Advanced Java Programming

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Te c h n o lo g y Ce n t e rs N o t e : Th is t u t o ria l is a va ila b le a s a b o o k fro m o n lin e b o o k s e lle rs Als o , s e n d yo u r

co m m e n t s a n d t h o u g h t s t o

jd cb o o k@s u n . co m

Co n t e n t s

Ch a p t e r 1 : Ma t ch in g Pro je ct Re q u ire m e n t s w it h Te ch n o lo g y

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S p e cia l t h a n ks t o e xp e rt s Is a a c Elia s , Da n ie l Liu , a n d Ma rk

Ho rw a t h fo r t h e ir co n t rib u t io n s t o t h e a d va n ce d e xa m p le s in t h e b o o k.

Re a d e r Fe e d b a c k

Te ll u s w h a t yo u t h in k o f t h is b o o k.

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[ Th is p a g e w a s u p d a t e d : 4 - Ju n - 2 0 0 1 ]

Glo s s a ry | Fe e d b a ck | A- Z In d e x

Fo r m o re in fo rm a t io n o n Ja va t e ch n o lo g y

a n d o t h e r s o ft w a re fro m S u n Micro s ys t e m s , ca ll:

( 8 0 0 ) 7 8 6 - 7 6 3 8

Ou t s id e t h e U. S . a n d Ca n a d a , d ia l yo u r co u n t ry's

AT&T Dire ct Acce s s Nu m b e r firs t .

Co p yrig h t © 1 9 9 5 - 2 0 0 1 S u n Micro s ys t e m s , In c.

All Rig h t s Re s e rve d . Te rm s o f Us e. Priva cy Po licy.

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Re q u ire s lo g in

Ea rly Ac c e s s

D o w n lo a d s

B u g D a t a b a s e

S u b m it a B u g Vie w D a t a b a s e

N e w s le t t e rs

B a c k I s s u e s S u b s c rib e

Le a rn in g Ce n t e rs

Art ic le s B o o k s h e lf Co d e S a m p le s N e w t o Ja v a

Qu e s t io n o f t h e W e e k Qu iz z e s

Te c h Tip s Tu t o ria ls

Fo ru m s

Tra in in g In d e x

W rit in g Ad v a n c e d Ap p lic a t io n s

Ch a p t e r 1 : Ma t c h in g P ro je c t Re q u ire m e n t s w it h Te c h n o lo g y

[< < BACK] [CONTENTS] [NEXT> >]

On e ch a lle n g e in w rit in g a b o o k o n a d va n ce d a p p lica t io n d e ve lo p m e n t fo r t h e Ja vaTM_{p la t fo rm is t o fin d a p ro je ct s m a ll}

e n o u g h t o w rit e a b o u t , w h ile a t t h e s a m e t im e , co m p le x e n o u g h t o w a rra n t a d va n ce d p ro g ra m m in g t e ch n iq u e s .

Th e p ro je ct p re s e n t e d in t h is b o o k is a w e b - b a s e d a u ct io n h o u s e . Th e a p p lica t io n is in it ia lly w rit t e n fo r t h e En t e rp ris e Ja va Be a n sTM p la t fo rm . La t e r ch a p t e rs e xp a n d t h e co re e xa m p le d e s crib e d h e re b y a d d in g a d va n ce d fu n ct io n a lit y, im p ro ve m e n t s , a n d a lt e rn a t ive s o lu t io n s t o d o s o m e o f t h e t h in g s yo u g e t fo r fre e w h e n yo u u s e t h e En t e rp ris e Ja va Be a n s p la t fo rm .

To ke e p t h e d is cu s s io n s im p le , t h e e xa m p le a p p lica t io n h a s o n ly a b a s ic s e t o f t ra n s a ct io n s fo r p o s t in g a n d b id d in g o n a u ct io n it e m s . Ho w e ve r, t h e a p p lica t io n s ca le s t o h a n d le m u lt ip le u s e rs , p ro vid e s a t h re e - t ie re d t ra n s a ct io n - b a s e d e n viro n m e n t , co n t ro ls s e cu rit y, a n d in t e g ra t e s le g a cy- b a s e d s ys t e m s . Th is ch a p t e r co ve rs h o w t o d e t e rm in e p ro je ct re q u ire m e n t s a n d m o d e l t h e

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Te c h n o lo g y Ce n t e rs Pro je ct Re q u ire m e n t s In t e rvie w Us e r Ba s e Mo d e l t h e Pro je ct

Mo d e lin g Ho u s e Id e n t ifie s Bu ye rs a n d S e lle rs Ho u s e De t e rm in e s Hig h e s t Bid d e r Ho u s e No t ifie s Bu ye rs a n d S e lle rs An yo n e S e a rch e s fo r a n It e m An yo n e Vie w s It e m s fo r S a le An yo n e Vie w s It e m De t a ils S e lle r Po s t s It e m s fo r S a le Bu ye r Bid s o n It e m s

Act ivit y Dia g ra m

Ch o o s in g S o ft w a re Ja vaTM_APIs

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Fo ru m s

W rit in g Ad v a n c e d Ap p lic a t io n s

Ch a p t e r 1 Co n t in u e d : P ro je c t Re q u ire m e n t s a n d Mo d e lin g

Th e firs t s t e p in d e t e rm in in g p ro je ct re q u ire m e n t s is t o in t e rvie w t h e u s e r b a s e t o fin d o u t w h a t t h e y w a n t in a n o n lin e a u ct io n . Th is is a n im p o rt a n t s t e p , a n d o n e t h a t ca n n o t b e o ve rra t e d b e ca u s e a s o lid b a s e o f u s e r- o rie n t e d in fo rm a t io n h e lp s yo u d e fin e yo u r ke y a p p lica t io n ca p a b ilit ie s .

Ch a p t e r 2 w a lks t h ro u g h t h e a p p lica t io n co d e , e xp la in s h o w t h e En t e rp ris e Ja va Be a n s p la t fo rm w o rks , a n d t e lls yo u h o w t o ru n a live d e m o n s t ra t io n . If yo u h a ve n e ve r s e e n o r u s e d a n o n lin e a u ct io n , h e re a re m o cku p s o f t h e e xa m p le a u ct io n a p p lica t io n HTML

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Te c h n o lo g y Ce n t e rs _{Aft e r a n a lyzin g t h e re q u ire m e n t s , yo u ca n b u ild a u s e ca s e}

d ia g ra m fo r t h e a p p lica t io n t o g a in a b e t t e r u n d e rs t a n d in g o f t h e e le m e n t s n e e d e d in t h e a p p lica t io n a n d h o w t h e y in t e ra ct .

