Nacos具备微服务注册和发现，以及配置管理的功能，本文详情描述【注册和发现】的原理，以及基本使用，包括如何进行跨group注册和发现。

一、Nacos配置 

spring:   cloud:     nacos:       discovery:         server-addr: nacosIP地址:8849         namespace: dev         group: Product       config:         server-addr: nacosIP地址:8849         namespace: dev         group: Product         file-extension: yaml         refresh-enabled: true         enable-remote-sync-config: true         name: product.yaml

spring:   cloud:     nacos:       discovery:         server-addr: nacosIP地址:8849         namespace: dev         group: Order       config:         server-addr: nacosIP地址:8849         namespace: dev         group: Order         file-extension: yaml         refresh-enabled: true         enable-remote-sync-config: true         name: order.yaml         extension-configs:           - data-id: config-global.yaml             group: Order             refresh: true

一、NacosServiceDiscovery 中 getInstances 获取注册在nacos上的服务实例清单 

public List getInstances(String serviceId) throws NacosException {     String group = this.discoveryProperties.getGroup();     List instances = this.namingService().selectInstances(serviceId, group, true);     return hostToServiceInstanceList(instances, serviceId); }

  但是原始功能不支持跨group服务发现，所以我们需要重写 getInstances方法。

二、NacosServiceDiscoveryV2 继承 NacosServiceDiscovery，并重写 getInstances

import com.alibaba.cloud.nacos.NacosServiceInstance; import com.alibaba.cloud.nacos.NacosServiceManager; import com.alibaba.cloud.nacos.discovery.NacosServiceDiscovery; import com.alibaba.nacos.api.exception.NacosException; import com.alibaba.nacos.api.naming.NamingService; import com.alibaba.nacos.api.naming.pojo.Instance; import com.alibaba.nacos.api.naming.pojo.ListView; import com.baomidou.mybatisplus.core.toolkit.CollectionUtils; import org.springframework.cloud.client.ServiceInstance;  import java.util.*;  import static com.baomidou.mybatisplus.core.toolkit.CollectionUtils.isEmpty; import static java.util.Objects.isNull;  /**  * @description: naocs服务发现重写  */ public class NacosServiceDiscoveryV2 extends NacosServiceDiscovery {      private final NacosDiscoveryPropertiesV2 discoveryProperties;      private final NacosShareProperties nacosShareProperties;      private final NacosServiceManager nacosServiceManager;      public NacosServiceDiscoveryV2(NacosDiscoveryPropertiesV2 discoveryProperties, NacosShareProperties nacosShareProperties, NacosServiceManager nacosServiceManager) {         super(discoveryProperties, nacosServiceManager);         this.discoveryProperties = discoveryProperties;         this.nacosShareProperties = nacosShareProperties;         this.nacosServiceManager = nacosServiceManager;     }      /**      * Return all instances for the given service.      * @param serviceId id of service      * @return list of instances      * @throws NacosException nacosException      */     @Override     public List getInstances(String serviceId) throws NacosException {         String group = discoveryProperties.getGroup();         List instances = discoveryProperties.namingServiceInstance()                 .selectInstances(serviceId, group, true);         if (isEmpty(instances)) {             Map> namespaceGroupMap = nacosShareProperties.getNamespaceGroupMap();             Map namespace2NamingServiceMap = discoveryProperties.shareNamingServiceInstances();             for (Map.Entry entry : namespace2NamingServiceMap.entrySet()) {                 String namespace;                 NamingService namingService;                 if (isNull(namespace = entry.getKey()) || isNull(namingService = entry.getValue()))                     continue;                 Set groupNames = namespaceGroupMap.get(namespace);                 List shareInstances;                 if (isEmpty(groupNames)) {                     shareInstances = namingService.selectInstances(serviceId, group, true);                     if (CollectionUtils.isNotEmpty(shareInstances))                         break;                 } else {                     shareInstances = new ArrayList<>();                     for (String groupName : groupNames) {                         List subShareInstances = namingService.selectInstances(serviceId, groupName, true);                         if (CollectionUtils.isNotEmpty(subShareInstances)) {                             shareInstances.addAll(subShareInstances);                         }                     }                 }                 if (CollectionUtils.isNotEmpty(shareInstances)) {                     instances = shareInstances;                     break;                 }             }         }         return hostToServiceInstanceList(instances, serviceId);     }      /**      * Return the names of all services.      * @return list of service names      * @throws NacosException nacosException      */     public List getServices() throws NacosException {         String group = discoveryProperties.getGroup();         ListView services = discoveryProperties.namingServiceInstance()                 .getServicesOfServer(1, Integer.MAX_VALUE, group);         return services.getData();     }      public static List hostToServiceInstanceList(             List instances, String serviceId) {         List result = new ArrayList<>(instances.size());         for (Instance instance : instances) {             ServiceInstance serviceInstance = hostToServiceInstance(instance, serviceId);             if (serviceInstance != null) {                 result.add(serviceInstance);             }         }         return result;     }      public static ServiceInstance hostToServiceInstance(Instance instance,                                                         String serviceId) {         if (instance == null || !instance.isEnabled() || !instance.isHealthy()) {             return null;         }         NacosServiceInstance nacosServiceInstance = new NacosServiceInstance();         nacosServiceInstance.setHost(instance.getIp());         nacosServiceInstance.setPort(instance.getPort());         nacosServiceInstance.setServiceId(serviceId);          Map metadata = new HashMap<>();         metadata.put("nacos.instanceId", instance.getInstanceId());         metadata.put("nacos.weight", instance.getWeight() + "");         metadata.put("nacos.healthy", instance.isHealthy() + "");         metadata.put("nacos.cluster", instance.getClusterName() + "");         metadata.putAll(instance.getMetadata());         nacosServiceInstance.setMetadata(metadata);          if (metadata.containsKey("secure")) {             boolean secure = Boolean.parseBoolean(metadata.get("secure"));             nacosServiceInstance.setSecure(secure);         }         return nacosServiceInstance;     }      private NamingService namingService() {         return nacosServiceManager                 .getNamingService(discoveryProperties.getNacosProperties());     } }

