host Android build on maven central

[CluEleSsUK]

Is your feature request related to a problem? Please describe.
Java 8/Android compatibility was added with #133, but presently I can't see the jar being hosted anywhere.

I was hoping to raise a PR on https://github.com/decentralized-identity/jsonld-common-java and https://github.com/decentralized-identity/did-common-java to provide Android support and titanium-json-ld is the key transitive dependency.

Describe the solution you'd like
titanium-json-ld uploaded under a separate artifactId to maven central or equivalent.

Describe alternatives you've considered
I've currently used git submodules to achieve the above, but it comes with problems:

• gradle doesn't have a proxy for maven profiles, so building the maven module from gradle requires a fiddly bit of groovy
• not sure if individual commits relate 1-1 to maven releases
• it's ugly

I had a look in your github actions to try and raise a PR, but it didn't seem like the maven-push action actually does a maven push and I assumed you do it manually - I could well be misunderstanding though!

Additional context
Thanks for your work so far!

[filip26]

Hi @CluEleSsUK,
the current pom.xml uses profiles to separate Java11 and Android -Pandroid builds, the same applies on deployment -Pmaven-central. Unfortunately, this approach does not allow to build and deploy both artifacts together.

We need to rethink this and find out the right solution. As I'm not an expert on maven nor nexus-staging-maven-plugin a help is needed and very welcome.

[CluEleSsUK]

I'm also no expert in maven or the nexus-staging plugin, but I'm happy to take a look. A cheap solution could be profiles for -Pmaven-central and -Pmaven-central-android - I'll see if I can come up with something tidier!

[filip26]

The tricky part is how to build all the artifact together.

e.g.

titanium-json-ld-1.0.3.jar
titanium-json-ld-1.0.3-android.jar
titanium-json-ld-1.0.3-javadoc.jar
titanium-json-ld-1.0.3-sources.jar
titanium-json-ld-1.0.3.pom

Some recommend https://maven.apache.org/plugins/maven-toolchains-plugin/ to get different builds done at once, to get rid off the android profile.

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment!

[filip26]

The easiest solution is to name android artifact like titanium-json-ld-androd or titanium-android and publish it as a separate artifact, including separate versioning, javadoc, and sources.

[pkozelka]

Yes, separate module that gets always compiled. I believe it's best; conditional compilation is rarely a good thing in Java.

[filip26]

@pkozelka The biggest downside of this approach is that it requires two pom.xml - one for JRE11 build and second one for JRE8. Beside duplicates in the files there is no IDE support (e.g. now, you can select a maven profile in Eclipse).

What about Gradle? Could that help?

[filip26]

I've just run into toolchains.

Guide for Supporting Multiple Versions of Java (8, 11, 14) in Your Maven Project.

[filip26]

Structure:

pom_parent.xml
pom.xml <- default, inherits pom_parent.xml
pom_jre8.xml <- android build, inherits pom_parent.xml

Use maven-flatten-plugin to get distributable pom

> export JAVA_HOME=<JDK11>
> mvn clean package

> export JAVA_HOME=<JDK8>
> mvn -f pom_jre8.xml clean package