RestTemplate 및 웹클라이언트: RESTful 웹 개발의 미래

RestTemplate은 사라지는 것이 아니라 스프링 5에서 유지 관리 모드로 전환되며, 스프링 6에서는 더 이상 사용되지 않거나 제거될 계획이 없습니다.

### 스프링 6의 RestTemplate과 웹클라이언트에 대한 진실
* 🚫 일반적인 생각과는 달리 **RestTemplate은 더 이상 사용되지 않으며 적어도 Spring 7.0까지는 지원될 예정**입니다.
* 🔄 RestTemplate은 **Spring 5.0 이후 유지 관리 모드**로 전환되었으며 새로운 기능은 계획되어 있지만 **기존의 동기식 Spring MVC 개발을 위한 실행 가능한 옵션**으로 남아 있습니다.
* 🕵 RestTemplate이 사라진다는 오해는 여러 문서와 블로그에서 **사용 중단을 암시**하는 내용에서 비롯된 것일 수 있습니다.
* 📝 2020년 2월 12일 커밋에서 **RestTemplate의 사용 중단을 알리는 공식 소스**가 슬그머니 삭제되었습니다.
* 🌐 WebClient는 최신 API 소비에 권장되며 **동기, 비동기 및 비동기 스트리밍 모드**를 지원하지만 기존의 동기식 사용 사례에는 큰 성능 이점을 제공하지 못할 수 있습니다.
* 📈 Spring 6에 새로 도입된 **HTTP 인터페이스**를 사용하면 Spring 데이터 JPA 리포지토리와 유사하게 주석을 사용하여 인터페이스를 정의함으로써 **API 클라이언트 코드를 자동으로 생성**할 수 있습니다.
* ✅ 팀에서 **RestTemplate과 WebClient를 모두 사용**해보고 사용 사례에 가장 적합한 것을 선택하는 것이 좋습니다.
* 🛠 ️ 라이브 코딩 세션에서는 **Spring 6에서 HTTP 인터페이스를 사용하는 방법**을 시연합니다.

In Spring 3.0, one of the technologies that has been receiving a lot of love is RestTemplate. You are probably familiar with it. When we create a feature in a server program that calls another API, like an HTTP API, what do we usually use? Most of the time, we use RestTemplate. However, last week and even today in the cheerful Spring chatroom, I heard someone saying, Is RestTemplate going to disappear? They mentioned this kind of thing. Last week, someone asked me a question saying that RestTemplate is going to be removed, so don't use it, use WebClient instead. But WebClient doesn't come out by just adding the Spring Web module to the project, so you need to add the Spring WebFlux module.

You need to add it. If it's Spring Boot, you need to add the one called WebFlux starter to be able to use a web client. Now, what he's saying is, I just want to do traditional servlet-based web development with Spring MVC, but since the WebClientRestTemplate is gone, I'm afraid to use it. And then they say to use WebClient instead, but when I try to use WebClient, the entire Spring WebFlux module comes in, along with a lot of libraries. So, it feels a bit burdensome, and I'm wondering what to do. He asked this kind of question. So, what do you think? The topic of WebClient OpenFeign also came up. Now, let me talk about the history and the current situation, and many people, not only Spring developers in Korea, but also many people.

There is a misunderstanding even among many people overseas. Whether there is a problem with this or because the complete technology for this has now emerged, it is not recommended to use it anymore. Next, this will be completely removed around the next version or the version after that. Don't use it. This is about not using it. The deprecated annotation that says not to use it is already included. What do you think in general documents? For example, if I use WebFlux, then you must use a web client. But I don't want to develop in a reactive way like WebFlux. I just want to do traditional Spring MVC development. Is it not allowed to use RestTemplate here from Spring 5? This was mentioned from Spring 5, but what about now, with Spring 6? Let's talk about it.

I wanted to say, so when I heard that story, I thought it was a bit strange. They are using RestTemplate well, so why is it disappearing? Why did you think that? Where did you hear that? Who is spreading fake news, rumors, or something like that? So, I got curious and searched on Google. After searching, I found a lot of results. Many documents containing that information appeared, and they were quite famous and authoritative sources. It seems like it even appears in search results from places like Melden. So, I guess that's where this information is coming from. Therefore, I went in and looked at the document. Where is it? Since when has it been saying that starting from Spring 5 and with the emergence of the web client, this will no longer be available, so do not use it anymore. Such a statement is written on a seemingly innocent blog. Also, now that I've looked into it.

Dodo of Linkin wrote an article, and here, maybe here, it's all in the title. So, what's next? I don't know what he's talking about, but why does this come up? Why do they keep talking about this? So, what on earth is this about? Oh, it's not mentioned here. Why did the search come up? Well, it's probably because of introducing the WebClient and such. So, now we need to find the exact source. If it's in the official document, Spring Reference Manual, or the RestTemplate City Predicate, it will have a source code diffication attached. And since it difricates on JavaDoc Connect, it will probably be removed around the next version. Don't use it. That's the kind of talk that should be in there. So, I looked it up. I downloaded the Spring source code, the latest Spring source code, version 6.0.6, now.

