This was actually an intentional design decision. The search algorithm used by the containers was problematic. It also causes problems when you want to develop an executable WAR as you often want a javax.servlet.ServletContainerInitializer for the WAR that is not executed when you run java -jar.

See the org.springframework.boot.context.embedded.ServletContextInitializer for an option that works with Spring Beans.

Do you have a specific case where this is causing problems or was it more of an observation?

The Cloud Foundry Java Buildpack contributes a JAR to do auto-reconfiguration (re-writing bean definitions, setting profiles, etc.). To get the auto-reconfiguration started we use a ServletContainerInitializer to set a ServletContext init-param.

I'm a little fuzzy on exactly how the ServletContextInitializer is supposed to work. Is it automatically detected in 3rd party JARs or does it have to be declared as a bean in an application's Context?

The org.springframework.boot.context.embedded.ServletContextInitializer currently needs to be a bean. You could possibly use a ApplicationContextInitializer via SpringFactoriesLoader to hook in the contributions.

I had a crack at the SpringFactoriesLoader this morning. I'm not claiming that I got it perfectly right, but my first impression is that it'll only work for JARs that are in the lib/ directory. Specifically, it seems that JARs passed in via -cp aren't scanned. Is that right? Would I need to make sure that any dependency I want scanned is located in the lib directory?

Not sure I follow. Are you saying that SpringFactoriesLoader doesn't pick up META-INF/spring.factories files for jars passed in via -cp?

That's my initial indication. I've put in on the back burner for a moment while I clear out some other stuff in our backlog. Leave this issue with me for a couple of days and I'll get back to you with a definitive answer.

@philwebb I've finally gotten back to this particular issue and yes, I believe that SpringFactoriesLoader doesn't pick up META-INF/spring.factories files for jars passed in via -cp? I don't have a "simple" test-case, but I do have an example where it isn't working. I'd be happy to walk you through it or provide a (non-miminal) JAR to demonstrate.

Unless @dsyer has time to look at this we might need to leave it as a known issue for 1.0.0. I need to focus the next few weeks on documentation and critical bugs.

Can we pick it up again when the pressure is off?

I don't think we'll ever be able to magically execute all SCIs. That's why I left it as "discussion". And there's definitely nothing happening to that in 1.0. We can take the SpringFactoriesLoader question to another issue maybe (seems like it's more of a Spring problem than a Boot problem, but maybe we are doing something in our classloaders that's messing it up).

Yeah, no worries. I left it until much too late for you guys, and am happy to let it go. I'll open another issue with the SpringFactoriesLoader stuff as well.