NacosPropertySourceLocator

我们去找PropertySourceLocator的实现类，发现除了我们自定义的GpJsonPropertySourceLocator以外，还有另外一个实现类NacosPropertySourceLocator.

于是，直接来看NacosPropertySourceLocator中的locate方法，代码如下。

public PropertySource<?> locate(Environment env) {
    this.nacosConfigProperties.setEnvironment(env);
    ConfigService configService = this.nacosConfigManager.getConfigService();
    if (null == configService) {
        log.warn("no instance of config service found, can't load config from nacos");
        return null;
    } else {
        //获取客户端配置的超时时间
        long timeout = (long)this.nacosConfigProperties.getTimeout();
        this.nacosPropertySourceBuilder = new NacosPropertySourceBuilder(configService, timeout);
        //获取name属性，
        String name = this.nacosConfigProperties.getName();
        //在Spring Cloud中，默认的name=spring.application.name。
        String dataIdPrefix = this.nacosConfigProperties.getPrefix();
        if (StringUtils.isEmpty(dataIdPrefix)) {
            dataIdPrefix = name;
        }

        if (StringUtils.isEmpty(dataIdPrefix)) {
            dataIdPrefix = env.getProperty("spring.application.name"); //获取spring.application.name，赋值给dataIdPrefix
        }
       //创建一个Composite属性源，可以包含多个PropertySource
        CompositePropertySource composite = new CompositePropertySource("NACOS");
        this.loadSharedConfiguration(composite);   //加载共享配置 
         //加载扩展配置
        loadExtConfiguration(composite);
        //加载自身配置
        loadApplicationConfiguration(composite, dataIdPrefix, nacosConfigProperties, env);
        return composite;
    }
}

上述代码的实现不难理解

1. 获取nacos客户端的配置属性，并生成dataId（这个很重要，要定位nacos的配置）
2. 分别调用三个方法从加载配置属性源，保存到composite组合属性源中

loadApplicationConfiguration

我们可以先不管加载共享配置、扩展配置的方法，最终本质上都是去远程服务上读取配置，只是传入的参数不一样。

• fileExtension，表示配置文件的扩展名
• nacosGroup表示分组
• 加载dataid=项目名称的配置
• 加载dataid=项目名称+扩展名的配置
• 遍历当前配置的激活点（profile），分别循环加载带有profile的dataid配置

private void loadApplicationConfiguration(
    CompositePropertySource compositePropertySource, String dataIdPrefix,
    NacosConfigProperties properties, Environment environment) {
    String fileExtension = properties.getFileExtension();  //默认的扩展名为： properties
    String nacosGroup = properties.getGroup(); //获取group
    //加载`dataid=项目名称`的配置
    loadNacosDataIfPresent(compositePropertySource, dataIdPrefix, nacosGroup,
                           fileExtension, true);
    //加载`dataid=项目名称+扩展名`的配置
    loadNacosDataIfPresent(compositePropertySource,
                           dataIdPrefix + DOT + fileExtension, nacosGroup, fileExtension, true);
    // 遍历profile（可以有多个），根据profile加载配置
    for (String profile : environment.getActiveProfiles()) {
        //此时的dataId=${spring.application.name}.${profile}.${fileExtension}
        String dataId = dataIdPrefix + SEP1 + profile + DOT + fileExtension;
        loadNacosDataIfPresent(compositePropertySource, dataId, nacosGroup,
                               fileExtension, true);
    }

}

loadNacosDataIfPresent

调用loadNacosPropertySource加载存在的配置信息。

把加载之后的配置属性保存到CompositePropertySource中。

private void loadNacosDataIfPresent(final CompositePropertySource composite,
      final String dataId, final String group, String fileExtension,
      boolean isRefreshable) {
    //如果dataId为空，或者group为空，则直接跳过
   if (null == dataId || dataId.trim().length() < 1) {
      return;
   }
   if (null == group || group.trim().length() < 1) {
      return;
   }
    //从nacos中获取属性源
   NacosPropertySource propertySource = this.loadNacosPropertySource(dataId, group,
         fileExtension, isRefreshable);
    //把属性源保存到compositePropertySource中
   this.addFirstPropertySource(composite, propertySource, false);
}

loadNacosPropertySource

private NacosPropertySource loadNacosPropertySource(final String dataId,
      final String group, String fileExtension, boolean isRefreshable) {
   if (NacosContextRefresher.getRefreshCount() != 0) {
      if (!isRefreshable) { //是否支持自动刷新，// 如果不支持自动刷新配置则自动从缓存获取返回(不从远程服务器加载)
         return NacosPropertySourceRepository.getNacosPropertySource(dataId,
               group);
      }
   }
    //构造器从配置中心获取数据
   return nacosPropertySourceBuilder.build(dataId, group, fileExtension,
         isRefreshable);
}

