COMP 7100: Computers in the Information society

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COMP 7100 Computers in the Information society

• MVC and Spring Framework
• Hongjun SongComputer ScienceThe University of
  Memphis

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MVC
3
What it is All About
?
mental model
?
data
?
?
Computer
usecases
operations
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Scripting vs. Direct Manipulation

• Out of main door
• Turn right
• 5th left
• Right at 4th light
• ½ left at 1st light
• Youre there

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Users Mental ModelActivity Planning Network
actC
actA
Code Algorithms
DefineUseCases
actD
2 weeks
3 weeks
System Integration
actB
Define CodeDomainClass attributes
2 weeks
7 weeks
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User Machine Interaction
usermental model
data
DomainData
User
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Model View - Controller
usermental model
data
Model
User
Run Demo
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Use Case exampleA Functional Requirement

• Use Case N frontloading function
• An activity is characterized by its duration,
  earlyStart time, earlyFinish time,its
  predecessors and successors activities.
• By default, earlyFinish earlyStart
  durationspecial activities may have more complex
  algorithms
• An activity can start when all its predecessors
  are finishedearlyStart MAX (earlyFinish all
  predecessors)

Run Demo
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frontloading 1UML Diagrams

• Critical Questions
• What are the roles?
• How are they interconnected?
• How do they interact?

1. What are the roles?2. How are they
interconnected?
3. How do they interact?
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The Essence of Object OrientationObjects
interact to achieve a given goal
Critical questions

• What are the relevant objects?
• The relevant objects are seen as a structure of
  Roles.
• A role names the usage of one or more objects.
• The name is seen as an alias for those objects.
• How are they connected?
• A Collaboration describes the structure of roles.
• How do they interact?
• An Algorithm specifies the interaction in terms
  of the roles.

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Class and Role 1Steven Pinker How The Mind
Works
Classification Group on common features
(inst.vars. methods)

• Role (Artifact) Group on common purpose
• People categorize objects in terms of the roles
  they play within intuitive theories about how
  the world operates.
• Roles are defined by what they can do and by
  what someone, somewhere, makes them to do at
  some time.

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Class and Role 2The TrumpeterHändel Messiah,
Hallelujah choir
One Role - Two Classes
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Role Playing in the TheatreHenrik Ibsen Peer
Gynt
The Royal Hall of the King of the Dovre-Trolls.
THE OLD MAN OF THE DOVRE sits on the throne,
crowned, and with his sceptre in his hand. His
CHILDREN and NEAREST RELATIONS are ranged on both
sides. PEER GYNT stands before him. Violent
commotion in the hall. ---------------- (THE
GREEN-CLAD ONE)
http//norsk.kameraklubb.net/coppermine/displayima
ge/album167/pos6.html
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frontloading 1UML Diagrams

• Critical Questions
• What are the roles?
• How are they interconnected?
• How do they interact?

1. What are the roles?2. How are they
interconnected?
3. How do they interact?
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frontloading-2 Algorithm
public void frontload (Integer startWeek)
FrontIntf frontloader ?? SetltFrontpredIntfgt
frontpreds ?? Integer earlyStart
startWeek for (FrontpredIntf pred frontpreds)
earlyStart Math.max(earlyStart,
pred.earlyFinish() 1) frontloader.setEarl
yStart(earlyStart)
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Class and Role - 2

• A Class is static, it groups objects with similar
  properties
• class Activity specifies all activity objects.
• A Role is dynamic, it groups objects with a given
  usage
• the object playing the frontloader role is the
  object currently in the focus of attention.
• the objects playing the frontpreds role are
  currently used as predecessors.
• When we say that frontloader sends earlyFinish()
  to frontpreds, we mean that the object currently
  playing the frontloader role sends earlyFinish()
  to all the objects currently playing the
  frontpreds role.
• a role is not an object, but an alias for one or
  more objects.

