Extending Spring for Custom Usage

Tailoring Spring for Custom Usage • Josh Long, SpringSource, a division of VMware 1Sunday, February 19, 12

About Josh Long (Spring Developer Advocate) @starbuxman josh.long@springsource.com th s i is im po rta nt ! 2Sunday, February 19, 12

Agenda Explore the value of a framework Exploit some of the lesser known, but powerful, extension hooks in the core Spring framework QA 3Sunday, February 19, 12

Spring’s aim: bring simplicity to java development data web tier integration batch access & service tier & mobile processing / NoSQL / RIA messaging Big Data The Spring framework the cloud: lightweight traditional CloudFoundry WebSphere tc Server VMForce JBoss AS Tomcat Google App Engine WebLogic Jetty Amazon Web Services (on legacy versions, too!) 4Sunday, February 19, 12

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 5Sunday, February 19, 12

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 6Sunday, February 19, 12

Spring Integration rules!! Not confidential. Tell everyone. 7Sunday, February 19, 12

...but??!? ...what if it doesn’t do what I want? 8Sunday, February 19, 12

What is Spring Integration?FLEXIBLE v Not confidential. Tell everyone. 9Sunday, February 19, 12

10Sunday, February 19, 12

do NOT reinvent the Wheel! 11Sunday, February 19, 12

The Open/Closed Principle "software entities (classes, modules, functions, etc.) should be open for extension, but closed for modiﬁcation” -Bob Martin 12Sunday, February 19, 12

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 13Sunday, February 19, 12

Spring, a walking tour • Demos: – Bean*PostProcessor – AspectJ 14Sunday, February 19, 12

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. 15Sunday, February 19, 12

Scopes • 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 16Sunday, February 19, 12

Scopes – Implement o.s.beans.factory.config.Scope – register the scope with a o.s.beans.factory.config.CustomScopeConfigurer public interface Scope { Object get(String name, ObjectFactory<?> objectFactory); Object remove(String name); void registerDestructionCallback(String name, Runnable callback); Object resolveContextualObject(String key); String getConversationId(); } 17Sunday, February 19, 12

Scopes – Implement o.s.beans.factory.config.Scope – register the scope with a o.s.beans.factory.config.CustomScopeConfigurer public interface Scope { Object get(String name, ObjectFactory<?> objectFactory); map-like lookup of beans in a Object remove(String name); given scope void registerDestructionCallback(String name, Runnable callback); Object resolveContextualObject(String key); String getConversationId(); } 17Sunday, February 19, 12

Scopes – Implement o.s.beans.factory.config.Scope – register the scope with a o.s.beans.factory.config.CustomScopeConfigurer public interface Scope { Object get(String name, ObjectFactory<?> objectFactory); map-like lookup of beans in a Object remove(String name); given scope void registerDestructionCallback(String name, Runnable callback); Object resolveContextualObject(String key); well known beans like the HttpServletRequest ‘request’ for String getConversationId(); ‘request’ scope } 17Sunday, February 19, 12

Scopes – Implement o.s.beans.factory.config.Scope – register the scope with a o.s.beans.factory.config.CustomScopeConfigurer public interface Scope { Object get(String name, ObjectFactory<?> objectFactory); map-like lookup of beans in a Object remove(String name); given scope void registerDestructionCallback(String name, Runnable callback); Object resolveContextualObject(String key); well known beans like the HttpServletRequest ‘request’ for String getConversationId(); ‘request’ scope } null, or storage specific ‘conversation’ ID 17Sunday, February 19, 12

Spring, a walking tour • Demos: – life cycle callbacks – scopes • using • creating your own 18Sunday, February 19, 12

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 19Sunday, February 19, 12

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 20Sunday, February 19, 12

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 = “#{ .. }” 21Sunday, February 19, 12

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 22Sunday, February 19, 12

Getting Beans from Strange Places • An ApplicationContextInitializer public interface ApplicationContextInitializer <C extends ConﬁgurableApplicationContext> { void initialize(C applicationContext); } 23Sunday, February 19, 12

Getting Beans from Strange Places • Demos: – FactoryBeans – SpEL – Proﬁles • ApplicationContextInitializers 24Sunday, February 19, 12

Using Spring’s Resources • Spring supports out of the box ClassPathResource, FileResource system, etc. • Writing your own Resource implementations public interface Resource extends InputStreamSource { boolean exists(); boolean isReadable(); boolean isOpen(); URL getURL() throws IOException; URI getURI() throws IOException; File getFile() throws IOException; long contentLength() throws IOException; long lastModiﬁed() throws IOException; Resource createRelative(String relativePath) throws IOException; String getFilename(); String getDescription(); } 25Sunday, February 19, 12

Object to XML Marshallers • Easy to add your own Marshaller (and Unmarshaller) public interface Marshaller { boolean supports(Class<?> clazz); void marshal(Object graph, Result result) throws IOException, XmlMappingException; } 26Sunday, February 19, 12

Object to XML Marshallers • Demos: – a custom object-to-XML marshaller 27Sunday, February 19, 12

REST • Spring MVC for the server @RequestMapping( value = “/crm/customers/{id}” , method =HttpMethod.GET) public @ResponseBody Customer lookupCustomerById( @PathVariable(“id”) long customerId ) { ... return customer; } 28Sunday, February 19, 12

