Add core-beans: bean scopes, the prototype-in-singleton trap, lifecycle callback order and graceful shutdown phases on Boot 4.1
Co-Authored-By: Claude Sonnet 5 <[email protected]> Claude-Session: https://claude.ai/code/session_01JoVmf2fWvcpoXndcDSwRf7
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Claude
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# How many instances did the container really construct?
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right after refresh():
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singleton instances : 1
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@Lazy singleton : 0
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prototype : 0
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after getBean() twice for singleton and lazy, three times for prototype:
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singleton instances : 1 same object both times: true
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@Lazy singleton : 1 same object both times: true
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prototype : 3 serials: 1, 2, 3
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two separate contexts, each with SingletonBean:
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singleton instances : 2 same object across contexts: false
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# @PreDestroy on a singleton and on a prototype, then context.close()
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prototype instances created: 1
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callbacks after close(): [singleton @PreDestroy called]
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# A singleton calls use() five times. How many prototype instances did it touch?
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how the prototype is obtained serials seen instances built
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---------------------------------- ---------------------- ---------------
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constructor injection (naive) [1, 1, 1, 1, 1] 1
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ObjectProvider.getObject() [1, 2, 3, 4, 5] 5
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@Lookup method [1, 2, 3, 4, 5] 5
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scoped proxy (TARGET_CLASS) [1, 2, 3, 4, 5] 5
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ApplicationContext.getBean() [1, 2, 3, 4, 5] 5
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ProxyConsumer's injected reference is a com.ankurm.corebeans.scopes.ScopedPrototypeBean$$SpringCGLIB$$0
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# Two threads call the same singleton; a latch forces the interleaving
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UnsafeGreeter (state in a field) : alice's call returned "Hello, bob"
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SafeGreeter (state in a local) : alice's call returned "Hello, alice"
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# request, session and application scope over real HTTP
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client response
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A #1 request=1 session=1 application=1 injectedRequestClass=RequestBean$$SpringCGLIB$$0
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A #2 request=2 session=1 application=1 injectedRequestClass=RequestBean$$SpringCGLIB$$0
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A #3 request=3 session=1 application=1 injectedRequestClass=RequestBean$$SpringCGLIB$$0
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B #1 request=4 session=2 application=1 injectedRequestClass=RequestBean$$SpringCGLIB$$0
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B #2 request=5 session=2 application=1 injectedRequestClass=RequestBean$$SpringCGLIB$$0
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instances constructed: request=5 session=2 application=1
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# A request-scoped bean (no proxy) injected into a singleton
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top exception : org.springframework.beans.factory.UnsatisfiedDependencyException
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top message : Error creating bean with name 'brokenRequestConsumer': Unsatisfied dependency expressed through constructor parameter 0: Error creating bean with name 'brokenRequestConsumer.RawRequestBean': Scope 'request' is not active for the current thread; consider defining a scoped proxy for this bean if you intend to refer to it from a singleton
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root cause : java.lang.IllegalStateException: No thread-bound request found: Are you referring to request attributes outside of an actual web request, or processing a request outside of the originally receiving thread? If you are actually operating within a web request and still receive this message, your code is probably running outside of DispatcherServlet: In this case, use RequestContextListener or RequestContextFilter to expose the current request.
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# Every callback for one bean, from constructor to the last destroy hook (SpringApplication, no web server)
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=== startup ===
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constructor
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setter injection (@Autowired setDependency)
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BeanNameAware.setBeanName("kitchenSink")
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BeanFactoryAware.setBeanFactory
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ApplicationContextAware.setApplicationContext
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BeanPostProcessor.postProcessBeforeInitialization
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@PostConstruct
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InitializingBean.afterPropertiesSet
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@Bean(initMethod = "customInit")
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BeanPostProcessor.postProcessAfterInitialization
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SmartInitializingSingleton.afterSingletonsInstantiated
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SmartLifecycle.start (phase 2147483647)
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ContextRefreshedEvent
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ApplicationStartedEvent
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ApplicationRunner.run
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ApplicationReadyEvent
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=== ctx.close() ===
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ContextClosedEvent
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SmartLifecycle.stop
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@PreDestroy
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DisposableBean.destroy
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@Bean(destroyMethod = "customDestroy")
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# A BeanPostProcessor declared with a non-static @Bean method
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2026-09-24T10:28:59.979+05:30 WARN 3358 --- [core-beans] [ main] trationDelegate$BeanPostProcessorChecker : Bean 'nonStaticProcessorConfig' of type [com.ankurm.corebeans.lifecycle.NonStaticProcessorConfig$$SpringCGLIB$$0] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying). The currently created BeanPostProcessor [quietProcessor] is declared through a non-static factory method on that class; consider declaring it as static instead.
