[Spring Boot] Rest Template 사용하기

우선 Client(보내는 입장)와 받는 입장인 Server 를 이용할 것이기 때문에 

IntelliJ를 두 개를 킨 후 각각의 프로젝트를 만든다. 

Client port는 8080, Server port는 9090으로 진행한다.

 

 

get API를 사용할 때 어떤 서버가 어떠한 데이터를 제공함.

JSON의 표준 규격을 보고 클래스를 생성한다.

클래스를 작성 후 RestTemplate의 통해서 get, post 등으로 데이터를 주고받음.

get같은 경우 이 예시는 주소를 호출하기만 하면 되기때문에 문제가 되지 않음.

post로 보낼 경우 RequestBody를 붙여서 보내야 하기 때문에 이후에 알아보기로 하자.


Client -> Server로 요청해서 응답을 받는 형태

Client 

 

- ApiController.java

package com.example.client.dto;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

// Req<T> -> 제네릭 타입 T

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Req<T> {
    // header 가 들어감

    private Header header;

    private T responseBody;

    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    public static class Header{
        private String responseCode;
    }

}

 

 

- Req.java

package com.example.client.dto;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

// Req<T> -> 제네릭 타입 T

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Req<T> {
    // header 가 들어감

    private Header header;

    private T responseBody;

    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    public static class Header{
        private String responseCode;
    }

}

 

- UserRequest.java

package com.example.client.dto;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class UserRequest {

    private String name;
    private int age;
}

 

- UserResponse.java

package com.example.client.dto;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class UserResponse {

    private String name;
    private int age;
}

 

- RestTemplateService.java

package com.example.client.service;


import com.example.client.dto.Req;
import com.example.client.dto.UserRequest;
import com.example.client.dto.UserResponse;
import org.springframework.core.ParameterizedTypeReference;
import org.springframework.http.MediaType;
import org.springframework.http.RequestEntity;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;
import org.springframework.web.util.UriComponentsBuilder;

import java.net.URI;

@Service
public class RestTemplateService {

    // http://localhost/api/server/hello
    // response
    // getBody 안에는 UserResponse가 들어있기 때문에 반환 값은 UserResponse
    public UserResponse hello(){
        URI uri = UriComponentsBuilder
                .fromUriString("http://localhost:9090")
                .path("/api/server/hello")
                .queryParam("name","aaaa")
                .queryParam("age",9999) // 주소 뒤에 쿼리파라미터가 붙음.
                .encode()
                .build()
                .toUri();
        System.out.println(uri.toString());

        RestTemplate restTemplate = new RestTemplate();

        //String result = restTemplate.getForObject(uri, String.class);

        ResponseEntity<UserResponse> result = restTemplate.getForEntity(uri, UserResponse.class);
        //헤더 내용이나 상세한 정보를 알기 위해서는 ResponseEntity로 받는 것이 용이
        // getForObject, getForEntity 에서의 get은 get,post메서드의 get임.

        System.out.println(result.getStatusCode()); //200 OK 출력
        System.out.println(result.getBody()); // hello server 출력

        return result.getBody();
    }


    public UserResponse post(){
        //http://localhost:9090/api/server/user/{userId}/name/{userName}

        //UriComponentBuilder에서 Path Variable 바꾸는 법
        URI uri = UriComponentsBuilder
                .fromUriString("http://localhost:9090")
                .path("/api/server/user/{userId}/name/{userName}")
                .encode()
                .build()
                .expand(100, "steve") // path의 1, 2번째 {}와 매칭. ","로 계속 이어 붙이면 됨.
                .toUri();
        System.out.println(uri);

        // http body -> object -> object mapper -> json -> rest tamplate ->
        // http body json
        UserRequest req = new UserRequest();
        req.setName("steve");
        req.setAge(10);

        RestTemplate restTemplate = new RestTemplate();

        //ResponseEntity를 UserResponse 타입으로 받음.
        //해당 주소(uri)에 req를 만들어서 UserResponse로 받음.
        ResponseEntity<UserResponse> response = restTemplate.postForEntity(uri, req, UserResponse.class);