When you go in and look, the explanation is quite lengthy, but the key part is probably the section labeled Notes below. So, from 5.0, this class rest template goes into the maintenance board and only does maintenance. What I mean is, in case there are serious security or significant issues, you can fix bugs of that level, but there are no plans to add new features or further develop here. And now, the following discussion is to consider using it for web clients. It supports much more modern APIs. Furthermore, it supports three scenarios: sync, async, and sync streaming modes. It covers all the way to async streaming, so it's really great. Use this. This is how it's being discussed. So, the latter part is similar to what I've heard.

Correct, but I can't find the word difricated anywhere here. Does it exist? Let me search just in case. Deprecated is here, which means the execute method is deprecated in Spring. It doesn't mean this class is deprecated, so in conclusion, RestTemplate will not disappear, it has not been deprecated. This means it will likely still be alive at least until Spring 7.0 comes out. Usually, once a major version goes up, they mark it as deprecated, and it tends to disappear around the time the next major version comes out. So, since it hasn't been attached up to 6.0, it will naturally not disappear in 6.0, and probably not in 7.0 either. When we get there, we might deprecate it, but that's uncertain. So, why do people say RestTemplate will disappear?

Because it might disappear when I do it, I'm scared of this, so I can't write it. I should use a web client, but now I like web flight, and I was very interested in developing with WebFlux or reactive, so I looked into this in detail. It's good, but in the traditional way of web development, just using it as a Spring MVC synchronous method, there are not many advantages to using a web client. Even if the WebClient section runs asynchronously in terms of performance, it doesn't really speed up the overall performance. On the contrary, it just makes it a bit slower. The good thing is that the API is more modern, so if you just use it simply in the WebClient template, it's fine. But if you insert things like headers, you have to create a request entity and create headers.

Inserting it and the code is a bit, how should I say, messy, but these days, we continue writing in a format we like, chaining with dots, so that we can complete one task before the sentence ends. In that aspect, it's more convenient. Moreover, now it can be used in an asynchronous manner when transitioning to Flux later, so there are advantages in using the same method. So, you can use a web client if you want, but personally, I'm fine with just the traditional REST template. This is supported by Spring, of course, it hasn't been discontinued, and Spring Boot also supports it well. Basically, when using Spring Boot, you have the REST template registered by default, so you can just use it, which is quite convenient. But why are these kinds of discussions coming up now, I wonder.

Now, someone said something wrong, and it spread like that. I used to think that way, but when I traced it, I found that there was actually a mention in the Spring official documentation that the rest template is deprecated. What I discovered yesterday while tracing this was that... And, oh, what is new is that no new features will be added, it will enter maintenance mode. Although it says the same thing, it clearly indicates that it is deprecated. It's shocking. So, for those of you who see this, you might think, Oh, so the template is disappearing, and this could cause a big problem. Some may think, Well, we have to use WebClient then. Some might think, Well, until it really disappears, it's supported, so let's use it for now.

It will be there, and that's why those documents and blogs I found on Google search will be duplicated in templates. They will disappear in the future. Don't use them anymore. Such advice is starting to come out now. But the interesting thing is that on February 12, 2020, when you look at the computer, it has changed. How did it change? The content disappears. They sneakily removed it. What exactly happened in between? Oh, originally, I was going to duplicate and remove this, but my mind changed. Oh, this won't work. I have to leave it. It's too perfect. Even if I don't add any additional features, I have to maintain it. This is how developers bring changes in their mindset and sneakily make changes. If you want to know a bit about this, about commits, what is it usually for now to handle some issues.

Make corrections and add issue numbers, usually creating a commit log. So, if you open this on GitHub and track it like this, you can see that this commit was made to close the issue. By following the issue, you can see what discussions led to this decision. It turns out there wasn't much discussion. Rossen Stoyanchev and Brian Clozel, thanks to the code that Brian Clozel uploaded as a PR, it was included in the Spring Web Test project, and later when it merged into the Spring Core, the code written by Brian Clozel was included in the Spring Core framework. In fact, this person has been leading the Spring MVC project and Spring Web Flux practically after version 3.0. So, you can consider him as the lead role player. What did this person discuss about the issue?

It would be much better to just say it's in maintenance mode rather than saying it's now deprecated. That would be more helpful, and what's more important is that it's more accurate. Saying it's accurate means we didn't plan to deprecate it. We weren't planning to do that originally. We just pushed towards WebFlux with the release of Spring 5.0. We thought Reactor was great, we pushed hard on it, but it didn't really catch on. There weren't as many WebFlux users as we thought, and there were various reasons for that. Anyway, in my opinion, I don't think the Spring core developers working on the Spring web side were planning to get rid of it. That's how I express it. Hey, now we're all going to the reactive world, and from there.

