本文阅读nacos-2.0.2的config源码，编写示例，分析推送配置、监听配置的原理。

客户端

创建NacosConfigService对象

Properties properties = new Properties();
properties.setProperty(PropertyKeyConst.SERVER_ADDR, NACOS_HOST);
NacosConfigService configService = new NacosConfigService(properties);

构造方法：

public NacosConfigService(Properties properties) throws NacosException {
    ValidatorUtils.checkInitParam(properties);
    
    initNamespace(properties);
    this.configFilterChainManager = new ConfigFilterChainManager(properties);
    ServerListManager serverListManager = new ServerListManager(properties);
    serverListManager.start();
    
    this.worker = new ClientWorker(this.configFilterChainManager, serverListManager, properties);
    // will be deleted in 2.0 later versions
    agent = new ServerHttpAgent(serverListManager);
}

1. 创建ConfigFilterChainManager - 过滤器链
2. 创建ServerListManager - 服务器列表管理
3. 创建ClientWorker - 用来发送请求，内部封装了一个ConfigRpcTransportClient类型对象agent，它能够获取到RpcClient与服务端进行通信

推送配置

Properties properties = new Properties();
properties.setProperty(PropertyKeyConst.SERVER_ADDR, NACOS_HOST);

NacosConfigService configService = new NacosConfigService(properties);

StringWriter out = new StringWriter();
properties.store(out, "test config");

// 推送配置到nacos服务器
configService.publishConfig(
    ORDER_SERVICE, Constants.DEFAULT_GROUP, out.toString(), "properties");

推送配置到nacos服务器：

public boolean publishConfig(String dataId,
                             String group,
                             String content,
                             String type) throws NacosException {
    return publishConfigInner(namespace, dataId, group, null, null, null, content, type, null);
}

private boolean publishConfigInner(String tenant, String dataId, String group, String tag, String appName,
        String betaIps, String content, String type, String casMd5) throws NacosException {
    group = blank2defaultGroup(group);
    ParamUtils.checkParam(dataId, group, content);

    ConfigRequest cr = new ConfigRequest();
    cr.setDataId(dataId);
    cr.setTenant(tenant);
    cr.setGroup(group);
    cr.setContent(content);
    cr.setType(type);
    configFilterChainManager.doFilter(cr, null);
    content = cr.getContent();
    String encryptedDataKey = (String) cr.getParameter("encryptedDataKey");

    return worker.publishConfig(
        dataId, group, tenant, appName, tag, betaIps, content, encryptedDataKey, casMd5, type);
}

worker使用agent推送配置：

// 1. 封装ConfigPublishRequest对象
ConfigPublishRequest request = new ConfigPublishRequest(dataId, group, tenant, content);
request.setCasMd5(casMd5);
request.putAdditionalParam(TAG_PARAM, tag);
request.putAdditionalParam(APP_NAME_PARAM, appName);
request.putAdditionalParam(BETAIPS_PARAM, betaIps);
request.putAdditionalParam(TYPE_PARAM, type);
request.putAdditionalParam(ENCRYPTED_DATA_KEY_PARAM, encryptedDataKey);
// 2. 获取RpcClient对象
// 3. 使用RpcClient发请求
ConfigPublishResponse response = (ConfigPublishResponse) requestProxy(getOneRunningClient(), request);

监听配置

Properties properties = new Properties();
properties.setProperty(PropertyKeyConst.SERVER_ADDR, NACOS_HOST);

NacosConfigService configService = new NacosConfigService(properties);

// 添加监听器
configService.addListener(ORDER_SERVICE, Constants.DEFAULT_GROUP, new AbstractListener() {
  @Override
  public void receiveConfigInfo(String configInfo) {
    Sys