plugins: support for overriding layout-provided launcher class

[patrikbeno]

Spring Boot plugins "hijack" application's manifest by redirecting Main-Class attribute to a layout-provided launcher class and embedding some core Spring Boot Loader classes. Original Main-Class attribute is copied to Start-Class attribute which is handled by loader.

The problem is, you might need to customize default launcher behavior, but the plugins do not provide any means.

For wider context, see https://github.com/patrikbeno/spring-boot/wiki/Requirements

[philwebb]

Have you signed the CLA?

[philwebb]

It feels a little odd to provide the option to override the launcher class without also offering a way to add custom launcher classes. Are you usually writing your custom launcher class inside your application? Or do you have some other process that adds the class files to the JAR?

We'll also need to consider the Maven plugin as well if we do make the change.

[patrikbeno]

Yes, CLA signed.

Maven plugin updated, too. See RepackageMojo. Or did you mean something else?

Sure, overriding launcher class is something you do not need usually. But it's nice to have an option. I only needed it once. That's enough for me to be bothered with this.

[philwebb]

Oh yes, I see the Mojo was also updated. I just missed that last night when reviewing.

[patrikbeno]

I suggest we close this and go with #2629

[patrikbeno]

Yes, @philwebb, reopen is a good idea. While #2629 does indeed provide means to customize launcher, it may not be as flexible as providing plugin with your own customized class already available in your own module (and usually extending the default launcher associated with a selected layout).

However, assuming #2629 is sort of accepted (scheduled for 1.3.0), I have some issues with automatic merging of this particular PR. I suggest I incorporate these changes in #2629, if you agree. Then we can actually close this PR as obsolete.

Let me know.

[patrikbeno]

Closing. See #2629 (comment)