DubboBootstrap bootstrap = DubboBootstrap.getInstance();
 bootstrap.application(new ApplicationConfig("dubbo-demo-api-provider"))
            .registry(new RegistryConfig("zookeeper://127.0.0.1:2181"))
            .protocol(new ProtocolConfig(CommonConstants.DUBBO, -1))
            .service(service)
            .start()
            .await();
 

registry(new RegistryConfig("zookeeper://127.0.0.1:2181"))

.registry(new RegistryConfig("zookeeper://127.0.0.1:2181"))

public RegistryConfig(String address) {
        setAddress(address);
 }

 public void setAddress(String address) {
 		//保存地址
        this.address = address;
        //下面是支持将参数在url地址后面 比如用户名,密码,协议,端口,这几个参数提前做解析放入成员变量中
        if (address != null) {
            try {
            	//地址转Dubbo的URL对象 这个URL是Dubbo自行实现的URL封装信息的类型
                URL url = URL.valueOf(address);

                // Refactor since 2.7.8
                //值不存在时候更新属性,非常巧妙的代码 重构了多个if判断
                //第一个参数值不存在则调用第二个方法,第二个方法的参数为第三方方法			 
                updatePropertyIfAbsent(this::getUsername, this::setUsername, url.getUsername());
                updatePropertyIfAbsent(this::getPassword, this::setPassword, url.getPassword());
                updatePropertyIfAbsent(this::getProtocol, this::setProtocol, url.getProtocol());
                updatePropertyIfAbsent(this::getPort, this::setPort, url.getPort());

				//移除掉url中的backup自定义参数 (备份的注册中心地址)
                Map<String, String> params = url.getParameters();
                if (CollectionUtils.isNotEmptyMap(params)) {
                    params.remove(BACKUP_KEY);
                }
                //将自定义参数存储到成员变量中
                updateParameters(params);
            } catch (Exception ignored) {
            }
        }
    }

  public DubboBootstrap registry(RegistryConfig registryConfig) {
        //将applicationModel对象设置给注册中心配置对象
        registryConfig.setScopeModel(applicationModel);
        //将注册中心配置对象添加到配置管理器中
        configManager.addRegistry(registryConfig);
        return this;
    }

public void addRegistry(RegistryConfig registryConfig) {
    addConfig(registryConfig);
}

public final <T extends AbstractConfig> T addConfig(AbstractConfig config) {
        if (config == null) {
            return null;
        }
        // ignore MethodConfig
        //检查当前配置管理器支持管理的配置对象
        //目前支持的配置有ApplicationConfig,MonitorConfig,MetricsConfig,SslConfig,
        //ProtocolConfig,RegistryConfig,ConfigCenterConfig,MetadataReportConfig   
      if (!isSupportConfigType(config.getClass())) {
            throw new IllegalArgumentException("Unsupported config type: " + config);
        }

        if (config.getScopeModel() != scopeModel) {
            config.setScopeModel(scopeModel);
        }
		//缓存中是否存在
        Map<String, AbstractConfig> configsMap = configsCache.computeIfAbsent(getTagName(config.getClass()), type -> new ConcurrentHashMap<>());
		//不是服务级接口配置则直接从缓存中读取到配置之后直接返回
        // fast check duplicated equivalent config before write lock
        if (!(config instanceof ReferenceConfigBase || config instanceof ServiceConfigBase)) {
            for (AbstractConfig value : configsMap.values()) {
                if (value.equals(config)) {
                    return (T) value;
                }
            }
        }

        // lock by config type
        //添加配置
        synchronized (configsMap) {
            return (T) addIfAbsent(config, configsMap);
        }
    }

private <C extends AbstractConfig> C addIfAbsent(C config, Map<String, C> configsMap)
        throws IllegalStateException {
		//配置信息为空直接返回
        if (config == null || configsMap == null) {
            return config;
        }

        // find by value
        //根据配置规则判断,配置存在则返回
        Optional<C> prevConfig = findDuplicatedConfig(configsMap, config);
        if (prevConfig.isPresent()) {
            return prevConfig.get();
        }
		
		//生成配置key
        String key = config.getId();
        if (key == null) {
            do {
                // generate key if id is not set
                key = generateConfigId(config);
            } while (configsMap.containsKey(key));
        }

		//不相同的配置key重复则抛出异常
        C existedConfig = configsMap.get(key);
        if (existedConfig != null && !isEquals(existedConfig, config)) {
            String type = config.getClass().getSimpleName();
            logger.warn(String.format("Duplicate %s found, there already has one default %s or more than two %ss have the same id, " +
                    "you can try to give each %s a different id, override previous config with later config. id: %s, prev: %s, later: %s",
                type, type, type, type, key, existedConfig, config));
        }

        // override existed config if any
        //将配置对象存入configsMap对象中,configsMap来源于configsCache
        configsMap.put(key, config);
        return config;
    }