前言

前段时间业务部门有这么一个业务场景，他们本人微服务注册核心是用eureka，他们有一些服务接口要调用兄弟部门的接口，他们定了一个服务调用计划，业务部门间接把他们服务注册到兄弟部门的注册核心，而后走rpc调用，兄弟部门注册核心是用nacos。

一开始业务部门研发间接在在pom.xml这么引入

    <dependency>            <groupId>org.springframework.cloud</groupId>            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>        </dependency>        <dependency>            <groupId>com.alibaba.cloud</groupId>            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>        </dependency>

而后我的项目启动报了如下错

Field registration in org.springframework.cloud.client.serviceregistry.ServiceRegistryAutoConfiguration$ServiceRegistryEndpointConfiguration required a single bean, but 2 were found:    - nacosRegistration: defined by method 'nacosRegistration' in class path resource [com/alibaba/cloud/nacos/NacosDiscoveryAutoConfiguration.class]    - eurekaRegistration: defined in BeanDefinition defined in class path resource [org/springframework/cloud/netflix/eureka/EurekaClientAutoConfiguration$RefreshableEurekaClientConfiguration.class]

业务部门是这么解决的，每次发版时，如果是要纳入兄弟部门的微服务，他们就先手动正文掉eureka的客户端依赖。

起初业务部门就向咱们部门提了一个需要，pom引入多个注册核心客户端，我的项目也要能失常启动

需要剖析

从我的项目异样剖析

Field registration in org.springframework.cloud.client.serviceregistry.ServiceRegistryAutoConfiguration$ServiceRegistryEndpointConfiguration required a single bean, but 2 were found:    - nacosRegistration: defined by method 'nacosRegistration' in class path resource [com/alibaba/cloud/nacos/NacosDiscoveryAutoConfiguration.class]    - eurekaRegistration: defined in BeanDefinition defined in class path resource [org/springframework/cloud/netflix/eureka/EurekaClientAutoConfiguration$RefreshableEurekaClientConfiguration.class]

能够看出springcloud默认的服务注册是只反对单服务注册核心。因而咱们解决的计划要么扩大springcloud源码，让它反对多注册核心，要么就是通知springcloud当存在多种注册核心客户端时，抉择一种咱们想要的注册核心客户端

本文就选实现绝对容易的计划，当存在多种注册核心客户端时，咱们通知springcloud，咱们想选的注册核心

实现计划

目前根本只有和springboot集成的开源我的项目，能够说大部分应用了主动拆卸，因而咱们的解决思路也是从主动拆卸搞起

前置常识

protected AutoConfigurationEntry getAutoConfigurationEntry(AutoConfigurationMetadata autoConfigurationMetadata,            AnnotationMetadata annotationMetadata) {        if (!isEnabled(annotationMetadata)) {            return EMPTY_ENTRY;        }        AnnotationAttributes attributes = getAttributes(annotationMetadata);        List<String> configurations = getCandidateConfigurations(annotationMetadata, attributes);        configurations = removeDuplicates(configurations);        Set<String> exclusions = getExclusions(annotationMetadata, attributes);        checkExcludedClasses(configurations, exclusions);        configurations.removeAll(exclusions);        configurations = filter(configurations, autoConfigurationMetadata);        fireAutoConfigurationImportEvents(configurations, exclusions);        return new AutoConfigurationEntry(configurations, exclusions);    }
    private List<String> filter(List<String> configurations, AutoConfigurationMetadata autoConfigurationMetadata) {        long startTime = System.nanoTime();        String[] candidates = StringUtils.toStringArray(configurations);        boolean[] skip = new boolean[candidates.length];        boolean skipped = false;        for (AutoConfigurationImportFilter filter : getAutoConfigurationImportFilters()) {            invokeAwareMethods(filter);            boolean[] match = filter.match(candidates, autoConfigurationMetadata);            for (int i = 0; i < match.length; i++) {                if (!match[i]) {                    skip[i] = true;                    candidates[i] = null;                    skipped = true;                }            }        }        if (!skipped) {            return configurations;        }        List<String> result = new ArrayList<>(candidates.length);        for (int i = 0; i < candidates.length; i++) {            if (!skip[i]) {                result.add(candidates[i]);            }        }        if (logger.isTraceEnabled()) {            int numberFiltered = configurations.size() - result.size();            logger.trace("Filtered " + numberFiltered + " auto configuration class in "                    + TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startTime) + " ms");        }        return new ArrayList<>(result);    }

