I get that Feign is declarative and hence it abstracts out a lot of things for the developer. But, when should one choose one over the other? Though feign is declarative, it has serious problems with oAuth. What are some of the considerations in using RestTemplate over Feign
Feign allows you to abstract the mechanics of calling a REST service. Once you configure and annotate the Feign interface, you can call a REST service by making a simple Java function call. The actual implementation of making a REST call is handled at runtime by Feign. This means that the implementation can be configured without changing your business logic code.
By just changing the Feign configuration in Java or using properties you can add encoding/decoding, logging, and change the REST call implementation library. All this is done through configuration only, while the business logic that calls the service remains unchanged.
Since Feign uses standard Java interfaces, it's also easy to mock them during unit tests.
There are certain advantages.
1.URLs are not hardcoded.
2.you don't have to write unit test cases for feign as there is no code to test however you have to write integration tests.
3.we can use Eureka Client ID instead of the URL.
4.Feign handled the actual code.
5.Feign integrates with Ribbon and Eureka Automatically.
6.Feign provides a very easy way to call RESTful services.
One of the advantages of using Feign over RestTemplate is that, we do not need to write any implementation to call the other services. So there is no
need to write any unit test as there is no code to test in the first place. However, it is advised that we write Integration tests.
Using Feign-clients over rest-templates has number of advantages. I will list down those below.
The developer need not worry about the implementation. Just to create abstract Feign interface and few annotations - declarative
principle. (If you want customized configuration, then it will hold
some code)
With Spring Cloud Eureka, Ribbon client-side load-balancer will be equipped with Feign client.
No need to worry about the unit test, because there is no implementation from you to test. (Arguable)
Supports Feign annotations and JAX-RS annotations.
Highly compatible and easily configurable with Spring Cloud (Specially with Eureka server registry)
Allows Feign client configuration via #Configuration class or application properties.
Allows us to add interceptors. (Add interceptors via #Configuration or application properties. Alternatively can use
Spring Cloud provided interceptors as well. Example -
BasicAuthRequestInterceptor)
Hystrix support for fall-back mechanism.
Logging
Error handling
Feign is a good choice, If you are fascinated with JPA and the way how it resolves your queries, then Feign is the tool for you. Feign will handle your server requests perfectly fine.
RestTemplate is used for making the synchronous call. When using RestTemplate, the URL parameter is constructed programmatically, and data is sent across to the other service. In more complex scenarios, we will have to get to the details of the HTTP APIs provided by RestTemplate or even to APIs at a much lower level.
Feign is a Spring Cloud Netflix library for providing a higher level of abstraction over REST-based service calls. Spring Cloud Feign works on a declarative principle. When using Feign, we write declarative REST service interfaces at the client, and use those interfaces to program the client. The developer need not worry about the implementation ...
Advantages of using Feign over RestTemplate:
Declarative approach: Feign provides a more declarative approach to define and use REST API clients, which can make the code more readable and easier to maintain.
Integrated with Eureka: Feign is integrated with Netflix Eureka for service discovery, making it easier to build and consume APIs in a microservices architecture.
Better error handling: Feign provides better error handling, including support for custom error handling and retries.
Support for multiple encodings: Feign supports multiple encoding types, including JSON, XML, and form data, while RestTemplate only supports JSON and XML.
Disadvantages of using Feign over RestTemplate:
Limited flexibility: Feign provides a more opinionated approach to defining and using REST API clients, which may limit flexibility in certain situations.
Limited control over HTTP request and response: Feign abstracts away some of the low-level details of the HTTP request and response, which can make it harder to control and customize these details if needed.
Lack of official support: Feign is not an officially supported library from Spring, which may be a consideration for some developers or organizations.
Related
which is better alternative for calling REST endpoint in springboot application, calling REST endpoints using WebClient or calling REST endpoints using RestTemplate ?
