“Lightweight Container”◦ Very loosely coupled◦ Components widely reusable and separately

packaged Created by Rod Johnson

◦ Based on “Expert one-on-one J2EE Design and Development”

◦ Currently on version 1.1.1

Wiring of components (Dependency Injection)◦ Promotes/simplifies decoupling, design to interfaces,

TDD Declarative programming without J2EE

◦ Easily configured aspects, esp. transaction support Simplify use of popular technologies

◦ Abstractions insulate application from specifics, eliminate redundant code, and handle common error conditions

◦ Underlying technology specifics still accessible (closures)

Conversion of checked exceptions to unchecked◦ (Or is this a reason not to use it?)

Not an all-or-nothing solution◦ Extremely modular and flexible

Well designed◦ Easy to extend◦ Many reusable classes

Inversion of Control (IoC) “Hollywood Principle”

◦ Don't call me, I'll call you “Container” resolves (injects) dependencies

of components by setting implementation object (push)

As opposed to component instantiating or Service Locator pattern where component locates implementation (pull)

Martin Fowler calls Dependency Injection

Variations on dependency injection◦ Interface based (Avalon)◦ Constructor-based (PicoContainer, Spring)◦ Setter-based (Spring)

BeanFactory provides configuration framework to initialize and “wire” JavaBeans◦ org.springframework.beans and

org.springframework.context Typically use the XmlBeanFactory, employing

XML configuration files

BeanFactory configured components need have no Spring dependencies◦ Simple JavaBeans

Beans are singletons by default Properties may be simple values or

references to other beans Built-in support for defining Lists, Maps,

Sets, and Properties collection types. ◦Custom PropertyEditors may be defined to convert string values to other, arbitrary types.

Property and constructor based IoC<bean id="exampleBean" class="examples.ExampleBean"> <property name="beanOne"><ref bean="anotherExampleBean"/></property> <property name="beanTwo"><ref bean="yetAnotherBean"/></property> <property name="integerProperty">1</property></bean>

<bean id="anotherExampleBean" class="examples.AnotherBean"/><bean id="yetAnotherBean" class="examples.YetAnotherBean"/>

<bean id="exampleBean" class="examples.ExampleBean"> <constructor-arg><ref bean="anotherExampleBean"/></constructor-arg> <constructor-arg><ref bean="yetAnotherBean"/></constructor-arg> <constructor-arg><value>1</value></constructor-arg></bean>

<bean id="anotherExampleBean" class="examples.AnotherBean"/><bean id="yetAnotherBean" class="examples.YetAnotherBean"/>

Direct instantiation◦ <bean id=“beanId” class=“className”>

BeanFactory instantiation◦ Same syntax but class is subclass of BeanFactory◦ getObject() called to obtain Bean

Static Factory◦ <bean id=“beanId” class=“className" factory-method="

staticCreationMethod“> Instance Factory Method

◦ <bean id=“beanId” factory-bean=“existingBeanId" factory-method=“nonStaticCreationMethod">

Beans may be singletons or “prototypes”◦ Attribute singleton=“false” causes instantiation

with each getBean() lookup◦ Singleton is default

XmlBeanFactory pre-instantiates singletons◦ May be overridden on per-instance basis by lazy-

init=“true” Beans may also be marked abstract,

allowing reuse of attribute values through inheritance

Beans may be auto-wired (rather than using <ref>)◦ Per-bean attribute autowire◦ Explicit settings override

autowire=“name”◦ Bean identifier matches property name

autowire=“type”◦ Type matches other defined bean

autowire=”constructor”◦ Match constructor argument types

autowire=”autodetect”◦ Attempt by constructor, otherwise “type”

Ensures properties are defined◦ Per-bean attribute dependency-check◦ None required by default◦ Verifies autowiring succeeded

“simple”◦ all but collaborators

“object”◦ collaborators only

“all”◦ Collaborators, primitive types, and collections

Can define init method called after properties set◦ init-method=”<method-name>”

Can define destroy method as shutdown hook◦ destroy-method=”<method-name>”

May alternatively implement InitializingBean and/or DisposableBean◦ At cost of Spring dependency

