Example – Application Error (duplicated username)

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Struts 1: Example - UserAction
public class RegisterAction extends Action {
public ActionForward execute(ActionMapping mapping,
ActionForm form, HttpServletRequest request,
HttpServletResponse response)
{ String username = ((RegistrationForm) form).getUsername();
String password = ((RegistrationForm) form).getUserpassword();
TransactionFactory txf = (TransactionFactory) request.
aaaagetSession().getServletContext().getAttribute(quot;transactionFactoryquot;);
try {
Transaction trans = txf.newTransaction(quot;RegisterTransquot;);
trans.getParameterMap().put(quot;usernamequot;, username);
trans.getParameterMap().put(quot;passwordquot;, password);
trans.execute();
request.getSession().setAttribute(quot;userquot;,username);
request.getSession().setAttribute(quot;userIDquot;,
trans.getParameterMap().get(quot;userIDquot;));
return (mapping.findForward(quot;successquot;));
}
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Struts 1: Example – UserAction (cont.)
catch (BusinessException ex)
{
if (ex.getMessageList().elementAt(0).startsWith(quot;Usernamequot;))
{
ActionMessages errors = new ActionMessages();
errors.add(quot;regDuplicatequot;,
new ActionMessage(quot;errors.duplicateUserquot;,username));
this.saveErrors(request, errors);
form.reset(mapping,request);
return (mapping.findForward(quot;duplicateUserquot;));
}
else {
request.setAttribute(quot;theListquot;,ex.getMessageList());
return (mapping.findForward(quot;failurequot;));
}
}
}
}
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Struts 1: Example - struts-config.xml (fragment)
<action-mappings>
<action path=quot;/registerquot;
type=quot;wallFront.RegisterActionquot;
name=quot;registrationFormquot;
scope=quot;requestquot;
validate=quot;truequot;
input=quot;/wall_register.vmquot;>
<forward name=quot;failurequot; path=quot;/error.vmquot;/>
<forward name=quot;duplicateUser“
path=quot;/wall_register.vmquot;/>
<forward name=quot;successquot;
path=quot;/wallquot; redirect=quot;truequot;/>
</action>
…
</action-mappings>

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Struts 1: Example - web.xml (fragment)

<servlet>
<servlet-name>action</servlet-name>
<servlet-class> org.apache.struts.action.ActionServlet
</servlet-class>
<init-param>
<param-name>config</param-name>
<param-value>/WEB-INF/struts-config.xml</param-value>
</init-param>
</servlet>


<servlet-mapping>
<servlet-name>action</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>

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Struts 1: Example - web.xml (fragment, cont.)
<servlet>
<servlet-name>velocity</servlet-name>
<servlet-class>
org.apache.velocity.tools.view.servlet.VelocityViewServlet
</servlet-class>
<init-param>
<param-name>org.apache.velocity.toolbox</param-name>
<param-value>/WEB-INF/toolbox.xml</param-value>
</init-param>
<init-param>
<param-name>org.apache.velocity.properties</param-name>
<param-value>/WEB-INF/velocity.properties</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>velocity</servlet-name>
<url-pattern>*.vm</url-pattern>
</servlet-mapping>
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Struts 2
 Struts 1 + Webwork = Struts 2
 Struts 2 vs Struts 1 (according to struts.apache.org/2.x)
 Enhanced Results - Unlike ActionForwards, Struts 2 Results can actually help
prepare the response.
 Enhanced Tags - Struts2 tags don't just output data, but provide stylesheet-
driven markup, so that we consistent pages can be created with less code.
 POJO forms - No more ActionForms: we can use any JavaBean we like or put
properties directly on our Action classes.
 POJO Actions - Any class can be used as an Action class. Even the interface is
optional!
 First-class AJAX support - The AJAX theme gives interactive applications a
boost.
Easy-to-test Actions – Struts 2 Actions are HTTP independent and can be

tested without resorting to mock objects.
 Intelligent Defaults - Most framework configuration elements have a default
value that we can set and forget.

