sentinel feign 源码分析

sentinal 对feign的支持需要设置feign.sentinel.enabled=true，这个要求可以从代码SentinelFeignAutoConfiguration看到

@Configuration
@ConditionalOnClass({ SphU.class, Feign.class })
public class SentinelFeignAutoConfiguration {
	@Bean
	@Scope("prototype") 
	@ConditionalOnMissingBean
	@ConditionalOnProperty(name = "feign.sentinel.enabled")
	public Feign.Builder feignSentinelBuilder() {
		return SentinelFeign.builder();
	}

}

feign默认使用hystrix，如何替换为sentinel的关键代码是自定义Feign.Builder，feign 本身有如下代码：

class HystrixTargeter implements Targeter {

	@Override
	public  T target(FeignClientFactoryBean factory, Feign.Builder feign, FeignContext context,
						Target.HardCodedTarget target) {
		if (!(feign instanceof feign.hystrix.HystrixFeign.Builder)) {
			return feign.target(target);
		}
		

但不是hystrix.HystrixFeign.Builder，调用自定义的target函数，在sentinel模式，最终转为调用
class SentinelFeign 内置public static final class Builder的public Feign build()函数。

调用feign.builder bean的关键函数如下（feign 代码）

class FeignClientFactoryBean implements FactoryBean