🌱 Spring Bean

🧠 What is a Bean in Spring Boot?

A bean is a Java object managed by the Spring framework. In Spring Boot, you often create beans using:

@Component
@Service
@Repository
@Configuration
@Bean

Spring Boot automatically detects and manages these beans through component scanning.

🔄 How Does the Bean Lifecycle Work in Spring Boot?

Spring Boot uses the standard Spring bean lifecycle, but simplifies it with annotations and auto-configuration.

✅ Common Lifecycle Hooks You Might Use:

@PostConstruct - Run code after dependencies are injected:

@Component
public class MyService {
    @PostConstruct
    public void init() {
        System.out.println("Bean is initialized");
    }
}

@PreDestroy - Run code before bean is destroyed (e.g., app shutdown):

@PreDestroy
public void cleanup() {
    System.out.println("Bean is being destroyed");
}

InitializingBean and DisposableBean interfaces:

@Component
public class MyService implements InitializingBean, DisposableBean {
    public void afterPropertiesSet() {
        System.out.println("Bean initialized via InitializingBean");
    }

    public void destroy() {
        System.out.println("Bean destroyed via DisposableBean");
    }
}

@Bean(initMethod = ..., destroyMethod = ...) in @Configuration classes:

@Bean(initMethod = "start", destroyMethod = "stop")
public MyBean myBean() {
    return new MyBean();
}

📦 Summary (Spring Boot Way)

Stage	What You Use
Initialization	@PostConstruct, InitializingBean, initMethod
Destruction	@PreDestroy, DisposableBean, destroyMethod

✅ Spring Bean Life Cycle (Super Simple)

• Create – Spring creates the object (bean).
• Inject – Spring injects dependencies (like other beans).
• Initialize – Spring runs setup code (@PostConstruct).
• Use – The bean is ready to be used.
• Destroy – Spring runs cleanup code (@PreDestroy).

🔁 One Line Summary:

Spring creates, injects, initializes, uses, and destroys your beans automatically.

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