Java 11. Spring boot 2.1.3 package not found when run as module

[revkov]

I use windows 10, Oracle JDK-11.0.2, Maven 3.6, Spring-boot 2.1.3.RELEASE
Hello. After #15810 fix module-info.class now place in root folder in fat-jar, but is broken jar running process. Before module-info.class was in /BOOT-INF/classes folder and jar was as automatic-module with name of jar. But now fat-jar is a normal module, but folder structure is not valid, and packages not found by JVM when you try running you jar as java --module-path <name_of>.jar --module <your_module_name> in 2.1.2 version it's work perfect (because automatic module)
I create a simpe sample which demonstrates this is behavior and maybe helpful for fix:
https://github.com/revkov/spring-boot-java11

[wilkinsona]

If you want your application to be an automatic module you should not have a module-info.class file. It was not causing a problem in the past as repackaging was incorrectly moving it to a location where it could not be found. That’s been fixed in 2.1.3. Deleting your module-info.java file should restore the behaviour you had with 2.1.2.

[revkov]

@wilkinsona I don't want what my application will be a automatic module. I want a normal Java 11 spring boot application with module-info.class. How I can do that without removing module-info.class? If I remove module-info.class this is not correct Java 11 module. Please reopen and fix this. Or spring boot doesn't support this?

[revkov]

It turns out that now modules which build with spring-boot are fully invalid and uselesses because has wrong structure and can't be running correctly or use as required for other modules. Maybe this is bug?

[thorntonrp]

A Spring Boot jar is designed to package an application, not a module. It was never intended for use as a dependency that exports packages to other modules. As it is not a library or module jar, there is little, if anything, to be gained by having a module-info.java in the project.

[wilkinsona]

I don't want what my application will be a automatic module

That’s what you had with 2.1.2. The module-info.class was moved to BOOT-INF/classes which effectively removed it and turned your jar into an automatic module.

If I remove module-info.class this is not correct Java 11 module. Please reopen and fix this. Or spring boot doesn't support this?

I don’t think there is anything more for us to fix. In 2.1.2 and earlier we moved the module-info.class file, effectively removing it. This made it impossible for a fat jar to be a module. In 2.1.3 it is now possible for a fat jar to be a module.

That said, I am not sure that there is much benefit in doing so. The entry point to the module will still have to be the JarLauncher (as specified in the main class attribute in the manifest) and the module won’t be able to export any of the packages in BOOT-INF/classes or in the jars in BOOT-INF/lib.

or use as required for other modules

A Spring Boot application is intended to be a self-contained unit, much like a war file. It is not intended to be used as a dependency on the classpath or on the module path. Please refer to the documentation about using an application as a dependency for further details.

[revkov]

@wilkinsona

I don’t think there is anything more for us to fix. In 2.1.2 and earlier we moved the module-info.class file, effectively removing it. This made it impossible for a fat jar to be a module. In 2.1.3 it is now possible for a fat jar to be a module.

But now (in 2.1.3) it's not possible for a fat jar to be a module, because he has wrong structure and java doesn't recognize it. Try my application. I think you don't need move module-info.class to root folder because you got wrong java module + invalid fat spring-boot jar (not working). Maybe you need remove module-info.class at all on repackage ?

[wilkinsona]

As a I tried to explain above, there’s little point in trying to make a Spring Boot fat jar be a module. If you still wish to do so, you’ll need to ensure that you provide module info that is compatible with a fat jar’s structure. That will require you to only reference Boot’s launcher and then rely on it to create a ClassLoader that can load classes from BOOT-INF/classes and from the jars in BOOT-INF/lib. I’m not even sure that this is possible given the module system’s current capabilities.

Let’s take a step back. You haven’t explained why you want your fat jar to be a module. What are you trying to achieve?

[revkov]

Let’s take a step back. You haven’t explained why you want your fat jar to be a module. What are you trying to achieve?

I don't want what fat-jar be a module, i want what this is run correctly. if in documentation says what spring-boot jar is not a dependency, then it is not a module. I suggest remove module-info.class at all on repackage cycle. if i manually delete module-info.class from my project it works correctly, but received jar is not a java module (it's standalone unique spring-boot fat jar, we are undestatnd this). I think need rollback #15810 and remove module-info on repackage. This make our fat-jar works as designed by spring-boot, because spring-boot jar is not a module and doesn't contains any module-info.class.

[wilkinsona]

I don't want what fat-jar be a module, i want what this is run correctly

If you don't want it to be a module, why do you have a module-info.java file?

I think need rollback #15810 and remove module-info on repackage

That would make it impossible for @swaechter to do what they were trying to do. You can achieve the same result by removing module-info.java and it won't cause problems for anyone else.

[revkov]

That would make it impossible for @swaechter to do what they were trying to do. You can achieve the same result by removing module-info.java and it won't cause problems for anyone else.

They custom jre will not worked anyway, because module is corrupted! Try youself.

/usr/lib/jvm/jdk-12/bin/jlink --no-header-files --no-man-pages --compress=2 --module-path target/springmodule-1.0.0.jar --add-modules springmodule --launcher launch=springmodule/ch.swaechter.springmodule.SpringModule --output custom_jre:

Error: Error reading module: target\springmodule-1.0.0.jar !

[wilkinsona]

This isn't going anywhere.

That command is incorrect. When you've built a fat jar and are trying to use it as a module, you can't launch its main class directly. As I said above, you need to launch it using the JarLauncher and that may not even be possible given the current capabilities of the module system.

We do not recommend trying to turn a fat jar into a module and we do not recommend using a Spring Boot application as a dependency. If you'd like me to spend any more time on this, can you please answer my question:

If you don't want it to be a module, why do you have a module-info.java file?