Spring Boot

Spring, en bref

Sur le papier...

• "Concurrent" de Java EE
• Inversion de contrôle (injection de dépendance), AOP, abstraction
• Conteneur léger
• Inspire Java EE

En pratique...

@Component
class MyDao {

	void save(String value) {
		// write to file
	}

}

@Component
class MyService {

	@Autowired
	MyDao dao;

	void doSomething() {
		dao.save("foo");
	}

}

L'histoire de Spring

[2003] Spring 1.0

<?xml version="1.0" encoding="UTF-8"?>
<beans ...>

	<bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
		<property name="url" value="..." />
	</bean>

	<bean id="sessionFactory" class="org.springframework.orm.hibernate5.LocalSessionFactoryBean">
		<property name="dataSource" ref="dataSource" />
		<property name="hibernateProperties">
			<props>
				<prop key="...">...</prop>
			</props>
		</property>
	</bean>

	<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
		<property name="dataSource" ref="dataSource" />
		<property name="persistenceUnitName" value="default" />
	</bean>

	<tx:annotation-driven />
	<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
		<property name="entityManagerFactory" ref="entityManagerFactory" />
	</bean>

</beans>

[2007] Spring 2.5

@Configuration
public class JpaDatabaseConfig {

	@Bean
	public DataSource dataSource() {
		DriverManagerDataSource dataSource = new DriverManagerDataSource();
		dataSource.setUrl(...);
		return dataSource;
	}

	@Bean
	public SessionFactory sessionFactory() {
		LocalSessionFactoryBean sessionFactory = new LocalSessionFactoryBean();
		sessionFactory.setDataSource(dataSource());
		Properties properties = new Properties();
		properties.put("...", ...);
		sessionFactory.setHibernateProperties(properties);
		return sessionFactory.getObject();
	}

	@Bean
	public LocalContainerEntityManagerFactoryBean entityManagerFactoryBean() {
		LocalContainerEntityManagerFactoryBean entityManagerFactoryBean = new LocalContainerEntityManagerFactoryBean();
		entityManagerFactoryBean.setDataSource(dataSource());
		entityManagerFactoryBean.setPersistenceUnitName("default");
		return entityManagerFactoryBean;
	}

	@Bean
	public PlatformTransactionManager transactionManager() {
		JpaTransactionManager transactionManager = new JpaTransactionManager();
		transactionManager.setEntityManagerFactory(entityManagerFactory);
		return transactionManager;
	}

}

[2014] - Spring Boot

spring.datasource.url=...

Démonstration de puissance

Webservice

Maven

<?xml version="1.0" encoding="UTF-8"?>
<project>
	<modelVersion>4.0.0</modelVersion>

	<groupId>fr.pinguet62</groupId>
	<artifactId>spring-boot</artifactId>
	<version>1.0-SNAPSHOT</version>

	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
			<version>1.5.4.RELEASE</version>
		</dependency>
	</dependencies>
</project> 

Webservice

Java

@SpringBootApplication
@RestController
public class MyController {

    public static void main(String[] args) throws Exception {
        SpringApplication.run(MyController.class, args);
    }

    @GetMapping("/")
    public String home() {
        return "Hello Davidson!";
    }
}

Webservice

$ curl localhost:8080/
Hello Davidson!

Mais encore ?

• Mavent : POM parent
• AOP, Cache, Mail (SMTP), i18n, Cloud, Batch, Security, LDAP, OAuth
• ActiveMQ (JMS), RabbitMQ (AMQP)
• Base de données
  • SQL : JDBC, JPA (Hibernate)
  • NoSQL : H2, Cassandra, Couchbase, Mongodb, Neo4j, Redis, Hazelcast, Elasticsearch, Solr, ...
• Webservice : REST & SOAP
• Social : Facebook, Twitter, LinkedIn, ...
• Liquibase, Flyway
• ...

Comment ça marche ? (1/2)

@Conditional

Code condionné par l'environnement d'exécution de l'application.

@Conditional

Solution 1 : le bon vieux if/else...

@Service
class MyService {

	void doSomething() {
		String currentEnv = System.getProperty("environment");
		if (currentEnv.equals("DEV"))
			System.out.println("I'm in development");
		else if (currentEnv.equals("PROD"))
			System.out.println("I'm in production");
	}

}

Moche !!!

