Difference Between @Controller and @Service Annotation in Spring

Last Updated : 04 May, 2022

Spring Annotations are a form of metadata that provides data about a program. Annotations are used to provide supplemental information about a program. It does not have a direct effect on the operation of the code they annotate. It does not change the action of the compiled program.

Spring @Controller Annotation

Spring @Controller annotation is a specialization of @Component annotation. The @Controller annotation indicates that a particular class serves the role of a controller. Spring Controller annotation is typically used in combination with annotated handler methods based on the @RequestMapping annotation. It can be applied to classes only. It’s used to mark a class as a web request handler. It’s mostly used with Spring MVC applications. This annotation acts as a stereotype for the annotated class, indicating its role. The dispatcher scans such annotated classes for mapped methods and detects @RequestMapping annotations.

Implementation: Project

Step 1: Create a Simple Spring Boot Project

Refer to this article Create and Setup Spring Boot Project in Eclipse IDE and create a simple spring boot project.

Step 2: Add the spring-web dependency in your pom.xml file. Go to the pom.xml file inside your project and add the following spring-web dependency.

XML

<dependency>     <groupId>org.springframework.boot</groupId>     <artifactId>spring-boot-starter-web</artifactId> </dependency>

Step 3: In your project create one package and name the package "controller". In the controller, the package creates a class and name it as DemoController. This is going to be our final project structure.

Java

// Java Program to Illustrate DemoController File  // Importing package in this code module package com.example.demo.controller; // Importing required classes import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.ResponseBody;  // Annotation @Controller // Main class public class DemoController {      @RequestMapping("/hello")     @ResponseBody      // Method     public String helloGFG()     {         return "Hello GeeksForGeeks";     } }

We have used the below annotations in our controller layer. Here in this example, the URI path is /hello.

@Controller: This is used to specify the controller.
@RequestMapping: This is used to map to the Spring MVC controller method.
@ResponseBody: Used to bind the HTTP response body with a domain object in the return type.

Step 4: Now, our controller is ready. Let's run our application inside the DemoApplication.java file. There is no need to change anything inside the DemoApplication.java file.

Example

Java

// Java Program to Illustrate DemoApplication File  // Importing package in this code module package com.example.demo; // Importing required classes import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication;  // Annotation @SpringBootApplication  // Main class public class DemoApplication {      // Main driver method     public static void main(String[] args)     {         SpringApplication.run(DemoApplication.class, args);     } }

Output:

Tip: Try Tomcat URL depicted in below media, which is running on http://localhost:8989/hello

Spring @Service Annotation

In an application, the business logic resides within the service layer so we use the @Service Annotation to indicate that a class belongs to that layer. It is also a specialization of @Component Annotation like the @Repository Annotation. One most important thing about the @Service Annotation is it can be applied only to classes. It is used to mark the class as a service provider. So overall @Service annotation is used with classes that provide some business functionalities. Spring context will autodetect these classes when annotation-based configuration and classpath scanning is used.

Example: Project

Step 1: Create a Simple Spring Boot Project.

tip: Do refer to this article prior to adhering forward on how to create and setup Spring Boot Project in Eclipse IDE and create a simple spring boot project.

Step 2: Add the spring-context dependency in your pom.xml file. Go to the pom.xml file inside your project and add the following spring-context dependency.

File: pom.xml

XML

<dependency>     <groupId>org.springframework</groupId>     <artifactId>spring-context</artifactId>     <version>5.3.13</version> </dependency>

Step 3: In your project create one package and name the package as "service". In the service, the package creates a class and name it "MyServiceClass".

File: MyServiceClass

Java

// Java Program to Illustrate MyServiceClass  // Importing package module to code module package com.example.demo.service; // Importing required classes import org.springframework.stereotype.Service;  // Annotation @Service  // Class public class MyServiceClass {      // Method     // To compute factorial     public int factorial(int n)     {         // Base case         if (n == 0)             return 1;          // Returning factorial of input number         return n * factorial(n - 1);     } }

Code explanation:

From the above code, we can easily perceive that it’s a simple java class that provides functionalities to calculate the factorial of a number. So we can call it a service provider. We have annotated it with @Service annotation so that spring-context can autodetect it and we can get its instance from the context.

Step 4: Spring Repository Test

So now our Spring Repository is ready, let’s test it out. Go to the DemoApplication.java file and refer to the below code.

File: DemoApplication.java

Java

// Java Program to Illustrate DemoApplication  // Importing package module to code fragment package com.example.demo; // Importing required classes import com.example.demo.service.MyServiceClass; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.context.annotation.AnnotationConfigApplicationContext;  // Annotation @SpringBootApplication  // Main class public class DemoApplication {      // Main driver method     public static void main(String[] args)     {         // Creating context of         // AnnotationConfigApplicationContext class         AnnotationConfigApplicationContext context             = new AnnotationConfigApplicationContext();          context.scan("com.example.demo");          context.refresh();          MyServiceClass myServiceClass             = context.getBean(MyServiceClass.class);          // Testing the factorial method         int factorialOf5 = myServiceClass.factorial(5);         System.out.println("Factorial of 5 is: "                            + factorialOf5);          // Closing the spring context         // using close() method         context.close();     } }

Output:

Lastly, let us do discuss the differences between @Controller annotation and @Service annotation.

@Controller Annotation	@Service Annotation
@Controller annotation indicates that a particular class serves the role of a controller.	@Service annotation is used with classes that provide some business functionalities.
@Controller annotation is a specialization of @Component annotation.	@Service Annotation is also a specialization of @Component Annotation.
It can be applied to classes only.	It can be applied to classes only.
It’s used to mark a class as a web request handler.	It is used to mark the class as a service provider.
It is a stereotype for the presentation layer (spring-MVC).	It is a stereotype for the service layer.
We cannot switch this annotation with any other like @Service or @Repository.	Switch can be possible.

Difference Between @Controller and @Service Annotation in Spring

AmiyaRanjanRout

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Java

Difference Between @Controller and @Service Annotation in Spring

Spring @Controller Annotation

Implementation: Project

Spring @Service Annotation

File: pom.xml

File: MyServiceClass

File: DemoApplication.java

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