原理：

1、根据 serviceId 和 group 获取当前实例

2、获取所有group清单，并根据group找到group下所有实例

3、将group清单，加入到自己的实例清单中。

三、NacosDiscoveryPropertiesV2 继承 NacosDiscoveryProperties，服务发现属性重写 shareNamingServiceInstances、getNacosProperties方法

import com.alibaba.cloud.nacos.NacosDiscoveryProperties; import com.alibaba.nacos.api.NacosFactory; import com.alibaba.nacos.api.naming.NamingService; import com.alibaba.nacos.client.naming.utils.UtilAndComs; import org.slf4j.Logger; import org.slf4j.LoggerFactory;  import java.util.*; import java.util.concurrent.ConcurrentHashMap; import java.util.function.Function; import java.util.function.Predicate;  import static com.alibaba.nacos.api.PropertyKeyConst.*; import static java.util.Objects.nonNull;  /**  * @description: naocs服务发现属性重写  */ public class NacosDiscoveryPropertiesV2 extends NacosDiscoveryProperties {      private static final Logger log = LoggerFactory.getLogger(NacosDiscoveryPropertiesV2.class);      private final NacosShareProperties nacosShareProperties;      private static final Map NAMESPACE_TO_NAMING_SERVICE_MAP = new ConcurrentHashMap<>();      public NacosDiscoveryPropertiesV2(NacosShareProperties nacosShareProperties) {         super();         this.nacosShareProperties = nacosShareProperties;     }      public Map shareNamingServiceInstances() {         if (!NAMESPACE_TO_NAMING_SERVICE_MAP.isEmpty()) {             return new HashMap<>(NAMESPACE_TO_NAMING_SERVICE_MAP);         }         List entities = Optional.ofNullable(nacosShareProperties)                 .map(NacosShareProperties::getEntities).orElse(Collections.emptyList());         entities.stream().filter(entity -> nonNull(entity) && nonNull(entity.getNamespace()))                 .filter(distinctByKey(NacosShareProperties.NacosShareEntity::getNamespace))                 .forEach(entity -> {                     try {                         NamingService namingService = NacosFactory.createNamingService(getNacosProperties(entity.getNamespace()));                         if (namingService != null) {                             NAMESPACE_TO_NAMING_SERVICE_MAP.put(entity.getNamespace(), namingService);                         }                     } catch (Exception e) {                         log.error("create naming service error! properties={}, e=", this, e);                     }                 });         return new HashMap<>(NAMESPACE_TO_NAMING_SERVICE_MAP);     }     private static  Predicate distinctByKey(Function keyExtractor) {         Map seen = new ConcurrentHashMap<>();         return t -> seen.putIfAbsent(keyExtractor.apply(t), Boolean.TRUE) == null;     }      private Properties getNacosProperties(String namespace) {         Properties properties = new Properties();         properties.put(SERVER_ADDR, getServerAddr());         properties.put(USERNAME, Objects.toString(getUsername(), ""));         properties.put(PASSWORD, Objects.toString(getPassword(), ""));         properties.put(NAMESPACE, namespace);         properties.put(UtilAndComs.NACOS_NAMING_LOG_NAME, getLogName());         String endpoint = getEndpoint();         if (endpoint.contains(":")) {             int index = endpoint.indexOf(":");             properties.put(ENDPOINT, endpoint.substring(0, index));             properties.put(ENDPOINT_PORT, endpoint.substring(index + 1));         }         else {             properties.put(ENDPOINT, endpoint);         }          properties.put(ACCESS_KEY, getAccessKey());         properties.put(SECRET_KEY, getSecretKey());         properties.put(CLUSTER_NAME, getClusterName());         properties.put(NAMING_LOAD_CACHE_AT_START, getNamingLoadCacheAtStart());  //        enrichNacosDiscoveryProperties(properties);         return properties;     } }

