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前提:本案例是基于 spring boot 2.7.5,spring cloud 3.1.6,其余版本可能会有些差异!
对于“Did you forget to include spring-cloud-starter-loadbalancer?”报错的起因,网上有一大堆博客供大家参考,这里我给大家提供一种新的参考。
先说论断:
报“Did you forget to include spring-cloud-starter-loadbalancer”的起因之一是可能没有引入 "spring-cloud-loadbalancer" pom 依赖。
spring boot 启动时执行 org.springframework.cloud.openfeign.FeignClientFactoryBean.loadBalance() 时,getOptional() 范畴为 null,而后抛出异样“Caused by: java.lang.IllegalStateException: No Feign Client for loadBalancing defined. Did you forget to include spring-cloud-starter-loadbalancer?”;
protected <T> T loadBalance(Feign.Builder builder, FeignContext context, HardCodedTarget<T> target) {
// 返回为 null
Client client = getOptional(context, Client.class);
if (client != null) {builder.client(client);
applyBuildCustomizers(context, builder);
Targeter targeter = get(context, Targeter.class);
return targeter.target(this, builder, context, target);
}
// 到这里抛出异样
throw new IllegalStateException("No Feign Client for loadBalancing defined. Did you forget to include spring-cloud-starter-loadbalancer?");
}
也就是说,DefaultListableBeanFactory 外面没有类型为“feign.Client”的 bean; 上面的图是以后我的项目里所有“feign.Client”的实现类:
图一
好的,我就拿 Default 类做为入口剖析一波:
@Configuration(proxyBeanMethods = false)
@EnableConfigurationProperties(LoadBalancerClientsProperties.class)
class DefaultFeignLoadBalancerConfiguration {
@Bean
@ConditionalOnMissingBean
@Conditional(OnRetryNotEnabledCondition.class)
public Client feignClient(LoadBalancerClient loadBalancerClient,
LoadBalancerClientFactory loadBalancerClientFactory) {return new FeignBlockingLoadBalancerClient(new Client.Default(null, null), loadBalancerClient,
loadBalancerClientFactory);
}
}
也就是说,在 DefaultFeignLoadBalancerConfiguration 类中会创立 FeignBlockingLoadBalancerClient 实例,而这个 FeignBlockingLoadBalancerClient
public class FeignBlockingLoadBalancerClient implements Client {private static final Log LOG = LogFactory.getLog(FeignBlockingLoadBalancerClient.class);
private final Client delegate;
private final LoadBalancerClient loadBalancerClient;
private final LoadBalancerClientFactory loadBalancerClientFactory;
}
同样也是 FeignClient 的实现类。而后咱们接着往下看,发现
@ConditionalOnClass(Feign.class)
@ConditionalOnBean({LoadBalancerClient.class, LoadBalancerClientFactory.class})
@AutoConfigureBefore(FeignAutoConfiguration.class)
@AutoConfigureAfter({BlockingLoadBalancerClientAutoConfiguration.class, LoadBalancerAutoConfiguration.class})
@EnableConfigurationProperties(FeignHttpClientProperties.class)
@Configuration(proxyBeanMethods = false)
// Order is important here, last should be the default, first should be optional
// see
// https://github.com/spring-cloud/spring-cloud-netflix/issues/2086#issuecomment-316281653
@Import({ HttpClientFeignLoadBalancerConfiguration.class, OkHttpFeignLoadBalancerConfiguration.class,
HttpClient5FeignLoadBalancerConfiguration.class, DefaultFeignLoadBalancerConfiguration.class })
public class FeignLoadBalancerAutoConfiguration {}
FeignLoadBalancerAutoConfiguration 主动配置类,引入了 DefaultFeignLoadBalancerConfiguration 主动配置类,失常状况下,我的项目启动时,FeignBlockingLoadBalancerClient 会被创立,然而因为 FeignBlockingLoadBalancerClient 的构造方法会依赖 LoadBalancerClientFactory,而 LoadBalancerClientFactory 存在“spring-cloud-loadbalancer”jar 包中,如果没有引入这个 jar, 我的项目启动时,会创立 FeignBlockingLoadBalancerClient 失败,最终会导致 DefaultListableBeanFactory 外面没有类型为“feign.Client”的 bean 实例,所以咱们启动我的项目时会报错“No Feign Client for loadBalancing defined. Did you forget to include spring-cloud-starter-loadbalancer?”!