环境：Springboot2.3.12.RELEASE + Spring Cloud Alibaba2.2.5.RELEASE + Spring Cloud Hoxton.SR12

应用的核心技术是：自定义PropertySourceLocator，然后配置spring.factories

在如下包中配置：

spring-cloud-context-xxx.jar中

org.springframework.cloud.bootstrap.BootstrapConfiguration=org.springframework.cloud.bootstrap.config.PropertySourceBootstrapConfiguration

Nacos加载配置的时候默认会通过一下三个DataId加载数据：

核心类：NacosPropertySourceLocator

自动配置核心

@Configuration(proxyBeanMethods = false)@ConditionalOnProperty(name = “spring.cloud.nacos.config.enabled”, matchIfMissing = true)public class NacosConfigBootstrapConfiguration { // Nacos Config相关的配置属性 @Bean @ConditionalOnMissingBean public NacosConfigProperties nacosConfigProperties() { return new NacosConfigProperties(); } // 管理Nacos Config相关的服务 @Bean @ConditionalOnMissingBean public NacosConfigManager nacosConfigManager( NacosConfigProperties nacosConfigProperties) { return new NacosConfigManager(nacosConfigProperties); } // 核心类自定义启动加载配置文件（Bootstraps） @Bean public NacosPropertySourceLocator nacosPropertySourceLocator( NacosConfigManager nacosConfigManager) { return new NacosPropertySourceLocator(nacosConfigManager); }}org.springframework.cloud.bootstrap.BootstrapConfiguration=com.alibaba.cloud.nacos.NacosConfigBootstrapConfiguration

自定义属性源

public class NacosPropertySourceLocator implements PropertySourceLocator { private NacosPropertySourceBuilder nacosPropertySourceBuilder; private NacosConfigProperties nacosConfigProperties; private NacosConfigManager nacosConfigManager; public NacosPropertySourceLocator(NacosConfigManager nacosConfigManager) { this.nacosConfigManager = nacosConfigManager; this.nacosConfigProperties = nacosConfigManager.getNacosConfigProperties(); } public PropertySource locate(Environment env) { nacosConfigProperties.setEnvironment(env); // 关键通过NacosConfigManager获取ConfigService服务 ConfigService configService = nacosConfigManager.getConfigService(); // … long timeout = nacosConfigProperties.getTimeout(); nacosPropertySourceBuilder = new NacosPropertySourceBuilder(configService, timeout); // 下面这些设置就是对应从配置文件中获取 String name = nacosConfigProperties.getName(); String dataIdPrefix = nacosConfigProperties.getPrefix(); if (StringUtils.isEmpty(dataIdPrefix)) { dataIdPrefix = name; } if (StringUtils.isEmpty(dataIdPrefix)) { dataIdPrefix = env.getProperty(“spring.application.name”); } CompositePropertySource composite = new CompositePropertySource( NACOS_PROPERTY_SOURCE_NAME);// NACOS_PROPERTY_SOURCE_NAME = NACOS // 加载共享配置 loadSharedConfiguration(composite); // 加载扩展配置 loadExtConfiguration(composite); // 加载应用程序配置（这里就以应用程序配置，深入查看） loadApplicationConfiguration(composite, dataIdPrefix, nacosConfigProperties, env); return composite; }}

获取配置服务

ConfigService配置服务是获取配置信息的核心方法：

public interface ConfigService { // 获取配置 String getConfig(String dataId, String group, long timeoutMs) throws NacosException; // 获取配置并设置监听 String getConfigAndSignListener(String dataId, String group, long timeoutMs, Listener listener) throws NacosException; // 给配置添加监听 void addListener(String dataId, String group, Listener listener) throws NacosException; // 发布配置 boolean publishConfig(String dataId, String group, String content) throws NacosException; // 删除配置 boolean removeConfig(String dataId, String group) throws NacosException; // 删除监听 void removeListener(String dataId, String group, Listener listener); // 获取服务状态 String getServerStatus(); // 关闭资源服务 void shutDown() throws NacosException;}

