首先是dubbo的泛化广播调用，泛化调用方式为GSON
然后不是有个全链路追踪插件叫 sofa-tracer 嘛，sofa-tracer的dubbo filter拦截器工作时候，要从 RpcContext.getUrl()，但是发现get出来是个空导致空指针
![image](https://user-images.githubusercontent.com/42512469/195077820-0731c73e-bb4f-4088-9142-8e3abbde29c1.png)

但是我用常规自带的广播调用模式，就没问题，只有 broadcastCluster1Invoker 有问题
        <dependency>
            <groupId>org.apache.dubbo.extensions</groupId>
            <artifactId>dubbo-cluster-broadcast-1</artifactId>
            <version>1.0.0</version>
            <scope>provided</scope>
        </dependency>
就是上面这种，有问题
* Also see {@link RpcContextAttachment#copyOf(boolean)}
     *
     * @param needCopy
     * @return a shallow copy of RpcServiceContext
     */
    public RpcServiceContext copyOf(boolean needCopy) {
        if (needCopy) {
            RpcServiceContext copy = new RpcServiceContext();
            copy.arguments = this.arguments;
            copy.consumerUrl = this.consumerUrl;
            copy.invocation = this.invocation;
            copy.invokers = this.invokers;
            copy.invoker = this.invoker;
            copy.localAddress = this.localAddress;
            copy.methodName = this.methodName;
            copy.needPrintRouterSnapshot = this.needPrintRouterSnapshot;
            copy.parameterTypes = this.parameterTypes;
            copy.remoteAddress = this.remoteAddress;
            copy.remoteApplicationName = this.remoteApplicationName;
            copy.request = this.request;
            copy.response = this.response;
            copy.url = this.url;
            copy.urls = this.urls;
            return copy;
        } else {
            return this;
        }
    }
}