Directory Structure
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>3.4.3</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>BeanExample</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>BeanExample</name>
<description>Demo project for Spring Boot</description>
<url/>
<licenses>
<license/>
</licenses>
<developers>
<developer/>
</developers>
<scm>
<connection/>
<developerConnection/>
<tag/>
<url/>
</scm>
<properties>
<java.version>17</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
📌 @bean Annotation Example in Spring Boot
The @bean annotation in Spring Boot is used to define a bean manually inside a @Configuration class. It tells Spring to manage an instance of the object and inject it wherever needed.
🔹 Example 1: Basic @bean Usage
✔ Scenario: You want to create and manage a HelloService bean manually instead of using @Component.
🚀 Implementation
Step 1: Create a Service Class
public class HelloService {
public String sayHello() {
return "Hello, Spring Boot!";
}
}
Step 2: Define Bean in a @Configuration Class
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
public class AppConfig {
@Bean
public HelloService helloService() {
return new HelloService();
}
}
Step 3: Use the Bean in a Controller
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
@RequestMapping("/hello")
public class HelloController {
private final HelloService helloService;
public HelloController(HelloService helloService) {
this.helloService = helloService;
}
@GetMapping
public String sayHello() {
return helloService.sayHello();
}
}
🌟 Expected Output
GET /hello --> Response: "Hello, Spring Boot!"
🛠When to Use @bean?
✅ When you need fine-grained control over bean creation.
✅ When the class does not use @Component, @Service, or @Repository.
✅ When you want to configure third-party libraries (e.g., RestTemplate, DataSource).
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