@Conditional

Solution 2 : le polymorphisme

interface Script {
	void execute();
}

class DevScript implements Script {
	@Override
	public void execute() {
		System.out.println("In development");
	}
}

class ProdScript implements Script {
	@Override
	public void execute() {
		System.out.println("In production");
	}
}

@Conditional

Solution 2 : le polymorphisme

@Service
class MyService {
	Script script;

	// Factory
	MyService() {
		String currentEnv = System.getProperty("environment");
		if (currentEnv.equals("DEV"))
			script = new DevScript();
		else if (currentEnv.equals("PROD"))
			script = new ProdScript();
	}

	void doSomething() {
		script.execute();
	}
}

Context Spring...

@Conditional

Solution : des @Bean

@Component
class DevScript implements Script { /*...*/ }

@Component
class ProdScript implements Script { /*...*/ }

@Service
class MyService {
	@Autowired
	Script script;

	void doSomething() {
		script.execute();
	}
}

Collision...

@Conditional

@Conditional(MyCondition.class)
@Component
class MyComponent {}

class MyCondition implements Condition {
	@Override
	public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
		return ...;
	}
}

• Meta-annotation
• Paramètres

@Conditional

class EnvCondition extends SpringBootCondition {
	@Override
	public ConditionOutcome getMatchOutcome(ConditionContext context, AnnotatedTypeMetadata metadata) {
		Map<String, Object> attributes = metadata.getAnnotationAttributes(ConditionalOnEnv.class.getName());
		String expectedEnv = (String) attributes.get("value");
		String currentEnv = System.getProperty("environment");
		boolean matches = currentEnv.equals(expectedEnv);
		return new ConditionOutcome(matches, (String) null);
	}
}

@Conditional(EnvCondition.class)
@interface ConditionalOnEnv {
	String value();
}

@Conditional

@ConditionalOnEnv("DEV")
@Component
class DevScript implements Script { /*...*/ }

@ConditionalOnEnv("PROD")
@Component
class ProdScript implements Script { /*...*/ }

@Conditional

Spring Boot...
• @ConditionalOnMissingBean
• @ConditionalOnClass
• @ConditionalOnProperty

Comment ça marche ? (2/2)

SpringFactoriesLoader

Properties properties = new MyConfig().getProperties();
String value = properties.getProperty("key");

SpringFactoriesLoader

Solution : EnvironmentPostProcessor

• Implémentation

  public class MyConfigEnvironmentLoader implements EnvironmentPostProcessor {
      @Override
      public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {
          Properties properties = new MyConfig().getProperties();
          PropertySource<?> propertySource = new PropertiesPropertySource("MyConfig", properties);
          environment.getPropertySources().addLast(propertySource);
      }
  }

• Référencement : /META-INF/spring.factories

  org.springframework.boot.env.EnvironmentPostProcessor = \
                  fr.pinguet62.MyConfigPropertiesEnvironmentLoader

SpringFactoriesLoader

• Cycle de vie :
  
  • PropertySourceLoader
  • SpringApplicationRunListener
  • ApplicationContextInitializer
  • ApplicationListener
  • ...
• Référencement : classpath :
  /META-INF/spring.factories

Spring Boot

# PropertySource Loaders
org.springframework.boot.env.PropertySourceLoader=\
	org.springframework.boot.env.PropertiesPropertySourceLoader,\
	org.springframework.boot.env.YamlPropertySourceLoader

# Run Listeners
org.springframework.boot.SpringApplicationRunListener=\
	org.springframework.boot.context.event.EventPublishingRunListener

# Application Context Initializers
org.springframework.context.ApplicationContextInitializer=\
	org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer,\
	org.springframework.boot.context.ContextIdApplicationContextInitializer,\
	org.springframework.boot.context.config.DelegatingApplicationContextInitializer,\
	org.springframework.boot.context.web.ServerPortInfoApplicationContextInitializer

# Application Listeners
org.springframework.context.ApplicationListener=\
	org.springframework.boot.context.FileEncodingApplicationListener,\
	org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener,\
	org.springframework.boot.logging.ClasspathLoggingApplicationListener,\
	org.springframework.boot.logging.LoggingApplicationListener

Attention !

• (que) un serveur web embarqué (Tomcat)
• un framework

Conclusion

• Ma configuration est-elle stable/évolutive ?
• Spring Boot : configure "tout" pour vous
• Existe-il déjà une configuration toute prête ?