A u s e ca s e d ia g ra m s h o w s t h e re la t io n s h ip s a m o n g a ct o rs a n d u s e ca s e s w it h in t h e s ys t e m . A u s e ca s e is a u n iq u e fu n ct io n in a

s ys t e m , a n d a n a ct o r is t h e p e rs o n o r s o ft w a re t h a t p e rfo rm s t h e a ct io n o r u s e ca s e . Fo r e xa m p le , a b u ye r is t h e a ct o r t h a t p e rfo rm s t h e fu n ct io n ( u s e ca s e ) o f b id d in g o n a n a u ct io n it e m , a n d t h e

s e lle r is t h e a ct o r t h a t p e rfo rm s t h e u s e ca s e o f p o s t in g a n it e m fo r a u ct io n .

No t a ll a ct o rs a re p e o p le , t h o u g h . Fo r e xa m p le , t h e s o ft w a re is t h e a ct o r t h a t d e t e rm in e s w h e n a n it e m h a s clo s e d , fin d s t h e h ig h e s t b id d e r, a n d n o t ifie s t h e b u ye r a n d s e lle r o f t h e s a le .

Th e Un ifie d Mo d e lin g La n g u a g e ( UML) is t h e t o o l o f ch o ice fo r cre a t in g u s e ca s e d ia g ra m s . Th e Us e Ca s e d ia g ra m b e lo w u s e s UML t o d e s crib e t h e b u ye r a n d s e lle r u s e ca s e s fo r t h e o n lin e a u ct io n a p p lica t io n .

In UML, s ys t e m s a re g ro u p e d in t o s q u a re s , a ct o rs a re re p re s e n t e d b y s t ick fig u re s , u s e ca s e s a re d e n o t e d b y o va ls , a n d t h e lin e s s h o w h o w a ct o rs u s e t h e s ys t e m .

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Th e fo llo w in g d e s crip t io n s fu rt h e r d e fin e t h e p ro je ct . Th e s e

d e s crip t io n s a re n o t p a rt o f UML, b u t a re a h e lp fu l t o o l in p ro je ct d e fin it io n .

Ho u s e I d e n t if ie s B u y e rs a n d S e lle rs

An a u ct io n a p p lica t io n is u s e d b y b u ye rs a n d s e lle rs . A b u ye r n e e d s t o kn o w w h o t h e s e lle r is t o p a y h im o r h e r, a n d t h e s e lle r n e e d s t o kn o w w h o t h e b u ye rs a re t o a n s w e r p ro d u ct q u e s t io n s a n d t o

fin a lize t h e s a le . S o , t o p o s t o r b id o n a n a u ct io n it e m , b u ye rs a n d s e lle rs a re re q u ire d t o re g is t e r. Re g is t ra t io n n e e d s t o g e t t h e

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Te c h n o lo g y Ce n t e rs

( 8 0 0 ) 7 8 6 - 7 6 3 8

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Fo ru m s

W rit in g Ad v a n c e d Ap p lic a t io n s

Ch a p t e r 2 : Au c t io n Ho u s e Ap p lic a t io n

[< < BACK] [ CONTENTS] [NEXT> >]

Th e e xa m p le a p p lica t io n is a w e b - b a s e d a u ct io n h o u s e w rit t e n fo r t h e En t e rp ris e Ja va Be a n sTM_{p la t fo rm . Th e u s e r in t e rfa ce is a s e t o f}

HTML p a g e s t h a t g e t in p u t fro m a n d s h o w in fo rm a t io n t o t h e u s e r.

Be h in d t h e HTML p a g e s is a s e rvle t t h a t p a s s e s d a t a b e t w e e n t h e

b ro w s e r a n d t h e En t e rp ris e Ja va Be a n s s e rve r. Th e En t e rp ris e Ja va Be a n s s e rve r h a n d le s re a d in g fro m a n d w rit in g t o t h e d a t a b a s e .

Th is ch a p t e r d e s crib e s t h e a p p lica t io n co d e , h o w it w o rks w it h t h e En t e rp ris e Ja va Be a n s s e rve r, a n d w h e re t o g e t a En t e rp ris e

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Duke's Auction

Need to clean out that old office, garage, or

closet? or looking for something so unique you

cannot find it anywhere—or at least not at a price

you are willing to pay?

Look no further. At Duke's Auction you can post

items for sale and bid what you want to pay for

the items you want.

Registration

To bid on or list an item for auction, you must

register

first. Registration gives buyers a way to

pay you and us a way to contact buyers and

sellers. You only need register once, and

registration is not required to browse items on

the auction floor.

Auction Floor

The auction floor is open to anyone for browsing, but to bid on an item, you must be

registered.

● New auction items today

● Items closing today

● All items (current and closed)

● Search for Items

Post Items for Auction

Once you register, you can

post items for sale

at auction any time you want.

Register

|

New Items

|

Closing Items

|

All Items

|

Sell Items

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Mu lt it ie re d Arc h it e c t u re

Mu lt it ie r a rch it e ct u re o r t h re e - t ie r a rch it e ct u re e xt e n d s t h e s t a n d a rd t w o - t ie r clie n t a n d s e rve r m o d e l b y p la cin g a m u lt it h re a d e d a p p lica t io n s e rve r b e t w e e n t h e clie n t a n d t h e d a t a b a s e . Clie n t p ro g ra m s co m m u n ica t e w it h t h e d a t a b a s e t h ro u g h t h e a p p lica t io n s e rve r u s in g h ig h - le ve l a n d p la t fo rm in d e p e n d e n t ca lls . Th e a p p lica t io n s e rve r re s p o n d s t o t h e clie n t re q u e s t s , m a ke s d a t a b a s e ca lls a s n e e d e d in t o t h e u n d e rlyin g d a t a b a s e , a n d re p lie s t o t h e clie n t p ro g ra m a s a p p ro p ria t e .

Th e t h re e t ie rs in t h e w e b - b a s e d a u ct io n h o u s e e xa m p le co n s is t s o f t h e t h in - clie n t s e rvle t , t h e En t e rp ris e Ja va Be a n s s e rve r ( t h e a p p lica t io n s e rve r) , a n d t h e d a t a b a s e s e rve r a s s h o w n in t h e fig u re .

En t it y a n d S e s s io n B e a n s

Th e re a re t w o t yp e s o f En t e rp ris e Be a n s : e n t it y Be a n s a n d s e s s io n Be a n s . An En t e rp ris e Be a n t h a t im p le m e n t s a b u s in e s s e n t it y is a n e n t it y Be a n, a n d a n En t e rp ris e Be a n t h a t im p le m e n t s a b u s in e s s t a s k is a s e s s io n Be a n .

Typ ica lly, a n e n t it y Be a n re p re s e n t s o n e ro w o f p e rs is t e n t d a t a s t o re d in a d a t a b a s e t a b le . In t h e a u ct io n h o u s e e xa m p le ,

RegistrationBean is a n e n t it y Be a n t h a t re p re s e n t s d a t a fo r o n e

re g is t e re d u s e r, a n d AuctionItemBean is a n e n t it y Be a n t h a t

re p re s e n t s t h e d a t a fo r o n e a u ct io n it e m . En t it y Be a n s a re t ra n s a ct io n a l a n d lo n g - live d . As lo n g a s t h e d a t a re m a in s , t h e e n t it y Be a n ca n a cce s s a n d u p d a t e t h a t d a t a . Th is d o e s n o t m e a n yo u n e e d a Be a n ru n n in g fo r e ve ry t a b le ro w . In s t e a d , En t e rp ris e Be a n s a re lo a d e d a n d s a ve d a s n e e d e d .