NacosConfigManager

public class NacosConfigManager { private static ConfigService service = null; private NacosConfigProperties nacosConfigProperties; public NacosConfigManager(NacosConfigProperties nacosConfigProperties) { this.nacosConfigProperties = nacosConfigProperties; // 创建配置服务 createConfigService(nacosConfigProperties); } static ConfigService createConfigService( NacosConfigProperties nacosConfigProperties) { if (Objects.isNull(service)) { synchronized (NacosConfigManager.class) { try { if (Objects.isNull(service)) { // 通过工厂创建服务 // assembleConfigServiceProperties方法 // 就是收集关于Nacos所有配置信息，如：地址，端口，用户名，密码等 // 详细查看NacosConfigProperties#assembleConfigServiceProperties service = NacosFactory.createConfigService( nacosConfigProperties.assembleConfigServiceProperties()); } } // … } } return service; }}// NacosFactorypublic class NacosFactory { public static ConfigService createConfigService(Properties properties) throws NacosException { return ConfigFactory.createConfigService(properties); }}public class ConfigFactory { public static ConfigService createConfigService(Properties properties) throws NacosException { try { Class driverImplClass = Class.forName(“com.alibaba.nacos.client.config.NacosConfigService”); Constructor constructor = driverImplClass.getConstructor(Properties.class); ConfigService vendorImpl = (ConfigService) constructor.newInstance(properties); // 通过反射构造了NacosConfigservice,同时设置属性信息 // 这些属性信息就是一些Naocs服务的地址，端口，用户名，密码等信息 return vendorImpl; } catch (Throwable e) { throw new NacosException(NacosException.CLIENT_INVALID_PARAM, e); } }}

