@Configuration and @Bean in Spring Boot - Mini Project: Build & Apply

Using @Configuration and @Bean in Spring Boot

📖 Scenario: You are building a simple Spring Boot application that needs a custom service bean to provide greetings. You want to configure this bean using Spring's @Configuration and @Bean annotations.

🎯 Goal: Create a Spring Boot configuration class that defines a bean of type GreetingService. This bean will be used to provide greeting messages in the application.

📋 What You'll Learn

Create a class annotated with @Configuration

Define a method annotated with @Bean that returns a GreetingService instance

The GreetingService class should have a method getGreeting() returning a greeting string

Use the bean method to return a new GreetingService object

💡 Why This Matters

🌍 Real World

Spring Boot applications use @Configuration and @Bean to manage and configure components and services cleanly and flexibly.

💼 Career

Understanding how to define and use beans with @Configuration and @Bean is essential for backend Java developers working with Spring Boot.

1

Create the GreetingService class

Create a public class called GreetingService with a public method getGreeting() that returns the string "Hello, Spring!".

Spring Boot

# Create the GreetingService class with getGreeting() method
// Your code here

Need a hint?

Define a simple class with a method that returns a fixed greeting string.

2

Create a configuration class with @Configuration

Create a public class called AppConfig and annotate it with @Configuration.

Spring Boot

public class GreetingService {
    public String getGreeting() {
        return "Hello, Spring!";
    }
}

// Create AppConfig class annotated with @Configuration
// Your code here

Need a hint?

Use @Configuration annotation from Spring to mark the class as a configuration.

3

Define a @Bean method returning GreetingService

Inside the AppConfig class, create a public method called greetingService() annotated with @Bean that returns a new instance of GreetingService.

Spring Boot

import org.springframework.context.annotation.Configuration;

public class GreetingService {
    public String getGreeting() {
        return "Hello, Spring!";
    }
}

@Configuration
public class AppConfig {
    // Add @Bean method greetingService() here
    // Your code here
}

Need a hint?

Use @Bean annotation on a method that returns a new GreetingService object.

4

Use the GreetingService bean in a component

Create a public class called GreetingPrinter with a private final GreetingService field. Add a constructor that accepts a GreetingService parameter and assigns it to the field. Add a public method printGreeting() that returns the result of greetingService.getGreeting().

Spring Boot

import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Bean;

public class GreetingService {
    public String getGreeting() {
        return "Hello, Spring!";
    }
}

@Configuration
public class AppConfig {
    @Bean
    public GreetingService greetingService() {
        return new GreetingService();
    }
}

// Create GreetingPrinter class with constructor injection and printGreeting() method
// Your code here

Need a hint?

Create a class that uses the GreetingService bean by constructor injection and calls its method.