A s e s s io n Be a n m ig h t e xe cu t e d a t a b a s e re a d s a n d w rit e s , b u t it is

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m ig h t u s e a n e n t it y Be a n t o m a ke t h e ca ll, in w h ich ca s e t h e

s e s s io n Be a n is a clie n t t o t h e e n t it y Be a n . A s e s s io n Be a n 's fie ld s co n t a in t h e s t a t e o f t h e co n ve rs a t io n a n d a re t ra n s ie n t . If t h e s e rve r o r clie n t cra s h e s , t h e s e s s io n Be a n is g o n e . A s e s s io n Be a n is o ft e n u s e d w it h o n e o r m o re e n t it y Be a n s a n d fo r co m p le x

o p e ra t io n s o n t h e d a t a .

S e s s io n Be a n s En t it y Be a n s

Fie ld s co n t a in co n ve rs a t io n

s t a t e . Re p re s e n t s d a t a in a d a t a b a s e .

Ha n d le s d a t a b a s e a cce s s fo r

clie n t . S h a re s a cce s s fo r m u lt ip le u s e rs .

Life o f clie n t is life o f Be a n . Pe rs is t s a s lo n g a s d a t a e xis t s . Ca n b e t ra n s a ct io n a w a re . Tra n s a ct io n a l.

Do e s n o t s u rvive s e rve r

cra s h e s . S u rvive s s e rve r cra s h e s .

No t fin e - g ra in e d d a t a h a n d lin g Fin e - g ra in e d d a t a h a n d lin g

N o t e : In t h e En t e rp ris e Ja va Be a n s s p e cifica t io n ,

En t e rp ris e Ja va Be a n s S e rve r s u p p o rt fo r s e s s io n Be a n s is m a n d a t o ry. En t e rp ris e Ja va Be a n s s e rve r s u p p o rt fo r e n t it y Be a n s w a s o p t io n a l, b u t is m a n d a t o ry fo r ve rs io n 2 . 0 o f t h e s p e cifica t io n .

Au c t io n Ho u s e W o rk in g s

Th e d ia g ra m s h o w s t h e En t e rp ris e Be a n s fo r t h e a u ct io n h o u s e a p p lica t io n a n d t h e ir re la t io n s h ip t o t h e En t e rp ris e Ja va Be a n s s e rve r. Th e t h in - clie n t s e rve r in vo ke s b u s in e s s lo g ic in t h e fo u r En t e rp ris e Be a n s t h ro u g h t h e ir h o m e a n d re m o t e in t e rfa ce s . Th e En t e rp ris e Ja va Be a n s s e rve r in t h is e xa m p le h a n d le s t h e lo w - le ve l d e t a ils in clu d in g d a t a b a s e re a d a n d w rit e o p e ra t io n s .

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s e rvice s t o lo ca t e re m o t e s e rve r o b je ct s ( t h e Be a n 's re m o t e

in t e rfa ce o b je ct ) , a n d d a t a co m m u n ica t io n s e rvice s t o m o ve d a t a fro m t h e clie n t , t h ro u g h t h e re m o t e s e rve r o b je ct , t o it s fin a l d e s t in a t io n in a s t o ra g e m e d iu m .

Lo o k u p S e rv ic e

To fin d re m o t e s e rve r o b je ct s a t ru n t im e , t h e clie n t p ro g ra m n e e d s a w a y t o lo o k t h e m u p . On e w a y t o lo o k re m o t e s e rve r o b je ct s u p a t ru n t im e is t o u s e t h e Ja va Na m in g a n d Dire ct o ry In t e rfa ceTM ( JNDI) API. JNDI is a co m m o n in t e rfa ce t o e xis t in g n a m in g a n d d ire ct o ry in t e rfa ce s . Th e En t e rp ris e Ja va Be a n s co n t a in e rs u s e JNDI a s a n in t e rfa ce t o t h e Re m o t e Me t h o d In vo ca t io n ( RMI) n a m in g s e rvice .

At d e p lo ym e n t t im e , t h e JNDI s e rvice re g is t e rs ( b in d s ) t h e re m o t e in t e rfa ce w it h a n a m e . As lo n g a s t h e clie n t p ro g ra m u s e s t h e s a m e n a m in g s e rvice a n d a s ks fo r t h e re m o t e in t e rfa ce b y it s re g is t e re d n a m e , it w ill b e a b le t o fin d it . Th e clie n t p ro g ra m ca lls t h e lookup m e t h o d o n a javax.naming.Context o b je ct t o a s k fo r t h e

re m o t e in t e rfa ce b y it s re g is t e re d n a m e . Th e javax.naming.Context

o b je ct is w h e re t h e b in d in g s a re s t o re d a n d is a d iffe re n t o b je ct fro m t h e En t e rp ris e Ja va Be a n s co n t e xt , w h ich is co ve re d la t e r.

D a t a Co m m u n ic a t io n

On ce t h e clie n t p ro g ra m g e t s a re fe re n ce t o a re m o t e s e rve r o b je ct , it m a ke s ca lls o n t h e re m o t e s e rve r o b je ct 's m e t h o d s . Be ca u s e t h e clie n t p ro g ra m h a s a re fe re n ce t o t h e re m o t e s e rve r o b je ct , a t e ch n iq u e ca lle d d a t a m a rs h a llin g is u s e d t o m a ke it

a p p e a r a s if t h e re m o t e s e rve r o b je ct is lo ca l t o t h e clie n t p ro g ra m . Da t a m a rs h a llin g is w h e re m e t h o d s ca lle d o n t h e re m o t e s e rve r o b je ct a re w ra p p e d w it h t h e ir d a t a a n d s e n t t o t h e re m o t e s e rve r o b je ct . Th e re m o t e s e rve r o b je ct u n w ra p s ( u n m a rs h a lls ) t h e m e t h o d s a n d d a t a , a n d ca lls t h e En t e rp ris e Be a n . Th e re s u lt s o f t h e ca ll t o t h e En t e rp ris e Be a n a re w ra p p e d a g a in , p a s s e d b a ck t o t h e clie n t t h ro u g h t h e re m o t e s e rve r o b je ct , a n d u n m a rs h a lle d . Th e En t e rp ris e Ja va Be a n s co n t a in e rs u s e RMI s e rvice s t o m a rs h a l d a t a . Wh e n t h e Be a n is co m p ile d , stub a n d skeleton file s a re

cre a t e d . Th e stub file p ro vid e s t h e d a t a w ra p p in g a n d u n w ra p p in g

co n fig u ra t io n o n t h e clie n t , a n d t h e skeleton p ro vid e s t h e s a m e

in fo rm a t io n fo r t h e s e rve r.

