1. Spring Framework 4.0 to 4.1
Sam Brannen
@sam_brannen
AJUG | Atlanta, GA, USA | April 22, 2014
Atlanta User Group

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Sam Brannen
• Spring and Java Consultant @ Swiftmind
• Georgia Tech College of Computing Alumnus
• Java Developer for over 15 years
• Spring Framework Core Committer since 2007
• Spring Trainer
• Speaker on Spring, Java, OSGi, and testing
• Swiss Spring User Group Lead

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Swiftmind
Your experts for Enterprise Java
Areas of expertise
• Spring *
• Java EE
• OSGi
• Software Architecture
• Software Engineering Best Practices
Where you find us
• Zurich, Switzerland
• @swiftmind
• http://www.swiftmind.com

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A Show of Hands…

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Agenda
• Spring 3.x in Review
• Themes in Spring 4.0
• Java EE & SE
• Spring 4 on Java 8
• Spring 4.1

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Spring 3.x in Review

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Major Themes in Spring 3.x
• Powerful annotated component model
• Spring Expression Language (SpEL)
• Comprehensive REST support
• Support for async MVC processing
• Validation and Formatting
• Scheduling
• Caching

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Spring 3.x: Key Specs (1/2)
• JSR-330
– Dependency Injection for Java
– @Inject, @Qualifier, Provider mechanism
• JSR-303
– Bean Validation 1.0
– declarative constraints
– embedded validation engine

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Spring 3.x: Key Specs (2/2)
• JPA 2.0
– persistence provider integration
– Spring transactions
• Servlet 3.0
– web.xml-free deployment
– async request processing

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Testing in Spring 3.x
• Embedded databases via <jdbc /> namespace
• @Configuration classes & @ActiveProfiles
• @WebAppConfiguration
• @ContextHierarchy
• Spring MVC Test framework

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Annotated Components

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Configuration Classes

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Composable Stereotypes
• Combining meta-annotations on a custom stereotype
• Automatically detected: no configuration necessary!

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Spring 4.0 Themes

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Ready for New Application Architectures
• Embedded web servers and non-traditional data stores
• Lightweight messaging and WebSocket-style architectures
• Custom asynchronous processing with convenient APIs

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New Baselines
• Java SE 6+
• Java EE 6+
– Servlet 3.0/3.1 focus
– Servlet 2.5 compatible
• All deprecated packages removed
• Many deprecated methods and fields removed as well

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Third Party Libraries
• Minimum versions ~ mid 2010 now
• For example
– Hibernate 3.6+
– Quartz 1.8+
– Ehcache 2.1+

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Java 8 Language and API Features
• Lambda expressions
• Method references
• JSR-310 Date and Time
• Repeatable annotations
• Parameter name discovery

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Groovy + Spring 4.0
• A smooth out-of-the-box experience for Groovy-based
Spring applications
• AOP adaptations
– special handling of GroovyObject calls
– consider a Spring application with all components
written in the Groovy language instead of Java
• Groovy-based bean definitions
– formerly known as the Bean Builder in Grails
– now lives alongside Spring's configuration class model

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Spring Bean Def’s with Groovy DSL
import org.mypackage.domain.Person;
beans {
xmlns util: 'http://www.springframework.org/schema/util'
person1(Person) {
name = "homer"
age = 45
props = [overweight: true, height: "1.8m"]
children = ["bart", "lisa"]
}
util.list(id: 'foo') {
value 'one'
value 'two'
}
}

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Conditional Beans
• A generalized model for conditional bean definitions
• A more flexible and more dynamic variant of bean
definition profiles (as known from Spring 3.1)
• Can be used for smart defaulting
• See Spring Boot J

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@Conditional
• @Conditional annotation with programmatic Condition
implementations
• Can react to rich context (existing bean definitions, etc.)
• @Profile support now simply a ProfileCondition
implementation class

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Composable Annotations w/ Overrides
• Composable annotations may override attributes of meta-
annotations
• Purely convention-based
– Matched by attribute name and type
• Cannot override the value attribute

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Optional Annotation Attribute Override
@Scope("session")
@Retention(RUNTIME)
public @interface SessionScoped {
ScopedProxyMode proxyMode() default ScopedProxyMode.NO;
}
@SessionScoped(proxyMode = TARGET_CLASS)
public class MyScopedService {
// ...
}
optional