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Struts 2: Tagging example
<s:actionerror/>
<s:form action=quot;Profile_updatequot; validate=quot;truequot;>
<s:textfield label=quot;Usernamequot;
name=quot;usernamequot;/>
<s:password label=quot;Passwordquot;
name=quot;passwordquot;/>
<s:password label=quot;(Repeat) Passwordquot;
name=quot;password2quot;/>
<s:textfield label=quot;Full Namequot; name=quot;fullNamequot;/>
<s:textfield label=quot;From Addressquot;
name=quot;fromAddressquot;/>
<s:textfield label=quot;Reply To Addressquot;
name=quot;replyToAddressquot;/>
<s:submit value=quot;Savequot; name=quot;Savequot;/>
<s:submit action=quot;Register_cancelquot;
value=quot;Cancelquot; name=quot;Cancelquot;
onclick=quot;form.onsubmit=nullquot;/> </s:form>

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Spring MVC
 Spring's own implementation of the Front Controller Pattern

 Flexible request mapping and handling

 Full forms support

 Supports several view technologies
 JSP/Tiles, Velocity, FreeMarker

 Support integration with other MVC frameworks
 Struts, Tapestry, JavaServerFaces, WebWork

 Provides a JSP Tag Library

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Spring Framework Architecture

Spring Web
Spring ORM
WebApplicationContext
Hibernate support
Struts integration
Spring MVC
iBatis support
Tiles integration
Spring AOP JDO support Web MVC
Web utilities
AOP infrastructure Framework
Metadata support JSP support
Declarative transaction Velocity/FreeMarker
Spring Context
Spring DAO
management support
PFD/Excel support
Transaction Infrastructure ApplicationContext
JDBC support JNDI, EJB support
DAO support Remoting

Spring Core
IoC Container

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Spring MVC: Request Lifecycle

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Spring MVC: Terminology wrt. J2EE Core Patterns

Spring MVC J2EE Core Patterns
Concept

DispatcherServlet Front Controller /
Application Controller

HandlerMapping Command Mapper

ModelAndView View Handle /
Presentation Model

ViewResolver View Mapper

Controller Business Helper

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Spring MVC: Setting Up
1. Add the Spring dispatcher servlet to the web.xml

2. Configure additional bean definition files in web.xml

3. Write Controller classes and configure them in a bean definition file,
typically META-INF/<appl>-servlet.xml

4. Configure view resolvers that map view names to to views (JSP,
Velocity etc.)

5. Write the JSPs or other views to render the UI

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Spring MVC: Controllers
public class ListCustomersController implements Controller {
private CustomerService customerService;
public void setCustomerService(CustomerService
customerService)
{ this.customerService = customerService; }

public ModelAndView handleRequest(HttpServletRequest req,
HttpServletResponse res) throws Exception
{
return new ModelAndView(“customerList”, “customers”,

customerService.getCustomers());
}
}
 ModelAndView object is simply a combination of a named view and
a Map of objects that are introduced into the request by the
dispatcher

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Spring MVC: Controllers (cont.)
 Interface based
Do not have to extend any base classes (as in Struts)


 Have option of extending helpful base classes
Multi-Action Controllers

 Command Controllers
Dynamic binding of request parameters to POJO (no


ActionForms)
Form Controllers

Hooks into cycle for overriding binding, validation, and inserting


reference data
Validation (including support for Commons Validation)


Wizard style controller


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JavaServer Faces (JSF)
 Sun’s “Official” Java-based Web application framework

 Specifications:
 JSF 1.0 (11-03-2004)
 JSF 1.1 (25-05-2004)
 JSF 1.2 (11-05-2006)
 JSF 2.0 (2009?)

