8/8/2019 Spring Talk 111204

1/57

Spring

Paul Jensen

Principal, Object Computing Inc.

8/8/2019 Spring Talk 111204

2/57

Spring Overview

Lightweight Container

Very loosely coupled

Components widely reusable and separately

packaged

Created by Rod Johnson

Based on Expert one-on-one J2EE Design andDevelopment

Currently on version 1.1.1

8/8/2019 Spring Talk 111204

3/57

Why Use Spring? 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)

8/8/2019 Spring Talk 111204

4/57

Why Use Spring?

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

8/8/2019 Spring Talk 111204

5/57

Spring Framework

8/8/2019 Spring Talk 111204

6/57

Spring Application

8/8/2019 Spring Talk 111204

7/57

Spring Dependency Injection 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 locatesimplementation (pull)

Martin Fowler calls Dependency Injection

8/8/2019 Spring Talk 111204

8/57

Dependency Injection Variants 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 andorg.springframework.context

Typically use the XmlBeanFactory, employing XML

configuration files

8/8/2019 Spring Talk 111204

9/57

Dependency Injection (cont'd) BeanFactory configured components need have

no Spring dependencies

Simple JavaBeans Beans are singletons by default

Properties may be simple values or references toother beans

Built-in support for defining Lists, Maps, Sets,and Properties collection types.

Custom PropertyEditors may be defined toconvert string values to other, arbitrary types.

8/8/2019 Spring Talk 111204

10/57

XmlBeanFactory Example Property and constructor based IoC

1

1

8/8/2019 Spring Talk 111204

11/57

Bean Creation Direct instantiation

BeanFactory instantiation Same syntax but class is subclass of BeanFactory

getObject() called to obtain Bean

Static Factory

Instance Factory Method

8/8/2019 Spring Talk 111204

12/57

Bean Creation Beans may be singletons or prototypes

Attributesingleton=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, allowingreuse of attribute values through inheritance

8/8/2019 Spring Talk 111204

13/57

Autowiring Properties Beans may be auto-wired (rather than using )

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

8/8/2019 Spring Talk 111204

14/57

Dependency Checking 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

8/8/2019 Spring Talk 111204

15/57

Lifecycle Customization Can define init method called after properties set

init-method=

Can define destroy method as shutdown hook

destroy-method=

May alternatively implement InitializingBean

and/or DisposableBean At cost of Spring dependency

8/8/2019 Spring Talk 111204

16/57

BeanFactory Miscellany 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()

8/8/2019 Spring Talk 111204

17/57

BeanFactory Usage

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

ApplicationContext ctx = newClassPathXmlApplicationContext("beans.xml");MyBeanClass bean = (MyBeanClass)ctx.getBean(myBean);

OR

8/8/2019 Spring Talk 111204

18/57

ApplicationContext Extends functionality of BeanFactory

Pre-instantiates singleton beans

Detects and registers BeanPostProcessors andBeanFactoryPostProcessors

Supports nesting of contexts

ApplicationListenerand ApplicationEvents

Initialized and closed predefined

Custom may be created

MessageSourceprovides i18n messaging

Contains list of bundle base names

8/8/2019 Spring Talk 111204

19/57

Web Initialization Web applications may use

ContextLoaderListener to initialize Spring

contextConfigLocation/WEB-INF/daoContext.xml /WEB-INF/applicationContext.xml

org.springframework.web.context.ContextLoaderListener

web.xml

Automatically done by Spring DispatcherServlet

8/8/2019 Spring Talk 111204

20/57

Specialized Beans 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

8/8/2019 Spring Talk 111204

21/57

ApplicationContext customization Defined beans inheriting from

BeanFactoryPostProcessorare detected and invoked

CustomEditorConfigurer

Registers customPropertyEditors 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

8/8/2019 Spring Talk 111204

22/57

ApplicationContext Example

database.properties

${database.connection.driver_class}

${database.connection.url}

8/8/2019 Spring Talk 111204

23/57

Spring AOP

8/8/2019 Spring Talk 111204

24/57

AOP Fundamentals 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

8/8/2019 Spring Talk 111204

25/57

AOP Fundamentals 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.

8/8/2019 Spring Talk 111204

26/57

Spring AOP 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

8/8/2019 Spring Talk 111204

27/57

Spring Pointcuts 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);}

8/8/2019 Spring Talk 111204

28/57

Pointcuts (cont'd)

public interface MethodMatcher {boolean matches(Method m, Class targetClass);

boolean isRuntime();boolean matches(Method m, Class targetClass, Object[] args);

}

Pointcut may be statically or dynamically

evaluated based on isRuntime()

Abstract class StaticMethodMatcherPointcut

requires override of 1st method only

Only called if isRuntime() == true

8/8/2019 Spring Talk 111204

29/57

Pointcuts (cont'd) 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

8/8/2019 Spring Talk 111204

30/57

Spring Advice 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.

