Unit 07: Design Patterns and Frameworks (3/3)

Unit 7: Design Patterns and Frameworks

 A framework “is an abstraction in which common code
providing generic functionality can be selectively overridden
or specialized by user code providing specific functionality.”
(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 - WoT’s New User

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Struts 1: Example – user_registration.vm (Velocity template)

<html><head> .... </head>
<body>
…
<form action = “register.do" method="post">
User’s Nickname:
<input name=“username"
value="$!registrationForm.username" size=40>
$!errors.wrongUsername.get(0)
Password :
<input name=“userpassword“ size=40>
$!errors.wrongPassword.get(0)
<!–- CAPTCHA CODE -->
<input type="submit" name="insert" value=“insert">
</form>
<center>$!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 reg_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 (reg_username == null || reg_username.equals("")) {
errors.add(“wrongUsername",
new ActionMessage("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).getReg_username();
String password = ((RegistrationForm) form).getReg_password();
Connection dbConnection = … ;
try {
Transaction trans = Transaction.newTransaction("RegisterTrans");
trans.getParameterMap().put("dbConnection", dbConnection);
trans.getParameterMap().put("username", username);
trans.getParameterMap().put("password", password);
trans.execute();
request.getSession().setAttribute("loggedUserNAME",username);
request.getSession().setAttribute("loggedUserID",trans.getPara
meterMap().get("userID"));
return (mapping.findForward("success"));
}

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Struts 1: Example – UserAction (cont.)
catch (BusinessException ex)
{
if (ex.getMessageList().elementAt(0).startsWith("Username"))
{
ActionMessages errors = new ActionMessages();
errors.add("regDuplicate",
new ActionMessage("errors.duplicateUser",username));
this.saveErrors(request, errors);
form.reset(mapping,request);
return (mapping.findForward("duplicateUser"));
}
else {
request.setAttribute("theList",ex.getMessageList());
return (mapping.findForward("failure"));
}
}
}
}

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Struts 1: Example - struts-config.xml (fragment)

<action-mappings>
<action path="/register"
type="woTFront.RegisterAction"
name="registrationForm"
scope="request"
validate="true"
input="/user_registration.vm">
<forward name="failure" path="/error.vm"/>
<forward name="duplicateUser“
path="/user_registration.vm"/>
<forward name="success"
path="/wall" redirect="true"/>
</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 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="Profile_update" validate="true">
<s:textfield label="Username" name="username"/>
<s:password label="Password" name="password"/>
<s:password label="(Repeat) Password"
name="password2"/>
<s:textfield label="Full Name" name="fullName"/>
<s:textfield label="From Address"
name="fromAddress"/>
<s:textfield label="Reply To Address"
name="replyToAddress"/>
<s:submit value="Save" name="Save"/>
<s:submit action="Register_cancel" value="Cancel"
name="Cancel" onclick="form.onsubmit=null"/>
</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
iBatis support Tiles integration Spring MVC
JDO support Web utilities
Spring AOP Web MVC Framework
AOP infrastructure JSP support
Metadata support Velocity/FreeMarker
Declarative transaction support
management PFD/Excel support
Spring DAO Spring Context
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 (28-06-2009)

 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

FacesServlet
Component Model Objects
Tree Managed JavaBeans

View
Resources Delegates
Config JavaBeans Converters
Property Files Validators
XML Renderers

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

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JSF: Request Processing Lifecycle

Response Complete Response Complete

Request Restore
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
Handling Render
Model

binds has
has

Id has has
Local Value UIComponent Validators
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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What’s new in JSF 2.0?
 New Page Declaration Language (PDL) based on Apache
Facelets
 Custom components much easier to develop

 Improved Ajax integration and support

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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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Unit 07: Design Patterns and Frameworks (3/3)

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