 Main characteristics:
UI component state management across requests

 Mechanism for wiring client-generated events to server side
application code
 Allow custom UI components to be easily built and re-used
 A well-defined request processing lifecycle
 Designed to be tooled

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JSF: Application Architecture

Servlet Container
Client
JSF Application
Devices

Business DB
Phone
Objects
JSF Framework
PDA
Model
Objects
Laptop EJB
Container

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JSF framework: MVC

Request Response

Model Objects
Component
FacesServlet
Tree Managed JavaBeans

View
Resources Delegates
JavaBeans Converters
Config
Property Files Validators
XML Renderers

Action
Business Objects
Handlers
Controller EJB Model
& Event
JDO
Listeners
JDBC

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JSF: Request Processing Lifecycle

Response Complete Response Complete

Restore
Request Apply Request Process Process Process
Component
Value Events Validations Events
Tree

Render Response

Response Complete Response Complete

Response Render Process Invoke Process Update Model
Response Events Application Events Values

Conversion Errors

Validation or
Conversion Errors

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 Restore Component Tree:
The requesting page’s component tree is retrieved/recreated.

 Stateful information about the page (if existed) is added to the request.

 Apply Request Value:
 Each component in the tree extracts its new value from the request
parameters by using its decode method.
 If the conversion of the value fails, an error message associated with
the component is generated and queued .
 If events have been queued during this phase, the JSF implementation
broadcasts the events to interested listeners.

 Process Validations:
 The JSF implementation processes all validators registered on the
components in the tree. It examines the component attributes that
specify the rules for the validation and compares these rules to the local
value stored for the component.

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 Update Model Values:
 The JSF implementation walks the component tree and set the
corresponding model object properties to the components' local values.
 Only the bean properties pointed at by an input component's value
attribute are updated

 Invoke Application:
 Action listeners and actions are invoked
 The Business Logic Tier may be called

 Render Response:
 Render the page and send it back to client

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JSF: Anatomy of a UI Component

Event
Render
Handling
Model

binds has
has

Id has has
Validators
UIComponent
Local Value
Attribute Map
has
has

Child
Converters
UIComponent

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JSF: Standard UI Components
 UIInput
 UICommand
 UIOutput
 UIForm
 UISelectBoolean
 UIColumn
 UISelectItem
 UIData
 UISelectMany
 UIPanel
 UISelectOne

 UISelectMany

 UIGraphic

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JSF: HTML Tag Library
 JSF Core Tag Library (prefix: f)
 Validator, Event Listeners, Converters

 JSF Standard Library (prefix: h)
 Express UI components in JSP

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JSF: HTML Tag Library
<f:view>
<h:form id=”logonForm”>
<h:panelGrid columns=”2”>
<h:outputLabel for=”username”>
<h:outputText value=”Username:”/>
</h:outputLabel>
<h:inputText id=”username” value=”#{logonBean.username}”/>
<h:outputLabel for=”password”>
<h:outputText value=”Password:”/>
</h:outputLabel>
<h:inputSecret id=”password”
value=”#{logonBean.password}”/>
<h:commandButton
id=”submitButton” type=”SUBMIT”
action=”#{logonBean.logon}”/>
<h:commandButton
id=”resetButton” type=”RESET”/>
</h:panelGrid>
</h:form>
</f:view>

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JSF: Managed (Model) Bean
 Used to separate presentation from business logic

 Based on JavaBeans

 Similar to Struts ActionForm concept

 Can also be registered to handle events and conversion and
validation functions

 UI Component binding example:

<h:inputText id=”username”
value=”#{logonBean.username}”/>

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References
 Books:
 B. Siggelkow. Jakarta Struts Cookbook. O'Reilly, 2005
 J. Carnell, R. Harrop. Pro Jakarta Struts, 2nd Edition. Apress, 2004
 C. Walls, R. Breidenbach. Spring in Action. Manning, 2006.
 B. Dudney, J. Lehr, B. Willis, L. Mattingly. Mastering JavaServer
Faces. Willey, 2004.

 Web sites:
 struts.apache.org
 rollerjm.free.fr/pro/Struts11.html
 www.springframework.org
 static.springframework.org/spring/docs/1.2.x/reference/mvc.html
 java.sun.com/javaee/javaserverfaces

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[DSBW Spring 2009] Unit 07: WebApp Design Patterns & Frameworks (3/3)

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