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What it still is All About
mental model
data
GUI
Model
usecases
operations
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Data ModelConceptual Schema
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Data ModelJava Domain Classes
public class Model public SetltActivitygt
activities new HashSetltActivitygt() public
SetltDependencygt dependencies n
ew HashSetltDependencygt() public class
Activity implements FrontpredIntf, FrontIntf
private Integer earlyStart, earlyFinish,
duration private String name public class
Dependency private Activity predecessor,
successor
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Roles and ObjectsBridging the gap with queries
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frontloading-3 Algorithm
public void frontload (Integer startWeek)
FrontIntf frontloader ?? SetltFrontpredIntfgt
frontpreds ?? Integer earlyStart
startWeek for (FrontpredIntf pred frontpreds)
earlyStart Math.max(earlyStart,
pred.earlyFinish() 1) frontloader.setEarl
yStart(earlyStart)
FrontCollab frontCollab new FrontCollab()Front
Intf frontloader frontCollab.frontloader SetltFr
ontpredIntfgt frontpreds frontCollab.frontpreds
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FrontCollabExternal Data View
public class FrontCollab public FrontIntf
frontloader public FrontpredIntf frontpreds
public FrontCollab () frontloader
selectFrontloader() frontpreds
predecessorsOf(frontloader)
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Select domain object tofrontloader role by Java
Query
private FrontIntf selectFrontloader() for
(Activity act model.allActivities()) if
(act.earlyStart() null) SetltFrontpredIntfgt
predSet predecessorsOf(act) if
(areAllDone(predSet)) frontloader
act return (frontloader)
return null
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Select domain objects tofrontpreds role by Java
Query
public FrontpredIntf predecessorsOf(FrontIntf
act) SetltFrontpredIntfgt preds new
HashSetltFrontpredIntfgt() for (Dependency assoc
model.dependencies() ) if
(assoc.successor() act) preds.add(assoc.p
redecessor()) return preds
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Conclusion 1 of 2 User NeedsBalance Thinking
and Doing
User needs are in two dimensions they should be
supported in harmony thinking ? mental model
? data model ? objects doing ? use case ?
collaboration ? role ? query ? objects
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Conclusion 2 of 2 Architecture Balance State
and Behavior
Mental Model
Use Cases
Algorithm role interaction
Conceptualschema
reference roles
Collaboration roles and links
Classattributes
select objects
state
behavior
Data Objects
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Questions?
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More reading

• Reenskaug, T. Original MVC notes from Xerox
  PARChttp//folk.uio.no/trygver/2007/MVC_Originals
  .pdf
• Reenskaug, T, The BabyUML discipline of
  programming (where A Program Data
  Communication Algorithms). SoSym 5,1 (April
  2006). DOI 10.1007/s10270-006-0008-x.http//heim
  .ifi.uio.no/trygver/2006/SoSyM/trygveDiscipline.p
  df
• Reenskaug, T. Programming with Roles and
  Classes the BabyUML ApproachTo be published by
  Nova publishers as a chapter in a book on
  Computer Software Engineering Research WEB
  PAGE http//folk.uio.no/trygver/2007/babyUML.pdf
  (.PDF))
• Unified Modeling Language Superstructure.
  Version 2.1. Object Management Group (OMG)
  document ptc/06-04-02. http//www.omg.org
• Arisholm, E. Sjøberg, D. A Controlled
  Experiment with Professionals to Evaluate the
  Effect of a Delegated versus Centralized Control
  ,Simula Research Laboratory Technical Report
  2003-6http//www.simula.no/publication_one.php?pu
  blication_id601
• Reenskaug, T Wold, P., Lehne, O. A. Working
  With Objects. This book is out of print. An
  early .pdf version kan be downloaded free from
  http//folk.uio.no/trygver/1996/book/book11d.pdf
  
• Wirfs-Brock, R. McKean, A. Object Design.
  Roles, Responsibilities, and Collaborations.
  ISBN 0-201-37943-0 Addison-Wesley Boston, MA,
  2003.
• Andersen, E. P. Conceptual Modeling of Objects.
  A Role Modeling Approach. D.Scient thesis,
  November 1997, University of Oslo. web page
  http//heim.ifi.uio.no/trygver/1997/
  EgilAndersen/ConceptualModelingOO.pdf
• Pinker, S. How the Mind Works ISBN
  0-393-04535-8 Norton New York, NY, 1997.

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Spring Framework
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What is the Spring Framework?

• Spring is a Lightweight Application Framework
• Where Struts, WebWork and others can be
  considered Web frameworks, Spring addresses all
  tiers of an application
• Spring provides the plumbing so that you dont
  have to!

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Spring Framework History

• Started 2002/2003 by Rod Johnson and Juergen
  Holler
• Started as a framework developed around Rod
  Johnsons book Expert One-on-One J2EE Design and
  Development
• Spring 1.0 Released March 2004
• 2004/2005 Spring is emerging as a leading
  full-stack Java/J2EE application framework

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Spring J2EE Application Server?

• Spring is NOT a J2EE application server
• Spring can integrate nicely with J2EE application
  servers (or any Java environment)
• Spring can, in many cases, elegantly replace
  services traditionally provided by J2EE
  application servers

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Lessons Learned from Struts

• Before Struts, everyone wrote their own front
  controllers (or YIKES! put their controller logic
  in JSP)
• After Struts, the custom front controllers could
  be thrown out
• Developers focus on solving business problems
• Productivity Gain!
• But with Struts (and most of the other web
  frameworks) you still have to write your own
  business delegates or service layers

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Spring Can Help!

