private String buildExtJson(final Method method) {
        final MetaDataRegisterDTO metaData = metaDataMap.get(method);
        if (Objects.isNull(metaData)) {
            return "{}";
        }
        ApiDocRegisterDTO.ApiExt ext = new ApiDocRegisterDTO.ApiExt();
        ext.setHost(getHost());
        ext.setPort(Integer.valueOf(getPort()));
        ext.setServiceName(metaData.getServiceName());
        ext.setMethodName(metaData.getMethodName());
        ext.setParameterTypes(metaData.getParameterTypes());
        ext.setRpcExt(metaData.getRpcExt());
        ext = customApiDocExt(ext);
        return GsonUtils.getInstance().toJson(ext);
    }
Instantiates a new context refreshed event listener.

@param clientConfig                   the shenyu client config
@param shenyuClientRegisterRepository the shenyuClientRegisterRepository
shenyu-client/shenyu-client-core/src/main/java/org/apache/shenyu/client/core/client/AbstractContextRefreshedEventListener.java