WebClient vs RestTemplate
SpringReactive ProgrammingResttemplateWeb ClientSpring Problem Overview
As per spring 5:
>WebClient is an interface representing the main entry point for performing web requests. > >It has been created as a part of the Spring Web Reactive module and will be replacing the classic RestTemplate in these scenarios. The new client is a reactive, non-blocking solution that works over the HTTP/1.1 protocol
Does that mean, we need to recode for the old applications using RestTemplate if we want to upgrade to Spring 5?
Or there is some workaround to work with RestTemplate in Spring 5?
Spring Solutions
Solution 1 - Spring
No, RestTemplate will continue to exist (at least for now). You don't have to replace it with WebClient.
One of the main differences is RestTemplate is synchronous and blocking i.e. when you do a rest call you need to wait till the response comes back to proceed further.
But WebClient is complete opposite of this. The caller need not wait till response comes back. Instead he will be notified when there is a response.
If you need such a functionality, then yes you need to replace your Resttemplate with WebClient.
You can in fact achieve Rest template like synchronous processing in webclient using .block(). But the other way is not possible.
EDIT:
RestTemplate will be deprecated in a future version(> 5.0) and will not have major new features added going forward
Solution 2 - Spring
According to the Java Doc the RestTemplate will be in maintenance mode. Spring team advise to use the WebClient if possible:
> NOTE: As of 5.0, the non-blocking, reactive > org.springframework.web.reactive.client.WebClient offers a modern > alternative to the RestTemplate with efficient support for both sync > and async, as well as streaming scenarios. The RestTemplate will be > deprecated in a future version and will not have major new features > added going forward.
Solution 3 - Spring
WebClient is Non-Blocking Client, RestTemplate is Blocking Client.
For a long time, spring serves as a web customer. Under the hood, RestTemplate uses the Java API API, which is based on the subject model.This means that the matter will be blocked until the client receives a response. The problem with the blockage code is due to the existence of any string of memory and cpu cycles. Let us consider a lot of applications that are waiting for low services that are needed to produce the result.Sooner or later, requests for the results are collected. As a result, the program creates many issues, which result in depletion of a pool of thread or occupying all of the available memory. We can also experience performance performance due to the cpu switching.
Solution 4 - Spring
WebClient supports asynchronous as well as synchronous calls. RestTemplate supports only synchronous calls. No changes are required in old code even if the RestTemplate is depracated(as long as you don't need asynchronous behaviour)
Solution 5 - Spring
RestTemplate is not really deprecated. But it will not be evolved in the future. So sticking to RestTemplate is perfectly valid if it does what you need.
Another way to put that is that if you need specific usage patterns like streaming, scatter/gatter, or custom timeouts, this won't be covered by RestTemplate and you need to use WebClient instead.
Now using WebClient in a blocking application is fine too. Using block() shouldn't hurt there and Spring MVC controller does partially support reactive return types.