REST • RestTemplate for the client (Android, SE, web applications, etc.) RestTemplate rt = new RestTemplate() ; String url = “http://mysvc.cloudfoundry.com/crm/customer/{id}”; Customer customer = rt.getForObject( url, Customer.class, 22); 29Sunday, February 19, 12

REST • Both need o.s.http.converter.HttpMessageConverters • Spring supports: – object-to-XML (JAXB as well as any Spring OXM impl) – object-to-JSON – binary data (o.s.resource.Resource references or byte[]) – ATOM/RSS – images • Easy to add your own 30Sunday, February 19, 12

Registering a custom HttpMessageConverter @EnableWebMvc public class WebConfiguration extends WebMvcConfigurerAdapter { @Override public void configureMessageConverters( List<HttpMessageConverter<?>> converters) { } } 31Sunday, February 19, 12

REST • Demos: – Writing and using a customer HttpMessageConverter 32Sunday, February 19, 12

Transactions • Spring supports declarative transaction management – @EnableTransactionManagement or <tx:annotation-driven/> • PlatformTransactionManager implementations used to manage transactions – lots of options out of the box: • AMQP, JMS, JTA, JDBC, JDO, JPA, WebLogic-specific, WebSphere-specific, OC4J-specific, etc. 33Sunday, February 19, 12

Transactions • PlatformTransactionManager abstracts the notion of a transactional “unit of work.” public interface PlatformTransactionManager { TransactionStatus getTransaction(TransactionDeﬁnition deﬁnition) throws TransactionException; void commit(TransactionStatus status) throws TransactionException; void rollback(TransactionStatus status) throws TransactionException; } 34Sunday, February 19, 12

Caching • CacheManager’s maintain Caches. – CacheManagers are like ‘connections’ – Caches are like regions of a cache public interface CacheManager { public interface Cache { Cache getCache(String name); Collection<String> getCacheNames(); interface ValueWrapper { } Object get(); } String getName(); Object getNativeCache(); ValueWrapper get(Object key); void put(Object key, Object value); void evict(Object key); void clear(); } 35Sunday, February 19, 12

Writing a custom View and View Resolver 36Sunday, February 19, 12

Writing a custom View and View Resolver • Easy to add your own View – supported views out of the box: FreeMarker, Velocity, Excel, PDFs, JasperReports, XSLT, Jackson, JSTL, etc. – Lots of contributions from the open source community: • Thymeleaf http://www.thymeleaf.org/ • Mustache by Sean Scanlon https://github.com/sps/mustache-spring-view 37Sunday, February 19, 12

Writing a custom View and View Resolver public interface ViewResolver { View resolveViewName(String viewName, Locale locale) throws Exception; } 38Sunday, February 19, 12

Writing a custom View and View Resolverpublic interface View { String RESPONSE_STATUS_ATTRIBUTE = View.class.getName() + ".responseStatus"; String getContentType(); void render(Map<String, ?> model, HttpServletRequest request, HttpServletResponse response) throws Exception;} 39Sunday, February 19, 12

Writing a custom View and View Resolver @Bean public ViewResolver myCustomViewResolver(){ ... } if ‘detectAllViewResolvers’ is true, all ViewResolvers types will be registered. @Bean public MyCustomViewResolver viewResolver() { ... } 40Sunday, February 19, 12

Writing a custom View and View Resolver @Bean public ViewResolver myCustomViewResolver(){ ... } if ‘detectAllViewResolvers’ is true, all ViewResolvers types will be registered. @Bean public MyCustomViewResolver viewResolver() { ... if ‘detectAllViewResolvers’ is false, it’ll lookup a bean by a } well known name 40Sunday, February 19, 12

Writing a custom View and View Resolver • Demo: writing a custom view/view resolver 41Sunday, February 19, 12

Writing Adapters in Spring Integration 42Sunday, February 19, 12

Writing Adapters in Spring Integration • MessageSource for inbound adapters • MessageHandler for outbound adapters MessageSource MessageHandler 43Sunday, February 19, 12

Writing Adapters in Spring Integration • Inbound channel adapter “receives” message from external system inward relative to Spring Integration code package org.springframework.integration.core; public interface MessageSource<T> { org.springframework.integration.Message<T> receive(); } <int:channel id = “in” /> <int:inbound-channel-adapter channel = “in” ref = “myCustomMessageSource” > <int:cron-trigger ... /> </int:inbound-channel-adapter> 44Sunday, February 19, 12

Writing Adapters in Spring Integration • Outbound channel adapter “publishes” message from Spring Integration outward relative to Spring Integration code package org.springframework.integration.core; public interface MessageHandler { void handleMessage( org.springframework.integration.Message<?> message) throws org.springframework.integration.MessagingException; } <int:channel id = “out” /> <int:outbound-channel-adapter channel = “out” ref = “myCustomMessageHandler” /> 45Sunday, February 19, 12

Spring Integration File System Adapters • Spring Integration provides rich ﬁle system adapters – FTP, SFTP, FTPS, ﬁles in general – But... what about SMB/CIFS? 46Sunday, February 19, 12

Writing Readers and Writers in Spring Batch • ItemReader for inbound adapters • ItemWriters for outbound adapters 47Sunday, February 19, 12

Summary / Questions • code: git.springsource.org:spring-samples/spring- samples.git • blog.springsource.org • josh.long@springsource.com • springsource.com/developer/sts 48Sunday, February 19, 12

Extending Spring for Custom Usage

by joshlong

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