====== Spring RestTemplate ======
  * [[https://spring.io/blog/2009/03/27/rest-in-spring-3-resttemplate|Rest in Spring 3 RestTemplate]]
  * [[http://www.baeldung.com/rest-template|Spring RestTemplate Tutorial]]
  * [[http://www.baeldung.com/spring-rest-template-list|Get and Post Lists of Objects with RestTemplate | Baeldung]]
  * [[https://www.baeldung.com/spring-rest-template-builder|Configure a RestTemplate with RestTemplateBuilder | Baeldung]]
  * [[https://howtodoinjava.com/spring-boot2/resttemplate/|Spring Boot RestTemplate Tutorials - HowToDoInJava]]
  * see [[springframework:feign|Fegin]]

===== HttpEntity =====
  * [[http://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/http/HttpEntity.html|org.springframework.http.HttpEntity]] HTTP 데이터를 세심하게 제어한다.

===== POST에서 파라미터 보내기 =====
  * [[http://stackoverflow.com/questions/11579621/spring-resttemplate-postforobject-with-header-webservice-cant-find-my-header-p|java - Spring RestTemplate postForObject with Header: webservice can't find my header parameters]]<code java>
MultiValueMap<String, String> parameters = new LinkedMultiValueMap<String, String>();
parameters.add("companyId", companyId);
parameters.add("password", password);  

HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);      

HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<>(parameters, headers);

// 메시지 컨버터 지정 안했으면
// List<HttpMessageConverter<?>> messageConverters = new ArrayList<HttpMessageConverter<?>>();
// messageConverters.add(new MappingJacksonHttpMessageConverter());    
// messageConverters.add(new FormHttpMessageConverter());
// restTemplate.setMessageConverters(messageConverters);

LoginResponse response = (LoginResponse) restTemplate.postForObject(url, request, LoginResponse.class); 

// ParemeterizedTypeReference를 사용하여 복잡한 Generic Type 으로 요청 결과 받기
public ParameterizedTypeReference<Map<Long, LoginUser>> loginUserMapType =
    new ParameterizedTypeReference<Map<Long, LoginUser>>() { };

restTemplate.exchange(url, HttpMethod.POST, request, loginUserMapType).getBody();
</code>

===== Exception 처리 =====
  * [[https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/ResponseErrorHandler.html|ResponseErrorHandler]]를 사용하여 예외를 일관성 있게 처리할 수 있다. [[https://stackoverflow.com/questions/38093388/spring-resttemplate-exception-handling|rest - Spring Resttemplate exception handling]]

<code java>
public class MyErrorHandler implements ResponseErrorHandler {
  @Override
  public void handleError(ClientHttpResponse response) throws IOException {
    // your error handling here
  }

  @Override
  public boolean hasError(ClientHttpResponse response) throws IOException {
    // ...
  }
}

// [...]

public static void main(String args[]) {
  RestTemplate restTemplate = new RestTemplate();
  restTemplate.setErrorHandler(new MyErrorHandler());
}
</code>
  * 기본 구현체인 [[https://docs.spring.io/spring/docs/current/javadoc-api/org/springframework/web/client/DefaultResponseErrorHandler.html|DefaultResponseErrorHandler]]를 상속하여 필요한 메소드만 override 해도 된다.

===== Interceptor를 통한 로깅 =====
  * [[http://eclipse4j.tistory.com/282|Spring RestTemplate 에서 로그 처리]]<code java>
// ClientHttpRequestInterceptor 인터페이스를 로깅을 남기게 구현해서 넣어주면 된다.

RestTemplate restTemplate = new RestTemplate();
restTemplate.setRequestFactory(new BufferingClientHttpRequestFactory(new SimpleClientHttpRequestFactory())); // body 스트림을 소모해버리지 않게 복제
restTemplate.setInterceptors(Lists.newArrayList(new RestTemplateLoggingInterceptor())); // RestTemplateLoggingInterceptor는 로그를 남기는 구현. body를 읽어버림.
</code>

===== SpringBoot =====
  * with [[springframework:springboot|SpringBoot]]
  * ''org.springframework.boot.autoconfigure.web.client.RestTemplateAutoConfiguration''
  * ''RestTemplateBuilder'' 가 존재하지 않을 경우 생성해준다.
  * ''RestTemplate'' 자체는 생성해주지 않고 Builder 만 만들어준다.
  * ''RestTemplateCustomizer'', ''RestTemplateRequestCustomizer'' Bean 들을 통해 조정해준다.

<code java>
@Bean
public RestTemplate restTemplate(RestTemplateBuilder restTemplateBuilder) {
    return restTemplateBuilder
            .requestFactory(() -> new BufferingClientHttpRequestFactory(new SimpleClientHttpRequestFactory()))
            .setConnectTimeout(Duration.ofMillis(5000)) // connection-timeout
            .setReadTimeout(Duration.ofMillis(5000)) // read-timeout
            .additionalMessageConverters(new StringHttpMessageConverter(Charset.forName("UTF-8")))
            .build();
}
</code>

===== 참조 =====
  * [[https://www.baeldung.com/spring-resttemplate-logging|Spring RestTemplate Request/Response Logging | Baeldung]]
  * [[https://enterkey.tistory.com/275|Spring에서 RestTemplate을 사용하여 REST 기반 서비스 요청과 테스트하기 - Hello World]]
  * [[https://luvstudy.tistory.com/78|RestTemplate 응답 log 확인하기]]
  * [[https://reflectoring.io/spring-resttemplate/|Complete Guide to Spring RestTemplate]]