when should i use a custom configuration class in spring boot?

Question

I am learning spring at the moment and cant figure out why and when we need to the use the custom @Configuration class and @Bean inside it as spring does everything automatically

@Configuration and @Bean uses and reasons?

Answer 1

@Configuration and @Bean are essential components in the Spring Framework that provide manual configuration and customization options when the automatic configuration provided by Spring Boot or other Spring modules is not sufficient. Here's when and why you might use them:

1. Custom Configuration: Spring Boot and other Spring modules offer automatic configuration based on convention and best practices. However, there may be cases where you need to define your custom beans, set up third-party integrations, or perform some custom logic during application startup. This is when you create a custom @Configuration class.

   @Configuration
   public class MyCustomConfiguration {
          // Define custom beans and configuration here using @Bean
   }
   

2. Customizing Bean Creation: By using the @Bean annotation within your @Configuration class, you can define and configure specific beans with non-default settings. For instance, you may want to initialize a bean with specific properties or dependencies.

   @Configuration
   public class MyCustomConfiguration {
      @Bean
      public MyCustomBean customBean() {
             // Define and configure a custom bean
      return new MyCustomBean();
      }
   }
   

3. Third-Party Integration: If you are integrating with libraries or frameworks that are not automatically configured by Spring, you can use @Configuration to set up and customize those integrations.

4. Conditional Bean Creation: You can use conditional logic inside your @Configuration class to conditionally create beans based on certain conditions, profiles, or environment variables.

   @Configuration
   @Profile("development")
   public class DevelopmentConfiguration {
    @Bean
    public MyDevBean devBean() {
              // Define and configure a bean for the development profile
        return new MyDevBean();
    }
   }
   

5. Testing: In unit testing scenarios, you may want to create and configure specific beans or mock dependencies using @Configuration classes, allowing you to isolate and control the components being tested.

In summary, while Spring's automatic configuration is powerful, there are situations where you need more control and customization over bean creation and application setup. This is where @Configuration and @Bean come into play, allowing you to define custom beans and configurations to suit your application's specific requirements.