        System.out.println(response.getStatusCode());
        System.out.println(response.getHeaders());
        System.out.println(response.getBody());

        return response.getBody();
    }

    public UserResponse exchange(){
        URI uri = UriComponentsBuilder
                .fromUriString("http://localhost:9090")
                .path("/api/server/user/{userId}/name/{userName}")
                .encode()
                .build()
                .expand(100, "steve") // path의 1, 2번째 {}와 매칭. ","로 계속 이어 붙이면 됨.
                .toUri();
        System.out.println(uri);

        // http body -> object -> object mapper -> json -> rest tamplate ->
        // http body json
        UserRequest req = new UserRequest();
        req.setName("steve");
        req.setAge(10);

        RequestEntity<UserRequest> requestEntity = RequestEntity
                .post(uri)
                .contentType(MediaType.APPLICATION_JSON)
                .header("x-authorization","abcd")
                .header("custom-header","fffff")
                .body(req);

        RestTemplate restTemplate = new RestTemplate();
        ResponseEntity<UserResponse> response = restTemplate.exchange(requestEntity, UserResponse.class);

        return response.getBody();
    }


    public Req<UserResponse> genericUserExChange(){
        URI uri = UriComponentsBuilder
                .fromUriString("http://localhost:9090")
                .path("/api/server/user/{userId}/name/{userName}")
                .encode()
                .build()
                .expand(100, "steve") // path의 1, 2번째 {}와 매칭. ","로 계속 이어 붙이면 됨.
                .toUri();
        System.out.println(uri);

        // http body -> object -> object mapper -> json -> rest tamplate ->
        // http body json

        UserRequest userRequest = new UserRequest();
        userRequest.setName("steve");
        userRequest.setAge(10);

        Req<UserRequest> req = new Req<UserRequest>();
        req.setHeader(
            new Req.Header()
        );

        req.setResponseBody(
            userRequest
        );

        RequestEntity<Req<UserRequest>> requestEntity = RequestEntity
                .post(uri)
                .contentType(MediaType.APPLICATION_JSON)
                .header("x-authorization","abcd")
                .header("custom-header","fffff")
                .body(req);

        // generic에는 class를 붙일 수 없음. 그래서 아래 코드를 작성하여 class 가 들어갈 곳으로 넣어줌.
        //new ParameterizedTypeReference<Req<UserResponse>>(){};
        RestTemplate restTemplate = new RestTemplate();

        ResponseEntity<Req<UserResponse>> response
                = restTemplate.exchange(requestEntity, new ParameterizedTypeReference<Req<UserResponse>>(){});

        return response.getBody();
    }

}

 

 

Server

 

- ServerApiController.java

package com.example.server.controller;

import com.example.server.dto.Req;
import com.example.server.dto.User;
import lombok.extern.slf4j.Slf4j;
import org.springframework.http.HttpEntity;
import org.springframework.web.bind.annotation.*;

@Slf4j
@RestController
@RequestMapping("/api/server")
public class ServerApiContoller {

    @GetMapping("/hello")
    public User hello(@RequestParam String name, @RequestParam int age){
        User user = new User();
        user.setName(name);
        user.setAge(age);
        return user;
    }
    // header 변수 넣어주기
    // JSON의 형태가 헤더와 바디로 이루어져 있을 경우가 있음.
    // 그럴 경우의 소스코드
    @PostMapping("/user/{userId}/name/{userName}")
    public Req<User> post(
                        //오류가 났을 때 뭐가 문제인지 모를 경우에, 아래 소스를 삽입
                        //함으로써 String의 형태로 로그를 찍어볼 수 있음.
                        //HttpEntity<String> entity,
                          @RequestBody Req<User> user,
                          @PathVariable int userId,
                          @PathVariable String userName,
                          @RequestHeader("x-authorization") String authorization,
                          @RequestHeader("custom-header") String customHeader
    ){
        //log.info("req : {}", entity.getBody());
        log.info("userId : {}, userName : {}",userId, userName);
        log.info("authorization : {}, custom : {}",authorization, customHeader);
        //log.info("client req: {}",user);

        Req<User> response = new Req<>();
        response.setHeader(
                new Req.Header()
        );
        response.setResponseBody(user.getResponseBody());

        return response;
    }

}

 

- Req.java

package com.example.server.dto;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class Req<T> {

    private Header header;
    private T responseBody;

    @Data
    @NoArgsConstructor
    @AllArgsConstructor
    public static class Header{
        private String responseCode;
    }

}

 

- User.java

package com.example.server.dto;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private String name;
    private int age;
}