@Override
    protected Mono<Void> handleSelectorIfNull(final String pluginName, final ServerWebExchange exchange, final ShenyuPluginChain chain) {
        return WebFluxResultUtils.noSelectorResult(pluginName, exchange);
    }
plugin is execute.

@return default false.
shenyu-plugin/shenyu-plugin-proxy/shenyu-plugin-websocket/src/main/java/org/apache/shenyu/plugin/websocket/WebSocketPlugin.java