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Required Annotation Attribute Override
@Transactional(rollbackFor = Exception.class)
@Service
@Retention(RUNTIME)
public @interface TransactionalService {
boolean readOnly(); // No default!
}
@TransactionalService(readOnly = true)
public class MyService {
// ...
}
required

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Lazy Bean Resolution Proxies
• @Autowired @Lazy on injection point
• Alternative to:
– Spring’s ObjectFactory
– JSR-330’s Provider<MyTargetType>

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Ordered Injection of Lists & Arrays
• Ordered / @Order on candidate beans
• Relative order within specific injection result

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DI and Generics
• Generic factory methods now fully supported in XML
configuration files
– Mockito
– EasyMock
– custom
• Type matching based on full generic type
– e.g., MyRepository<Account>

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Generics-based Injection Matching
@Bean
public MyRepository<Account> accountRepository() {
return new MyAccountRepositoryImpl();
}
@Service
public class MyBookService implements BookService {
@Autowired
public MyBookService(MyRepository<Account> repo) {
// ...
}
}

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Target-class Proxies & Arbitrary Ctors
• Before:
– Constructor invoked when creating proxy with CGLIB
– Potentially with adverse side effects
• constructor invoked twice
• Now:
– Using Objenesis instead of CGLIB directly
– Constructor not invoked on proxy
– Arbitrary constructor supported on target

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spring-messaging
• New org.springframework.messaging module
• Extracted from Spring Integration
• Core message and channel abstractions

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WebSockets
• WebSocket endpoint model along the lines of Spring MVC
• JSR-356 but also covering SockJS and STOMP
• Endpoints using generic messaging patterns

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STOMP over WebSocket
@Controller
public class MyStompController {
@SubscribeMapping("/portfolios")
public List<Portfolio> getPortfolios(Principal user) {
// ...
}
@MessageMapping("/trade")
public void executeTrade(Trade trade, Principal user) {
// ...
}
}

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AsyncRestTemplate
• Analogous to existing RestTemplate
• Based on ListenableFuture return values
• Custom listeners implement ListenableFutureCallback

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Spring + Java SE & Java EE

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Java SE Support
• Spring 3.1 / 3.2
– explicit Java 7 support
– JDK 5 à JDK 7
• Spring 4.0
– introduces explicit Java 8 support
– JDK 6 à JDK 8

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Java EE Support
• Spring 3.1 / 3.2
– strong Servlet 3.0 focus
– J2EE 1.4 (deprecated) à Java EE 6
• Spring 4.0
– introduces explicit Java EE 7 support
– Java EE 5 (with JPA 2.0 feature pack) à Java EE 7

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Enterprise API Updates
• JMS 2.0
– delivery delay, JMS 2.0 createSession() variants, etc.
• JTA 1.2
– @javax.transaction.Transactional annotation
• JPA 2.1
– unsynchronized persistence contexts
• Bean Validation 1.1
– method parameter and return value constraints

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Java 8 Programming Model

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Java 8 Bytecode Level
• Generated by -target 1.8
– compiler's default
• Not accepted by ASM 4.x
– Spring's bytecode parsing library
• Spring Framework 4.0 comes with a patched, inlined (i.e.,
jarjar’ed) ASM 4.1 variant
• Spring Framework 4.0.3 comes with ASM 5.0 inlined (i.e.,
jarjar’ed)

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HashMap / HashSet Differences
• Different hash algorithms in use
• Leading to different hash iteration order
• Code shouldn't rely on such an order but sometimes does

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Java 8 Lambda Conventions
Simple rule: interface with single method
– typically callback interfaces
– for example: Runnable, Callable
– formerly “Single Abstract Method” (SAM) types
– now “functional interfaces”
• see @FunctionalInterface

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Lambda + Spring = Natural Fit
Many Spring APIs are candidates for lambdas
– simply by following the lambda interface conventions

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Lambdas with JmsTemplate
MessageCreator
Message createMessage(Session session)
throws JMSException

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Lambdas with TransactionTemplate
TransactionCallback
Object doInTransaction(TransactionStatus status)

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Lambdas with JdbcTemplate
RowMapper
Object mapRow(ResultSet rs, int rowNum)
throws SQLException