NacosPropertySourceBuilder.build

NacosPropertySource build(String dataId, String group, String fileExtension,
      boolean isRefreshable) {
        //调用loadNacosData加载远程数据
   List<PropertySource<?>> propertySources = loadNacosData(dataId, group,
         fileExtension);
    //构造NacosPropertySource(这个是Nacos自定义扩展的PropertySource，和我们前面演示的自定义PropertySource类似)。
//    相当于把从远程服务器获取的数据保存到NacosPropertySource中。
   NacosPropertySource nacosPropertySource = new NacosPropertySource(propertySources,
         group, dataId, new Date(), isRefreshable);
    //把属性缓存到本地缓存
   NacosPropertySourceRepository.collectNacosPropertySource(nacosPropertySource);
   return nacosPropertySource;
}

NacosPropertySourceBuilder.loadNacosData

这个方法，就是连接远程服务器去获取配置数据的实现，关键代码是configService.getConfig

private List<PropertySource<?>> loadNacosData(String dataId, String group,
      String fileExtension) {
   String data = null;
   try {
      data = configService.getConfig(dataId, group, timeout); //加载Nacos配置数据
      if (StringUtils.isEmpty(data)) {
         log.warn(
               "Ignore the empty nacos configuration and get it based on dataId[{}] & group[{}]",
               dataId, group);
         return Collections.emptyList();
      }
      if (log.isDebugEnabled()) {
         log.debug(String.format(
               "Loading nacos data, dataId: '%s', group: '%s', data: %s", dataId,
               group, data));
      }
       //对加载的数据进行解析，保存到List<PropertySource>集合。
      return NacosDataParserHandler.getInstance().parseNacosData(dataId, data,
            fileExtension);
   }
   catch (NacosException e) {
      log.error("get data from Nacos error,dataId:{} ", dataId, e);
   }
   catch (Exception e) {
      log.error("parse data from Nacos error,dataId:{},data:{}", dataId, data, e);
   }
   return Collections.emptyList();
}

阶段性总结

通过上述分析，我们知道了Spring Cloud集成Nacos时的关键路径，并且知道在启动时，Spring Cloud会从Nacos Server中加载动态数据保存到Environment集合。

从而实现动态配置的自动注入。

Nacos客户端的数据的加载流程

配置数据的最终加载，是基于 configService.getConfig，Nacos提供的SDK来实现的。

public String getConfig(String dataId, String group, long timeoutMs) throws NacosException

关于Nacos SDK的使用教程： https://nacos.io/zh-cn/docs/sdk.html

也就是说，接下来我们的源码分析，直接进入到Nacos这个范畴。

NacosConfigService.getConfig

@Override
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 = blank2defaultGroup(group); //获取group，如果为空，则为default-group
    ParamUtils.checkKeyParam(dataId, group);   //验证请求参数
    ConfigResponse cr = new ConfigResponse(); //设置响应结果
    
    cr.setDataId(dataId); 
    cr.setTenant(tenant);
    cr.setGroup(group);
    
    // 优先使用本地配置
    String content = LocalConfigInfoProcessor.getFailover(agent.getName(), dataId, group, tenant);
    if (content != null) { //如果本地缓存中的内容不为空
        
