Parses META-INF/services files for annotations #5912

pkriens · 2023-12-01T15:00:07Z

It is possible to add addnotions in the comments of the service files of the Service Loader.

Signed-off-by: Peter Kriens [email protected]

It is possible to add addnotions in the comments of the service files of the Service Loader. Fixes bndtools#5903 --- Signed-off-by: Peter Kriens <[email protected]> Signed-off-by: Peter Kriens <[email protected]>

HannesWell

Thank you a lot for working on this.

Adding the annotation comments to the services file is a clever idea to still have control about which services are processed and to handle the non default cases.

Just for clarification, in the simplest case I could to something like

META-INF/services/com.example.ServiceType:
   #import aQute.bnd.annotation.spi.ServiceProvider
   #@ServiceProvider
   com.example.impl.Impl2
   #@ServiceProvider
   com.example.impl.Impl1

or

META-INF/services/com.example.ServiceType:
   #@aQute.bnd.annotation.spi.ServiceProvider.ServiceProvider
   com.example.impl.Impl2
   #@aQute.bnd.annotation.spi.ServiceProvider.ServiceProvider
   com.example.impl.Impl1

and would have Impl1 and Impl2 registered?

And if I would do

META-INF/services/com.example.ServiceType:
   #@aQute.bnd.annotation.spi.ServiceProvider.ServiceProvider
   com.example.impl.Impl2
   com.example.impl.Impl1

... I only would have Impl2 registered respectively if the annotation were only above Impl1 only Impl1 would be registered?

HannesWell · 2023-12-01T18:49:24Z

biz.aQute.bndlib/src/aQute/bnd/osgi/MetaInfService.java

+	static final Pattern	IMPORT_P					= Pattern
+		.compile("#import\\s+(?<fqn>" + FQN_S + ")\\s*;?\\s*$");
+	static final Pattern	ANNOTATION_P				= Pattern
+		.compile("#@(?<fqn>" + FQN_S + ")\\((?<attrs>.*)" + "\\)\\s*;?\\s*$");


Could we make the braces optional if no attributes are specified for an annotation?
And naming the capturing group type or just name would avoid possible confusion with the IMPORT_P Pattern.

Suggested change

.compile("#@(?<fqn>" + FQN_S + ")\$(?<attrs>.*)" + "\$\\s*;?\\s*$");

.compile("#@(?<type>" + FQN_S + ")(\$(?<attrs>.*))?" + "\$\\s*;?\\s*$");

I am ok with this, but if you change 'fqn', don't you then also not have to change the code where we get the group?

Yes, of course the code below has to be adjusted.
In fact I mainly noticed this when reading the code below where it was first read like it would look up a fully-qualified name in the imports (which is of course not necessary), when it actually just looked up the class-name.

I just wanted to keep the suggestion short. :)

HannesWell · 2023-12-01T18:52:42Z

biz.aQute.bndlib/src/aQute/bnd/osgi/MetaInfService.java

+		/**
+		 * Get the comments that preceded this implementation definition
+		 */
+		public Optional<String> getComments() {


Is this used?

Not yet, but it is important information for use. I always make my code handle a use case but try to stay away from the specifics. I compare it with drawing a rectangle around a messy curvy perimeter of requirements.

I find it very important that all code is refective so outsiders can use it in many different ways. Notice that this class has no clue about Service Provider

Ok. I just wanted to make sure it is not left-over from early development steps and ended up here accidentally.

pkriens · 2023-12-02T10:30:34Z

I've played with the idea of automatically repeating the annotations but decided against it. I think it is confusing and it would require a new mechanism to stop the repetition.

And this is a rather bad thing anyway. Using the Java annotation is so much cleverer. It gets you all the IDE help, it adds your type to the services file, and the compiler verifies, you can use constants, etc. It is pretty dumb to use this over the real annotations. The only reason I worked on this is because there are a lot of people out there that prefer to cut off their nose to spite their face :-(

It would be nice if we had a good article somewhere to explain what the annotations do and how useful they are outside OSGi. After all, most open source programs actually use the bnd mvn plugin already. Why not use it to maintain your META-INF/services directory?

pkriens · 2023-12-02T10:32:36Z

The key advantage of using the annotations is that the the actual manifest code as orchestrated by the ServiceProvider and its Capability and Requirement annotations is used.

You realize that you can make a custom application annotation in a similar way?

HannesWell · 2023-12-03T10:19:18Z

I've played with the idea of automatically repeating the annotations but decided against it. I think it is confusing and it would require a new mechanism to stop the repetition.

That's right.
When requesting it in #5903, I only wanted to cover the most basic use-cases where all services should have the @ServiceProvider annotation, without any attributes different from the default well knowing that it would have limitations (all services would be processed and not attribute configuration possible).
Your approach is a good idea to make this much more powerful.

