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What is the working principle of Feign? I believe many inexperienced people don't know what to do about it. Therefore, this paper summarizes the causes and solutions of the problem. Through this article, I hope you can solve this problem.

How Feign works

The @ EnableFeignClients annotation has been added to the main program entry to enable FeignClient scan loading processing. According to the FeignClient development specification, define the interface and annotate the @ FeignClientd.

When the program starts, it scans the package, scans all @ FeignClients annotated classes, and injects this information into the Spring IOC container. When the method in the defined Feign interface is called, the concrete RequestTemplate is generated through the JDK proxy. When a proxy is generated, Feign creates a RequestTemplate for each interface method. When generating a proxy, Feign will create a RequestTemplate object for each interface method, which encapsulates all the information needed for the HTTP request, such as the request parameter name, request method and other information is determined in this process.

Then RequestTemplate generates Request, and then hands the Request to Client for processing. Here, Client can be the native HttpClient of JDK or OKhttp. Finally, Client is encapsulated into the LoadBalanceClient class, which combines the calls between Ribbon load balancer server services.

After reading the above, have you mastered how Feign works? If you want to learn more skills or want to know more about it, you are welcome to follow the industry information channel, thank you for reading!

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