A short introduction to Spring Framework and the main points of interest for the Spring application developer

1. Spring
“Less” is More
Based on the official reference docs (v4.3.2)

2. What is it?
- Application framework
- Inversion of Control (IoC) container
- Dependency Injection (DI)
- “Ask the framework for the resource”
- Many additional (optional) modules
- AOP, Web MVC, Data, Security, Mobile, ...
- “Alternative” to Java EE
- Actually, on top and ahead of it

3. Why is it?..
- Historically, greatly eased application
development
- Java EE implementations has since caught up nicely
- Not held back by standardization committees
- Advanced features not yet in the Java EE spec
- No need for a full application server
- Servlet container is enough
- Highly modular and granular DI

4. Spring Projects

5. Spring Framework

6. Bootstrapping
- Configuration
- XML
- Java-based
- IoC container init
- ApplicationContext
- Wiring
- Run-time factory

7. Basic XML Configuration
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
<import resource="helloOtherWorldConfig.xml"/>
<bean id="helloWorld" class="com.world.HelloWorld" scope="prototype" lazy-init="true">
<property name="param1" value="21"/>
<property name="param2" ref="helloOtherWorld"/>
</bean>
</beans>

8. Basic Java Configuration

9. Basic Usage
// create and configure beans - XML
ApplicationContext context =
new ClassPathXmlApplicationContext("helloWorldConfig.xml");
// create and configure beans - Java-based
ApplicationContext context =
new AnnotationConfigApplicationContext(HelloWorldConfig.class);
// retrieve configured instance
HelloWorld greeter = context.getBean("helloWorld", HelloWorld.class);
// use configured instance
String greeting = greeter.greet();

10. Naming
- Each bean must have a unique identifier
- If none provided in configuration - names are
camel-cased
- Derived similar to JSON convention:
- objectProperty -> objectProperty
- ObjectProperty -> objectProperty
- OBJECTPROPERTY -> oBJECTPROPERTY

11. Beans
- Essentially - POJO
- But works with convoluted hierarchies
- @Bean + @Configuration / @Component
- @Lazy
- @Scope
- singleton, prototype, request, session
- @Profile
- …, …, …

12. Beans Wiring
- @Autowired
- Inferred
- Can be advised
- Constructor-based DI for mandatory
dependencies
- Usually - prefer this method
- Setter-based DI for optional dependencies
- Useful for cases of circular dependencies

13. AOP
- Crosscutting concerns
- Spring, logging, security, etc.
- @Aspect
- @Pointcut(“...”)
- E.g.: "execution (* com.company.*.*(..))
- JoinPoint
- @Before
- @After, @AfterReturning, @AfterThrowing
- @Around

14. MVC
- Model
- @Repository
- View
- @Controller + @ResponseBody
- @RestController
- @RequestMapping - controller and/or method
- @RequestParam, @PathVariable, @RequestBody
- Controller
- @Service

15. MVC Flow

16. Data
- JDBC abstractions
- Programmatic and declarative transactions
- @Transactional
- ORM
- Hibernate, JPA, JDO
- OXM
- JAXB, Castor, XMLBeans, JiBX, XStream
- JMS

17. Testing
- Run application with a different context
- Bean mocks
- Alternate implementations
- Compatible with standard runners
- @RunWith(...)
- E.g.: SpringJUnit4ClassRunner.class
- @ContextConfiguration(...)
- Pass the requested context configurations

18. Features Configuration
- XML:
- Context: <context:annotation-config/>
- Component scan:
<context:component-scan base-package=”...”/>
- AOP: <aop:aspectj-autoproxy/>
- Transactions: <tx:annotation-driven/>
- MVC: <mvc:annotation-driven/>
- Beans can be configured manually in XML
- Lots of hard (and brittle) work...

19. Features Configuration
- Java-based:
- Configuration: @Configuration
- Context: @AnnotationDrivenConfig
- Component scan: @ComponentScan(“...”)
- AOP: @EnableAspectJAutoProxy
- Transactions: @EnableTransactionManagement
- MVC: @EnableWebMvc

20. Spring Boot
- start.spring.io
- Just choose what you need and go
- Config automatically according to libraries in
classpath
- @SpringBootApplication
- @Configuration
- @EnableAutoConfiguration
- @ComponentScan

21. “You can generally trust Spring
to do the right thing.”

22. Additional Resources
●http://springtutorials.com/spring-ecosystem
●http://start.spring.io
●https://spring.io/projects
●https://spring.io/guides
●http://docs.spring.io/spring/docs/current/sprin
g-framework-reference/htmlsingle