Can @Service Replace @Controller in Spring Boot? A Deep Dive

Preface

In Spring Boot development, @Controller marks a controller class that handles web requests, while @Service marks a service class responsible for business logic. This article investigates whether a class annotated with @Service can be used to handle controller responsibilities.

Using @Service Instead of @Controller

We define a ServiceController class annotated with @Service and @RequestMapping("/ts"). The class autowires a UserMapper to interact with the data layer and exposes a getServices method via @GetMapping("get-services"):

@Service
@RequestMapping("/ts")
public class ServiceController {

    @Autowired
    private UserMapper userMapper;

    @GetMapping("get-services")
    @ResponseBody
    public User getServices() {
        User user = userMapper.selectOne(Wrappers.lambdaQuery(User.class)
                .eq(User::getUsername, "zhangSan"));
        return user;
    }
}

Sending a GET request to http://localhost:8080/ts/get-services with PostMan returns the expected JSON response, confirming that the @Service -annotated class can handle HTTP requests just like a traditional controller.

Underlying Mechanism

Both @Controller and @Service are detected by Spring’s component scanning, which is triggered by the @SpringBootApplication meta‑annotation (composed of @EnableAutoConfiguration, @ComponentScan, and @Configuration). Classes annotated with either stereotype that reside in the main application package or its sub‑packages are registered as beans in the Spring container.

During startup, ConfigurationClassPostProcessor processes bean definitions, and AbstractHandlerMethodMapping later maps URLs to methods based on @RequestMapping (or its shortcut annotations). As long as the class is a bean and carries request‑mapping annotations, Spring MVC can treat it as a controller, regardless of whether it is marked with @Controller or @Service.

Summary

In Spring Boot, @Controller and @Service are both component stereotypes that can be discovered and registered by the container. When a @Service -annotated class also carries @RequestMapping (or related) annotations, Spring MVC will route HTTP requests to its methods, effectively allowing @Service to function as a controller. This behavior stems from Spring’s component scanning, bean registration, and the request‑mapping mechanism within AbstractHandlerMethodMapping.