In Spring Boot, what is the use of @PostConstruct? Explain using Example.

Use of @PostConstruct in Spring Boot

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In Spring Boot, @PostConstruct is used to annotate a method that should be executed after dependency injection is complete and before the bean is put into service.

Example:

Suppose we have a class UserService that requires some initialization logic after its dependencies are injected. We can use @PostConstruct to annotate a method for this purpose.

import javax.annotation.PostConstruct;

import org.springframework.stereotype.Service;

@Service
public class UserService {

    @PostConstruct
    public void init() {
        // Initialization logic, e.g., loading configuration, setting up resources, etc.
        System.out.println("UserService initialized!");
    }

    // Other methods of UserService
}

In this example:

• The UserService class is annotated with @Service to indicate it as a Spring-managed bean.
• The init method is annotated with @PostConstruct, ensuring it runs automatically after all dependencies of UserService are injected by Spring.
• Any initialization logic needed for UserService can be placed within the init method.

Conclusion:

@PostConstruct in Spring Boot provides a convenient way to perform initialization tasks for a bean after its dependencies are injected. It ensures that the initialization logic is executed exactly once before the bean is used, contributing to the robustness and reliability of the application.