四、共享share属性类 NacosShareProperties

import com.baomidou.mybatisplus.core.toolkit.CollectionUtils; import org.springframework.boot.context.properties.ConfigurationProperties; import org.springframework.context.annotation.Configuration;  import java.util.*; import java.util.concurrent.ConcurrentHashMap;  import static java.util.Objects.nonNull;  /**  * 
  *  @description: 共享nacos属性  *  
  */ @Configuration @ConfigurationProperties(prefix = "nacos.share") public class NacosShareProperties {      private final Map> NAMESPACE_TO_GROUP_NAME_MAP = new ConcurrentHashMap<>();      /**      * 共享nacos实体列表      */     private List entities;      public List getEntities() {         return entities;     }      public void setEntities(List entities) {         this.entities = entities;     }      public Map> getNamespaceGroupMap() {         if (CollectionUtils.isEmpty(entities)) {             return new HashMap<>();         }         entities.stream().filter(entity -> nonNull(entity) && nonNull(entity.getNamespace()))                 .forEach(entity -> {                     Set groupNames = NAMESPACE_TO_GROUP_NAME_MAP.computeIfAbsent(entity.getNamespace(), k -> new HashSet<>());                     if (nonNull(entity.getGroupNames()))                         groupNames.addAll(entity.getGroupNames());                 });         return new HashMap<>(NAMESPACE_TO_GROUP_NAME_MAP);     }      @Override     public String toString() {         return "NacosShareProperties{" +                 "entities=" + entities +                 '}';     }      /**      * 共享nacos实体      */     public static final class NacosShareEntity {          /**          * 命名空间          */         private String namespace;          /**          * 分组          */         private List groupNames;          public String getNamespace() {             return namespace;         }          public void setNamespace(String namespace) {             this.namespace = namespace;         }          public List getGroupNames() {             return groupNames;         }          public void setGroupNames(List groupNames) {             this.groupNames = groupNames;         }          @Override         public String toString() {             return "NacosShareEntity{" +                     "namespace='" + namespace + '\'' +                     ", groupNames=" + groupNames +                     '}';         }     } }

五、整合配置类 NacosDiscoveryAutoConfigurationV2

import com.alibaba.cloud.nacos.ConditionalOnNacosDiscoveryEnabled; import com.alibaba.cloud.nacos.NacosServiceManager; import com.alibaba.cloud.nacos.discovery.NacosDiscoveryAutoConfiguration; import com.alibaba.cloud.nacos.discovery.NacosServiceDiscovery; import org.springframework.boot.autoconfigure.AutoConfigureBefore; import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean; import org.springframework.cloud.client.ConditionalOnDiscoveryEnabled; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration;  /**  * @Auther: yangjian  */ @Configuration(proxyBeanMethods = false) @ConditionalOnDiscoveryEnabled @ConditionalOnNacosDiscoveryEnabled @AutoConfigureBefore({NacosDiscoveryAutoConfiguration.class}) public class NacosDiscoveryAutoConfigurationV2 {     @Bean     @ConditionalOnMissingBean     public NacosDiscoveryPropertiesV2 nacosProperties(NacosShareProperties nacosShareProperties) {         return new NacosDiscoveryPropertiesV2(nacosShareProperties);     }      @Bean     @ConditionalOnMissingBean     public NacosServiceDiscovery nacosServiceDiscovery(NacosDiscoveryPropertiesV2 discoveryPropertiesV2             , NacosShareProperties nacosShareProperties, NacosServiceManager nacosServiceManager) {         return new NacosServiceDiscoveryV2(discoveryPropertiesV2, nacosShareProperties, nacosServiceManager);     } }