16th July 2007

Better architecture by designJAVAWUG BOF 27, Skills Matter, London

*PP* © 2007

Peter PilgrimJava EE Software Designer ArchitectIndependent ContractorFinancial ServicesJava Championhttp://jroller.com/page/peter_pilgrim http://jroller.com/page/javawug

Spring Framework Best Practices

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Talk Outline

Spring Framework Primary School ClassSpring Version 1.xSpring Version 2.0Spring Version 2.1 and JSR 316Spring Hints & TipsSummary

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What is Spring?

Managed Dependency Injection FrameworkLife-cycle of POJOSDependency Injection for JavaBeans & InterfacesPlethora of Utility APIs and idioms

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What is Spring Version 1?

Core SpringDynamicAOP

Data Access

DeclarativeTXMail

RemotingMVC

Bean FactoryContainer

Scheduling

Simplifying J2EE Development

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What is Spring Version 2?

Core Spring

DynamicAOP

Data Access

DeclarativeTXMail

RemotingServlet MVC

Bean FactoryContainer

Scheduling

Simplifying J(2)EE Development

Annotations (TX)

AspectJLibraries

Task Executor

XML NamespacesTag Libs

Java 5

Portlet MVC

Scripting Languages

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What is expected in Spring Version 2.1?

Core Spring

DynamicAOP

Alternative DataAccess

DeclarativeTXMail

RemotingServlet MVC

Bean FactoryContainer

Scheduling

Simplifying Java EE Development

AspectJIntegration

Task ExecutorExtra XML

Namespaces Tag Libs

Java EE 5

Portlet MVC

Annotation Driven Injection

OSGi Modules

Annotation TX

Annotation Componentisation

Familiar DataAccess

Spring Security

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Goals of Spring 2.0

Backwards compatibleAnnotation Driven TransactionsSimplified Java 5 SupportXML Namespace extension for ease-of-configurationImproved JMS Messaging, local and XA transactionsTask ExecutorAspectJ library supportJPA IntegrationPortlet MVC

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Goals of Spring 2.1

OSGi is the biggest value addModule JARSSpecial OSGi XML namespaceAnnotation Driven InjectionSpring Back-ends (JCA and LDAP support)Enhanced JPA support

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Goals of Spring 2.1

OSGi is the biggest value addModule JARSSpecial OSGi XML namespaceAnnotation Driven InjectionSpring Back-ends (JCA and LDAP support)Enhanced JPA support

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Future of Spring Development Java EE JSR 316

Eventually we will be locked into Spring, but not yet!!!Spring OSGi does obscure the raw APIsJava EE 6 has a new JSR 316Java EE may incorporate Spring's ideasModularisation of Java EE (JSR 277 and 294)

JSR 277 Java Module SystemJSR 294 Improved Modularity Support

OSGi forces future EE architects to research new “materials” for building software

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Configuration of Transactions: Manager & Advice

<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"xsi:schemaLocation="...">

<tx:advice id="txAdvice" transaction-manager="txManager"><tx:attributes>

<tx:method name="get*" read-only="true" /><tx:method name="find*" read-only="true" /><tx:method name="*" />

</tx:attributes> </tx:advice>

<bean id="txManager" class="org.springframework.orm.hibernate3.

HibernateTransactionManager"><property name="sessionFactory" ref="sessionFactory" />

</bean> </beans>

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Configuration of Transactions: Pointcuts

<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"xsi:schemaLocation="...">

<aop:config><aop:pointcut id="projectServiceOperation"

expression="execution(* websitetracker.service.*.*(..))" /><aop:advisor advice-ref="txAdvice"

pointcut-ref="projectServiceOperation" /> </aop:config> <aop:config>...</aop:config>

...</beans>

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Configuration: Hibernate Session Factory

<beans ...> <bean id="sessionFactory" class="org.springframework.orm.

hibernate3.LocalSessionFactoryBean"> <property name="mappingResources"> <list> <value>websitetracker/domain/IpAddressReverse.hbm.xml</value> <value>websitetracker/domain/Website.hbm.xml</value> </list></property> <property name="hibernateProperties"> <props> <prop key="hibernate.dialect">

org.hibernate.dialect.MySQLDialect</prop> <prop key="hibernate.show_sql">true</prop>

<prop key="hibernate.generate_statistics">false</prop> </props></property> <property name="dataSource"><ref bean="dataSource"/></property>

<property name="eventListeners"> <map>

<entry key="merge"> <bean class="org.springframework.orm.hibernate3.support.

