Demystifying Spring Internals
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Anyone who has used Spring knows that annotations are a quick and easy way to configure a Spring application. But how does the framework use annotations to decide what to do and what not to do? In this session we’ll take a look under the covers of Spring. You’ll learn about how Spring processes your application code and configures all your beans, helping you to be even more productive when developing native Spring applications. It will also help you understand the approach Spring takes to generate native images with Spring Framework 6.0.
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Demystifying Spring Internals
- 1. │©2022 VMware, Inc. Demystifying Spring Internals Madhura Bhave
- 2. 🤔 It's just annotations... how hard can it be?
- 3. to the code...
- 4. @ComponentScan
- 5. @Component Scan
- 6. @Component Scan @Controller @Service @Repository @RestController 🧐
- 7. Scan 🧐 class HelloUtils @Service class HelloService @RestController class HelloController class MyOtherUtils 💩 💩
- 8. Scan 🧐 class HelloUtils @Service class HelloService @RestController class class MyOtherUtils 💩 💩 HelloController
- 9. @RestController class HelloController
- 10. HelloController 📒 ✍ Bean Instance Bean De fi nition (makes)
- 11. 📒 ✍ Bean De fi nition BeanDefinition •Lazy •Primary •Scope •Type •Factory Method Name •Init Method Name •Destroy Method Name
- 12. 📒 ✍ 📒 ✍ 📒 ✍ 📒 ✍ 📒 ✍
- 13. 📒 ✍ 📒 ✍ 📒 ✍ 📒 ✍ 📒 ✍ BeanFactory BeanDefinitionRegistry ↪ ↩ Let me get beans Let me register bean definitions
- 14. BeanFactory BeanDefinitionRegistry ↪ ↩ Let me get beans Let me register bean definitions
- 15. BeanFactory BeanDefinitionRegistry DefaultListableBeanFactory Let me get beans Let me register bean definitions
- 16. DefaultListableBeanFactory •The 💚 of Spring •Manages Bean De fi nitions •Manages Bean Instances
- 17. to the code...
- 18. BeanFactory ApplicationContext spring-beans.jar spring-context.jar Environment MessageSource ApplicationEvent @Configuration
- 19. ApplicationContext AbstractApplicationContext GenericApplicationContext AnnotationConfigApplicationContext Provides @Configuration support Contains a DefaultListableBeanFactory Basic implementation that detects special Beans
- 20. to the code...
- 21. AnnotationConfigApplicationContext @Configuration class ApplicationConfiguration { @Bean public HelloMessageProvider messageProvider() { return new HelloMessageProvider(); } } This is also a @Component Turns the method signature into a BeanDefinition Invoked when the bean instance is needed 📒 ✍ type = HelloMessageProvider factoryBean = "applicationCon fi guration" factoryMethodName = "messageProvider"
- 22. 📒 ✍ type = HelloMessageProvider factoryBean = "applicationCon fi guration" factoryMethodName = "messageProvider" 📒 ✍ type = HelloController 👋 Get me the HelloController Bean 🧐 OK, let me get that BeanDe fi nition 🤔 Wait... its constructor needs a HelloMessageProvider 🧐 OK, let me get that BeanDe fi nition 🤔 Wait it needs an 'applicationCon fi guration' factory bean 📒 ✍ type = ApplicationCon fi guration 🧐 <sigh> OK, let me get that BeanDe fi nition 🥳 Create ApplicationCon fi guration Bean instance 🥳 Invoke messageProvider() method to create HelloMessageProvider Bean instance 🥳 Create HelloController Bean instance injecting HelloMessageProvider DefaultListableBeanFactory AnnotationConfigApplicationContext
- 23. AnnotationConfigApplicationContext (uses) ConfigurationClassPostProcessor BeanDefinitionRegistryPostProcessor BeanFactoryPostProcessor
- 24. to the code...
- 25. GraalVM 🧐 🤷 main SpringApplication.run @ComponentScan @Configuration @Bean 🤔 🛏 💩 💡 🩹Add re fl ection hints Write better code 😎 🤨
- 26. Make this... @Configuration class ApplicationConfiguration { @Bean public HelloMessageProvider messageProvider() { return new HelloMessageProvider(); } } Into something more like this... BeanDefinition bd = new RootBeanDefinition(HelloMessageProvider.class, HelloMessageProvider::new); registry.registerBeanDefinition("helloMessageProvider", bd);
- 27. 🤔 It's just annotations... how hard can it be? 💡 📒 ✍ 📒 ✍ 📒 ✍ 📒 ✍ 📒 ✍ 📒 ✍ 📒 ✍
- 28. 📦 🧐 Run the app so we have bean de fi nitions 📒 ✍ 📒 ✍ 📒 ✍ DefaultListableBeanFactory AnnotationConfigApplicationContext ✋ Stop before we create the bean instances 📒 ✍ 😎 Create code that can recreate the bean de fi nitions 🧠 Let GraalVM do its thing 💾 💾 💾 💾 * * There's a little more to it than that
- 29. to the code...
- 30. Thanks!