Th e d a t a is p a s s e d b e t w e e n t h e clie n t p ro g ra m a n d t h e s e rve r u s in g s e ria liza t io n . S e ria liza t io n is a w a y t o re p re s e n t a t Ja vaTM

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o b je ct s a s b yt e s t h a t ca n b e s e n t o ve r t h e n e t w o rk a s a s t re a m a n d re co n s t ru ct e d o n t h e o t h e r s id e in t h e s a m e s t a t e t h e y w e re in w e n t o rig in a lly s e n t .

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Te c h n o lo g y Ce n t e rs N o t e : Th is t u t o ria l is a va ila b le a s a b o o k fro m o n lin e b o o k s e lle rs Als o , s e n d yo u r

co m m e n t s a n d t h o u g h t s t o

jd cb o o k@s u n . co m

Co n t e n t s

Ch a p t e r 1 : Ma t ch in g Pro je ct Re q u ire m e n t s w it h Te ch n o lo g y

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S p e cia l t h a n ks t o e xp e rt s Is a a c Elia s , Da n ie l Liu , a n d Ma rk

Ho rw a t h fo r t h e ir co n t rib u t io n s t o t h e a d va n ce d e xa m p le s in t h e b o o k.

Re a d e r Fe e d b a c k

Te ll u s w h a t yo u t h in k o f t h is b o o k.

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Fo ru m s

W rit in g Ad v a n c e d Ap p lic a t io n s

Ch a p t e r 2 Co n t in u e d : En t it y a n d S e s s io n B e a n s

Th e e xa m p le u s e s t w o e n t it y Be a n s a n d t w o s e s s io n Be a n s . Th e e n t it y Be a n s , AuctionItemBean a n d RegistrationBean, re p re s e n t

p e rs is t e n t it e m s t h a t co u ld b e s t o re d in a d a t a b a s e , a n d t h e s e s s io n Be a n s , SellerBean a n d BidderBean, re p re s e n t s h o rt - live d

o p e ra t io n s w it h t h e clie n t a n d d a t a .

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Th e AuctionServlet m e t h o d s s h o w n a b o ve in vo ke b u s in e s s lo g ic

t h a t e xe cu t e s o n t h e s e rve r b y lo o kin g u p a n En t e rp ris e Be a n a n d ca llin g o n e o r m o re o f it s m e t h o d s . Wh e n t h e s e rvle t a d d s HTML

co d e s t o a p a g e fo r d is p la y t o t h e u s e r, t h a t lo g ic e xe cu t e s o n t h e clie n t .

Fo r e xa m p le , t h e listAllItems(out) m e t h o d e xe cu t e s co d e o n t h e

clie n t t o d yn a m ica lly g e n e ra t e a n HTML p a g e t o b e vie w e d b y t h e

clie n t in a b ro w s e r. Th e HTML p a g e is p o p u la t e d w it h t h e re s u lt s o f

a ca ll t o BidderBean t h a t e xe u ct e s lo g ic o n t h e s e rve r t o g e n e ra t e a

lis t o f a ll a u ct io n it e m s .

private void listAllItems(ServletOutputStream out) throws IOException{

//Put text on HTML page

setTitle(out, "Auction results");

String text = "Click Item number for description and to place bid.";

try{

addLine("<BR>"+text, out);

//Look up Bidder bean home interface.

BidderHome bhome=(BidderHome) ctx.lookup("bidder"); //Create Bidder bean remote interface.

Bidder bid=bhome.create();

//Call Bidder bean method through remote interface. Enumeration enum=(Enumeration)bid.getItemList();

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//Put retrieved items on servlet page. displayitems(enum, out);

addLine("", out); }

} catch (Exception e) { //Pring error on servlet page.

addLine("AuctionServlet List All Items error",out); System.out.println("AuctionServlet <list>:"+e); }

out.flush(); }

En t it y B e a n s

AuctionItemBean a n d RegistrationBean a re e n t it y Be a n s .

AuctionItemBean a d d s n e w a u ct io n it e m s t o t h e d a t a b a s e a n d

u p d a t e s t h e b id a m o u n t a s u s e rs b id o n t h e it e m . RegistrationBean

a d d s in fo rm a t io n t o t h e d a t a b a s e o n re g is t e re d u s e rs . Bo t h Be a n s co n s is t o f t h e cla s s e s d e s crib e d h e re .

Au c t io n I t e m En t it y B e a n

He re a re t h e AuctionItemBean cla s s e s . Re m e m b e r t h a t t h e s e

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s e rve r re q u ire s a co n t a in e r- m a n a g e d e n t it y Be a n t o h a ve a

p rim a ry ke y cla s s w it h a p u b lic p rim a ry ke y fie ld ( o r fie ld s , if u s in g co m p o s it e p rim a ry ke ys ) . Th e Be a n d e ve lo p e r im p le m e n t s t h is cla s s . Th e ID fie ld is t h e p rim a ry ke y in t h e AUCTIONITEMS t a b le

s h o w n ju s t b e lo w , s o t h e id fie ld is a p u b lic fie ld in t h is cla s s . Th e id fie ld is a s s ig n e d a va lu e w h e n t h e p rim a ry ke y cla s s is

co n s t ru ct e d .

Yo u ca n re q u e s t t h e co n t a in e r m a n a g e d a t a b a s e p e rs is t e n ce fo r a n En t e rp ris e Be a n o r w rit e t h e co d e t o m a n a g e t h e p e rs is t e n ce yo u rs e lf. In t h is ch a p t e r, a ll b e a n s ( e n t it y a n d s e s s io n ) a re

co n t a in e r- m a n a g e d . Wit h co n t a in e r- m a n a g e d Be a n s , a ll yo u d o is s p e cify w h ich fie ld s a re co n t a in e r m a n a g e d a n d le t t h e En t e rp ris e Ja va Be a n s s e rve r d o t h e re s t . Th is is g re a t fo r s im p le a p p lica t io n s , b u t if yo u a re co d in g s o m e t h in g t h a t is fa irly co m p le x, yo u m ig h t n e e d m o re co n t ro l.

Ho w t o o ve rrid e t h e u n d e rlyin g En t e rp ris e Ja va Be a n s s e rvice s t o g a in m o re co n t ro l o r p ro vid e s im ila r s e rvice s fo r n o n - En t e rp ris e Ja va Be a n a p p lica t io n s is co ve re d in Ch a p t e r 3 .