        LOGGER.warn("[{}] [get-config] get failover ok, dataId={}, group={}, tenant={}, config={}", agent.getName(),
                dataId, group, tenant, ContentUtils.truncateContent(content));
        cr.setContent(content); //把内容设置到cr中。
        //获取容灾配置的encryptedDataKey
        String encryptedDataKey = LocalEncryptedDataKeyProcessor
                .getEncryptDataKeyFailover(agent.getName(), dataId, group, tenant);
        cr.setEncryptedDataKey(encryptedDataKey); //保存到cr
        configFilterChainManager.doFilter(null, cr); //执行过滤(目前好像没有实现)
        content = cr.getContent(); //返回文件content
        return content;
    }
    //如果本地文件中不存在相关内容，则发起远程调用
    try {
        ConfigResponse response = worker.getServerConfig(dataId, group, tenant, timeoutMs);
        //把响应内容返回
        cr.setContent(response.getContent());
        cr.setEncryptedDataKey(response.getEncryptedDataKey());
        
        configFilterChainManager.doFilter(null, cr);
        content = cr.getContent();
        
        return content;
    } catch (NacosException ioe) {
        if (NacosException.NO_RIGHT == ioe.getErrCode()) {
            throw ioe;
        }
        LOGGER.warn("[{}] [get-config] get from server error, dataId={}, group={}, tenant={}, msg={}",
                agent.getName(), dataId, group, tenant, ioe.toString());
    }
    //如果出现NacosException，且不是403异常，则尝试通过本地的快照文件去获取配置进行返回。
    LOGGER.warn("[{}] [get-config] get snapshot ok, dataId={}, group={}, tenant={}, config={}", agent.getName(),
            dataId, group, tenant, ContentUtils.truncateContent(content));
    content = LocalConfigInfoProcessor.getSnapshot(agent.getName(), dataId, group, tenant);
    cr.setContent(content);
    String encryptedDataKey = LocalEncryptedDataKeyProcessor
            .getEncryptDataKeyFailover(agent.getName(), dataId, group, tenant);
    cr.setEncryptedDataKey(encryptedDataKey);
    configFilterChainManager.doFilter(null, cr);
    content = cr.getContent();
    return content;
}

从本地缓存读取配置

默认情况下，nacos先从本地缓存的配置中读取文件：C:\Users\mayn\nacos\config\fixed-192.168.8.133_8848-6a382560-ed4c-414c-a5e2-9d72c48f1a0e_nacos

如果本地缓存内容存在，则返回内容数据，否则返回空值。

public static String getFailover(String serverName, String dataId, String group, String tenant) {
    File localPath = getFailoverFile(serverName, dataId, group, tenant);
    if (!localPath.exists() || !localPath.isFile()) {
        return null;
    }

    try {
        return readFile(localPath);
    } catch (IOException ioe) {
        LOGGER.error("[" + serverName + "] get failover error, " + localPath, ioe);
        return null;
    }
}

从指定文件目录下读取文件内容。

static File getFailoverFile(String serverName, String dataId, String group, String tenant) {
    File tmp = new File(LOCAL_SNAPSHOT_PATH, serverName + "_nacos");
    tmp = new File(tmp, "data");
    if (StringUtils.isBlank(tenant)) {
        tmp = new File(tmp, "config-data");
    } else {
        tmp = new File(tmp, "config-data-tenant");
        tmp = new File(tmp, tenant);
    }
    return new File(new File(tmp, group), dataId);
}

ClientWorker.getServerConfig

ClientWorker，表示客户端的一个工作类，它负责和服务端交互。

public ConfigResponse getServerConfig(String dataId, String group, String tenant, long readTimeout)
        throws NacosException {
    ConfigResponse configResponse = new ConfigResponse();
    if (StringUtils.isBlank(group)) { //如果group为空，则返回默认group
        group = Constants.DEFAULT_GROUP;
    }
    