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Ex: Lambdas with JdbcTemplate #1
JdbcTemplate jt = new JdbcTemplate(dataSource);
jt.query(
"SELECT name, age FROM person WHERE dep = ?",
ps -> ps.setString(1, "Sales"),
(rs, rowNum) -> new Person(rs.getString(1),
rs.getInt(2))
);

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Ex: Lambdas with JdbcTemplate #2
JdbcTemplate jt = new JdbcTemplate(dataSource);
jt.query(
"SELECT name, age FROM person WHERE dep = ?",
ps -> {
ps.setString(1, "Sales");
},
(rs, rowNum) -> {
return new Person(rs.getString(1), rs.getInt(2));
}
);

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Method References
public List<Person> getPersonList(String department) {
JdbcTemplate jt = new JdbcTemplate(dataSource);
return jt.query(
"SELECT name, age FROM person WHERE dep = ?",
ps -> {
ps.setString(1, "Sales");
},
this::mapPerson);
}
private Person mapPerson(ResultSet rs, int rowNum)
throws SQLException {
return new Person(rs.getString(1), rs.getInt(2));
}

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JSR-310 Date and Time
import java.time.*;
import org.springframework.format.annotation.*;
public class Customer {
// @DateTimeFormat(iso=ISO.DATE)
private LocalDate birthDate;
@DateTimeFormat(pattern="M/d/yy h:mm")
private LocalDateTime lastContact;
// ...
}

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@Repeatable Annotations
@Scheduled(cron = "0 0 12 * * ?")
@Scheduled(cron = "0 0 18 * * ?")
public void performTempFileCleanup() { /* ... */ }
@Schedules({
@Scheduled(cron = "0 0 12 * * ?"),
@Scheduled(cron = "0 0 18 * * ?")
})
public void performTempFileCleanup() { /* ... */ }
JDK 8
JDK 5+
container
repeated

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Parameter Name Discovery
• Java 8 defines a Parameter reflection type for methods
– application sources compiled with –parameters
• Spring's StandardReflectionParameterNameDiscoverer
– reads parameter names via Java 8's new Parameter
type
• Spring's DefaultParameterNameDiscoverer
– now checks Java 8 first (-parameters)
– ASM-based reading of debug symbols next (-debug)

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Ex: Parameter Name Discovery
@Controller
public void BookController {
@RequestMapping(value = "/books/{id}", method = GET)
public Book findBook(@PathVariable long id) {
return this.bookService.findBook(isbn);
}
}
path variable
parameter name

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Spring Framework 4.1

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Themes in Spring 4.1
• Comprehensive web resource handling
– Resource pipelining, cache control refinements
• Caching support revisited
– Alignment with JCache 1.0 final, user-requested enhancements
• JMS support overhaul
– Alignment with messaging module, annotation-driven endpoints
• Performance and container improvements
– Application startup, SpEL expression evaluation, DI for generics and factory
methods
• Unified meta-annotation programming model
– Custom attribute overrides, value-aliases, etc.
• Numerous new testing features
– Groovy config, SQL script execution, bootstrap strategy, programmatic
transaction management, etc.

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Spring MVC and Messaging
• GroovyWebApplicationContext (SPR-11371)
• Static resource handling in Spring MVC (SPR-10933)
• WebSocket scope (SPR-11305)

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Static Resource Handling in Web MVC
• ResourceResolver API for resolving:
– Internal static resources
– External resource paths (i.e., links)
• ResourceResolverChain
– Maintains a chain of resolvers
– Allowing for delegation
• Configured via ResourceHandlerRegistry
– For example, via WebMvcConfigurationSupport

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ResourceResolver Implementations
• PathResourceResolver
– Default
– Configure at end of chain
• PrefixResourceResolver
– Custom prefix: version, release date, etc.
• FingerprintResourceResolver
– MD5 hash in file name
• GzipResourceResolver
– gzip compressed resources

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Ex: Registering Resource Resolvers
@Configuration
public class WebConfig extends WebMvcConfigurationSupport {
@Override
public void addResourceHandlers(ResourceHandlerRegistry
registry) {
registry.addResourceHandler("/resources/**")
.addResourceLocations("classpath:/web-resources/")
.setResourceResolvers(new FingerprintResourceResolver(),
new PathResourceResolver());
}
}
resolver chain