Au c t io n I t e m s Ta b le

He re is t h e AUCTIONITEMS t a b le .

create table AUCTIONITEMS (SUMMARY VARCHAR(80) , ID INT ,

COUNTER INT ,

DESCRIPTION VARCHAR(1000) , STARTDATE DATE ,

ENDDATE DATE ,

STARTPRICE DOUBLE PRECISION , INCREMENT DOUBLE PRECISION , SELLER VARCHAR(30) ,

MAXBID DOUBLE PRECISION, BIDCOUNT INT,

HIGHBIDDER VARCHAR(30) )

Re g is t ra t io n En t it y B e a n

RegistrationBean co n s is t s o f t h e s a m e kin d s o f cla s s e s a n d

d a t a b a s e t a b le a s t h e AuctionItem Be a n , e xce p t t h e a ct u a l

b u s in e s s lo g ic, d a t a b a s e t a b le fie ld s , a n d p rim a ry ke y a re s o m e w h a t d iffe re n t . Ra t h e r t h a n d e s crib e t h e cla s s e s , yo u ca n b ro w s e t h e m a n d re fe r b a ck t o t h e AuctionItem Be a n d is cu s s io n if

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clie n t ca lls re m o t e ly.

BidderHome is t h e h o m e in t e rfa ce . It d e s crib e s h o w t h e Be a n is

cre a t e d in , fo u n d in , a n d re m o ve d fro m it s co n t a in e r.

BidderBean is t h e En t e rp ris e Be a n . It im p le m e n t s SessionBean,

p ro vid e s t h e b u s in e s s lo g ic fo r t h e d e ve lo p e r- d e fin e d m e t h o d s , a n d im p le m e n t s SessionBean m e t h o d s fo r cre a t in g t h e Be a n a n d

s e t t in g t h e s e s s io n co n t e xt .

Auction.java co n t a in s a s m a ll cla s s t h a t d e cla re s va ria b le s u s e d b y

BidderBean.

S e lle r S e s s io n B e a n

SellerBean co n s is t s o f t h e s a m e kin d s o f cla s s e s a s BidderBean,

e xce p t t h e b u s in e s s lo g ic is d iffe re n t . Ra t h e r t h a n d e s crib e t h e cla s s e s , yo u ca n b ro w s e t h e m a n d re fe r b a ck t o t h e BidderBean

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t h e s e rve r.

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Fo ru m s

W rit in g Ad v a n c e d Ap p lic a t io n s

Ch a p t e r 2 Co n t in u e d : Ex a m in in g a Co n t a in e r- Ma n a g e d B e a n

Th is s e ct io n w a lks t h ro u g h t h e Re g is t ra t io n Be a n . ja va co d e t o s h o w h o w e a s y it is t o h a ve t h e co n t a in e r m a n a g e p e rs is t e n t d a t a

s t o ra g e t o a n u n d e rlyin g m e d iu m s u ch a s a d a t a b a s e ( t h e d e fa u lt ) . Ch a p t e r 3 m o d ifie s RegistrationBean t o u s e Be a n - m a n a g e d

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Te c h n o lo g y Ce n t e rs public String theuser, password, creditcard, _{emailaddress;}

public double balance;

Cre a t e Me t h o d

Th e Be a n 's ejbCreate m e t h o d is ca lle d b y t h e co n t a in e r a ft e r t h e

clie n t p ro g ra m ca lls t h e create m e t h o d o n t h e remote in t e rfa ce a n d

p a s s e s in t h e re g is t ra t io n d a t a . Th is m e t h o d a s s ig n s t h e in co m in g va lu e s t o t h e m e m b e r va ria b le s t h a t re p re s e n t u s e r d a t a . Th e co n t a in e r h a n d le s s t o rin g a n d lo a d in g t h e d a t a , a n d cre a t in g n e w e n t rie s in t h e u n d e rlyin g s t o ra g e m e d iu m .

public RegistrationPK ejbCreate(String theuser, String password, String emailaddress, String creditcard) throws CreateException, RemoteException {

this.theuser=theuser; this.password=password;

this.emailaddress=emailaddress; this.creditcard=creditcard; this.balance=0;

En t it y Co n t e x t Me t h o d s

An e n t it y Be a n h a s a n a s s o cia t e d EntityContext in s t a n ce t h a t g ive s

t h e Be a n a cce s s t o co n t a in e r- m a n a g e d ru n t im e in fo rm a t io n s u ch a s t h e t ra n s a ct io n co n t e xt .

public void setEntityContext(

javax.ejb.EntityContext ctx) throws RemoteException { this.ctx = ctx;

}

public void unsetEntityContext() throws RemoteException{ ctx = null;

}

Lo a d Me t h o d

Th e Be a n 's ejbLoad m e t h o d is ca lle d b y t h e co n t a in e r t o lo a d d a t a

fro m t h e u n d e rlyin g s t o ra g e m e d iu m . Th is w o u ld b e n e ce s s a ry w h e n BidderBean o r SellerBean n e e d t o ch e ck a u s e r's ID o r

p a s s w o rd a g a in s t t h e s t o re d va lu e s .

N o t e : No t a ll Be a n o b je ct s a re live a t a n y o n e t im e . Th e En t e rp ris e Ja va Be a n sTM s e rve r m ig h t h a ve a co n fig u ra b le

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n u m b e r o f Be a n s t h a t it ke e p s in m e m o ry.

Th is m e t h o d is n o t im p le m e n t e d b e ca u s e t h e En t e rp ris e Ja va Be a n s co n t a in e r s e a m le s s ly lo a d s t h e d a t a fro m t h e u n d e rlyin g s t o ra g e m e d iu m fo r yo u .

public void ejbLoad() throws RemoteException {}

S t o re Me t h o d

Th e Be a n 's ejbStore m e t h o d is ca lle d b y t h e co n t a in e r t o s a ve u s e r

d a t a . Th is m e t h o d is n o t im p le m e n t e d b e ca u s e t h e En t e rp ris e Ja va Be a n s co n t a in e r s e a m le s s ly s t o re s t h e d a t a t o t h e u n d e rlyin g s t o ra g e m e d iu m fo r yo u .

public void ejbStore() throws RemoteException {}

Co n n e c t io n P o o lin g

Lo a d in g d a t a fro m a n d s t o rin g d a t a t o a d a t a b a s e ca n t a ke a lo t t im e a n d re d u ce a n a p p lica t io n 's o ve ra ll p e rfo rm a n ce . To re d u ce d a t a b a s e co n n e ct io n t im e , t h e BEA We b lo g ic s e rve r u s e s a JDBCTM co n n e ct io n p o o l t o ca ch e d a t a b a s e co n n e ct io n s s o co n n e ct io n s a re a lw a ys a va ila b le w h e n t h e a p p a lica t io n n e e d s t h e m .

Ho w e ve r, yo u a re n o t lim it e d t o t h e d e fa u lt JDBC co n n e ct io n p o o l. Yo u ca n o ve rrid e t h e Be a n - m a n a g e d co n n e ct io n p o o lin g b e h a vio u r a n d s u b s t it u t e yo u r o w n . Ch a p t e r 8 : Pe rfo rm a n ce Te ch n iq u e s

e xp la in s h o w .