And this is a rather bad thing anyway. Using the Java annotation is so much cleverer. It gets you all the IDE help, it adds your type to the services file, and the compiler verifies, you can use constants, etc. It is pretty dumb to use this over the real annotations. The only reason I worked on this is because there are a lot of people out there that prefer to cut off their nose to spite their face :-(

Fully agree, but I can only speculate about why other projects are reluctant to use them.
Maybe it is because OSGi is not the hottest topic anymore or maybe because they don't know BND and it is often in the human nature to have some distrust in foreign things. I don't know.

It would be nice if we had a good article somewhere to explain what the annotations do and how useful they are outside OSGi. After all, most open source programs actually use the bnd mvn plugin already. Why not use it to maintain your META-INF/services directory?

Absolutely. That would be great. I'm trying to contribute OSGi metadata to the libraries and projects I'm getting in touch (slowly but steadily) and therefore it would be great to have something to reference instead of explaining it again and again.

You realize that you can make a custom application annotation in a similar way?

I didn't, but you are right. But can you tell a use-case where I would need that? I would need my own processor of these annotations to use it, wouldn't I?

laeubi · 2023-12-03T10:30:54Z

It would be nice if we had a good article somewhere to explain what the annotations do and how useful they are outside OSGi. After all, most open source programs actually use the bnd mvn plugin already. Why not use it to maintain your META-INF/services directory?

Actually there are a few approaches already, for example https://metainf-services.kohsuke.org/ and also some maven-plugin was to do it here and there.

What mostly bugs people I think is that these are bnd specific and the don't (and don't want to) know about OSGi and all that stuff. So it might help to have these @MetaInfServices like one or similar a separate artifact so they don't need to reference full bnd lib to use the annotation, if then there would be a tiny maven plugin similar to service-generator that just do the annotation processing it could be another pice in the puzzle

--- Signed-off-by: Peter Kriens <[email protected]> Signed-off-by: Peter Kriens <[email protected]>

pkriens · 2023-12-04T11:05:13Z

I've added an article https://bnd.discourse.group/t/automate-meta-inf-services-chores/397

HannesWell · 2023-12-05T07:27:51Z

Thank you for this PR. :)

pkriens · 2023-12-05T14:55:38Z

Can you take a look at the article, suggest improvements if anything is missing? If you let me know if it is ok, I will send a post on X.

this is an experiment based on an idea mentioned in bndtools#6304 it leverages the recent addition of PR bndtools#5912 that allowed to add annotations in comments of files in META-INF/services. But in this PR we basically pretent and add a aQute.bnd.annotation.spi.ServiceProvider annotation artificially. this causes bnd to generate Provide-Capability manifest headers for the services make sure biz.aQute.bndlib is on the buildpath which contains the 'aQute.bnd.annotation.spi.ServiceProvider' annotation Signed-off-by: Christoph Rueger <[email protected]>

it leverages the recent addition of PR bndtools#5912 that allowed to add annotations in comments of files in META-INF/services. But in this PR we basically pretent and add a aQute.bnd.annotation.spi.ServiceProvider annotation artificially. this causes bnd to generate Provide-Capability manifest headers for the services Signed-off-by: Christoph Rueger <[email protected]>

Parses META-INF/services files for annotations

16c6497

It is possible to add addnotions in the comments of the service files of the Service Loader. Fixes bndtools#5903 --- Signed-off-by: Peter Kriens <[email protected]> Signed-off-by: Peter Kriens <[email protected]>

pkriens requested a review from HannesWell December 1, 2023 15:00

HannesWell reviewed Dec 1, 2023

View reviewed changes

Moved to plugin, allow annotations without parenthesis

fd2d4d1

--- Signed-off-by: Peter Kriens <[email protected]> Signed-off-by: Peter Kriens <[email protected]>

pkriens merged commit 58b8818 into bndtools:master Dec 4, 2023
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chrisrueger mentioned this pull request Sep 28, 2024

Trying to wrap a non-OSGi jar using bnd, where the jar contains META-INF/services #6304

Closed

chrisrueger mentioned this pull request Oct 3, 2024

auto register capabilities for META-INF/services #6309

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Parses META-INF/services files for annotations #5912

Parses META-INF/services files for annotations #5912

pkriens commented Dec 1, 2023

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pkriens commented Dec 5, 2023

	.compile("#@(?<fqn>" + FQN_S + ")\\((?<attrs>.)" + "\\)\\s;?\\s*$");
	.compile("#@(?<type>" + FQN_S + ")(\\((?<attrs>.))?" + "\\)\\s;?\\s*$");

Parses META-INF/services files for annotations #5912

Parses META-INF/services files for annotations #5912

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