Spring Basics 1

8/8/2019 Spring Basics 1

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Spring FrameworkBasics


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objectives

Aft er th e comple t ion o f th is t opic th epar t icipan t s h ould be aware o f th ef ollowing t opics

Wh a t is spring f rame workDependency injec t ionS h ould be able t o work wi th di ff eren t wring


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T opics

Wh a t is Spring f ramework?Wh y Spring f ramework?Spring f ramework arc h it ec t ure

Usage scenarioDependency Injec t ion (DI)

BeanFac t oryA u t owiringA

pplicationCon

tex

t


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Wh a t is Spring Framework?


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Light- weig ht ye t compre h ensivef ramework f or building Java SE and JavaEE applica t ions


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Th e Spring Framework MissionStatement

J2 EE s h ould be easier t o useI t' s bes t t o program t o in t er f aces, ra th er

th an classes. Spring reduces th e complexi t ycos t o f using in t er f aces t o zeroJavaBeans o ff er a grea t way o f con f iguring

applica t ionsOO design is more impor t an t th an any

implemen t a t ion t ec h nology, suc h as J 2 EECh ecked excep t ions are overused. A

f ramework s h ould no t f orce t o ca t ch


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K ey Fea t ures

JavaBeans - based con f igura t ion managemen t ,applying Inversion - o f- Con t rol principles,speci f ically using th e Dependency Injec t iont ec h nique

T h is aims t o reduce dependencies o f componen t s onspeci f ic implemen t a t ions o f o th er componen t s.

A core bean f ac t ory, w h ich is usable globallyGeneric abs t rac t ion layer f or da t abase

t ransac t ion managemen t


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K ey Fea t ures

Buil t- in generic s t ra t egies f or J T A and a singleJDBC Da t aSource

T h is removes th e dependency on a Java EE

environment f or

transac

tion suppor

t.

In t egra t ion wi th persis t ence f rameworksHiberna t e, JDO and iB A T IS.

MVC web applica t ion f ramework, buil t on coreSpring f unc t ionali t y, suppor t ing manyt ec h nologies f or genera t ing views, includingJSP, FreeMarker, Veloci t y, T iles, i T ex t , and POI.


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K ey Fea t ures

Ex t ensive aspec t- orien t ed programming( A OP) f ramework t o provide servicessuc h as t ransac t ion managemen t

A s wi th th e Inversion - o f- Con t rol par t s o f th e sys t em , th is aims t o improve th emodulari t y o f sys t ems crea t ed using th ef ramework.


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Wh y UseSpring Framework?


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Wh y Use Spring?

Wiring o f componen t s th roug h Dependency Injec t ion

Promo t es de - coupling among th e par t s th a t

make th e applica t ionDesign t o in t er f aces

Insula t es a user o f a f unc t ionali t y f romimplemen t a t ion de t ails

T es t- Driven Developmen t ( T DD)POJO classes can be t es t ed wi th ou t being

t ied up wi th th e f ramework


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Wh y Use Spring?

Declara t ive programming th roug h A OPEasily con f igured aspec t s, esp. t ransac t ion

suppor t

Simpli f y use o f popular t ec h nologiesA bs t rac t ions insula t e applica t ion f rom

speci f ics, elimina t e redundan t codeHandle common error condi t ions

Underlying t ec h nology speci f ics s t illaccessible


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Wh y Use Spring?

Conversion o f ch ecked excep t ions t ounc h ecked

(Or is th is a reason no t t o use i t ?)

No t an all - or - no th ing solu t ionEx t remely modular and f lexible

Well designedEasy t o ex t endMany reusable classes


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Wh y Use Spring?

In t egra t ion wi th o th er t ec h nologiesEJB f or J 2 EEHiberna t e, iBa t es, JDBC ( f or da t a access)

Veloci t y ( f or presen t a t ion)S t ru t s and WebWork (For web)


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Spring so ft ware

You can download th e Spring dis t ribu t ionf rom Springs websi t e:htt p://www.spring f ramework.org.