D e p lo y m e n t D e s c rip t o r

Th e re m a in in g co n fig u ra t io n fo r a co n t a in e r- m a n a g e d p e rs is t e n t Be a n s o ccu rs a t d e p lo ym e n t t im e . Th e fo llo w in g is t h e t e xt - b a s e d De p lo ym e n t De s crip t o r u s e d in a BEA We b lo g ic En t e rp ris e

Ja va Be a n s s e rve r.

Te x t D e p lo y m e n t D e s c rip t o r

(environmentProperties

(persistentStoreProperties

persistentStoreType jdbc

(jdbc

tableName registration dbIsShared false

poolName ejbPool

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Th is s e ct io n w a lks t h ro u g h t h e d iffe re n t p a rt s o f t h e finder- b a s e d

s e a rch co d e . Ch a p t e r 3 d e s crib e s h o w t o cre a t e a Be a n - m a n a g e d s e a rch t o h a n d le co m p le x q u e rie s a n d s e a rch e s t h a t s p a n m o re t h a n o n e Be a n t yp e ( e n t it y a n d s e s s io n Be a n s ) o r d a t a b a s e t a b le s .

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"(= enddate $closedtoday)"

"findAllMatchingItems(String searchString)" "(like summary $searchString)"

); end finderDescriptors

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Fo ru m s

W rit in g Ad v a n c e d Ap p lic a t io n s

Ch a p t e r 3 : D a t a a n d Tra n s a c t io n Ma n a g e m e n t

Wh e n yo u u s e t h e En t e rp ris e Ja va Be a n sTM a rch it e ct u re , d a t a is w rit t e n t o a n d re a d fro m t h e d a t a b a s e w it h o u t yo u r w rit in g a n y S QL co d e t o d o it . Bu t w h a t if yo u d o n o t w a n t t o s t o re t h e d a t a in a d a t a b a s e , o r w a n t t o w rit e yo u r o w n S QL co m m a n d s , o r m a n a g e t ra n s a ct io n s ? Yo u ca n o ve rrid e t h e b u ilt - in co n t a in e r- m a n a g e d p e rs is t e n ce a n d im p le m e n t Be a n - m a n a g e d p e rs is t e n ce u s in g yo u r o w n d a t a s t o ra g e a n d t ra n s a ct io n m a n a g e m e n t co d e .

Be a n - m a n a g e d p e rs is t e n ce co m e s in u s e fu l w h e n yo u w a n t m o re co n t ro l t h a n t h e co n t a in e r- m a n a g e d p e rs is t e n ce p ro vid e s . Fo r e xa m p le yo u m ig h t w a n t t o o ve rrid e t h e d e fa u lt o f m o s t

co n t a in e rs t o m a p t h e d a t a in o n e Be a n t o o n e ro w in a t a b le , im p le m e n t yo u r o w n finder m e t h o d s , o r cu s t o m ize ca ch in g .

Th is ch a p t e r p re s e n t s t w o ve rs io n s o f t h e RegistrationBean cla s s

fro m Ch a p t e r 2 . On e ve rs io n re a d s u s e r d a t a fro m a n d w rit e s it t o a file u s in g s e ria lize d in p u t a n d o u t p u t s t re a m s . Th e o t h e r ve rs io n p ro vid e s it s o w n S QL co m m a n d s fo r re a d in g fro m a n d w rit in g t o t h e d a t a b a s e . It a ls o e xp la in s h o w yo u ca n w rit e yo u r o w n

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Te c h n o lo g y Ce n t e rs Be a n - Ma n a g e d Pe rs is t e n ce a n d t h e JDBC Pla t fo rm

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Fo ru m s

W rit in g Ad v a n c e d Ap p lic a t io n s

Ch a p t e r 3 Co n t in u e d : B e a n - Ma n a g e d P e rs is t e n c e a n d t h e JD B CTM_{P la t f o rm}

Th e re m ig h t b e t im e s w h e n yo u w a n t t o o ve rrid e co n t a in e r-m a n a g e d p e rs is t e n ce a n d ir-m p le r-m e n t e n t it y o r s e s s io n Be a n

m e t h o d s t o u s e t h e S QL co m m a n d s yo u p ro vid e . Th is t yp e o f Be a n -m a n a g e d p e rs is t e n ce ca n b e u s e fu l if yo u n e e d t o i-m p ro ve

p e rfo rm a n ce o r m a p d a t a in m u lt ip le Be a n s t o o n e ro w in a d a t a b a s e t a b le .

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W h y Ma n a g e Tra n s a c t io n s ?

Wh e n yo u a cce s s a d a t a b a s e s u s in g t h e JDBCTM_{a p p lica t io n}

p ro g ra m m in g in t e rfa ce ( API) , a ll o p e ra t io n s a re ru n w it h a n e xp licit a u t o co m m it b y d e fa u lt . Th is m e a n s a n y o t h e r a p p lica t io n vie w in g t h is d a t a w ill s e e t h e u p d a t e d d a t a a ft e r e a ch JDBC ca ll.

Fo r s im p le a p p lica t io n s t h is m a y b e a cce p t a b le , b u t co n s id e r t h e a u ct io n a p p lica t io n a n d t h e s e q u e n ce s t h a t o ccu r w h e n SellerBean

in s e rt s a n a u ct io n it e m . Th e u s e r's a cco u n t is firs t ch a rg e d fo r lis t in g t h e it e m , a n d t h e it e m is t h e n a d d e d t o t h e lis t o f it e m s u p fo r a u ct io n . Th e s e o p e ra t io n s in vo lve RegistrationBean t o d e b it t h e

a cco u n t a n d AuctionItemBean t o a d d t h e it e m t o t h e a u ct io n lis t .

In a u t o co m m it m o d e , if t h e a u ct io n it e m in s e rt io n fa ils , o n ly t h e lis t in g is b a cke d o u t , a n d yo u h a ve t o m a n u a lly a d ju s t t h e u s e r's a cco u n t t o re fu n d t h e lis t in g ch a rg e . In t h e m e a n t im e , a n o t h e r t h re a d m ig h t t ry t o d e d u ct fro m t h e s a m e u s e r's a cco u n t , fin d n o cre d it le ft , a n d a b o rt w h e n p e rh a p s a fe w m illis e co n d s la t e r it w o u ld h a ve co m p le t e d .

Th e re a re t w o w a ys t o e n s u re t h e d e b it is b a cke d o u t if t h e a u ct io n it e m in s e rt io n fa ils :

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Co n t a in e r- Ma n a g e d Ex a m p le

SellerBean is a s e s s io n Be a n t h a t u s e s RegistrationBean t o ch e ck

t h e u s e r ID a n d p a s s w o rd w h e n s o m e o n e p o s t s a n a u ct io n it e m a n d d e b it t h e s e lle r's a cco u n t fo r a lis t in g , a n d AuctionItemBean t o

a d d n e w a u ct io n it e m s t o t h e d a t a b a s e .

