Last July, I started a thread[1] here about ways to get native jakarta namespace variants of artifacts, which we need for our move to EE 10. One of the items discussed there was "5) New maven module, transform source and build". I'm posting here as a kind of status update and tutorial about that approach.
At this point there are 11 maven modules in the WildFly main source tree[2] that are producing artifacts using the approach described there, and there are PRs open for at least a couple more. I have filed or soon will file JIRAs[3] for all the remaining WF main tree's modules that produce artifacts that WildFly Preview currently is transforming when it provisions a server[4], so there will be more coming.
Overview
The high level overview of how these work is that a pom-only maven module is created that corresponds to an existing module that produces an javax artifact. The new module's pom uses the batavia maven plugin[5] (and Eclipse Transformer under the covers) to find the source code from the existing maven module, transform it, and write the transformed output to the target/ dir of the new module, specifically in the 'generated-resources', 'generated-sources', 'generated-test-resources' and 'generated-test-sources' dirs. That generated source is then associated with the overall maven execution for the module, and thereafter gets included as part of the subsequent compile, test, package, install and deploy goals executed for the module. So, presto we have native jakarta source available that is then compiled and tested and used to package/install/deploy binary, source and javadoc jars.[6]
The generated source does not get committed into the git repository. The git repo only has the pom.
It's a common thing for generated source to be used in an artifact build; for example it's the technique we use to generate implementation classes from the XXXLogger interfaces we have for each of our subsystems. What we're doing here just takes this concept to the max by generating 100% of the source, including test source.
Tutorial
I'm going to use a PR I sent up yesterday to illustrate how to create one of these:
Steps:
1) Decide whether the module you want to work on is ready. If you're not the component lead responsible for the module, ask that lead. To see if a module is 'ready', look at its compile time dependencies and see if it still depends on other artifacts for which a native jakarta variant is needed and doesn't exist yet. Ask here or in zulip if you are not sure! Things can change quickly, and there also may be some edge cases where you'd think you need a jakarta namespace dependency but you really don't.
If there are dependencies that are not ready yet, stop and wait until they are available. Or be prepared for your new module to not build, at which point you can save your work and wait.
2) Create a new dir under ee-9/source-transform for your new module. If the module you are transforming isn't directly under the root of the WF source, then create a matching structure under ee-9/source-transform. For example, I created ee-9/source-transform/jpa/spi to produce a jakarta.* variant of jpa/spi.
3) Copy the pom.xml from an *existing source-transform module* into your new dir. Easiest is to use one that comes from a dir the same # of levels below source-transform as your new dir, so a couple relative paths in your new pom are correct. For my PR I copied over
Don't start with the pom from your source input module. Unless you want to work out how to adapt it to use the source transformation. :) Granted it's not rocket science. But it's easier for code reviewers to look at these if they look like the other ones.
4) Change the artifactId in your new pom to *exactly* match the artifactId of the module you're transforming, but with "-jakarta" appended:
5) Change the 'name' tag to something appropriate, like
6) Change the 'transformer-input-dir' maven property to point to the root of the module you are transforming:
This property is used in the batavia maven plugin config in the parent source-transform dir. Each child module sets the property to point to the correct input source for that module.
This one small tweak is the only thing you need to deal with to get the source transformation set up.
7) Configure dependencies.
a) Delete the existing 'dependency' entries in your new pom, as they are for whatever random file you copied in.
b) Copy over the 'dependency' entries from the pom of the module you are transforming.
c) For any entries where your new artifact uses a dependency with a different groupId:artifactId from the one you're transforming, change the GA. For example:
EE 8 JTA
became EE 9.1 JTA
Or, in another example
an EE 8 based 'ee' subsystem module dep:
became instead a dep on the new '-jakarta' variant:
d) A nice to have is to separate from the others in the dependency listing deps where WF Preview is using a different artifact from what standard WF is using. For example see
This separation helps code reviewers.
8) Tell your new module's parent to include it in the build:
9) The ee-9/pom.xml maintains a dependencyManagement set for all artifacts that differ in WF Preview from what is in standard WF. These can either be artifacts whose GA is not used at all in standard WF, or ones where WF Preview uses a different version. Add your new artifact to this dependencyManagement:
10) Allow re-use of the module.xml that incorporates this artifact between standard WF and WF Preview. This is done by modifying the module.xml to add an expression that the maven-resource-plugin replaces when preparing the module.xml resource file for use in the FP build:
The added @module.jakarta.suffix@ gets replaced either with an empty string (standard WF) or "-jakarta" (WF Preview)