Ch oose th e downloads link f rom th e le ft-h and menu and look f or th e Spring 2 . 5 download.Download spring -f ramework -2 . 5 - wi th-dependencies.jar f ile


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Some o f th e spring jarsspring.jar Con t ains mos t o f th e modules o f th e Spring Framework

in one convenien t JAR f ile.spring - aspec t s.jar Springs A spec t J- speci f ic classes.

spring - aop.jar T h e Spring A OP module.

spring - beans.jarT h e Spring bean f ac t ory module.

spring - core.jar Classes th a t are core t o th e Spring Framework.

spring - dao.jar T h e basis f or Springs D A O suppor t .

spring -h iberna t e 3 .jar Hiberna t e 3 suppor t

spring - jdbc.jar Spring jdbc module

spring - webmvc.jar Springs web applica t ion con t ex t and u t ilit ies.

spring - web.jar Spring mvc module


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Spring FrameworkA rc h it ec t ure


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Spring Framework


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Core Package

Core package is th e mos t f undamen t al par t o f th e f ramework and provides th e IoC andDependency Injec t ion f ea t uresT h e basic concep t h ere is th e BeanFac t ory,

wh ich provides a sop h is t ica t ed implemen t a t iono f th e f ac t ory pa tt ern w h ich removes th e needf or programma t ic single t ons and allows you t odecouple th e con f igura t ion and speci f ica t ion o f

dependencies f rom your ac t ual program logic


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DA O Package

T h e D A O package provides a JDBC -abs t rac t ion layer th a t removes th e needt o do t edious JDBC coding and parsing

o f da t abase - vendor speci f ic error codesT h e JDBC package provides a way t o do

programma t ic as well as declara t ivet ransac t ion managemen t , no t only f orclasses implemen t ing special in t er f aces,bu t f or all your POJOs (plain old Javaobjec t s)


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OR M Package

T h e O R M package provides in t egra t ionlayers f or popular objec t- rela t ionalmapping A PIs, including JP A , JDO,

Hiberna t e, and iBa t is.Using th e O R M package you can use all

th ose O/ R- mappers in combina t ion wi th all th e o th er f ea t ures Spring o ff ers, suc h as th e simple declara t ive t ransac t ionmanagemen t f ea t ure men t ionedpreviously


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A OP Package

Spring ' s A OP package provides an A OPA lliance - complian t aspec t- orien t edprogramming implemen t a t ion allowing you t ode f ine, f or example, me th od - in t ercep t ors andpoin t cu t s t o cleanly decouple codeimplemen t ing f unc t ionali t y th a t s h ould logicallyspeaking be separa t edUsing source - level me t ada t a f unc t ionali t y you

can also incorpora t e all kinds o f be h avioralin f orma t ion in t o your code


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MVC Package

Spring ' s MVC package provides aModel - View - Con t roller (MVC)implemen t a t ion f or webapplica t ions

Spring ' s MVC f ramework is no t jus t anyold implemen t a t ion; i t provides a cleansepara t ion be t ween domain model codeand web f orms, and allows you t o use allth e o th er f ea t ures o f th e SpringFramework.


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Usage Scenarios


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Usage Scenarios

You can use Spring in all sor t s o f scenarios, f rom apple t s up t o f ully -f ledged en t erprise applica t ions using

Spring ' s t ransac t ion managemen t f unc t ionali t y and web f rameworkin t egra t ion


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T ypical Full -f ledged Spring WebA pplica t ion


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Spring Middle -t ier Using 3 rd par t yWeb Framework


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R emo t ing Usage Scenario


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Dependency Injec t ion (DI):Basic concep t


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Spring Dependency Injection

A kind of Inversion of Control (IoC)Hollywood Principle

Don't call me, I'll call you

Container resolves (injects) dependenciesof components by setting implementationobject (push)

A s opposed to component instantiating or ServiceLocator pattern where component locatesimplementation (pull)

Martin Fowler calls Dependency Injection


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Bene f it s o f Dependency Injec t ion

FlexibleA void adding lookup code in business logic

T es t ableNo need t o depend on ex t ernal resources or

con t ainers f or t es t ing

Main t ainableA llows reuse in di ff eren t applica t ion environmen t s by

ch anging con f igura t ion f iles ins t ead o f code

Promotes a consis

ten

tapproac

hacross allapplica t ions and t eams


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T wo Dependency Injec t ion Varian t s