Th e t ra n s a ct o n b e g in s in t h e insertItem m e t h o d w it h t h e a cco u n t

d e b it a n d e n d s w h e n t h e e n t ire t ra n s a ct io n e it h e r co m m it s o r ro lls b a ck. Th e e n t ire t ra n s a ct io n in clu d in g t h e 5 0 ce n t s d e b it ro lls b a ck if t h e a u ct io n it e m is null ( t h e in s e rt io n fa ile d ) , o r if a n e xce p t io n

is ca u g h t . If t h e a u ct io n it e m is n o t null a n d t h e in s e rt io n

s u cce e d s , t h e e n t ire t ra n s a ct io n in clu d in g t h e 5 0 ce n t s d e b it co m m it s .

Co d e

To u s e s e s s io n s yn ch ro n iza t io n , a s e s s io n Be a n im p le m e n t s t h e

SessionSynchronzation in t e rfa ce a n d it s t h re e m e t h o d s , afterBegin, beforeCompletion, a n d afterCompletion. Th is e xa m p le a d a p t s t h e

S e lle rBe a n . ja va co d e t o u s e s e s s io n s yn ch ro n iza t io n .

public class SellerBean implements SessionBean, SessionSynchronization {

private transient SessionContext ctx;

private transient Properties p = new Properties(); private transient boolean success = true;

public void afterBegin() {}

public void beforeCompletion() { if (!success ) {

ctx.setRollbackOnly(); }

}

public void afterCompletion(boolean state) {}

afterBegin: Th e co n t a in e r ca lls t h is m e t h o d b e fo re t h e d e b it t o

n o t ify t h e s e s s io n Be a n a n e w t ra n s a ct io n is a b o u t t o b e g in . Yo u ca n im p le m e n t t h is m e t h o d t o d o a n y p re lim in a ry d a t a b a s e w o rk t h a t m ig h t b e n e e d e d fo r t h e t ra n s a ct io n . In t h is e xa m p le , n o p re lim in a ry d a t a b a s e w o rk is n e e d e d s o t h is m e t h o d h a s n o im p le m e n t a t io n .

beforeCompletion: Th e co n t a in e r ca lls t h is m e t h o d w h e n it is re a d y

t o w rit e t h e a u ct io n it e m a n d d e b it t o t h e d a t a b a s e , b u t b e fo re it a ct u a lly d o e s ( co m m it s ) . Yo u ca n im p le m e n t t h is m e t h o d t o w rit e o u t a n y ca ch e d d a t a b a s e u p d a t e s o r ro ll b a ck t h e t ra n s a ct io n . In

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}

//Call to beforeCompletion //Call to afterCompletion

}

Tra n s a c t io n Co m m it Mo d e

If yo u co n fig u re t h e JDBC s e rvice s t o t ra n s a ct io n co m m it m o d e , yo u ca n h a ve t h e Be a n m a n a g e t h e t ra n s a ct io n . To s e t t h e JDBC s e rvice s t o co m m it , ca ll con.setAutoCommit(false) o n yo u r JDBC

co n n e ct io n . No t a ll JDBC d rive rs s u p p o rt co m m it m o d e , b u t t o h a ve t h e Be a n co n t ro l a n d m a n a g e t ra n s a ct io n s , yo u n e e d a JDBC d rive r t h a t d o e s .

Tra n s a ct io n co m m it m o d e le t s yo u a d d co d e t h a t cre a t e s a s a fe t y n e t a ro u n d a s e q u e n ce o f d e p e n d e n t o p e ra t io n s . Th e Ja vaTM

Tra n s a ct io n API ( JTA) p ro vid e s t h e h o o ks yo u n e e d t o cre a t e t h a t s a fe t y n e t . Bu t , if yo u a re u s in g t h e En t e rp ris e Ja va Be a n s

a rch it e ct u re , yo u ca n d o it w it h a lo t le s s co d e . Yo u o n ly h a ve t o co n fig u re t h e En t e rp ris e Ja va Be a n s s e rve r, a n d s p e cify w h e re t h e t ra n s a ct io n s t a rt s , s t o p s , ro lls b a ck, a n d co m m it s in yo u r co d e .

S e rv e r Co n f ig u ra t io n

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He re a re t h e t ra n s a ct io n a t t rib u t e s w it h a b rie f d e s crip t io n fo r e a ch o n e . Th e a t t rib u t e n a m e s ch a n g e d b e t w e e in t h e 1 . 0 a n d 1 . 1

ve rs io n s o f t h e En t e rp ris e Ja va Be a n s s p e cifica t io n . 1 . 1 S p e cifica t io n 1 . 0 S p e cifica t io n

REQUIRED TX_REQUIRED

Co n t a in e r- m a n a g e d t ra n s a ct io n . Th e s e rve r e it h e r s t a rt s a n d m a n a g e s a n e w t ra n s a ct io n o n b e h a lf o f t h e u s e r o r co n t in u e s u s in g t h e t ra n s a ct io n t h a t w a s s t a rt e d b y t h e co d e t h a t ca lle d t h is Be a n .

REQUIRESNEW TX_REQUIRED_NEW

Co n t a in e r- m a n a g e d t ra n s a ct io n . Th e s e rve r s t a rt s a n d m a n a g e s a n e w t ra n s a ct io n . If a n e xis t in g t ra n s a ct io n s t a rt s t h is t ra n s a ct io n , it s u s p e n d s u n t il t h is t ra n s a ct io n co m p le t e s .

Specified as Bean transaction-type in deployment descriptor

TX_BEAN_MANAGED

Be a n - m a n a g e d t ra n s a ct io n . Yo u a cce s s t h e t ra n s a ct io n co n t e xt t o b e g in , co m m it , o r ro llb a ck t h e t ra n s a ct io n a s n e e d e d .

SUPPORTS TX_SUPPORTS

If t h e co d e ca llin g t h is Be a n h a s a t ra n s a ct io n ru n n in g , in clu d e t h is Be a n in t h a t t ra n s a ct io n .

NEVER TX_NOT_SUPPORTED

If t h e co d e ca llin g a m e t h o d in t h is Be a n h a s a t ra n s a ct io n

ru n n in g , s u s p e n d t h a t t ra n s a ct io n u n t il t h e m e t h o d ca lle d in t h is Be a n co m p le t e s . No t ra n s a ct io n co n t e xt is cre a t e d fo r t h is Be a n .

MANDATORY TX_MANDATORY

Th e t ra n s a ct io n a t t rib u t e fo r t h is Be a n is s e t w h e n a n o t h e r Be a n ca lls o n e o f it s m e t h o d s . In t h is ca s e , t h is Be a n g e t s t h e

t ra n s a ct io n a t t rib u t e o f t h e ca llin g Be a n . If t h e ca llin g Be a n h a s n o t ra n s a ct io n a t t rib u t e , t h e m e t h o d ca lle d in t h is Be a n t h ro w s a

TransactionRequired e xce p t io n .