    HttpRestResult<String> result = null;
    try {
        Map<String, String> params = new HashMap<String, String>(3);  //构建请求参数
        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);
        }
        //发起远程调用
        result = agent.httpGet(Constants.CONFIG_CONTROLLER_PATH, null, params, agent.getEncode(), readTimeout);
    } catch (Exception ex) {
        String message = String
                .format("[%s] [sub-server] get server config exception, dataId=%s, group=%s, tenant=%s",
                        agent.getName(), dataId, group, tenant);
        LOGGER.error(message, ex);
        throw new NacosException(NacosException.SERVER_ERROR, ex);
    }
    //根据响应结果实现不同的处理
    switch (result.getCode()) { 
        case HttpURLConnection.HTTP_OK: //如果响应成功，保存快照到本地，并返回响应内容
            LocalConfigInfoProcessor.saveSnapshot(agent.getName(), dataId, group, tenant, result.getData());
            configResponse.setContent(result.getData());
            String configType;  //配置文件的类型，如text、json、yaml等
            if (result.getHeader().getValue(CONFIG_TYPE) != null) {
                configType = result.getHeader().getValue(CONFIG_TYPE);
            } else {
                configType = ConfigType.TEXT.getType();
            }
            configResponse.setConfigType(configType); //设置到configResponse中，后续要根据文件类型实现不同解析策略
            //获取加密数据的key
            String encryptedDataKey = result.getHeader().getValue(ENCRYPTED_DATA_KEY);
            //保存
            LocalEncryptedDataKeyProcessor
                    .saveEncryptDataKeySnapshot(agent.getName(), dataId, group, tenant, encryptedDataKey);
            configResponse.setEncryptedDataKey(encryptedDataKey);
            return configResponse;
        case HttpURLConnection.HTTP_NOT_FOUND: //如果返回404， 清空本地快照
            LocalConfigInfoProcessor.saveSnapshot(agent.getName(), dataId, group, tenant, null);
            LocalEncryptedDataKeyProcessor.saveEncryptDataKeySnapshot(agent.getName(), dataId, group, tenant, null);
            return configResponse;
        case HttpURLConnection.HTTP_CONFLICT: {
            LOGGER.error(
                    "[{}] [sub-server-error] get server config being modified concurrently, dataId={}, group={}, "
                            + "tenant={}", agent.getName(), dataId, group, tenant);
            throw new NacosException(NacosException.CONFLICT,
                    "data being modified, dataId=" + dataId + ",group=" + group + ",tenant=" + tenant);
        }
        case HttpURLConnection.HTTP_FORBIDDEN: {
            LOGGER.error("[{}] [sub-server-error] no right, dataId={}, group={}, tenant={}", agent.getName(),
                    dataId, group, tenant);
            throw new NacosException(result.getCode(), result.getMessage());
        }
        default: {
            LOGGER.error("[{}] [sub-server-error]  dataId={}, group={}, tenant={}, code={}", agent.getName(),
                    dataId, group, tenant, result.getCode());
            throw new NacosException(result.getCode(),
                    "http error, code=" + result.getCode() + ",dataId=" + dataId + ",group=" + group + ",tenant="
                            + tenant);
        }
    }
}

ServerHttpAgent.httpGet

发起远程请求的实现。

@Override
public HttpRestResult<String> httpGet(String path, Map<String, String> headers, Map<String, String> paramValues,
        String encode, long readTimeoutMs) throws Exception {
    final long endTime = System.currentTimeMillis() + readTimeoutMs;
    injectSecurityInfo(paramValues);  //注入安全信息
    String currentServerAddr = serverListMgr.getCurrentServerAddr();//获取当前服务器地址
    int maxRetry = this.maxRetry; //获取最大重试次数，默认3次
    //配置HttpClient的属性，默认的readTimeOut超时时间是3s
    HttpClientConfig httpConfig = HttpClientConfig.builder()
            .setReadTimeOutMillis(Long.valueOf(readTimeoutMs).intValue())
            .setConTimeOutMillis(ConfigHttpClientManager.getInstance().getConnectTimeoutOrDefault(100)).build();
    do {
       
        try {
            //设置header
            Header newHeaders = getSpasHeaders(paramValues, encode);
            if (headers != null) {
                newHeaders.addAll(headers);
            }
            //构建query查询条件
            Query query = Query.newInstance().initParams(paramValues);
            //发起http请求，http://192.168.8.133:8848/nacos/v1/cs/configs
            HttpRestResult<String> result = NACOS_RESTTEMPLATE
                    .get(getUrl(currentServerAddr, path), httpConfig, newHeaders, query, String.class);
            if (isFail(result)) { //如果请求失败，
                LOGGER.error("[NACOS ConnectException] currentServerAddr: {}, httpCode: {}",
                        serverListMgr.getCurrentServerAddr(), result.getCode());
            } else {
                // Update the currently available server addr
                serverListMgr.updateCurrentServerAddr(currentServerAddr);
                return result;
            }
        } catch (ConnectException connectException) {
            LOGGER.error("[NACOS ConnectException httpGet] currentServerAddr:{}, err : {}",
                    serverListMgr.getCurrentServerAddr(), connectException.getMessage());
        } catch (SocketTimeoutException socketTimeoutException) {
            LOGGER.error("[NACOS SocketTimeoutException httpGet] currentServerAddr:{}， err : {}",
                    serverListMgr.getCurrentServerAddr(), socketTimeoutException.getMessage());
        } catch (Exception ex) {
            LOGGER.error("[NACOS Exception httpGet] currentServerAddr: " + serverListMgr.getCurrentServerAddr(),
                    ex);
            throw ex;
        }
        //如果服务端列表有多个，并且当前请求失败，则尝试用下一个地址进行重试
        if (serverListMgr.getIterator().hasNext()) {
            currentServerAddr = serverListMgr.getIterator().next();
        } else {
            maxRetry--; //重试次数递减
            if (maxRetry < 0) {
                throw new ConnectException(
                        "[NACOS HTTP-GET] The maximum number of tolerable server reconnection errors has been reached");
            }
            serverListMgr.refreshCurrentServerAddr();
        }
        
