Breaking the Magician's Code - Diving deeper into Spring Boot internals

Presented @DevNexus '17

Transcript

1. Breaking the Magician's Code Diving deeper into Spring Boot internals
2. @phillip_webb @madhurabhave23
4. DEMO start.spring.io
5. DEMO Starting from scratch
6. Embedded Servlet Container Tomcat WAR ServletContainerInitializer AbstractAnnotationConfigDispatcherServletInitializer WebApplicationContext Dispatcher Servlet
7. Embedded Servlet Container WebApplicationContext Embedded EmbeddedServletContainerFactory EmbeddedServletContainer getEmbeddedServletContainer( ServletContextInitializer... initializers); EmbeddedServletContainer start() stop() getPort()
8. DEMO Back to the CODE
9. Servlets WebApplicationContext Embedded Servlet Filter ServletContextInitializer ServletRegistrationBean FilterRegistrationBean
10. Servlets WebApplicationContext Embedded Servlet DispatcherServlet @RequestMapping(“/foo”) @RequestMapping(“/bar”)
11. DEMO Back to the CODE
12. Component scanning • @Componentscan • base Packages • base Package Classes • (default)
13. Component Scanning com.example.demo.core.* com.example.demo.domain.* com.example.demo.Application com.example.demo.config.*
14. Component Scanning example demo com config core domain
15. Component Scanning example demo com config core domain .Application
16. Component Scanning example demo com config core domain .Application
17. Component Scanning example demo com config core domain .Application
18. Component Scanning example demo com config core domain .Application
19. DEMO Back to the CODE
20. Meta-Annotations • Most Spring Annotations can be used as meta-annotations • Use in your own code • Used extensively in the framework: •@RestController •@GetMapping
21. META-Annotations • @AliasFor for advanced mappings: @SpringBootConfiguration @EnableAutoConfiguration @ComponentScan public @interface SpringBootApplication { @AliasFor(annotation = EnableAutoConfiguration.class, attribute = "exclude") Class<?>[] exclude() default {}; @AliasFor(annotation = ComponentScan.class, attribute = "basePackages") String[] scanBasePackages() default {};
22. DEMO Back to the CODE
23. Advanced ImportS • @Import(Regular.class) • ImportSelector • Return String[] • ImportBeanDefinitionRegistrar • Direct registration
24. Spring Factories • Dirt simple way to discover implementations • Similar to Java Service Loader • Simple properties file • /META-INF/spring.factories
25. DEMO Back to the CODE
26. Conditions • @Conditional annotation • Condition interface public interface Condition { boolean matches( ConditionContext context, AnnotatedTypeMetadata metadata); }
27. Conditions • Spring Framework @Profile • Spring Boot (Bean,Class,Property) • Ordered so fastest run first
28. DEMO Back to the CODE
29. Spring Boot Code •ConditionalOnAClass -> ConditionalOnClass • MagicApplication -> SpringBootApplication • EnableMagicAutoConfiguration -> EnableAutoConfiguration • EnableMagicProperties -> EnableConfigurationProperties • *Configuration -> *AutoConfiguration
30. Summary • There’s no such thing as magic • Follow the breadcrumbs • Annotations • Import Selectors • Spring Factories • Conditions • Use the source!
31. Thanks! Questions? @madhurabhave23 @phillip_webb speakerdeck.com/philwebb https://github.com/mbhave/non-magic-demo