BeanFactoryAware interface provides BeanFactory for bean◦ setBeanFactory(BeanFactory)

BeanNameAware interface provides bean name◦ setBeanName(String)

FactoryBean for beans which are themselves factories◦ Object getObject()◦ Boolean isSingleton()◦ Class getObjectType()

InputStream is = new FileInputStream("beans.xml"); XmlBeanFactory factory = new XmlBeanFactory(is);MyBeanClass bean = (MyBeanClass)factory.getBean(“myBean”);

ApplicationContext ctx = new ClassPathXmlApplicationContext("beans.xml"); MyBeanClass bean = (MyBeanClass)ctx.getBean(“myBean”);

OR

Extends functionality of BeanFactory Pre-instantiates singleton beans Detects and registers BeanPostProcessors

and BeanFactoryPostProcessors Supports nesting of contexts ApplicationListener and ApplicationEvents

◦ Initialized and closed predefined◦ Custom may be created

MessageSource provides i18n messaging◦ <bean id=”messageSource”

class=”...ResourceBundleMessageSource”/>◦ Contains list of bundle base names

Web applications may use ContextLoaderListener to initialize Spring

<context-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/daoContext.xml /WEB-INF/applicationContext.xml </param-value> </context-param>

<listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener>

web.xml

Automatically done by Spring DispatcherServlet

MethodInvokingFactoryBean◦ Invokes method on registered beans or any

static methods◦ Stores return value

SingletonBeanFactoryLocator and ContextSingletonBeanFactoryLocator◦ Useful for sharing BeanFactories◦ Eliminate duplication of beans in multiple similar

factories or contexts

Defined beans inheriting from BeanFactoryPostProcessor are detected and invoked

CustomEditorConfigurer◦ Registers custom PropertyEditors for converting

configuration string values to specific types AutoProxyCreators

◦ Wrap beans in proxies based on various criteria (name, metadata, etc)

PropertyResourceConfigurer Sets from property file and/or system properties

<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="location"><value>database.properties</value></property> </bean>

<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource"> <property name="driverClassName"> <value>${database.connection.driver_class}</value> </property> <property name="url"> <value>${database.connection.url}</value> </property></bean>

Aspect-oriented programming (AOP) provides for simplified application of cross-cutting concerns◦ Transaction management◦ Security◦ Logging◦ Auditing◦ Locking

AOP sometimes (partially) achieved via Decorators or Proxies◦ CORBA Portable Interceptors◦ Servlet Filters

Aspect - Implementation of a cross-cutting concern. ◦ Spring Advisors or Interceptors

Joinpoint - Execution point to target◦ Typically, methods

Advice - Action taken at a particular joinpoint. Pointcut - A set of joinpoints specifying where

advice should be applied (e.g. Regular expression) Introduction/Mixin - Adding methods or fields to an

advised class. Weaving - Assembling aspects into advised objects.

Generally, applies aspects to beans using BeanFactory◦ Uses Dynamic Proxies if interface available

otherwise CGLIB◦ CGLIB creates derived class which proxies

requests Bean class may not be final

Less capable than AspectJ◦ does not have field interception◦ only runtime weaving solution is available◦ Closer integration with AspectJ anticipated

Pointcut applicability to a class may be evaluated statically or dynamically

Spring only creates proxies where necessary

public interface Pointcut { ClassFilter getClassFilter(); MethodMatcher getMethodMatcher();}public interface ClassFilter { boolean matches(Class clazz);}

Pointcut may be statically or dynamically evaluated based on isRuntime()

Abstract class StaticMethodMatcherPointcut requires override of 1st method only

public interface MethodMatcher { boolean matches(Method m, Class targetClass); boolean isRuntime(); boolean matches(Method m, Class targetClass, Object[] args);}

Only called if isRuntime() == true

Spring predefined pointcuts◦ In org.springframework.aop.support package

RegexpMethodPointcut◦ Union of multiple regular expressions◦ Uses Jakarta ORO package

ControlFlowPointcut◦ Similar to AspectJ cflow◦ Applied if call stack includes specific class and,

optionally, method UnionPointcut

◦ Merges pointcuts

Can have per-class or per-instance Advice Spring provides several Advice types Around Advice

