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Explain @Service annotation with example?

Explain @Service annotation with example?

The `@Service` annotation in Spring is a specialization of the `@Component` annotation. It is used to annotate classes that perform service tasks, typically containing the business logic. The main goal of using `@Service` is to indicate that the annotated class holds the business logic and to make it easier to find and configure services within the Spring context.

Service annotation

Example

Step 1: Create a Spring Boot Application

Ensure you have the necessary dependencies in your `pom.xml` (for Maven) or `build.gradle` (for Gradle).

Example
Maven Dependency:
```xml
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
```

Gradle Dependency:
```groovy
implementation 'org.springframework.boot:spring-boot-starter-web'
```

Step 2: Create the Main Application Class

Create the main class for the Spring Boot application.

Example
```java
package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}
```

Explanation:

  • @SpringBootApplication: Indicates a configuration class that declares one or more @Bean methods and also triggers auto-configuration and component scanning.

Step 3: Create a Service

Create a simple service class using the @Service annotation.

Example
```java
package com.example.demo.service;

import org.springframework.stereotype.Service;

@Service
public class GreetingService {

    public String getGreeting() {
        return "Hello, World!";
    }
}
```

Explanation:

  • @Service: Indicates that this class is a service that holds the business logic.
  • getGreeting: Method that returns a greeting message.

Step 4: Create a Controller

Create a controller that uses the GreetingService to handle web requests.

Example
```java
package com.example.demo.controller;

import com.example.demo.service.GreetingService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
@RequestMapping("/web")
public class HelloController {

    private final GreetingService greetingService;

    @Autowired
    public HelloController(GreetingService greetingService) {
        this.greetingService = greetingService;
    }

    @GetMapping("/hello")
    public String sayHello(Model model) {
        model.addAttribute("message", greetingService.getGreeting());
        return "hello";
    }
}
```

Explanation:

  • @Autowired: Injects the GreetingService into the HelloController.
  • sayHello: Method that uses the GreetingService to get a greeting message and adds it to the model.

Step 5: Create a View

Create an HTML file named hello.html in the src/main/resources/templates directory.

Example
```html
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Hello</title>
</head>
<body>
    <h1>${message}</h1>
</body>
</html>
```

Explanation:

  • ${message}: Placeholder that will be replaced by the actual message passed from the controller.

Step 6: Running the Application

Run the application from the main class (DemoApplication). When you navigate to http://localhost:8080/web/hello in your web browser, you should see the message: “Hello, World!” displayed on the page.

Conclusion of Service annotation

  • @Service: Used to define a service that holds the business logic in a Spring application.
  • Example: Demonstrated how to use @Service to create a simple service class and integrate it with a controller to display a greeting message.

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