• Spring brings a consistent structure to your
  entire application
• Spring provides a consistent way to glue your
  whole application together
• Spring provides elegant integration points with
  standard and defacto-standard interfaces
  Hibernate, JDO, TopLink, EJB, RMI, JNDI, JMS, Web
  Services, Struts, etc.
• Just as Struts did on the web tier, we can
  realize huge productivity gains by not having to
  write the common integration points across your
  application

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The Spring Framework Mission Statement

• From springframework.org
• The authors of Spring believe that
• J2EE should be easier to use
• It's best to program to interfaces, rather than
  classes. Spring reduces the complexity cost of
  using interfaces to zero.
• JavaBeans offer a great way of configuring
  applications.
• OO design is more important than any
  implementation technology, such as J2EE.
• Checked exceptions are overused in Java. A
  framework shouldn't force you to catch exceptions
  you're unlikely to be able to recover from.
• Testability is essential, and a framework such as
  Spring should help make your code easier to test.

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Spring Framework Mission Statement (continued)

• The authors of Spring aim that
• Spring should be a pleasure to use
• Your application code should not depend on Spring
  APIs
• Spring should not compete with good existing
  solutions, but should foster integration. (For
  example, JDO and Hibernate are great O/R mapping
  solutions. We don't need to develop another one.)

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Spring Overview

• from springframework.org

Note Spring distribution comes as one big jar
file and alternatively as a series of smaller
jars broken out along the above lines (so you can
include only what you need)
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Spring is Non-Invasive

• What does that mean?
• You are not forced to import or extend any Spring
  APIs
• An invasive API takes over your code.
• Anti-patterns
• EJB forces you to use JNDI
• Struts forces you to extend Action
• Invasive frameworks are inherently difficult
  to test. You have to stub the runtime that is
  supplied by the application server

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But really, what IS Spring?

• At its core, Spring provides
• An Inversion of Control Container
• Also known as Dependency Injection (Fowlers
  term)
• An AOP Framework
• Spring provides a proxy-based AOP framework
• You can alternatively integrate with AspectJ or
  AspectWerkz
• A Service Abstraction Layer
• Consistent integration with various standard and
  3rd party APIs
• These together enable you to write powerful,
  scalable applications using POJOs.

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Seriously though, what IS Spring?

• Spring at its core, is a framework for wiring up
  your entire application
• BeanFactories are the heart of Spring

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BeanFactories

• A BeanFactory is typically configured in an XML
  file with the root element ltbeansgt
• The XML contains one or more ltbeangt elements
• id (or name) attribute to identify the bean
• class attribute to specify the fully qualified
  class

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BeanFactories

• By default, beans are treated as singletons
• Can also be prototypes
• Here is an example

The beans fully- qualified classname
The beans ID
ltbeansgt ltbean idwidgetService
classcom.zabada.base.WidgetServicegt
ltproperty namepoolSizegt lt!-property
value here--gt lt/propertygt lt/beangt lt/beansgt
Maps to a setPoolSize() call
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Property Values for BeanFactories

• Strings and Numbers
• Arrays and Collections

ltproperty namesizegtltvaluegt42lt/valuegtlt/propertygt
ltproperty namenamegtltvaluegtJimlt/valuegtlt/property
gt
ltproperty namehobbiesgt ltlistgt
ltvaluegtBasket Weavinglt/valuegt ltvaluegtBreak
Dancinglt/valuegt lt/listgt lt/propertygt
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Property Values for BeanFactories (continued)

• The real magic comes in when you can set
• a property on a bean that refers to another
• bean in the configuration
• This is the basic concept
• of Inversion of Control

ltbean namewidgetService classcom.zabada.base.
WidgetServiceImplgt ltproperty
namewidgetDAOgt ltref beanmyWidgetDAO/gt
lt/propertygt lt/beangt
calls setWidgetDAO(myWidgetDAO) where myWidgetDAO
is another bean defined in the configuration
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Dependency Injection(Inversion of Control)

• Complicated sounding terms for a fairly simple
  concept
• The Hollywood Principle Dont call me, Ill
  call you
• Dependencies used from within a bean arent asked
  for outwardly, but are injected into the bean by
  the container

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Dependency Injection(Inversion of Control)

• Eliminates lookup code from within your
  application
• Allows for pluggablity and hot swapping
• Promotes good OO design
• Enables reuse of existing code
• Makes your application extremely testable

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A Very Special BeanFactorythe ApplicationContext

• An ApplicationContext is a BeanFactory, but adds
  framework features such as
• i18n messages
• Event notifications
• This is what you will probably most often use in
  your Spring applications

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AOP (Aspect-Oriented Programming)

• AOP decomposes a system into concerns, instead of
  objects.
• Deals with "aspects" that cross-cut across the
  code and can be difficult or impossible to
  modularize with OOP
• The most common example given is logging
• Code for doing logging typically must be
  scattered all over a system
• With AOP, you can declare, for example, that a
  system should write a log record at the beginning
  and end of all method invocations.