    } while (System.currentTimeMillis() <= endTime);
    
    LOGGER.error("no available server");
    throw new ConnectException("no available server");
}

Nacos Server端的配置获取

客户端向服务端加载配置，调用的接口是：/nacos/v1/cs/configs ， 于是，在Nacos的源码中找到该接口

定位到Nacos源码中的ConfigController.getConfig中的方法，代码如下：

@GetMapping
@Secured(action = ActionTypes.READ, parser = ConfigResourceParser.class)
public void getConfig(HttpServletRequest request, HttpServletResponse response,
        @RequestParam("dataId") String dataId, @RequestParam("group") String group,
        @RequestParam(value = "tenant", required = false, defaultValue = StringUtils.EMPTY) String tenant,
        @RequestParam(value = "tag", required = false) String tag)
        throws IOException, ServletException, NacosException {
    // check tenant
    ParamUtils.checkTenant(tenant);
    tenant = NamespaceUtil.processNamespaceParameter(tenant); //租户，也就是namespaceid
    // check params
    ParamUtils.checkParam(dataId, group, "datumId", "content"); //检查请求参数是否为空
    ParamUtils.checkParam(tag);
    
    final String clientIp = RequestUtil.getRemoteIp(request); //获取请求的ip
    inner.doGetConfig(request, response, dataId, group, tenant, tag, clientIp); //加载配置
}

inner.doGetConfig

public String doGetConfig(HttpServletRequest request, HttpServletResponse response, String dataId, String group,
        String tenant, String tag, String clientIp) throws IOException, ServletException {
    final String groupKey = GroupKey2.getKey(dataId, group, tenant);
    String autoTag = request.getHeader("Vipserver-Tag");
    String requestIpApp = RequestUtil.getAppName(request); //请求端的应用名称
   
    int lockResult = tryConfigReadLock(groupKey);  //尝试获取当前请求配置的读锁（避免读写冲突）
    
    final String requestIp = RequestUtil.getRemoteIp(request); //请求端的ip
    
    boolean isBeta = false;
    //lockResult>0 ，表示CacheItem(也就是缓存的配置项)不为空，并且已经加了读锁，意味着这个缓存数据不能被删除。
    //lockResult=0 ,表示cacheItem为空，不需要加读锁
    //lockResult=01 , 表示加锁失败，存在冲突。
    //下面这个if，就是针对这三种情况进行处理。
    if (lockResult > 0) {
        // LockResult > 0 means cacheItem is not null and other thread can`t delete this cacheItem
        FileInputStream fis = null;
        try {
            String md5 = Constants.NULL;
            long lastModified = 0L;
            //从本地缓存中，根据groupKey获取CacheItem
            CacheItem cacheItem = ConfigCacheService.getContentCache(groupKey);
            //判断是否是beta发布，也就是测试版本
            if (cacheItem.isBeta() && cacheItem.getIps4Beta().contains(clientIp)) {
                isBeta = true;
            }
            //获取配置文件的类型
            final String configType =
                    (null != cacheItem.getType()) ? cacheItem.getType() : FileTypeEnum.TEXT.getFileType();
            response.setHeader("Config-Type", configType);
            //返回文件类型的枚举对象
            FileTypeEnum fileTypeEnum = FileTypeEnum.getFileTypeEnumByFileExtensionOrFileType(configType);
            String contentTypeHeader = fileTypeEnum.getContentType();
            response.setHeader(HttpHeaderConsts.CONTENT_TYPE, contentTypeHeader);
            