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# @PostConstruct runs before the @Async proxy exists
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@PostConstruct sees this = com.ankurm.corebeans.lifecycle.AsyncMailer, isAopProxy(this) = false
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the bean other code receives : com.ankurm.corebeans.lifecycle.AsyncMailer$$SpringCGLIB$$0
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# An exception thrown from @PostConstruct
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context started: false
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top exception : org.springframework.beans.factory.BeanCreationException
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top message : Error creating bean with name 'failingInit': Invocation of init method failed
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root cause : java.lang.IllegalStateException: cache warm-up failed
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# Three SmartLifecycle beans registered in the order 300, 100, 200
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=== refresh() ===
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start A (phase 100)
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start B (phase 200)
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start C (phase 300)
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=== close() ===
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stop C (phase 300)
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stop B (phase 200)
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stop A (phase 100)
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# Three SmartLifecycle beans in the SAME phase, each needing 400 ms to stop
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stop(Runnable) blocks (the default) : close() took >= 1100 ms (sequential)
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stop(Runnable) returns immediately : close() took < 800 ms (concurrent)
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# Lifecycle vs SmartLifecycle: who starts at refresh()?
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after refresh() : events=[] isRunning=false
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after start() : events=[PlainLifecycle.start] isRunning=true
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# A SmartLifecycle whose stop(callback) never calls the callback, timeout 500 ms
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close() returned after roughly the timeout: true
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2026-09-24T10:28:58.263+05:30 INFO 3358 --- [core-beans] [ main] o.s.c.support.DefaultLifecycleProcessor : Shutdown phase 2147483647 ends with 1 bean still running after timeout of 500ms: [neverStops]
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# Every SmartLifecycle bean in a Boot web application, highest phase (stops first) at the top
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phase bean name class
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2147483647 earlyWorker EarlyWorker
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2147482623 webServerGracefulShutdown WebServerGracefulShutdownLifecycle
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2147481599 webServerStartStop WebServerStartStopLifecycle
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1073741823 applicationTaskExecutor ThreadPoolTaskExecutor
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1000 lateWorker LateWorker
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-2147483647 springBootLoggingLifecycle Lifecycle
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SmartLifecycle.DEFAULT_PHASE = 2147483647
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# A /slow?ms=1500 request is in flight when the context closes
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settings the client saw close() blocked handler ran to the end
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-------------------------------------------- ---------------------------------------------------- -------------------------------- ----------------------
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server.shutdown=graceful, virtual threads HTTP 200: finished after 1500 ms, virtual thread = true >= 1 s (waited for the request) yes
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server.shutdown=graceful, platform threads HTTP 200: finished after 1500 ms, virtual thread = false >= 1 s (waited for the request) yes
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server.shutdown=immediate, virtual threads FAILED: connection dropped, no response >= 1 s (waited for the request) yes
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# SmartLifecycle beans with the default phase and with phase 1000, while a request is in flight
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EarlyWorker.stop (phase 2147483647): requests still in flight = 1
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LateWorker.stop (phase 1000): requests still in flight = 0
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the client saw: HTTP 200: finished after 1500 ms, virtual thread = true
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# Property defaults read from spring-configuration-metadata.json (Boot 4.1.1 jars)
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spring.lifecycle.timeout-per-shutdown-phase type=java.time.Duration default=30s
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spring.threads.virtual.enabled type=java.lang.Boolean default=False
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server.shutdown type=org.springframework.boot.web.server.Shutdown default=graceful
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# The BeanPostProcessors registered in a plain Spring Boot context, in the order they run
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1 org.springframework.context.support.ApplicationContextAwareProcessor
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2 org.springframework.context.annotation.ConfigurationClassPostProcessor$ImportAwareBeanPostProcessor
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3 org.springframework.context.support.PostProcessorRegistrationDelegate$BeanPostProcessorChecker
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4 com.ankurm.corebeans.lifecycle.TracingPostProcessor
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5 org.springframework.context.annotation.CommonAnnotationBeanPostProcessor
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6 org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor
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7 org.springframework.context.support.ApplicationListenerDetector
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