@FeignClient注解中属性contextId的使用说明 @FeignClient注解中属性contextId的

一、概述
二、解决方案

2.1 方案1
2.2 方案2

三、源代码分析

相关代码1
相关代码2

一、概述如果我们使用Feign定义了两个接口，但是目标服务是同一个，那么在SpringBoot启动时就会遇到一个问题：

Description:
The bean 'xxxxxxxx.FeignClientSpecification', defined in null, could not be registered. A bean with that name has already been defined in null and overriding is disabled.
Action:
Consider renaming one of the beans or enabling overriding by setting spring.main.allow-bean-definition-overriding=true

二、解决方案
2.1 方案1
修改yml配置：spring.main.allow-bean-definition-overriding=true

spring:main:allow-bean-definition-overriding: true

2.2 方案2
在每个Feign的接口中，在注解上加 contextId属性
contextId在Feign Client的作用是在注册Feign Client Configuration的时候需要一个名称，名称是通过getClientName方法获取的

@FeignClient(name = "sale-service",contextId= "saleservice1") public interface saleClient{ @RequestMapping(value = "https://www.it610.com/sale/add", method = RequestMethod.GET) String add(@RequestParam("saleNum") String queryStr); }

备注：contextId= "名称" 中的名称，不能用“_”会报错，可以用“-”

三、源代码分析

包名：spring-cloud-openfeign-core-2.2.5.RELEASE.jar
类路径：org.springframework.cloud.openfeign.FeignClientsRegistrar

相关代码1

private void registerFeignClient(BeanDefinitionRegistry registry, AnnotationMetadata annotationMetadata, Map attributes) {String className = annotationMetadata.getClassName(); BeanDefinitionBuilder definition = BeanDefinitionBuilder.genericBeanDefinition(FeignClientFactoryBean.class); this.validate(attributes); definition.addPropertyValue("url", this.getUrl(attributes)); definition.addPropertyValue("path", this.getPath(attributes)); String name = this.getName(attributes); definition.addPropertyValue("name", name); String contextId = this.getContextId(attributes); definition.addPropertyValue("contextId", contextId); definition.addPropertyValue("type", className); definition.addPropertyValue("decode404", attributes.get("decode404")); definition.addPropertyValue("fallback", attributes.get("fallback")); definition.addPropertyValue("fallbackFactory", attributes.get("fallbackFactory")); definition.setAutowireMode(2); String alias = contextId + "FeignClient"; AbstractBeanDefinition beanDefinition = definition.getBeanDefinition(); beanDefinition.setAttribute("factoryBeanObjectType", className); boolean primary = (Boolean)attributes.get("primary"); beanDefinition.setPrimary(primary); String qualifier = this.getQualifier(attributes); if (StringUtils.hasText(qualifier)) {alias = qualifier; } BeanDefinitionHolder holder = new BeanDefinitionHolder(beanDefinition, className, new String[]{alias}); BeanDefinitionReaderUtils.registerBeanDefinition(holder, registry); }

代码截图：

文章图片

相关代码2
可以看到, name应该是从注解中的属性取值来的, 再看看getClientName()方法.

private String getClientName(Map client) {if (client == null) {return null; } else {String value = https://www.it610.com/article/(String)client.get("contextId"); if (!StringUtils.hasText(value)) {value = https://www.it610.com/article/(String)client.get("value"); } if (!StringUtils.hasText(value)) {value = https://www.it610.com/article/(String)client.get("name"); } if (!StringUtils.hasText(value)) {value = https://www.it610.com/article/(String)client.get("serviceId"); } if (StringUtils.hasText(value)) {return value; } else {throw new IllegalStateException("Either 'name' or 'value' must be provided in @" + FeignClient.class.getSimpleName()); }}}

代码截图：