            File file = null;
            ConfigInfoBase configInfoBase = null;
            PrintWriter out = null;
            if (isBeta) { //如果是测试配置
                md5 = cacheItem.getMd54Beta();
                lastModified = cacheItem.getLastModifiedTs4Beta();
                if (PropertyUtil.isDirectRead()) {
                    configInfoBase = persistService.findConfigInfo4Beta(dataId, group, tenant);
                } else {
                    file = DiskUtil.targetBetaFile(dataId, group, tenant); //从磁盘中获取文件，得到的是一个完整的File
                }
                response.setHeader("isBeta", "true");
            } else {
                if (StringUtils.isBlank(tag)) { //判断tag标签是否为空，tag对应的是nacos配置中心的标签选项
                    if (isUseTag(cacheItem, autoTag)) {
                        if (cacheItem.tagMd5 != null) {
                            md5 = cacheItem.tagMd5.get(autoTag);
                        }
                        if (cacheItem.tagLastModifiedTs != null) {
                            lastModified = cacheItem.tagLastModifiedTs.get(autoTag);
                        }
                        if (PropertyUtil.isDirectRead()) {
                            configInfoBase = persistService.findConfigInfo4Tag(dataId, group, tenant, autoTag);
                        } else {
                            file = DiskUtil.targetTagFile(dataId, group, tenant, autoTag);
                        }
                        
                        response.setHeader("Vipserver-Tag",
                                URLEncoder.encode(autoTag, StandardCharsets.UTF_8.displayName()));
                    } else {//直接走这个逻辑（默认不会配置tag属性）
                        md5 = cacheItem.getMd5(); //获取缓存的md5
                        lastModified = cacheItem.getLastModifiedTs(); //获取最后更新时间
                        if (PropertyUtil.isDirectRead()) {  //判断是否是stamdalone模式且使用的是derby数据库，如果是，则从derby数据库加载数据
                            configInfoBase = persistService.findConfigInfo(dataId, group, tenant);
                        } else {
                            //否则，如果是数据库或者集群模式，先从本地磁盘得到文件
                            file = DiskUtil.targetFile(dataId, group, tenant);
                        }
                        //如果本地磁盘文件为空，并且configInfoBase为空，则表示配置数据不存在，直接返回null
                        if (configInfoBase == null && fileNotExist(file)) {
                            // FIXME CacheItem
                            // No longer exists. It is impossible to simply calculate the push delayed. Here, simply record it as - 1.
                            ConfigTraceService.logPullEvent(dataId, group, tenant, requestIpApp, -1,
                                    ConfigTraceService.PULL_EVENT_NOTFOUND, -1, requestIp);
                            
                            // pullLog.info("[client-get] clientIp={}, {},
                            // no data",
                            // new Object[]{clientIp, groupKey});
                            
                            response.setStatus(HttpServletResponse.SC_NOT_FOUND);
                            response.getWriter().println("config data not exist");
                            return HttpServletResponse.SC_NOT_FOUND + "";
                        }
                    }
                } else {//如果tag不为空，说明配置文件设置了tag标签
                    if (cacheItem.tagMd5 != null) {
                        md5 = cacheItem.tagMd5.get(tag); 
                    }
                    if (cacheItem.tagLastModifiedTs != null) {
                        Long lm = cacheItem.tagLastModifiedTs.get(tag);
                        if (lm != null) {
                            lastModified = lm;
                        }
                    }
                    if (PropertyUtil.isDirectRead()) {
                        configInfoBase = persistService.findConfigInfo4Tag(dataId, group, tenant, tag);
                    } else {
                        file = DiskUtil.targetTagFile(dataId, group, tenant, tag);
                    }
                    if (configInfoBase == null && fileNotExist(file)) {
                        // FIXME CacheItem
                        // No longer exists. It is impossible to simply calculate the push delayed. Here, simply record it as - 1.
                        ConfigTraceService.logPullEvent(dataId, group, tenant, requestIpApp, -1,
                                ConfigTraceService.PULL_EVENT_NOTFOUND, -1, requestIp);
                        
                        // pullLog.info("[client-get] clientIp={}, {},
                        // no data",
                        // new Object[]{clientIp, groupKey});
                        