Spring’s documentation recommends using WebClient, but that’s only a valid recommendation for reactive apps. If you aren’t writing a reactive app, use OpenFeign instead. Like anything else in software, it fits well for some cases, but might complicate things for others. Choosing WebClient to implement the REST endpoint calls is strongly coupled to making your app reactive
RestTemplate gives many advantages if you are using it from within Springboot application, i.e. in your server side to another part of your own app - sort of like an internal call. Because the RestTemplate "knows" all your entities and beans and so if you need to send over or receive an object which is known within your springboot application RestTemplate can map them automatically which is a very nice advantage. If you sending a request to some third party api and do not pass or receive your known entities RestTemplate is still a valid option but it just becomes just another Http client. Its just simply there as part of Springboot provided tools. But in this case you may use any other client as well.
I want to consume a couple of rest services. Before I have used RestTemplate, but now I want to know What is main diffrences of SpringBoot FeignClient and WebClient?
when they should be used?
To be able to answer “when” one needs to understand the capabilities of each.
Spring WebClient is a non-blocking reactive client to make HTTP requests. Hence if you intend to use Spring Reactive Stream API to stream data asynchronously then this is the way to go. Think event-driven architecture. WebClient is part of the Spring WebFlux library.
[Feign]3 is a declarative REST library that uses annotations based architecture with thread-per-request model. This means that the thread will block until the feign client receives the response. The problem with the blocking code is it must wait until the consuming thread completes, hence think memory and CPU cycles.
So use Spring WebClient when needing non-blocking HTTP requests otherwise Feign due to simple usage model.
(Note: There is no reason as to why one cannot use WebClient for blocking operations but Feign is more mature and it’s annotation based model makes it easier)
The main difference is that WebClient supports Reactive calls.
You can achieve that with 3rd party feign clients like https://github.com/Playtika/feign-reactive but basically for a reactive way you should consider using WebClient with some neat async connector like Jetty. On the other hand, If you want a blocking way with minimal hassle then Feign could be your best choice.
WebClient is a non-blocking reactive.
Feign is blocking.
I'm developing a reactive service and preparing to use the WebClient to exchange with HTTP APIs,but the service is not in a reactive web stack so how can I use it(WebClient) without depending on Webflux or is there any alternative reactive HTTP client?
Thanks in advance.
I am not sure if I get your question correct: You want to use an inherently reactive class without the reactive lib in which it is contained?
As you can see via the link you put in your question, the WebClient is part of spring-webflux and depends e.g. on reactor.core.publisher.Mono which resides in compile("io.projectreactor:reactor-core"). I can not imagine any scenario in which this WebClient would work or make any sense as you've asked "without depending on Webflux".
Other reactive HTTP clients are:
RxHttpClient
Java HTTP Client introduced in Java 11
May be you could elaborate a little bit more on your needs, why you won't rely on WebFlux or why you want to use a reactive client in a non-reactive stack.
Is it possible to configure Feign Client in other way, instead of annotations ? I am asking this, because I am trying to separate my business logic and infrastructure in to different layers.
We have developed a software proxy based on spring boot and zuul, that is meant to govern services within our integration layer. We do not own the systems consuming the various services, nor do we own the actual services themselves. The services are SOAP based webservices at present. We make use of pre, post , error and route filters. Validations are database driven, including which client is allowed to call what webservice. All service definitions reside in the database (request endpoint, request xsd, response xsd, which clients are allowed to invoke, etc.).
The aim now is to add hystrix commands to handle service failures, as well as a hystrix dashboard.
The standard way to use hystrix commands involves annotating service methods with javanica. Is there a way to dynamically declare/register hystrix commands for these webservices at runtime after reading the configurations from the database? The hystrix interception will need to happen based on the multiple webservice endpoints being invoked from a single point.
Hoping this is achievable ...if not, I would really appreciate any alternative proposals for how hystrix commands could be declared in this way.
Thanks!
You're saying that you are already using Spring Boot and Zuul. How are you mapping the routes? Through the url param? Then you'll have to enroll your own. But if you define the routes as ribbon services and pass the routes as ribbon servers as described in the documentation you will get Hystrix for free.