}}

8/8/2019 Spring Talk 111204

31/57

Spring Advice 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

8/8/2019 Spring Talk 111204

32/57

Spring Advice IntroductionInterceptor provides ability to define

mixins

public class RollbackAdvice extends DelegatingIntroductionInterceptorimplements 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

}}

8/8/2019 Spring Talk 111204

33/57

InjectingAdviceSpring

8/8/2019 Spring Talk 111204

34/57

InjectingAdvice (cont'd)

myAdvisordebugInterceptor

Advisors applied in order

All methods

using CGLibif none defined

8/8/2019 Spring Talk 111204

35/57

Autoproxying 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 toall beans, proxying appropriately

8/8/2019 Spring Talk 111204

36/57

Metadata support 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 viaA

ttributesinterface

Amenable to mocking unlike JDK reflection and

Commons static methods

8/8/2019 Spring Talk 111204

37/57

Metadata autoproxying 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

8/8/2019 Spring Talk 111204

38/57

Transactions

8/8/2019 Spring Talk 111204

39/57

AOP Transactions Spring provides AOP support for declarative

transactions

Delegates to a PlatformTransactionManager

instance

DataSourceTransactionManager

HibernateTransactionManager JdoTransactionManager

JtaTransactionManager

8/8/2019 Spring Talk 111204

40/57

Transaction Configuration

com/../model/*.hbm.xml

8/8/2019 Spring Talk 111204

41/57

Declarative Transactions 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)

8/8/2019 Spring Talk 111204

42/57

Injecting Transaction Support

8/8/2019 Spring Talk 111204

43/57

Transaction Autoproxy

Caches metadatafrom classes

Generic autoproxysupport

Applies transactionusing transactionManager

Invokes interceptorbased on attributes

8/8/2019 Spring Talk 111204

44/57

Data Access

8/8/2019 Spring Talk 111204

45/57

Data Access DAO support provides pluggable framework for

persistence

Currently supports JDBC, Hibernate, JDO, andiBatis

Defines consistent exception hierarchy (based onRuntimeException)

Provides abstract Support classes for eachtechnology

Template methods define specific queries

8/8/2019 Spring Talk 111204

46/57

Hibernate DAO Examplepublic 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);

}

8/8/2019 Spring Talk 111204

47/57

Hibernate DAO (contd)

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()]);

8/8/2019 Spring Talk 111204

48/57

Hibernate DAO (contd)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()]);

}

}

8/8/2019 Spring Talk 111204

49/57

Hibernate Example

com/jensenp/Reservation/Room.hbm.xml

com/jensenp/Reservation/Reservation.hbm.xmlcom/jensenp/Reservation/Resource.hbm.xml

${hibernate.dialect}${hibernate.hbm2ddl.auto}${hibernate.show_sql}

8/8/2019 Spring Talk 111204

50/57

JDBC Support JDBCTemplate provides

Translation of SQLExceptions to more

meaningful Spring Runtime exceptions

Integrates thread-specific transactions

MappingSQLQuery simplifies mapping of

ResultSets to Java objects

8/8/2019 Spring Talk 111204

51/57

Web Framework

8/8/2019 Spring Talk 111204

52/57

DispatcherServlet The DispatcherServlet is the Spring Front

Controller

InitializesWebApplicationContext

Uses /WEB-INF/[servlet-name]-servlet.xmlby

default

WebApplicationContext is bound intoServletContext

8/8/2019 Spring Talk 111204

53/57

DispatcherServlet Configuration 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

8/8/2019 Spring Talk 111204

54/57

Dispatcher Servlet Configuration MultipartResolver

Handling of file upload

LocaleResolver

Default uses HTTP accept header, cookie, or

session

8/8/2019 Spring Talk 111204

55/57

Controllers 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

8/8/2019 Spring Talk 111204

56/57

Controller Implementations CommandControllers bind parameters to data

objects

AbstractCommandController

AbstractFormController

SimpleFormController

WizardFormController

8/8/2019 Spring Talk 111204

57/57

References Springs homepage: http://www.springframework.org

Introducing the Spring Framework by Rod Johnson:

http://theserverside.com/news/thread.jsp?thread_id=21893

Inversion of control containers and dependency injection by

Martin Fowler:

http://www.martinfowler.com/articles/injection.html

AOP Alliance: http://aopalliance.sourceforge.net