Now, since the web client will be the main one, RestTemplate may disappear. So, I probably left a comment there, but that's not accurate. Explaining it like that won't be helpful. So, I changed it. So, I briefly mentioned the issue and changed the comment as before. It's already been three years since that, in 2020, February, not 2001, 2 or 3 years ago. But developers still believe in stories that spread from old memories. Since RestTemplate will be gone in the future, web clients must be used. So, please don't misunderstand. This is a very simple story, so I think we can finish here. So, in my opinion, about RestTemplate and web...

Clients, you must be curious about the pros and cons, when to use it, what is a better choice for the future, and so on. Let me confess a bit, and then in Spring 6, in Spring 5, there were two rest clients. Do you happen to know what they are? In Spring 6, there is a new rest client technology added. If anyone knows about it, please leave a comment in the chat. Now, here in the latest documentation for Spring 6.0, there are two options, and now a third one, the HTTP interface, has been added. I'm not sure if any of you have used openfeign-like libraries, or maybe in places like Android, this style of code is used a lot. It means just defining interfaces. When you use Spring Data JPA, you only create interfaces for the repository, right? Then the implementation for that is...

Dynamic automatically, now frameworks create many technologies like this are commonly used, and how it works is defined only by annotations. Similarly, just like that, if you create an interface with annotations for the client code that calls the API, all the client code that actually calls it is automatically generated. This technology has officially entered Spring 6. Therefore, it is called the HTTP interface. This is used a lot in Android. Anyway, the HTTP interface has been introduced, so let's take a look at roughly how the code looks when written with this. First of all, the West template does not disappear, so you can just use it comfortably. You can continue to use it as you like. While the client provides convenience, there are also inconveniences.

Yes, please try both of them, and if you use both of them in the team, it might be a bit, so choose one and use it. Now, I will try a simple live coding session. This is a new one.

RestTemplate은 스프링에서 제거되나요?

토비의 스프링 

스프링 개발에서 RestTemplate에서 WebClient로 전환하기

서버 프로그램에서 HTTP API를 호출하는 데 일반적으로 사용되는 RestTemplate이 WebClient를 위해 지원 중단될 것이라는 소문이 돌고 있습니다.

WebClient를 사용하려면 Spring WebFlux 모듈을 추가해야 하므로 기존 서블릿 기반 개발을 고수하려는 사람들에게는 부담스러울 수 있습니다.

신뢰할 수 있는 출처와 검색 결과에 근거한 정보임에도 불구하고, RestTemplate에서 WebClient로의 전환에 대한 소문은 Spring 개발자들 사이에서 혼란과 우려를 불러일으키고 있습니다.

Spring 프레임워크의 RestTemplate 클래스는 버전 6.

0에서 더 이상 사용되지 않으며 버전 7.

0에서도 사라지지 않을 것입니다.

이 클래스는 심각한 문제에 대한 유지 관리를 계속 받겠지만 새로운 기능은 추가되지 않을 것입니다.

웹 클라이언트에서 보다 최신 API를 제공하고 동기화, 비동기화 및 동기화 스트리밍 모드를 지원하는 WebClient와 함께 RestTemplate를 사용할지 여부에 대한 논의가 계속 진행 중입니다.

스프링 개발에서 REST 템플릿의 진화

REST 템플릿은 작업을 완료하는 데 편리하다는 이유로 선호되는 형식이었습니다.

그러나 Spring 공식 문서에서 더 이상 사용되지 않으며 새로운 기능이 추가되지 않고 유지 관리 모드로 전환됩니다.

이로 인해 REST 템플릿이 점차 단계적으로 폐지됨에 따라 WebClient로 전환하는 것에 대한 논의가 이루어지고 있습니다.

Spring 프레임워크 유지 관리 및 웹 클라이언트 전환에 대한 업데이트

처음에 Spring Web Test 프로젝트의 일부였던 Brian Clozel의 코드는 나중에 Spring Core 프레임워크에 통합되었으며, 그는 Spring MVC 프로젝트와 Spring Web Flux에서 주도적인 역할을 해왔습니다.

Spring Core 개발자들은 원래 WebFlux 프레임워크를 더 이상 사용하지 않을 계획이었지만, 그 채택이 제한적이기 때문에 이제 반응형 세계로 전환하고 있으며, 이는 향후 RestTemplate이 단계적으로 폐지될 수 있음을 시사합니다.

또한 이 토론에서는 이러한 변화가 즉각적으로 이루어지지는 않을 것이며, 이전 개발 관행에 대한 믿음이 여전히 남아 있음을 분명히 했습니다.

0에서는 인터페이스 어노테이션을 통해 클라이언트 코드를 자동으로 생성할 수 있는 새로운 HTTP 인터페이스가 휴식 클라이언트를 위한 세 번째 옵션으로 추가되었습니다.

Android에서 일반적으로 사용되는 이 기술은 편리함을 제공하지만 몇 가지 불편함을 초래할 수도 있습니다.

0에서 API를 호출할 때 West 템플릿과 같은 기존 rest 클라이언트 옵션과 함께 선택할 수 있습니다.