Feature: Java bindings for libktx

[ShukantPal]

Fixes #479

Todo

I need you to answer some questions:

• Will you publish the JAR to maven?
• The current CMakeLists.txt for the JNI bindings assumes libktx is already installed on the system. Is that ok? (It isn't integrated with the main build)
• I don't have Windows so can't test the build on it - would be nice if someone can help?
• JUnit tests in CI?

[CLAassistant]

All committers have signed the CLA.

[MarkCallow]

* Will you publish the JAR to maven?

If that is the standard way to publish JNI stuff, then sure, let's do it. Neither Appveyor nor Travis support direct deployment to Maven. I haven't checked GitHub Actions yet. Can it be done via FTP/SFTP?

* The current `CMakeLists.txt` for the JNI bindings assumes libktx is already installed on the system. Is that ok? (It isn't integrated with the main build)

I'd prefer it to be integrated, i.e., the JNI build should have the ktx target as a dependency.

* I don't have Windows so can't test the build on it - would be nice if someone can help?

The Appveyor build which is done using VS 2015, 2017 and 2019 succeeded. I haven't reviewed the changes yet so I don't know if anything related to this JNI addition was actually built. The Travis build failed. Please look at it. I may be able to try on Windows.

* JUnit tests in CI?

Tests would be great. It will also be a way to test on Windows. Please add this.

[MarkCallow]

This is only a partial review. I am submitting this to unblock replying to other comments (I hope).

[ShukantPal]

@MarkCallow I moved the build script to jni.cmake in the cmake directory. It is now included as a part of the main build. It requires the environment variable JAVA_HOME to be defined; if it isn't, it will log a non-fatal warning.

How can I make sure it fails the CI if JAVA_HOME isn't defined?

[ShukantPal]

@MarkCallow It would be nice if you could look into the "jni_md.h" not being found on Windows 😄.

[MarkCallow]

If you publish to maven central, people can add libktx as a dependency and maven will install for them. That's a pro; however, its hard to get access to that repository and the person who will own the artifact (you) will have to prove that they're a part of Khronos Group (to get the org.khronos groupId). That's the con.

Releasing with GitHub is super simple - you simply publish the JAR in the artifacts. People can download it and add it to their classpath manually to bundle it in their Java applications.

I will look into getting access to maven central when I am preparing the next release. Assuming I get access what do I need to do here in order to send the artifacts to maven? Make sure the necessary code is here in this PR commented out.

[MarkCallow]

Please

• answer my question about the macOS build and fix the build, but then comment out the lines as, with it, it will likely exceed the CI time limit.
• add the code, again commented out, for submitting to maven central.
• Fix the conflicts and rebase.

I want to get this PR merged.

[ShukantPal]

I'll address this this weekend. Sorry for the delay - am exceptionally busy this month.

[ShukantPal]

@MarkCallow I haven't published to Maven before. I'm following instructions from https://dzone.com/articles/publish-your-artifacts-to-maven-central.

You don't need additional code for publishing to Maven Central. Instead, once you have your username / password to the repository, you'll need to add this to $HOME/.m2/settings.xml (as listed in the article) on the machine that will publish libktx for Java:

<settings>

<servers>
<server>
<id>ossrh</id>
<username>your-jira-id</username>
<password>your-jira-pwd</password>
</server>
</servers>

<profiles>
<profile>
<id>ossrh</id>
<activation>
<activeByDefault>true</activeByDefault>
</activation>
<properties>
<gpg.passphrase>[your_gpg_passphrase]</gpg.passphrase>
</properties>
</profile>
</profiles>

</settings>

Note that you'll need to generate a GPG key and put the passphrase in the settings.xml

Once this configuration is done, you'll need to run the following commands in the Java project folder (interface/java_binding):

mvn clean
mvn release:prepare
mvn release:perform

[ShukantPal]

✅ Fixed the macOS build and answered the question
✅ Posted instructions for publishing to maven. No code needed (some config needed on your machine with credentials)
✅ Fixed conflicts

[MarkCallow]

The conflicts still need to be fixed.

[ShukantPal]

The conflicts still need to be fixed.

What?

[MarkCallow]

The conflicts still need to be fixed.

What?

This is what I am seeing. I don't know why you are seeing something different.

[ShukantPal]

@MarkCallow Can you do a merge commit? (change from rebase and merge to just merge?)

[ShukantPal]

Any way I can help here @MarkCallow ?

[MarkCallow]

Sorry for the delay. I've been away from the computer for a couple of days. Thank you very much for this great addition to KTX.