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JCache (JSR-107) and Spring
• JCache 1.0 annotations now supported in Spring
• Integration based on Spring’s own Cache and CacheManager
APIs
– JCacheCache and JCacheCacheManager
• Enabled via Spring’s standard mechanisms:
– XML: <cache:annotation-driven />
– Java: @EnableCaching
• Cache Abstraction: JCache (JSR-107) Annotations Support
– https://spring.io/blog/2014/04/14/cache-abstraction-
jcache-jsr-107-annotations-support

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Caching Annotation Comparison
Spring JCache
@Cacheable @CacheResult
@CachePut @CachePut
@CacheEvict @CacheRemove
@CacheEvict(allEntries=true) @CacheRemoveAll

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JMS Overhaul
• Alignment with spring-messaging module
• Annotation-driven endpoints
– Analogous to <jms:listener-container />
– Listener methods declared via @JmsListener
– Configured via:
• XML: <jms:annotation-driven />
• Java: @EnableJms and JmsListenerConfigurer

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Ex: @EnableJms and JavaConfig
@Configuration
@EnableJms
public class JmsConfig {
@Bean
public JmsListenerContainerFactory jmsListenerContainerFactory() {
DefaultJmsListenerContainerFactory factory =
new DefaultJmsListenerContainerFactory();
factory.setConnectionFactory(connectionFactory());
factory.setDestinationResolver(destinationResolver());
factory.setConcurrency("5");
return factory;
}
// other @Bean definitions
}

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Ex: @JmsListener
@Service
public class MyService {
@JmsListener(destination = "myQueue")
public void process(String msg) {
// process incoming message
}
}

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Container Odds & Ends
• @javax.annotation.Priority can be used as an
alternative to Spring’s:
– @Order (SPR-11639)
– @Primary (SPR-10548)
• Annotation-driven application event listeners (SPR-11622)
– @Listen methods instead of implementing
ApplicationListener
• Unified meta-annotation programming model (SPR-11511)
– Custom attribute overrides, value-aliases, etc.

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Testing with Spring 4.1
• Groovy config for bean definitions
• SQL script execution and database configuration
– ScriptUtils, ResourceDatabasePopulator, @SqlScript
• TestContextBootstrapper strategy
– Programmatic configuration for default
TestExecutionListeners and SmartContextLoader
– Configured via @BootstrapWith
• Programmatic starting and stopping of transactions in
integration tests
• Numerous configuration, caching, and performance
improvements

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Ex: EmbeddedDatabaseBuilder
EmbeddedDatabase db = new EmbeddedDatabaseBuilder()
.setType(H2)
.setScriptEncoding("UTF-8")
.ignoreFailedDrops(true)
.addScript("schema.sql")
.addScripts("user_data.sql", "country_data.sql")
.build();
// ...
db.shutdown();

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Spring Framework 4.1 Roadmap
• 4.1 RC1: June 2014
• 4.1 RC2: July 2014
• 4.1 GA: September 2014

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In Closing…

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Upgrade Considerations
• Spring 3.2 does not support 1.8 bytecode level
– upgrade to Spring 4.0+ to enable Java 8 language features
– caveat: partial support added in 3.2.9 (SPR-11656)
• We strongly recommend an early upgrade to Spring 4
– Spring Framework 4.0 still compatible with JDK 6 and 7
– Spring Framework 3.2 is in maintenance mode
• Spring Framework 4.0 GA released in December 2013
– 4.0.3 was released on March 26th, 2014
– 4.0.4 scheduled for end of April 2014
• Spring Framework 4.1 GA scheduled for Sep. 2014

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Acknowledgements
Thanks to Jürgen Höller and Stéphane Nicoll for
permitting reuse of some of their content.

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Spring Resources
• Spring Framework
– http://projects.spring.io/spring-framework
• Spring Guides
– http://spring.io/guides
• Spring Forums
– http://forum.spring.io
• Spring JIRA
– https://jira.spring.io
• Spring on GitHub
– https://github.com/spring-projects/spring-framework

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Blogs
• Swiftmind Blog
– http://www.swiftmind.com/blog
• Spring Blog
– http://spring.io/blog

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Q & A
Sam Brannen
twitter: @sam_brannen
www.slideshare.net/sbrannen
www.swiftmind.com