Cons t ruc t or dependency Injec t ionDependencies are provided th roug h th e

cons t ruc t ors o f th e componen t

Se tt er dependency injec t ionDependencies are provided th roug h th e

JavaBean s t yle se tt er me th ods o f th ecomponen t

More popular th an Cons t ruc t or dependencyinjec t ion


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Cons t ruc t or Dependency Injec t ion

public class Cons t ruc t orInjec t ion {priva t e Dependency dep;public Cons t ruc t orInjec t ion(Dependency

dep) {th is.dep = dep;}

}


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Se tt er Dependency Injec t ion

public class Se tt erInjec t ion {priva t e Dependency dep;public void se t MyDependency(Dependency

dep) {th is.dep = dep;}

}


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Dependency Injec t ion (DI):DI Suppor t in Spring


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Sub -t opics

BeanFactory in t er f aceXml BeanFactory implemen t a t ionBean con f igura t ion f ile

Se tt er dependency injec t ionCons t ruc t or dependency injec t ion

Beans

Injec t ion parame t ers


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BeanFac t ory

BeanFac t ory objec t is responsible f ormanaging beans and th eir dependencies

Your applica t ion in t erac t s wi th Spring ' s DIcon t ainer th roug h BeanFac t ory in t er f ace

BeanFac t ory objec t h as t o be crea t ed by th eapplica t ion t ypically XmlBeanFac t oryBeanFac t ory objec t , w h en i t ge t s crea t ed, read bean

conf igura

tion

f ile and per

f orms

the wiringOnce crea t ed, th e applica t ion can access th e beans

via BeanFac t ory in t er f ace


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BeanFac t ory Implemen t a t ions

XmlBeanFac t oryConvenience ex t ension o f

De f aul t Lis t ableBeanFac t oryth

at

reads bean def ini

tions

f rom an XMLdocumen t


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R eading XML Con f igura t ion File via Xml BeanFactory class

public class XmlConfigWithBeanFactory {

public static void main(String[] args) {

XmlBeanFactory factory =

new XmlBeanFactory( new FileSystemResource( "beans.xml" ));

SomeBeanInterface b =

(SomeBeanInterface) factory.getBean(nameOftheBean);

}

}


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Bean Con f igura t ion File

E ach bean is defined using tag under the root of the tagT he id attribute is used to give the bean its

default nameT he cl ass attribute specifies the type of the

bean


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Bean Con f igura t ion File Example

"htt p://www.spring f ramework.org/d t d/spring - beans.d t d">

< beans >

< bean id=" renderer " class =" S t andardOu t Message R enderer ">

< proper t y name =" messageProvider ">

< re f local =" provider "/>

< bean id=" provider " class =" HelloWorldMessageProvider "/>


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Wiring a Bean


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Wh a t is Wiring?

T h e ac t o f crea t ing associa t ions be t weenapplica t ion componen t s is re f erred t o aswiring

T h ere are many ways t o wire a bean bu t common approac h is via XML


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Wiring example



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Wiring th e beans

Pro t o t ype and Single t on beansall spring beans are single t onbu t pro t o t ype beans can also be de f ined

single t on = f alse re t urns a pro t o t ype bean

singleton =

true re

turns a single

ton beande f aul t value f or single t on is t rue


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Wiring th e beans

Ini t ializa t ion and Des t ruc t ionbeans can be ini t ialized and des t royed bycalling bean speci f ic me th ods

init-

meth

od : calls bean specif ic ini

tializa

tionme th od

des t roy - me th od : calls bean speci f ic cleanupme th od


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Wiring th e beans

Ini t ializa t ion and Des t ruc t ion (example)public class MyConnec t ionPool {

public void ini t ialize(){ //ini t ialize a connec t ion;

}public void cleanup() {

//release connec t ion;}

}

con f igura t ion:


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Spring Dependency Injec t ionR evisted.

T wo t ypes o f Dependency Injec t ionse tt er injec t ion

dependency injec t ed via se tt er me th ods

cons t ruc t or injec t iondependency injec t ed via cons t ruc t or


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Se tt er Injec t ion

Hello f riends

Spring Dependency Injec t ion

Set the greet property bycalling setGreeting ( Hello Friends )


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Cons t ruc t or Injec t ion

Hello f riends

Spring Dependency Injec t ion

constructs a TestBeanobject throughits constructor


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Wiring Collec t ions

Spring suppor t s Many t ypes o f Collec t ions asbean proper t iesSuppor t ed t ypes are:

XML Types java.u t il.Lis t , arrays

java.u t il.Se t

java.u t il.Map java.u t il.Proper t ies


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Dependency Injec t ion:A u t owiring