AOP Alliance compliant Must call invocation.proceed() to call target

public class MyAdvice implements AroundAdvice { Object invoke(MethodInvocation invocation) { // change arguments, start transaction, lock, etc. invocation.proceed(); // change return value, stop transaction, unlock,etc. }}

MethodBeforeAdvice◦ void before(Method m, Object[] args, Object target)◦ Cannot alter return type

ThrowsAdvice◦ Marker interface◦ Implementors define methods of form:

afterThrowing([Method], [args], [target], subclassOfThrowable)

AfterReturningAdvice◦ void afterReturning(Object returnValue, Method, m,

Object[] args, Object target)◦ Cannot modify return value

IntroductionInterceptor provides ability to define mixins

public class RollbackAdvice extends DelegatingIntroductionInterceptor implements RollbackSupport { Map map = new HashMap(); void rollback(Date date) { // rollback to state at given time }

public Object invoke(MethodInvocation invocation) { // record change and time of change }}

<bean id=“meetingTarget" class=“ex.DefaultMeeting“ singleton=“false”> <property name=“topic">Spring</property></bean>

<bean id="myAdvisor" class=“ex.RollbackAdvice" singleton=”false”></bean>

<bean id="debugInterceptor" class="org.springframework.aop.interceptor.DebugInterceptor"></bean>

<bean id=“meeting" class="org.springframework.aop.framework.ProxyFactoryBean"> <property name="proxyInterfaces"> <value>ex.Meeting</value> </property>

<property name="target"><ref local=“meetingTarget"/></property>

<property name="interceptorNames"> <list> <value>myAdvisor</value> <value>debugInterceptor</value> </list> </property></bean>

Advisors applied in order

All methodsusing CGLib if none defined

Autoproxy bean definitions automatically proxy selected beans.

BeanNameAutoProxyCreator◦Adds listed advisors/interceptors to beans with names matching regular expression

DefaultAdvisorAutoProxyCreator◦Generic autoproxy infrastructure support◦Applies all advisors defined in the context to all beans, proxying appropriately

Spring supports obtaining meta data Object attributes at class, method, and field level◦ Not yet argument level (as JSR-175)

Currently supports Jakarta Commons Attributes

Support for JSR-175 in work Metadata support provided via Attributes

interface◦ Amenable to mocking unlike JDK reflection and

Commons static methods

Configuration of autoproxying based on metadata attributes simplifies configuration◦ Define custom attribute class◦ Define Advisor with pointcut based on custom

attribute◦ Add Advisor in ApplicationContext with autoproxy

Examples◦ Transaction Attributes◦ Security Attributes◦ Pooling◦ Mapping of controllers to URLs

Spring provides AOP support for declarative transactions

Delegates to a PlatformTransactionManager instance◦ DataSourceTransactionManager◦ HibernateTransactionManager◦ JdoTransactionManager◦ JtaTransactionManager

<bean id="sessionFactory" class="org.springframework.orm.hibernate.LocalSessionFactoryBean"> <property name="dataSource"><ref bean="dataSource"/></property> <property name="mappingResources"> <list> <value>com/../model/*.hbm.xml</value> </list> </property></bean>

<bean id="transactionManager” class="org.springframework.orm.hibernate.HibernateTransactionManager"> <property name="sessionFactory"> <ref bean="sessionFactory"/> </property></bean>

Declarative transactional support can be added to any bean by using TransactionProxyFactoryBean

Similar to EJB, transaction attributes may be defined on a per-method basis

Also allows definition of pre- and post- interceptors (e.g. for security)

<bean id=“reservationService" class="org.springframework.transaction.interceptor.TransactionProxyFactoryBean"> <property name="transactionManager"> <ref bean="transactionManager"/> </property> <property name="target"><ref local=“reservationServiceTarget"/></property> <property name="transactionAttributes"> <props> <prop key=“reserveRoom*">PROPAGATION_REQUIRED</prop> <prop key="*">PROPAGATION_REQUIRED,readOnly</prop> </props> </property> </bean>

