Using Spring's IOC Model

© 2009 VMware Inc. All rights reserved

IOC Options in Spring

Josh Long @starbuxmanSpring Developer AdvocateSpringSource, a division of VMware

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About Josh Long

engineer, advocate for SpringSource

blog.springsource.org

@starbuxman

josh.long@springsource.com

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About Josh Long (cont’d)

Wrote “Getting Started with Spring Roo”

• free book download: http://bit.ly/ppv1Lx

• SpringSource.org/roo for information

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About SpringSource

SpringSource is the organization that develops the Spring framework, the leading enterprise Java framework

SpringSource was acquired by VMware in 2009

VMware and SpringSource bring you to the cloud and deliver on the mission of “build, run, manage”

• established partnerships with the major players in the business, including Adobe, SalesForce, and Google to help deliver the best experience for Spring users across multiple platforms

Leading contributor to projects like Apache HTTPD and Apache Tomcat

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At its core, the Spring Framework...

Provide comprehensive infrastructural support for developing enterprise Java™ applications

• Spring deals with the plumbing

• So you can focus on solving the domain problem

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Spring’s aim:

bring simplicity to java development

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web tier web tier & &

RIARIA

web tier web tier & &

RIARIA

service tierservice tierservice tierservice tier batch batch processingprocessing

batch batch processingprocessing

integration integration & &

messagingmessaging

integration integration & &

messagingmessaging

data data accessaccess

/ NoSQL / / NoSQL / Big DataBig Data

data data accessaccess

/ NoSQL / / NoSQL / Big DataBig Data

mobilemobilemobilemobile

tc Servertc ServerTomcatTomcat

JettyJetty

lightweightlightweight

CloudFoundryCloudFoundryVMForce VMForce

Google App EngineGoogle App EngineAmazon Web ServicesAmazon Web Services

the cloud: the cloud:

WebSphereWebSphereJBoss ASJBoss ASWebLogicWebLogic

(on legacy versions, too!) (on legacy versions, too!)

traditionaltraditional

The Spring frameworkThe Spring framework

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Application Configuration

A typical application system consists of several parts working together to carry out a use case

• lots of collaborating objects

component Bcomponent Bcomponent Bcomponent B

component Ccomponent Ccomponent Ccomponent C

component Acomponent Acomponent Acomponent A

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Application Configuration

A typical application system consists of several parts working together to carry out a use case

• lots of collaborating objects

MyServiceMyServiceMyServiceMyService

DB Driver DB Driver configurationconfiguration

DB Driver DB Driver configurationconfiguration

DataSourceDataSourceDataSourceDataSource

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Spring Has Only One Type of Component: a POJO

POJO: Plain ‘Ol Java Object

• standard objects

• objects have dependencies

public class CustomerRepository {

// ‘depends’ on a database connection private javax.sql.DataSource dataSource; }

• objects have lifecycles:

Connection conn = ... ; conn.open() ;...conn.close();

beginning andend of the lifecycle

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The Spring ApplicationContext

Spring Beans are Managed by An ApplicationContext

• whether you’re in an application server, a web server, in regular Java SE application, in the cloud, Spring is initialized through an ApplicationContext

• In a Java SE application:

• In a web application, you will configure an application context in your web.xml

<servlet> <servlet-name>Spring Dispatcher Servlet</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/spring/myAppContext*.xml</param-value> </init-param> <load-on-startup>1</load-on-startup> </servlet>

ApplicationContext ctx = new AnnotationConfigApplicationContext( “com.foo.bar.my.package”); or ApplicationContext ctx = new ClassPathXmlApplicationContext( “my-context.xml”);

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The Spring ApplicationContext

Spring Manages the beans you tell it to manage

• use annotations (JSR 250, JSR 330, native)

• XML

• Java configuration

• component scanning

You can of course use all of them! Mix ‘n match

All configuration styles tell the ApplicationContext how to manage your beans

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Spring, a walking tour

Demos:

• introduce the tool chain

• how to “setup” Spring

• basic dependency injection

• annotations (JSR 250, JSR 330, native)

• xml

• java configuration

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@Qualifiers

Provide a way to discriminate for @Autowired / @Inject for ambiguous types

• by bean name (meh)

• by presence of annotation (yay!)

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Spring, a walking tour

Demos:

• Qualifiers

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Working with Lots of Beans

To Modify or Transform Beans in the Context...

• You need to “select” the beans you want to modify

• You need to provide the code that represents the modification or augmentation

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Working with Lots of Beans

One way to selectively augment beans at the lower level:

• BeanPostProcessor

• are regular beans and are run after the configured beans have been created, but before the context is finished setting up

• BeanFactoryPostProcessor

• is run before any of the beans definitions are realized

• comes before BPP

A more natural alternative is Spring’s AOP support

• built on top of AspectJ

• provides a very convenient, powerful way to solve cross cutting problems

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Spring, a walking tour

Demos:

• Bean*PostProcessor

• AspectJ

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Life Cycles

Life Cycles for different folks

• “safe and consistent” - use the interfaces

• InitializingBean, DisposableBean

• correspond to init-method and destroy-method attributes

• Simple and component-centric : use the annotations

• @PostConstruct, @PreDestroy

• correspond to init-method and destroy-method attributes

• More power: SmartLifecycle

• gives you the ability to dynamically start and stop beans in a certain order as well as to query whether the bean’s been started or not.

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Life Cycles

Spring beans have scopes

• default: singleton

• can be:

• prototype

• HTTP session

• HTTP request

• HTTP application (servlet, basically)

• “step” in Spring batch

• thread-local

• Spring Web Flow “flow” scoped

• Spring Web Flow “conversation scoped”

• Spring Web Flow “view” scoped (in JSF)

• Activiti BPMN2 process-scoped

• any scope you want. It’s simple to add your own!

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Spring, a walking tour

Demos:

• life cycle callbacks

• scopes

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Getting Beans from Strange Places

FactoryBeans

Spring Expression Language

• convenient way to get at values and inject them

Spring environment specific beans (profiles)

• introduced in Spring 3.1

• make it easy to conditionally define an object based on some sort of runtime condition

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Getting Beans from Strange Places

FactoryBeans

• interface that’s used to provide a reusable definition of how to create a complicated object with many dependencies

• Related: Java configuration, and builders

• prefer both over FactoryBeans where possible

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Getting Beans from Strange Places

Spring Expression Language

• convenient way to get at values and inject them

• Andy Clement’s a genius

• like the Unified JSF EL, on steroids

• Can be used in Java, XML

• @Value(“#{ ... }”) or value = “#{ .. }”

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Getting Beans from Strange Places

Spring profiles

• @Profile(“production”) @Configuration ...

• <beans profile = ‘production’> ... </beans>

• Use System properties or simply specify the active profile on the environment

• Use ApplicationContextInitializer in web applications

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Spring, a walking tour

Demos:

• FactoryBeans

• SpEL

• Profiles

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Summary / Questions

code: git.springsource.org:spring-samples/spring-samples.git

blog.springsource.org

josh.long@springsource.com

springsource.com/developer/sts