Improving Your Code with POJOs, Dependency Injection, AOP, and

80 Pages·2007·1.4 MB·English

by  Peggy Kovsky

Colorado Software Summit: October 21 – 26, 2007 © Copyright 2007, Chris Richardson
Improving Your Code with POJOs,
Dependency Injection, AOP, and
O/R Mapping
Chris Richardson
Author of POJOs in Action
Chris Richardson Consulting, Inc
http://www.chrisrichardson.net
Chris Richardson: Improving Your Code with POJOs, Dependency Injection, AOP, and O/R Mapping Slide 1
Colorado Software Summit: October 21 – 26, 2007 © Copyright 2007, Chris Richardson
About Chris
(cid:1) Grew up in England
(cid:1) Live in Oakland, CA
(cid:1) Over twenty years of
software development
experience
(cid:3) Building object-oriented
software since 1986
(cid:3) Using Java since 1996
(cid:3) Using J2EE since 1999
(cid:1) Author of POJOs in Action
(cid:1) Speaker at JavaOne,
JavaPolis, NFJS, JUGs, ….
(cid:1) Chair of the eBIG Java SIG
in Oakland (www.ebig.org)
(cid:1) Run a consulting and
training company that helps
organizations build better
software faster
Chris Richardson: Improving Your Code with POJOs, Dependency Injection, AOP, and O/R Mapping Slide 2
Colorado Software Summit: October 21 – 26, 2007 © Copyright 2007, Chris Richardson
Overall presentation goal
Show how
dependency injection,
aspect-oriented programming
object/relational mapping
makes code easier to
develop and maintain
Chris Richardson: Improving Your Code with POJOs, Dependency Injection, AOP, and O/R Mapping SSlliiddee 33
Colorado Software Summit: October 21 – 26, 2007 © Copyright 2007, Chris Richardson
Agenda
(cid:1) Tangled code, tight coupling and
duplication
(cid:1) Using dependency injection
(cid:1) Simplifying code with aspects
(cid:1) Simplifying DAOs with O/R mapping
Chris Richardson: Improving Your Code with POJOs, Dependency Injection, AOP, and O/R Mapping SSlliiddee 44
Colorado Software Summit: October 21 – 26, 2007 © Copyright 2007, Chris Richardson
Common pattern: Big Fat
Service
(cid:1) Services are tightly coupled to other
components/infrastructure APIs
(cid:1) Services contain a tangle of business
logic and infrastructure logic
(cid:1) Implementation of infrastructure concerns
is scattered/duplicated throughout the
service layer
(cid:1) Code is difficult to: write, test and
maintain
(cid:1) Dies with the infrastructure frameworks
Chris Richardson: Improving Your Code with POJOs, Dependency Injection, AOP, and O/R Mapping SSlliiddee 55
Colorado Software Summit: October 21 – 26, 2007 © Copyright 2007, Chris Richardson
Example banking application
Chris Richardson: Improving Your Code with POJOs, Dependency Injection, AOP, and O/R Mapping Slide 6
Colorado Software Summit: October 21 – 26, 2007 © Copyright 2007, Chris Richardson
Example design
Web Tier
AccountServiceDelegate
void create (Account)
BankingTransaction transfer (fromAccountId , toAccountId , amount)
Business Tier AccountService BankingSecurityManager
void create (Account) verifyCallerAuthorized () {static }
BankingTransaction transfer (fromAccountId , toAccountId , amount)
<<singleton>>
AuditingManager
Account
audit()
accountId
balance
JdbcBanking
overdraftType
JdbcAccountDao TransactionDao
Account findAccount (accountId ) addTransaction () <<singleton>>
TransactionManager
BankingTransaction
begin()
commit()
txnId rollback()
date
<<singleton>>
JdbcConnection
Manager
getConnection()
cleanUp()
Chris Richardson: Improving Your Code with POJOs, Dependency Injection, AOP, and O/R Mapping Slide 7
Colorado Software Summit: October 21 – 26, 2007 © Copyright 2007, Chris Richardson
Demo
(cid:1) Let’s walk through the code
Chris Richardson: Improving Your Code with POJOs, Dependency Injection, AOP, and O/R Mapping SSlliiddee 88
Colorado Software Summit: October 21 – 26, 2007 © Copyright 2007, Chris Richardson
The good news
(cid:1) Code is relatively clean
(cid:1) Database access logic is encapsulated
by DAOs
(cid:1) Other concerns, e.g. transaction
management, are implemented by
other classes
BUT
Chris Richardson: Improving Your Code with POJOs, Dependency Injection, AOP, and O/R Mapping SSlliiddee 99
Colorado Software Summit: October 21 – 26, 2007 © Copyright 2007, Chris Richardson
Procedural code
(cid:1) Anemic Domain Model
public class AccountServicelImpl
implements AccountService {
(cid:3) AccountService =
public BankingTransaction transfer(String
Business logic
fromAccountId, String toAccountId,
double amount) {
(cid:3) Account and
…
BankingTransaction = Account fromAccount =
accountDao.findAccount(fromAccountId);
dumb data objects
Account toAccount =
(cid:1) Code is more difficult to:
accountDao.findAccount(toAccountId);
double newBalance = fromAccount.getBalance() –
(cid:3) Develop amount;
(cid:3) Understand fromAccount.setBalance(newBalance);
toAccount.setBalance(toAccount.getBalance() +
(cid:3) Maintain
amount);
….
(cid:3) Test
(cid:1) Solution: Attend my
other talk
Chris Richardson: Improving Your Code with POJOs, Dependency Injection, AOP, and O/R Mapping SSlliiddee 1100