IdTransferringMergeEventListener" /></entry></map></property>

</bean> ...</beans>

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Configuration: Hibernate DAO & Services

<beans ...>

<bean id="hibernateTemplate" class="org.springframework.orm.hibernate3.HibernateTemplate">

<property name="sessionFactory"> <ref local="sessionFactory" /> </property>

</bean>

<bean id="ipAddressReverseDao" class="websitetracker.dao.IpAddressReverseDao" > <property name="sessionFactory" ref="sessionFactory" />

</bean>

<bean id="trackReportService" class="websitetracker.engine.impl.TrackReportServiceImpl" >

<property name="hibernateTemplate" ref="hibernateTemplate" />

</bean> ...</beans>

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Multiple Application Contexts

Parent and Child bean factory contexts can help modularise complexityApplicationContexts can retrieve wildcarded configuration files.For Spring managed EJBs and MDB prefer to use ContextSingletonBeanFactoryLocatorpublic class StartUpBean extends AbstractStatelessSessionBean {

public boolean start( ... )setBeanFactoryLocator( ContextSingletonBeanFactoryLocator

.getInstance(“classpath:fitrader-context.xml”)); setBeanFactoryLocatorKey(“FI-TRADER”); return true;}

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Define A Master Application Context

<!-- “fitrader-context.xml” --><beans ...>

<!-- defines the entire container context --><bean id="FI-TRADER" class="org.springframework.context.

support.ClassPathXmlApplicationContext"><constructor-arg index="0">

<list> <!-- service layer -->

<value>fitrader/service/beans-context-service.xml</value><!-- dao layer -->

<value>fitrader/dao/beans-context-dao.xml</value> <!-- Transaction Manager -->

<value>fitrader/dao/tx/beans-context-transaction.xml</value> <!-- AOP -->

<value>fitrader/aop/beans-context-aop.xml</value>

</list></constructor-arg><constructor-arg index="1"><value>true</value></constructor-arg>

</bean></beans>

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Share Contexts Among Spring Managed EJBs

Standard Spring managed EJB examples from books create and retrieve application contexts separatelyConsumes memory per deployment and EJB instance!Arrange for Spring managed EJBs to retrieve master application context insteadShare application context Message Driven Beans especially with point-to-point queue

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Spring Managed EJB Example

public class TradeRouteProcessorRemoteEJB extends AbstractStatelessSessionBeanimplements ITradeRouteProcessor{ private static final String BEAN_NAME = "tradeRouteProcessor"; private ITradeRouteProcessorScheduler delegate; public TradeRouteProcessorRemoteEJB() { super();

setBeanFactoryLocator( ContextSingletonBeanFactoryLocator

.getInstance(“classpath:fitrader-context.xml”)); setBeanFactoryLocatorKey(“FI-TRADER”); } protected void onEjbCreate() throws CreateException { delegate = (ITradeRouteProcessor)

getBeanFactory().getBean( BEAN_NAME); } ...}

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Test Driven Development

Write to Java interfaces or refactor them outConsider EasyMock for functional testingAbstractSpringDatabaseTestCase is a great class to extend for an application database unit testTactile techniques can help insert dummy data for test purposes. (JdbcTemplate)

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Easy Mock Advice

Consider a base test class for functional testingPull up useful DAO & Service classes in the base classRefactor common ground in concrete classesWrite creational methods on the base classesCall EasyMock.verify() !!!

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Maven 2.0 Spring Framework Java EE Setup

Eclipse IDE with Maven 2.0, Spring & Hibernate issues (prefer parallel project structure)Configure a general application context

Please store under src\main\resources!Configure at least one test application context

Please store under src\test\resources!Organise multiple file support for large applicationsInstall into local repository frequently!

Select all projects and hit F5!! (Grab a Biscuit and tea)Prefer Profiles to filtered resources! Eclipse tramples.

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A Generic DAO

Java 5 makes strong-typed collections easierWe can write a generic DAOWe can use the auto-complete feature in our IDEsWe are less likely to make errors in RTTI / casting!Extendible to named queries and criterion

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Generic DAO Interface

public interface IPersistenceDao<E, PK extends Serializable> {

public abstract void saveOrUpdate(E transientInstance); public abstract void attachDirty(E instance); public abstract void attachClean(E instance); public abstract void delete(E persistentInstance); public abstract E merge(E detachedInstance); public abstract E findById(PK id); public abstract List<E> findByExample(E instance);}

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Abstract Persistence DAO

public abstract class AbstractPersistenceDao<E, PK extends Serializable> extends HibernateDaoSupport

implements IPersistenceDao<E, PK> {

private Class<E> type;

public AbstractPersistenceDao( Class<E> type ) { super(); this.type = type; } public void saveOrUpdate(E transientInstance) { getHibernateTemplate().saveOrUpdate(transientInstance); } public E findById(PK id) { logger.debug("getting "+type.getName()+" instance with id: " + id); return (E) getHibernateTemplate().get( packageClassName, id); }...}

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Concrete Generic DAO

public class IpAddressReverseDao extends AbstractPersistenceDao<IpAddressReverse,Integer> {

public IpAddressReverseDao() { super( IpAddressReverse.class ); } @SuppressWarnings("unchecked") public List<IpAddressReverse> getAll() { return getHibernateTemplate().find(

"select i from IpAddressReverse as i"); }

...}

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Executive Summary

Review of Spring Framework 2.0 / 2.1 Discussion about the future of this frameworkCompeting frameworks such as Google GuiceRelevance to modularisation and architectural assemblySharing application contexts TestingGeneric DAO

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Time for Questions?

Q & A

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Illustration