前言
前段时间业务部门有这么一个业务场景，他们自己微服务注册中心是用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方案，业务部门直接把他们服务注册到兄弟部门的注册中心，然后走rpc调用，兄弟部门注册中心是用nacos。
一开始业务部门研发直接在在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>
然后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，他们就先手动注释掉eureka的客户端依赖。
后来业务部门就向我们部门提了一个需求，pom引入多个注册中心客户端，项目也要能正常启动
需求分析
从项目异常分析
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]
可以看出springcloud默认的服务注册是只支持单服务注册中心。因此我们解决的方案要么扩展springcloud源码，让它支持多注册中心，要么就是告诉springcloud当存在多种注册中心客户端时，选择一种我们想要的注册中心客户端
本文就选实现相对容易的方案，当存在多种注册中心客户端时，我们告诉springcloud，我们想选的注册中心
实现方案
目前基本只要和springboot集成的开源项目，可以说大部分使用了自动装配，因此我们的解决思路也是从自动装配搞起
前置知识
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，一个是自动装配的代码片段，一个是过滤候选哪些不需要进行自动装配
方案一：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的自动装配；反之排除nacos的自动装配
1、核心实现
public class RegistrationCenterAutoConfigurationImportFilter implements AutoConfigurationImportFilter, EnvironmentAware {
private Environment environment;
/**
* 因为springboot自动装配，默认会把spring.factories的配置的类先全部加载到候选集合中，
* 因此当我们代码配置启用nacos，则需把其他注册中心，比如eureka先从候选集合排除
* @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
方案二：利用application-${指定注册中心标识} + spring.profiles.active
1、在要激活的注册中心的文件禁用其他注册中心客户端
比如appliication-nacos.yml禁用eureka
spring:
cloud:
nacos:
discovery:
server-addr: localhost:8848
# 禁用eureka客户端自动注册
eureka:
client:
enabled: false
2、激活想要注册的注册中心
spring:
application:
name: springboot-registration-client
profiles:
active: nacos
总结
这两种方案个人是比较推荐方案二，因为改动最小。方案一比较适用于没有提供是否需要激活注册中心开关的注册中心。其次如果我们要排除某些开源自动装配的组件，也可以考虑用方案一
demo链接
https://github.com/lyb-geek/springboot-learning/tree/master/springboot-registrationcenter-switch