Spring Boot - RESTful API

Hướng dẫn xây dựng RESTful service bằng Spring Boot

Server side

Configuration

Thêm dependency trong pom.xml

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

Thêm cấu hình port listen cho server trong file application.yml

server:
  port : 8082

Write controller

Viết class controller bằng cách sử dụng RestController

@RestController
@RequestMapping("/api")
public class Controller {

  @Autowired
  GreetUseCase greetUseCase;

  @GetMapping("/get-mapping")
  public Greeting getMapping() {
    return greetUseCase.greet(0, "GetMapping");
  }
}

RequestMapping và GetMapping tạo nên path của api (Ví dụ: /api/get-mapping)

Mapping request

Tạo mapping lấy variable từ path của api

  @GetMapping("/path-variable/{user_id}")
  public Greeting pathVariable(@PathVariable(name = "user_id") int userId) {
    return greetUseCase.greet(userId, "PathVariable");
  }

Tạo api nhận request param

  @GetMapping("/request-param")
  public Greeting requestParam(@RequestParam(name = "user_id") int userId) {
    return greetUseCase.greet(userId, "RequestParam");
  }

Tạo post request

  @PostMapping("/request-body")
  public Greeting requestBody(@RequestBody User user) {
    return greetUseCase.greet(user.getUserId(), "RequestBody");
  }

Client side

Thư viện sử dụng
- OpenFeign: a HTTP client
- spring-cloud-openfeign: a REST client for Spring Boot apps
Thêm dependency trong file pom.xml

<dependencies>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-openfeign</artifactId>
        <version>2.2.3.RELEASE</version>
    </dependency>
</dependencies>

Cấu hình url, path trong file application.yml

greeting-service:
  url: http://localhost:8082
  path:
    get-mapping: /api/get-mapping
    path-variable: /api/path-variable/{user_id}
    request-param: /api/request-param
    request-body: /api/request-body

Sử dụng FeignClient annotation để tạo RestClient

@FeignClient(value = "greeting", url = "${greeting-service.url}")
public interface GreetingRestClient {

  @RequestMapping(method = RequestMethod.GET, value = "${greeting-service.path.get-mapping}")
  public Greeting getMapping();

  @RequestMapping(method = RequestMethod.GET, value = "${greeting-service.path.path-variable}")
  public Greeting pathVariable(@PathVariable(name = "user_id") int userId);

  @RequestMapping(method = RequestMethod.GET, value = "${greeting-service.path.request-param}")
  public Greeting requestParam(@RequestParam(name = "user_id") int userId);

  @RequestMapping(method = RequestMethod.POST, value ="${greeting-service.path.request-body}")
  public Greeting requestBody(@RequestBody User user);

}

Autowired GreetingRestClient bean để giao tiếp server side

  @Autowired
  GreetingRestClient greetingRestClient;

  public String getMapping() {
    Greeting getResponse = greetingRestClient.getMapping();
    log.info(getResponse.toString());

    Greeting pathVariableResponse = greetingRestClient.pathVariable(1);
    log.info(pathVariableResponse.toString());

    Greeting requestParamResponse = greetingRestClient.requestParam(1);
    log.info(requestParamResponse.toString());

    Greeting requestBodyResponse = greetingRestClient.requestBody(new User(1));
    log.info(requestBodyResponse.toString());

    return "Hello world!";
  }

Source code ở đây