这两个代码片段，一个是主动拆卸的代码片段，一个是过滤候选哪些不须要进行主动拆卸

计划一：利用AutoConfigurationImportFilter + 自定义标识

实现的原理： 当自定的标识为nacos，通过AutoConfigurationImportFilter排除eureka的主动拆卸；反之排除nacos的主动拆卸

1、外围实现
public class RegistrationCenterAutoConfigurationImportFilter implements AutoConfigurationImportFilter, EnvironmentAware {    private Environment environment;    /**     * 因为springboot主动拆卸，默认会把spring.factories的配置的类先全副加载到候选汇合中，     * 因而当咱们代码配置启用nacos，则需把其余注册核心，比方eureka先从候选汇合排除     * @param autoConfigurationClasses     * @param autoConfigurationMetadata     * @return     */    @Override    public boolean[] match(String[] autoConfigurationClasses, AutoConfigurationMetadata autoConfigurationMetadata) {        Set<String> activeProfiles = Arrays.stream(environment.getActiveProfiles()).collect(Collectors.toSet());        if(activeProfiles.contains(RegistrationCenterConstants.ACTIVE_PROFILE_NACOS)){            return excludeMissMatchRegistrationAutoConfiguration(autoConfigurationClasses, new String[]{RegistrationCenterConstants.EUREKA_AUTO_CONFIGURATION_CLASSES});        }else if (activeProfiles.contains(RegistrationCenterConstants.ACTIVE_PROFILE_EUREKA)){            return excludeMissMatchRegistrationAutoConfiguration(autoConfigurationClasses, new String[]{RegistrationCenterConstants.NACOS_DISCOVERY_AUTO_CONFIGURATION_CLASSES,RegistrationCenterConstants.NACOS_DISCOVERY_CLIENT_AUTO_CONFIGURATION_CLASSES,RegistrationCenterConstants.NACOS_DISCOVERY_ENDPOINT_AUTO_CONFIGURATION_CLASSES});        }        return new boolean[0];    }    private boolean[] excludeMissMatchRegistrationAutoConfiguration(String[] autoConfigurationClasses,String[] needExcludeRegistrationAutoConfigurationClasse) {        Map<String,Boolean> needExcludeRegistrationAutoConfigurationClzMap = initNeedExcludeRegistrationAutoConfigurationClzMap(needExcludeRegistrationAutoConfigurationClasse);        boolean[] match = new boolean[autoConfigurationClasses.length];        for (int i = 0; i < autoConfigurationClasses.length; i++) {            String autoConfigurationClz = autoConfigurationClasses[i];            match[i] = !needExcludeRegistrationAutoConfigurationClzMap.containsKey(autoConfigurationClz);        }        return match;    }    private Map<String,Boolean> initNeedExcludeRegistrationAutoConfigurationClzMap(String[] needExcludeRegistrationAutoConfigurationClasse){        Map<String,Boolean> needExcludeRegistrationAutoConfigurationClzMap = new HashMap<>();        for (String needExcludeRegistrationAutoConfigurationClz : needExcludeRegistrationAutoConfigurationClasse) {            needExcludeRegistrationAutoConfigurationClzMap.put(needExcludeRegistrationAutoConfigurationClz,false);        }        return needExcludeRegistrationAutoConfigurationClzMap;    }    @Override    public void setEnvironment(Environment environment) {         this.environment = environment;    }}
2、配置spring.factories
org.springframework.boot.autoconfigure.AutoConfigurationImportFilter=\com.github.lybgeek.registration.autoconfigure.filter.RegistrationCenterAutoConfigurationImportFilter

计划二：利用application-${指定注册核心标识} + spring.profiles.active

1、在要激活的注册核心的文件禁用其余注册核心客户端

比方appliication-nacos.yml禁用eureka

spring:  cloud:    nacos:      discovery:        server-addr: localhost:8848# 禁用eureka客户端主动注册eureka:  client:    enabled: false
2、激活想要注册的注册核心
spring:  application:    name: springboot-registration-client  profiles:    active: nacos

总结

这两种计划集体是比拟举荐计划二，因为改变最小。计划一比拟实用于没有提供是否须要激活注册核心开关的注册核心。其次如果咱们要排除某些开源主动拆卸的组件，也能够思考用计划一

demo链接

https://github.com/lyb-geek/springboot-learning/tree/master/springboot-registrationcenter-switch