I s o la t io n Le v e l D e s c rip t io n s: An e n t e rp ris e Be a n u s e s a n

is o la t io n le v e l t o n e g o t ia t e it s o w n in t e ra ct io n w it h s h a re d d a t a a n d t h e in t e ra ct io n o f o t h e r t h re a d s w it h t h e s a m e s h a re d d a t a . As t h e n a m e im p lie s , t h e re a re va rio u s le ve ls o f is o la t io n w it h

TRANSACTION_SERIALIZABLE p ro vid in g t h e h ig h e s t le ve l o f d a t a

in t e g rit y.

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N o t e : Be s u re t o ve rify yo u r d a t a b a s e ca n h a n d le t h e le ve l yo u ch o o s e . In t h e En t e rp ris e Ja va Be a n s 1 . 1 s p e cifica t io n , o n ly Be a n - m a n a g e d p e rs is t e n ce s e s s io n Be a n s ca n s e t t h e is o la t io n le ve l.

If t h e d a t a b a s e ca n n o t h a n d le t h e is o la t io n le ve l, t h e En t e rp ris e Ja va Be a n s s e rve r w ill g e t a fa ilu re w h e n it t rie s t o ca ll t h e setTransactionIsolation JDBC m e t h o d .

TRANSACTION_SERIALIZABLE: Th is le ve l p ro vid e s m a xim u m d a t a

in t e g rit y. Th e Be a n g e t s w h a t a m o u n t s t o e xclu s ive a cce s s t o t h e d a t a . No o t h e r t ra n s a ct io n ca n re a d o r w rit e t h is d a t a u n t il t h e s e ria liza b le t ra n s a ct io n co m p le t e s .

S e ria liza b le in t h is co n t e xt m e a n s p ro ce s s a s a s e ria l o p e ra t io n, a n d s h o u ld n o t b e co n fu s e d w it h s e ria lizin g o b je ct s t o p re s e rve a n d re s t o re t h e ir s t a t e s . Ru n n in g t ra n s a ct io n s a s a s in g le s e ria l

o p e ra t io n is t h e s lo w e s t s e t t in g . If p e rfo rm a n ce is a n is s u e , u s e a n o t h e r is o la t io n le ve l t h a t m e e t s yo u r a p p lica t io n re q u ire m e n t s , b u t p ro vid e s b e t t e r p e rfo rm a n ce .

TRANSACTION_REPEATABLE_READ: At t h is le ve l, d a t a re a d b y a

t ra n s a ct io n ca n b e re a d , b u t n o t m o d ifie d , b y a n o t h e r t ra n s a ct io n . Th e d a t a is g u a ra n t e e d t o h a ve t h e s a m e va lu e it h a d w h e n firs t re a d , u n le s s t h e firs t t ra n s a ct io n ch a n g e s it a n d w rit e s t h e ch a n g e d va lu e b a ck.

TRANSACTION_READ_COMMITTED: At t h is le ve l, d a t a re a d b y a

t ra n s a ct io n ca n n o t b e re a d b y o t h e r t ra n s a ct io n s u n t il t h e fris t t ra n s a ct io n e it h e r co m m it s o r ro lls b a ck.

TRANSACTION_READ_UNCOMMITTED: At t h is le ve l, d a t a in vo lve d in a t ra n s a ct io n ca n b e re a d b y o t h e r t h re a d s b e fo re t h e firs t

t ra n s a ct io n e it h e r co m p le t e s o r ro lls b a ck. Th e o t h e r t ra n s a ct io n s ca n n o t t e ll if t h e d a t a w a s fin a lly co m m it t e d o r ro lle d b a ck

B e a n - Ma n a g e d Ex a m p le

SellerBean is a s e s s io n Be a n t h a t u s e s RegistrationBean t o ch e ck

t h e u s e r ID a n d p a s s w o rd w h e n s o m e o n e p o s t s a n a u ct io n it e m a n d d e b it t h e s e lle r's a cco u n t fo r a lis t in g , a n d AuctionItemBean t o

a d d n e w a u ct io n it e m s t o t h e d a t a b a s e .

Th e t ra n s a ct o n b e g in s in t h e insertItem m e t h o d w it h t h e a cco u n t

d e b it a n d e n d s w h e n t h e e n t ire t ra n s a ct io n e it h e r co m m it s o r ro lls b a ck. Th e e n t ire t ra n s a ct io n in clu d in g t h e 5 0 ce n t s d e b it ro lls b a ck

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if(ai == null) { //Roll transaction back uts.rollback();

return Auction.INVALID_ITEM; }

else {

//Commit transaction uts.commit();

return(ai.getId()); }

}catch(Exception e){

System.out.println("insert problem="+e); //Roll transaction back if insert fails

uts.rollback();

return Auction.INVALID_ITEM; }

}

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Fo ru m s

W rit in g Ad v a n c e d Ap p lic a t io n s

Ch a p t e r 3 Co n t in u e d : B e a n - Ma n a g e d f in d e r Me t h o d s

Th e co n t a in e r- m a n a g e d s e a rch d e s crib e d in Ch a p t e r 2 is b a s e d o n a finder m e t h o d m e ch a n is m w h e re t h e d e p lo ym e n t d e s crip t o r,

ra t h e r t h a n t h e Be a n , s p e cifie s t h e finder m e t h o d b e h a vio r. Wh ile

t h e finder m e ch a n is m w o rks w e ll fo r s im p le q u e rie s a n d s e a rch e s ,

it ca n n o t h a n d le co m p le x o p e ra t io n s t h a t s p a n m o re t h a n o n e Be a n t yp e o r d a t a b a s e t a b le . Als o , t h e En t e rp ris e Ja va Be a n sTM 1 . 1

s p e cifica t io n cu rre n t ly p ro vid e s n o s p e cifica t io n fo r p u t t in g finder

ru le s in t h e d e p lo ym e n t d e s crip t o r.

S o , fo r m o re co m p le x q u e rie s a n d s e a rch e s , yo u h a ve t o w rit e Be a n - m a n a g e d q u e rie s a n d s e a rch e s . Th is s e ct io n e xp la in s h o w t o w rit e a Be a n - m a n a g e d ve rs io n o f t h e a u ct io n h o u s e s e a rch fa cilit y fro m Ch a p t e r 2 . Th e Be a n - m a n a g e d s e a rch in vo lve s ch a n g e s t o t h e AuctionServlet.searchItems m e t h o d a n d a n e w s e s s io n Be a n ,

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( 8 0 0 ) 7 8 6 - 7 6 3 8

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Fo ru m s

W rit in g Ad v a n c e d Ap p lic a t io n s

Ch a p t e r 4 : Lo o k u p S e rv ic e s

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