                        response.setStatus(HttpServletResponse.SC_NOT_FOUND);
                        response.getWriter().println("config data not exist");
                        return HttpServletResponse.SC_NOT_FOUND + "";
                    }
                }
            }
            //把获取的数据结果设置到response中返回
            
            response.setHeader(Constants.CONTENT_MD5, md5);
            
            // Disable cache.
            response.setHeader("Pragma", "no-cache");
            response.setDateHeader("Expires", 0);
            response.setHeader("Cache-Control", "no-cache,no-store");
            if (PropertyUtil.isDirectRead()) {
                response.setDateHeader("Last-Modified", lastModified);
            } else {
                fis = new FileInputStream(file);
                response.setDateHeader("Last-Modified", file.lastModified());
            }
            //如果是单机模式，直接把数据写回到客户端
            if (PropertyUtil.isDirectRead()) {
                out = response.getWriter();
                out.print(configInfoBase.getContent());
                out.flush();
                out.close();
            } else {//否则，通过trasferTo
                fis.getChannel()
                        .transferTo(0L, fis.getChannel().size(), Channels.newChannel(response.getOutputStream()));
            }
            
            LogUtil.PULL_CHECK_LOG.warn("{}|{}|{}|{}", groupKey, requestIp, md5, TimeUtils.getCurrentTimeStr());
            
            final long delayed = System.currentTimeMillis() - lastModified;
            
            // TODO distinguish pull-get && push-get
            /*
             Otherwise, delayed cannot be used as the basis of push delay directly,
             because the delayed value of active get requests is very large.
             */
            ConfigTraceService.logPullEvent(dataId, group, tenant, requestIpApp, lastModified,
                    ConfigTraceService.PULL_EVENT_OK, delayed, requestIp);
            
        } finally { 
            releaseConfigReadLock(groupKey); //释放锁
            IoUtils.closeQuietly(fis);
        }
    } else if (lockResult == 0) { //说明缓存为空，
        
        // FIXME CacheItem No longer exists. It is impossible to simply calculate the push delayed. Here, simply record it as - 1.
        ConfigTraceService
                .logPullEvent(dataId, group, tenant, requestIpApp, -1, ConfigTraceService.PULL_EVENT_NOTFOUND, -1,
                        requestIp);
        
        response.setStatus(HttpServletResponse.SC_NOT_FOUND);
        response.getWriter().println("config data not exist");
        return HttpServletResponse.SC_NOT_FOUND + "";
        
    } else {//
        
        PULL_LOG.info("[client-get] clientIp={}, {}, get data during dump", clientIp, groupKey);
        
        response.setStatus(HttpServletResponse.SC_CONFLICT);
        response.getWriter().println("requested file is being modified, please try later.");
        return HttpServletResponse.SC_CONFLICT + "";
        
    }
    
    return HttpServletResponse.SC_OK + "";
}

persistService.findConfigInfo

从derby数据库中获取数据内容,这个就是一个基本的数据查询操作。

@Override
public ConfigInfo findConfigInfo(final String dataId, final String group, final String tenant) {
    final String tenantTmp = StringUtils.isBlank(tenant) ? StringUtils.EMPTY : tenant;
    final String sql = "SELECT ID,data_id,group_id,tenant_id,app_name,content,md5,type FROM config_info "
            + " WHERE data_id=? AND group_id=? AND tenant_id=?";
    final Object[] args = new Object[] {dataId, group, tenantTmp};
    return databaseOperate.queryOne(sql, args, CONFIG_INFO_ROW_MAPPER);
    
}

DiskUtil.targetFile

从磁盘目录中获取目标文件，直接根据dataId/group/tenant ，查找指定目录下的文件即可

public static File targetFile(String dataId, String group, String tenant) {
    File file = null;
    if (StringUtils.isBlank(tenant)) {
        file = new File(EnvUtil.getNacosHome(), BASE_DIR);
    } else {
        file = new File(EnvUtil.getNacosHome(), TENANT_BASE_DIR);
        file = new File(file, tenant);
    }
    file = new File(file, group);
    file = new File(file, dataId);
    return file;
}

至此，NacosPropertySourceLocator 完成了从Nacos Server上动态获取配置并缓存到本地，从而实现Nacos动态配置获取的能力！