Jackson bundles are missing OSGi's osgi.serviceloader metadata

[chrisr3]

Bundles need to include extra metadata to support java.util.ServiceLoader inside an OSGi framework. Jackson's bundles are all missing this metadata.

In theory, it should just be a matter of applying Bnd's @ServiceConsumer and @ServiceProvider annotations in the correct places as described here, where these annotations can be provided like this:

diff --git a/base/pom.xml b/base/pom.xml
index 6235a67..4972957 100644
--- a/base/pom.xml
+++ b/base/pom.xml
@@ -30,9 +30,17 @@ of Jackson: application code should only rely on `jackson-bom`
          parent pom, and then also allow override as need be
       -->
     <jackson-bom.version>${project.parent.version}</jackson-bom.version>
+
+    <version.bnd.annotation>6.3.1</version.bnd.annotation>
   </properties>
 
   <dependencies>
+    <dependency>
+      <groupId>biz.aQute.bnd</groupId>
+      <artifactId>biz.aQute.bnd.annotation</artifactId>
+      <version>${version.bnd.annotation}</version>
+      <scope>provided</scope>
+    </dependency>
     <dependency> <!-- all components use junit for testing -->
       <groupId>junit</groupId>
       <artifactId>junit</artifactId>

I am struggling to wrap my head around your myriad of separate repositories, and so you may have a better way of providing this dependency.

[cowtowncoder]

Being bit of OSGi newbie, quick question: is this really needed for jackson-core which does not provide Service of any type -- meaning there is no life-cycle or such. It is simply a library with visibility as defined by exports (and theoretically imports but in practice having few).

So what would be the meaning of ServiceLoader for this particular component? (or for others, jackson-databind)
It sounds like there is a problem to solve, I just want to understand what that is.

[chrisr3]

So what would be the meaning of ServiceLoader for this particular component? (or for others, jackson-databind) It sounds like there is a problem to solve, I just want to understand what that is.

jackson-core contains META-INF/services/com.fasterxml.jackson.core.JsonFactory, which means that it "provides" the classes inside this file as ServiceLoader "services". As a rule, the classes listed inside META-INF/services/* files need to be annotated as @ServiceProvider, and classes which directly invoke ServiceLoader.load(...) need to be annotated as @ServiceConsumer. These annotations instruct the Maven plugin to generate extra OSGi metadata inside the bundles, which can be used by OSGi's Service Loader Mediator

The story becomes more complicated with jackson-databind because e.g. jackson-databind-xml uses XMLInputFactory.newFactory() etc which use ServiceLoader.load(...) indirectly. The Apache Aries SPI-Fly bundle supports extra OSGi metadata for cases like these. I know there is an issue with at least jackson-databind-xml and woodstox-core because I have tripped over it.

[cowtowncoder]

Thank you @chrisr3! Interesting that this hadn't been reported before but I guess better late than never :)

[chrisr3]

Thank you @chrisr3! Interesting that this hadn't been reported before but I guess better late than never :)

No worries. The maven-bundle-plugin will do the "heavy lifting" for you; all you need to do is apply the @ServiceProvider and @ServiceConsumer annotations. The @ServiceProvider ones are easier because the classes are by definition listed inside each bundle's META-INF/services/* files. However, as I understand SPI, I don't see how these woodstox ones can be correct 😕:

org.codehaus.stax2.validation.XMLValidationSchemaFactory.dtd
org.codehaus.stax2.validation.XMLValidationSchemaFactory.relaxng
org.codehaus.stax2.validation.XMLValidationSchemaFactory.w3c

I'll also mention that I haven't found any direct invocations of ServiceLoader.load(...) anywhere in Jackson yet, which would mean there are no suitable candidates for @ServiceConsumer. But even just adding appropriate @ServiceProvider annotations would help.

[cowtowncoder]

Yeah I wouldn't count on Woodstox having it correct. Would obv. love help there too if someone could point out better ways.

As to Jackson, there is no ServiceLoader usage (or even JDK SPI outside of OSGi): all OSGi metadata is meant for "external consumption" (by something else using Jackson).
I guess there can't be any external usage either since metadata is missing tho. :)

[chrisr3]

I guess there can't be any external usage either since metadata is missing tho. :)

There are "ways" around bundles having broken metadata. However, it's much easier if the bundles are fixed at source 😉.

[cowtowncoder]

note to self: Woodstox PR FasterXML/woodstox#151 should work as template here.
Needs some care wrt merging from 2.x to 3.0, but otherwise fine.
Going forward I assume jackson-databind would benefit from the same process, after which dataformat modules (jackson-dataformats-binary, jackson-dataformats-text, jackson-dataformat-xml) likewise.

[chrisr3]

note to self: ..., after which dataformat modules (jackson-dataformats-binary, jackson-dataformats-text, jackson-dataformat-xml) likewise.

jackson-dataformat-xml will also require upgrading to use woodstox-core v6.3.0, of course 😉.

[cowtowncoder]

Yes. I'll go ahead and do that now, then:

FasterXML/jackson-dataformat-xml#536

EDIT: Done.