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AOP (Aspect-Oriented Programming)

• AOP enables the delivery of services to POJOs
• Spring provides pre-packaged AOP services
• Declarative Transaction Management
• Security
• Logging
• You can write custom AOP services for
• Auditing
• Caching
• Custom security

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Service Abstraction Layers

• Spring provides abstraction for
• Transaction Management
• JTA, JDBC, others
• Data Access
• JDBC, Hibernate, JDO, TopLink, iBatis
• Email
• Remoting
• EJB, Web Services, RMI, Hessian/Burlap

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Service Abstraction Layers

• Benefits
• No implicit contracts with JNDI, etc.
• Insulates you from the underlying APIs
• Greater reusability
• Spring abstractions always consist of interfaces
• This makes testing simpler
• For data access, Spring uses a generic
  transaction infrastructure and DAO exception
  hierarchy that is common across all supported
  platforms

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Spring on the Web Tier

• Spring integrates nicely with Struts, WebWork,
  JSF, Tapestry, Velocity and other web frameworks
• Spring also provides its own web framework,
  Spring Web MVC

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Spring on the Web Tier Spring MVC

• The Spring MVC Framework offers a simple
  interface based infrastructure for handing web
  MVC architectures
• Spring MVC components are treated as first-class
  Spring beans
• Other Spring beans can easily be injected into
  Spring MVC components
• Spring MVC components are easy to test

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Spring MVC Key Interfaces

• Controller (org.springframework.web.servlet.mvc.Co
  ntroller)
• Must implement ModelAndView handleRequest(request,
  response)
• This is the base controller interface, comparable
  to the notion of a Struts Action.
• View (org.springframework.web.servlet.mvc.View)
• Must implement void render( model, request,
  response)
• This is the MVC view for a web interaction.
  Implementations are responsible for rendering
  content, and exposing the model.
• Model
• To complete the MVC trio, note that the model is
  typically handled as a java.util.Map which is
  returned with the view
• the values of the model are available, for
  example in a JSP, using a ltjspuseBean/gt where
  the id corresponds to the key value in the Map

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Spring on the Web Tier Integration with Other
Frameworks

• Spring integrates nicely with other web
  frameworks with two methodologies
• Look up Spring beans within Controllers/Actions
  via the convenience static method
  WebApplicationContextUtils.getWebApplicationContex
  t( servletContext).getBean(beanName)
• Configure the Controllers/Actions for the web
  framework in a Spring BeanFactory and then use
  Spring provided proxies in the actual web
  framework configuration
• When available, this methodology is preferred
• This approach lets you design your
  Controllers/Actions with dependency injection and
  makes your Controller/Actions more testable

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Spring Related Tools and Add-Ons

• ACEGI Security - comprehensive security services
  for the Spring Framework
• Spring IDE - graphical user interface for the
  configuration files used by the Spring Framework
• Spring BeanDoc - tool that facilitates
  documentation and graphing of Spring bean
  factories and application context files
• XDoclet Spring Tags - support for generating
  Spring XML config files from annotations in Java
  classes (you could also use JDK1.5 annotations to
  achieve this)
• Spring Web Flow - for web applications with
  demanding page flow requirements
• AppFuse Not really a tool or add-on, but AppFuse
  is Matt Raible's project to jumpstart your Java
  web projects. It uses Spring at it's core and
  studying it is a great way to learn about Spring.
  
• Spring Framework .NET Spring Clone for the Dark
  Side ?

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Spring Framework / Spring Related References
The Official Spring Reference Manual
http//www.springframework.org/docs/reference/ Int
roduction to Spring by Rod Johnson
http//www.theserverside.com/articles/article.tss
?lSpringFramework Spring in Action by Craig
Walls and Ryan Breidenbach Pro Spring by Rob
Harrop and Jan Machacek J2EE Without EJB by Rod
Johnson and Juergen Holler Expert One-on-One
J2EE Design and Development by Rod Johnson
Spring Developers Notebook by Bruce Tate and
Justin Gehtland Better, Faster, Lighter Java by
Bruce Tate and Justin Gehtland Spring Live by
Matt Raible Professional Java Development with
the Spring Framework