到此就得到了一个ConfigService服务类NacosConfigService。

获取应用程序配置

接着95.2获取到了ConfigService以后继续执行

public class NacosPropertySourceLocator implements PropertySourceLocator { private NacosPropertySourceBuilder nacosPropertySourceBuilder; public PropertySource locate(Environment env) { nacosConfigProperties.setEnvironment(env); // 关键通过NacosConfigManager获取ConfigService服务 ConfigService configService = nacosConfigManager.getConfigService(); // … nacosPropertySourceBuilder = new NacosPropertySourceBuilder(configService, timeout); CompositePropertySource composite = new CompositePropertySource( NACOS_PROPERTY_SOURCE_NAME); loadApplicationConfiguration(composite, dataIdPrefix, nacosConfigProperties, env); return composite; } private void loadApplicationConfiguration( CompositePropertySource compositePropertySource, String dataIdPrefix, NacosConfigProperties properties, Environment environment) { // 获取文件扩展 String fileExtension = properties.getFileExtension(); // 获取分组 String nacosGroup = properties.getGroup(); // … // load with suffix, which have a higher priority than the default // 这里就以这里为例 loadNacosDataIfPresent(compositePropertySource, dataIdPrefix + DOT + fileExtension, nacosGroup, fileExtension, true); // Loaded with profile, which have a higher priority than the suffix // 这里会根据不同配置的profiles再次加载不同环境的配置 for (String profile : environment.getActiveProfiles()) { String dataId = dataIdPrefix + SEP1 + profile + DOT + fileExtension; loadNacosDataIfPresent(compositePropertySource, dataId, nacosGroup, fileExtension, true); } } private void loadNacosDataIfPresent(final CompositePropertySource composite, final String dataId, final String group, String fileExtension, boolean isRefreshable) { if (null == dataId || dataId.trim().length() < 1) { return; } if (null == group || group.trim().length() < 1) { return; } // 加载Nacos属性源 NacosPropertySource propertySource = this.loadNacosPropertySource(dataId, group, fileExtension, isRefreshable); this.addFirstPropertySource(composite, propertySource, false); } private NacosPropertySource loadNacosPropertySource(final String dataId, final String group, String fileExtension, boolean isRefreshable) { // … return nacosPropertySourceBuilder.build(dataId, group, fileExtension, isRefreshable); } private void addFirstPropertySource(final CompositePropertySource composite, NacosPropertySource nacosPropertySource, boolean ignoreEmpty) { if (null == nacosPropertySource || null == composite) { return; } if (ignoreEmpty && nacosPropertySource.getSource().isEmpty()) { return; } composite.addFirstPropertySource(nacosPropertySource); }}// 这里面开始加载数据public class NacosPropertySourceBuilder { NacosPropertySource build(String dataId, String group, String fileExtension, boolean isRefreshable) { Map p = loadNacosData(dataId, group, fileExtension); NacosPropertySource nacosPropertySource = new NacosPropertySource(group, dataId, p, new Date(), isRefreshable); NacosPropertySourceRepository.collectNacosPropertySource(nacosPropertySource); return nacosPropertySource; } // 加载数据 private Map loadNacosData(String dataId, String group, String fileExtension) { String data = null; try { // 通过ConfigService加载配置内容（从远程服务获取） data = configService.getConfig(dataId, group, timeout); if (StringUtils.isEmpty(data)) { return EMPTY_MAP; } Map dataMap = NacosDataParserHandler.getInstance() .parseNacosData(data, fileExtension); return dataMap == null ? EMPTY_MAP : dataMap; } // … return EMPTY_MAP; }}public class NacosConfigService implements ConfigService { public String getConfig(String dataId, String group, long timeoutMs) throws NacosException { return getConfigInner(namespace, dataId, group, timeoutMs); } private String getConfigInner(String tenant, String dataId, String group, long timeoutMs) throws NacosException { group = null2defaultGroup(group); ParamUtils.checkKeyParam(dataId, group); ConfigResponse cr = new ConfigResponse(); cr.setDataId(dataId); cr.setTenant(tenant); cr.setGroup(group); // 这里会从缓存文件中获取，如果能获取就不会再从远程加载了 // 会从如下缓存目录下加载配置： // System.getProperty("JM.SNAPSHOT.PATH", // System.getProperty("user.home")) + File.separator + "nacos" // + File.separator + "config" String content = LocalConfigInfoProcessor.getFailover(agent.getName(), dataId, group, tenant); if (content != null) { cr.setContent(content); configFilterChainManager.doFilter(null, cr); content = cr.getContent(); return content; } try { // 缓存总无法获取则从远程服务上拉取数据 String[] ct = worker.getServerConfig(dataId, group, tenant, timeoutMs); cr.setContent(ct[0]); configFilterChainManager.doFilter(null, cr); content = cr.getContent(); return content; } catch (NacosException ioe) { if (NacosException.NO_RIGHT == ioe.getErrCode()) { throw ioe; } } content = LocalConfigInfoProcessor.getSnapshot(agent.getName(), dataId, group, tenant); cr.setContent(content); configFilterChainManager.doFilter(null, cr); content = cr.getContent(); return content; }}public class ClientWorker implements Closeable { // 这里就是从远程服务拉取配置 public String[] getServerConfig(String dataId, String group, String tenant, long readTimeout) throws NacosException { String[] ct = new String[2]; if (StringUtils.isBlank(group)) { group = Constants.DEFAULT_GROUP; } HttpRestResult result = null; try { Map params = new HashMap(3); if (StringUtils.isBlank(tenant)) { params.put("dataId", dataId); params.put("group", group); } else { params.put("dataId", dataId); params.put("group", group); params.put("tenant", tenant); } result = agent.httpGet(Constants.CONFIG_CONTROLLER_PATH, null, params, agent.getEncode(), readTimeout); } catch (Exception ex) { throw new NacosException(NacosException.SERVER_ERROR, ex); } switch (result.getCode()) { case HttpURLConnection.HTTP_OK: // 获取成功后会将数据保存到缓存目录下 LocalConfigInfoProcessor.saveSnapshot(agent.getName(), dataId, group, tenant, result.getData()); ct[0] = result.getData(); if (result.getHeader().getValue(CONFIG_TYPE) != null) { ct[1] = result.getHeader().getValue(CONFIG_TYPE); } else { ct[1] = ConfigType.TEXT.getType(); } return ct; case HttpURLConnection.HTTP_NOT_FOUND: LocalConfigInfoProcessor.saveSnapshot(agent.getName(), dataId, group, tenant, null); return ct; case HttpURLConnection.HTTP_CONFLICT: { throw new NacosException(NacosException.CONFLICT, "data being modified, dataId=" + dataId + ",group=" + group + ",tenant=" + tenant); } throw new NacosException(result.getCode(), result.getMessage()); } default: { throw new NacosException(result.getCode(), "http error, code=" + result.getCode() + ",dataId=" + dataId + ",group=" + group + ",tenant=" + tenant); } } }}

到此就完成了远程配置数据的加载

总结：Nacos Config先从本地缓存中获取数据，如果不能获取才从远程拉取（如果远程服务无法连接，那么会不断重试，前提是本地能够加载到数据，否则服务将无法正常启动）。

完毕！！！

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