The Freedom to Achieve

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The Freedom to Achieve

• Introduction to Spring
• Platinum Solutions
• All Hands Meeting
• 2/18/2007
• Navid Norouzi

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What is Spring?

• An open source J2EE Framework
• Spring is made up of different components
• Spring Core
• Spring Web
• Spring ORM
• Spring DAO
• Spring AOP
• Other

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Spring Components
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Why Use It?

• Enables better use of POJOs (Plain Old Java
  Objects)
• Promotes Decoupling, Reusability, Testing
• Built to integrate with other Popular Open Source
  Projects (e.g. Hibernate)

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Inversion of Control (IoC)?

• Inversion of Control is a programming principle
• Also known as Dependency Injection
• IoC Promotes Decoupling, Reusability, Testing (as
  mentioned before)

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Non-IoC Example
interface Cup drink() isReusable()
class PaperCup implements Cup private String
liquid Public PaperCup (liquid) this.liquid
liquid drink() isReusable() return
false
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Non-IoC Example Continued
class ThirstyPerson Private Cup myCup public
ThirstyPerson() myCup new PaperCup(WATER)

• Weve coupled our Thirsty Person to drink only
  water if he/she wants to use their Cup

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IoC Version

• We can set our Thirsty Person to drink other
  liquids besides water (de-coupling)
• First, we need to make a change to our
  ThirstyPerson class
• We will allow the liquid to be set via the
  constructor and a setter method

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IoC Version Continued
class ThirstyPerson Private Cup myCup //
constructor injection public ThirstyPerson(LIQUID)
myCup new PaperCup(LIQUID)
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IoC Version Continued

• Next we wire the liquid we want with the
  Thirsty Person in a configuration file outside of
  the code
• A XML file serves as the configuration file
• Spring will process the configuration file

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Spring Beans Definition XML

• This will tell Spring to instantiate a
  ThirstyPerson object with Apple Juice as the
  liquid passed to the constructor

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IoC Version Continued
class ThirstyPerson Private Cup myCup public
ThirstyPerson() // empty constructor //
setter injection public setLiquid(LIQUID)
myCup new PaperCup(LIQUID)
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Spring Beans Definition XML

• This will tell Spring to instantiate a
  ThirstyPerson object, and then call the setter
  method of the liquid property with the value of
  Coffee

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IoC Version Continued

• We used an XML file to instantiate our object
  and decoupled our Thirsty Person from being
  forced to start with water
• Note that Thirsty Person does not really have a
  LIQUID property, but a CUP property and that
  Thirsty Person is coupled with a Paper Cup no
  matter what
• Lets make our objects a little cleaner

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Further Decoupling
class ThirstyPerson Private Cup myCup // empty
constructor public ThirstyPerson() //
constructor injection public ThirstyPerson(CUP)
myCup CUP // setter injection public
setCup(CUP) myCup CUP
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Further Decoupling Continued
interface Cup drink() setLiquid() getLiquid() isRe
usable() setReusable()
class AnyCup implements Cup private String
liquid private boolean reusable // empty
constructor Public AnyCup () drink() setLiquid(
) getLiquid() isReusable() setReusable()
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Further Decoupling Continued

• Now ThirstyPerson class only deals with CUPs, and
  our CUP class is now generic
• We need to change our Spring XML file since we
  changed our Class
• We can now create CUP beans and pass them into
  our ThirstyPerson

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Further Decoupling Continued

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Further Decoupling Continued

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Introduction to Spring

• If your properties are REQUIRED to be set, use
  Constructor Injection, to force the properties to
  get set during instantiation
• We have decoupled (ThirstyPerson) and reused
  (AnyCup)
• Most likely, we should further de-couple our Cups
  from their fixed liquid contents
• We can now make changes to the choice of drink,
  outside of our compiled code

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Spring Promotes Testing

• Now well take a look at a simple JUnit Test Case
• Our test will create an Application from our
  configuration file

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Spring Promotes Testing
class CeramicCupTest extends TestCase Private
AnyCup anyCeramicCup setUp() // create the
application from our configuration file // this
will instantiate our beans ApplicationContext
context new ClassPathXmlApplicationContext(Ou
rSpringXMLFile.xml) // ceramicCup is
defined as a bean in our configuration
file anyCeramicCup (AnyCup) context.getBean(ce
ramiCup) testCeramiCup() assertTrue(anyCera
micCup.isReusable)
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Spring Promotes Testing

• Can more easily test your Application using Stubs
  and Mocks
• Stubs
• Provide canned answers to calls made during a
  test replacing a method with code that returns
  a specific result
• Mock Objects
• Are preprogrammed with expectations so you can
  assert if the expectation was met (was a method
  called?)

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Introduction to Spring

• In Summary, Spring, due to its Inversion of
  Control nature, promotes
• Decoupling
• Reusability
• Testing
• Programming to Interfaces
• Centralized Configuration
• Other

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Spring Application Context Lifecycle

• Initialization
• Application resources (beans) are created
• Use
• Used by application services
• Destruction
• Releases resources for garbage collection

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Bean properties

• Beans also have various properties
• Scope
• Session a new instance is created once per
  session
• Request a new instance is created once per
  request
• Other
• Other properties, such as Lazy Instantiation
• Will not be created until referenced
• Beans can have inheritance!
• Inner Beans
• An anonymous bean only available to its parent
  bean
• Other

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Spring AOP?

• AOP
• Stands for Aspect Oriented Programming
• Object Oriented Programming
• Concentrates on Classes
• Aspect Oriented Programming
• Concentrates on Aspects

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Spring AOP Continued

• AOP works with the Compiler
• Modularizes concerns in your Application,
  concerns that cross-cut across your application
• Logging
• Tracing
• Transactions
• Security
• Caching
• Error Handling
• Custom Business Rules
• Other
• Can provide a lot of flexibility and power, can
  also be abused
• Example Using AOP, log each time a specific
  variable is changed via its setter method

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Other Spring Components

• Spring Data Access
• Spring provides libraries that support and
  simplify writing data access code
• Supports JDBC, Hibernate, iBatis, JPA, other
• Spring Web
• Spring MVC
• Request driven framework (Similar to Struts)
• Requests are routed through Controllers by the
  Dispatcher Servlet
• The Controllers determine how to render the
  results
• Spring Web Flow
• State and Flow management
• Wizards, Step-by-Step navigation
• Adds a scope Page, Request, Flow, Session,
  Application

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Other Spring Components Continued

• Spring Security
• Formerly known as ACEGI Security
• Where did the name come from A B C D E F G H I
• Spring Web Services
• Spring Remoting
• In place of direct RMI
• Spring JMS
• Simplified Messaging / Producer and Consumer
  cases
• Other Components

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Introduction to Spring

• Thank you.