Declarative transaction support for single bean

<bean id="autoproxy" class="org...DefaultAdvisorAutoProxyCreator"></bean>

<bean id="transactionAdvisor" class="org...TransactionAttributeSourceAdvisor" autowire="constructor" ></bean>

<bean id="transactionInterceptor" class="org...TransactionInterceptor" autowire="byType"> </bean>

<bean id="transactionAttributeSource" class="org...AttributesTransactionAttributeSource" autowire="constructor"></bean>

<bean id="attributes" class="org...CommonsAttributes"/>

Caches metadatafrom classes

Generic autoproxysupport

Applies transactionusing transactionManager

Invokes interceptorbased on attributes

DAO support provides pluggable framework for persistence

Currently supports JDBC, Hibernate, JDO, and iBatis

Defines consistent exception hierarchy (based on RuntimeException)

Provides abstract “Support” classes for each technology◦ Template methods define specific queries

public class ReservationDaoImpl extends HibernateDaoSupport implements ReservationDao {

public Reservation getReservation (Long orderId) { return (Reservation)getHibernateTemplate().load(Reservation .class, orderId); }

public void saveReservation (Reservation r) { getHibernateTemplate().saveOrUpdate(r); }

public void remove(Reservation Reservation) { getHibernateTemplate().delete(r); }

public Reservation[] findReservations(Room room) { List list = getHibernateTemplate().find( "from Reservation reservation “ + “ where reservation.resource =? “ + “ order by reservation.start", instrument); return (Reservation[]) list.toArray(new Reservation[list.size()]);

public Reservation[] findReservations(final DateRange range) { final HibernateTemplate template = getHibernateTemplate(); List list = (List) template.execute(new HibernateCallback() { public Object doInHibernate(Session session) { Query query = session.createQuery( "from Reservation r “ + “ where r.start > :rangeStart and r.start < :rangeEnd “); query.setDate("rangeStart", range.getStartDate() query.setDate("rangeEnd", range.getEndDate()) return query.list(); } }); return (Reservation[]) list.toArray(new Reservation[list.size()]); }}

<bean id="sessionFactory" class="org.springframework.orm.hibernate.LocalSessionFactoryBean"> <property name="dataSource"><ref bean="dataSource"/></property> <property name="mappingResources"> <list> <value>com/jensenp/Reservation/Room.hbm.xml</value> <value>com/jensenp/Reservation/Reservation.hbm.xml</value> <value>com/jensenp/Reservation/Resource.hbm.xml</value> </list> </property> <property name="hibernateProperties"> <props> <prop key="hibernate.dialect">${hibernate.dialect}</prop> <prop key="hibernate.hbm2ddl.auto">${hibernate.hbm2ddl.auto} </prop> <prop key="hibernate.show_sql">${hibernate.show_sql}</prop> </props> </property> </bean>

<bean id=“reservationDao" class="com.jensenp.Reservation.ReservationDaoImpl"> <property name="sessionFactory"><ref bean="sessionFactory"/> </property> </bean>

JDBCTemplate provides◦ Translation of SQLExceptions to more meaningful

Spring Runtime exceptions◦ Integrates thread-specific transactions

MappingSQLQuery simplifies mapping of ResultSets to Java objects

The DispatcherServlet is the Spring Front Controller

Initializes WebApplicationContext Uses /WEB-INF/[servlet-name]-servlet.xml

by default WebApplicationContext is bound into

ServletContext

HandlerMapping◦ Routing of requests to handlers

HandlerAdapter◦ Adapts to handler interface. Default utilizes

Controllers HandlerExceptionResolver

◦ Maps exceptions to error pages◦ Similar to standard Servlet, but more flexible

ViewResolver◦ Maps symbolic name to view

MultipartResolver◦ Handling of file upload

LocaleResolver◦ Default uses HTTP accept header, cookie, or

session

Controller interface defines one method◦ ModelAndView

handleRequest(HttpServletRequest req, HttpServletResponse resp) throws Exception

ModelAndView consists of a view identifier and a Map of model data

CommandControllers bind parameters to data objects

AbstractCommandController AbstractFormController SimpleFormController WizardFormController