Add additional guard for web application detection in AOT

[dsyer]

This code in SpringApplication blows up at runtime in a native image when WebApplicationContext is not on the classpath:

	private boolean isWebApplicationContext(Class<?> applicationContextClass) {
		try {
			return WebApplicationContext.class.isAssignableFrom(applicationContextClass);
		}
		catch (NoClassDefFoundError ex) {
			return false;
		}
	}

Probably we could add an additional check that WebApplicationContext is present before we check for isAssignableFrom() it?

Adding this check worked for me:

	    if (!ClassUtils.isPresent("org.springframework.web.context.WebApplicationContext", null)) {
	        return false;
	    }

but it didn't work to simply catch Throwable.

[snicoll]

That's a pattern we use in other places so if that becomes problematic, I'd prefer to understand where this is coming from.

[dsyer]

I haven't seen that pattern anywhere else in Spring or Spring Boot, which isn't to say that it's something we necessarily have to fix here. I opened oracle/graal#622, so we can see what they say over there before we do anything, I guess.

[snicoll]

There is OnBeanCondition that does that or am I missing something?

[dsyer]

OnBeanCondition does not call isAssignableFrom(). Am I missing something?

[snicoll]

No but I surely was. Sorry.

[philwebb]

See #14157 (comment). Closing for now and awaiting the result of oracle/graal#622