HandshakeWebSocketService assumes jakarta websocket is present

[MFAshby]

HandshakeWebSocketService#initUpgradeStrategy does not check for the availability of relevant classes before attempting to instanciate StandardWebSocketUpgradeStrategy.

	static RequestUpgradeStrategy initUpgradeStrategy() {
		if (tomcatWsPresent) {
			return new TomcatRequestUpgradeStrategy();
		}
		else if (jettyWsPresent) {
			return new JettyRequestUpgradeStrategy();
		}
		else if (undertowWsPresent) {
			return new UndertowRequestUpgradeStrategy();
		}
		else if (reactorNettyPresent) {
			// As late as possible (Reactor Netty commonly used for WebClient)
			return ReactorNettyStrategyDelegate.forReactorNetty1();
		}
		else if (reactorNetty2Present) {
			// As late as possible (Reactor Netty commonly used for WebClient)
			return ReactorNettyStrategyDelegate.forReactorNetty2();
		}
		else {
			// Let's assume Jakarta WebSocket API 2.1+
			return new StandardWebSocketUpgradeStrategy();
		}
	}

This breaks when you attempt to load a context without a dependency on jakarta.websocket-client-api.

It looks like it should be handled gracefully by the following code in WebFluxConfigurationSupport:

	private WebSocketService initWebSocketService() {
		WebSocketService service = getWebSocketService();
		if (service == null) {
			try {
				service = new HandshakeWebSocketService();
			}
			catch (IllegalStateException ex) {
				// Don't fail, test environment perhaps
				service = new NoUpgradeStrategyWebSocketService();
			}
		}
		return service;
	}

but because a ClassNotFoundException is thrown instead of IllegalStateException; the context simply fails to load instead of falling back to NoUpgradeStrategyWebSocketService

[MFAshby]

The workaround in my case was to add the following dependencies (my problem was loading a minimal context for a test case):

        <!-- SpringBootConfigStorageIntegrationTest loads the whole spring context, which winds up creating a 
             HandshakeWebSocketService, which falls back to jakarta websocket without testing if it's actually
             on the classpath -->
        <dependency>
            <groupId>jakarta.websocket</groupId>
            <artifactId>jakarta.websocket-api</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>jakarta.websocket</groupId>
            <artifactId>jakarta.websocket-client-api</artifactId>
            <scope>test</scope>
        </dependency>

[zhanyan-Ader1y]

I created a new repository for this problem.

Class not found reason is jakarta.websocket dependency not passed down from webflux module.

Whether it is necessary to verify the existence of jakarta.websocket , and throw IllegalStateException?

optional("jakarta.websocket:jakarta.websocket-api")
optional("jakarta.websocket:jakarta.websocket-client-api")