Bean lifecycle overview in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

What is the correct order of Spring Bean lifecycle phases?

Arrange the following Spring Bean lifecycle phases in the correct order from bean creation to destruction.

A 1,2,3,4

B 2,1,3,4

C 1,3,2,4

D 1,2,4,3

💡 Hint

Think about what happens first: creating the bean, then setting its dependencies, then running any setup code, and finally cleaning up.

The Spring Bean lifecycle starts with instantiation, then dependency injection sets required properties. After that, post-initialization callbacks like @PostConstruct run. Finally, before the bean is removed, pre-destruction callbacks like @PreDestroy execute.

❓ component_behavior

intermediate

What happens if a Spring Bean implements InitializingBean?

Consider a Spring Bean that implements the InitializingBean interface. What method is called and when during the bean lifecycle?

A The constructor is called after the bean is fully initialized.

B The destroy() method is called before the bean is destroyed.

C The init() method is called before dependency injection.

D The afterPropertiesSet() method is called after dependency injection is complete.

💡 Hint

Look for the method that runs after all properties are set.

When a bean implements InitializingBean, Spring calls its afterPropertiesSet() method right after dependency injection finishes. This allows the bean to perform any setup needed before use.

❓ lifecycle

advanced

What error occurs if a Spring Bean's @PostConstruct method throws an exception?

If a method annotated with @PostConstruct in a Spring Bean throws a RuntimeException, what is the effect on the application context startup?

A The exception is ignored and the bean is created normally.

B The application context fails to start and throws a BeanCreationException.

C The bean is created but marked as lazy and initialized later.

D The exception is logged but the application continues without the bean.

💡 Hint

Think about what happens if initialization code fails during startup.

If a @PostConstruct method throws an exception, Spring treats it as a failure to create the bean. This causes the application context startup to fail with a BeanCreationException, preventing the app from running.

❓ state_output

advanced

What is the output of this Spring Bean lifecycle log?

Given a Spring Bean with methods logging messages in constructor, @PostConstruct, and @PreDestroy, what is the order of log messages when the application starts and then shuts down?

Spring Boot

public class MyBean {
  public MyBean() { System.out.println("Constructor called"); }
  @PostConstruct
  public void init() { System.out.println("PostConstruct called"); }
  @PreDestroy
  public void cleanup() { System.out.println("PreDestroy called"); }
}

A Constructor called\nPostConstruct called\nPreDestroy called

B PostConstruct called\nConstructor called\nPreDestroy called

C Constructor called\nPreDestroy called\nPostConstruct called

D PreDestroy called\nConstructor called\nPostConstruct called

💡 Hint

Remember the bean is created first, then initialized, then destroyed.

The constructor runs first when the bean is created. Then the @PostConstruct method runs after dependencies are set. Finally, when the app shuts down, the @PreDestroy method runs.

🔧 Debug

expert

Why does this Spring Bean's @PreDestroy method not run on shutdown?

A Spring Bean has a method annotated with @PreDestroy, but when the application stops, the method is never called. What is the most likely cause?

Spring Boot

@Component
public class MyBean {
  @PreDestroy
  public void cleanup() {
    System.out.println("Cleaning up");
  }
}

A The @PreDestroy annotation is misspelled and ignored by Spring.

B The cleanup method is private and cannot be called by Spring.

C The bean is not managed by Spring because it was created with new instead of injected.

D The application context is not closed properly, so destroy callbacks are skipped.

💡 Hint

Think about how Spring knows which beans to manage and call lifecycle methods on.

If a bean is created manually with new instead of letting Spring inject it, Spring does not manage its lifecycle. Therefore, lifecycle callbacks like @PreDestroy are never called.