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A u t o Wiring

So f ar we wired beans explici t ly using t agSpring can also do Wiring au t oma t ically


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A u t owiring Proper t ies

Beans may be au t o - wired (ra th er th an using )Per - bean a tt ribu t e autowireExp l icit settings override

autowire=na m e

Bean iden t if ier ma t ch es proper t y nameautowire=type

T ype ma t ch es o th er de f ined bean

autowire=constructor Ma t ch cons t ruc t or argumen t t ypes

autowire=autodetect Att emp t by cons t ruc t or, o th erwise t ype


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A pplica t ionCon t ex t


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Wh a t is A pplica t ionCon t ex t ?

Ex t ension o f BeanFac t oryI t provides all th e same f unc t ionali t y and moreR educes th e amoun t o f code you needIn a more f ramework - orien t ed s t yle

A dd new f ea t ures over BeanFac t oryR esource managemen t and accessA ddi t ional li f e - cycle in t er f acesImproved au t oma t ic con f igura t ion o f in f ras t ruc t ure

componen t sEven t publica t ionIn t erna t ionaliza t ion


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Wh en t o Use A pplica t ionCon t ex t ?

Use A pplicationContext overBeanFactory t o t ake advan t age o f it sex t ended f unc t ionali t y

Excep t f or a f ew limi t ed si t ua t ions suc h asper h aps in an A pple t , w h ere memoryconsump t ion mig ht be cri t ical, and a f ewex t ra kiloby t es mig ht make a di ff erence


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Propaga t ing Even t s

Even t h andling in th eA pplica t ionCon t ex t is provided th roug h th e A pplica t ionEven t class andA

pplicationLis

tener in

ter

f aceI f a bean w h ich implemen t s th e

A pplica t ionLis t ener in t er f ace is deployed in t oth e con t ex t , every t ime an A pplica t ionEven t ge t s publis h ed t o th e A pplica t ionCon t ex t ,th a t bean will be no t if iedEssen t ially, th is is th e s t andard Observer

design pa tt ern.


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T h ree Buil t- in Even t s

Con t ex tR e f res h Even tA pplica t ionCon t ex t is ini t ialized or re f res h ed

Con t ex t ClosedEven t

A pplica t ionCon t ex t is closedR eques t HandleEven t

A web - speci f ic even t t elling all beans th a t aHTT P reques t h as been serviced


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Example: Even t Handling

Con f igura t ion< bean id =" emailer " class =" example.EmailBean ">

< proper t y name =" blackLis t ">

< lis t >

< value > [email protected]

< value > wh it e@lis t .org

< value > jo h [email protected]

< bean id =" blackLis t Lis t ener " class =" example.BlackLis t No t if ier ">< proper t y name =" no t if ica t ion A ddress " value =" spam@lis t .org "/>


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P roperty place h older configurer


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How t o use A pplica t ionCon t ex t ?

Many users will use A pplica t ionCon t ex t in a comple t ely declara t ive f as h ion, no t even h aving t o crea t e i t manually, bu t

instead relying on suppor

tclasses suc

h as Con t ex t Loader t o au t oma t ically s t ar t

an A pplica t ionCon t ex t as par t o f th enormal s t ar t up process o f a J 2 EE

webappit is s t ill possible t o programma t icallycrea t e an A pplica t ionCon t ex t

A l


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Spring A pplica t ionCon t ex t

A Spring A pplica t ionCon t ex t allows you t o ge t accesst o th e objec t s th a t are con f igured in a BeanFac t ory ina f ramework manner.A pplica t ionCon t ex t ex t ends BeanFac t ory

A dds services suc h as in t erna t ional messagingcapabili t ies.A dd th e abili t y t o load f ile resources in a genericf as h ion.

Several ways t o con f igure a con t ex t :X MLWeb A pplicationContext Con f igura t ion f or aweb applica t ion.Class P at h X ML A pplicationContext s t andalone XMLapplica t ion con t ex tFileSystem X ml A pplicationContext

A llows you t o avoid wri t ing Service Loca t ors


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Summary

Using dependency injec t ion we caninjec t th e dependencies in t o ourapplica t ion

IOC reduces th e programmers burdenDiff eren t t ypes o f wring gives us moref lexibili t y

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Spring Basics 1