Export classpath and mainClass as environment variables.

[thomasmey]

Jib automatically determines the main class and sets the image'
entrypoint accordingly.
This extension exports these values also as environment variables
in the created image, so a custom entrypoint script can do some processing
and then jump into java with:
java -cp ${JIB_JAVA_CLASSPATH} ${JIB_JAVA_MAIN_CLASS}

See also issue GoogleContainerTools/jib#3147

[thomasmey]

@googlebot I signed it

[chanseokoh]

Thanks for the awesome contribution! This is indeed what many people have asked for multiple times and what we really wanted to do eventually. This will be super useful!

And this extension can be expanded in the future so that not only it sets the environment variables but it directly substitutes these values for some keywords in an entrypoint.

    <pluginExtensions>
      <pluginExtension>
        <implementation>com.google.cloud.tools.jib.maven.extension.classpathmainclass.JibClasspathMainClassExtension</implementation>
        <configuration implementation="com.google.cloud.tools.jib.maven.extension.classpathmainclass.Configuration">

          <!-- extension configuration -->
          <entrypoint>java,-cp,JIB_JAVA_CLASSPATH:/my/classpath,-Dmy.prop=value,JIB_JAVA_MAIN_CLASS</entrypoint>
        </configuration>
      </pluginExtension>
    </pluginExtensions>

But that's another idea going forward, and I think this extension is already very useful!

[chanseokoh]

And you can do ./gradlew build to run tests locally.

[chanseokoh]

@thomasmey just checking in, will you keep working on this?

[thomasmey]

Hi,

Yes, will do so.

I want to add some unit tests.
Can you please review the current state again, after forced push update?

[chanseokoh]

Thanks!

[chanseokoh]

We shouldn't have a common project. The Maven and Gradle extensions will be published as separate JARs, so unless we publish the common project as another separate JAR, having a common package will result in split packages.

[chanseokoh]

That is, we should duplicate the code in Maven and Gradle, and that's fine.

[thomasmey]

Hi, another update. now with tests! 😄

[chanseokoh]

Mostly looks good!

You will be able to see that ./gradlew build is failing on GitHub Actions unit tests. I think it can be fixed by copying necessary things from a build.gradle file in other first-party extensions.

[codecov]

Codecov Report

Merging #82 (2bbade9) into master (ad3293f) will decrease coverage by 1.88%.
The diff coverage is 58.33%.

@@             Coverage Diff              @@
##             master      #82      +/-   ##
============================================
- Coverage     84.87%   82.98%   -1.89%     
- Complexity      152      160       +8     
============================================
  Files            14       18       +4     
  Lines           628      676      +48     
  Branches         73       81       +8     
============================================
+ Hits            533      561      +28     
- Misses           83       93      +10     
- Partials         12       22      +10     

Impacted Files	Coverage Δ	Complexity Δ
...spathmainclass/JibClasspathMainClassExtractor.java	50.00% <50.00%> (ø)	2.00 <2.00> (?)
...spathmainclass/JibClasspathMainClassExtractor.java	50.00% <50.00%> (ø)	2.00 <2.00> (?)
...spathmainclass/JibClasspathMainClassExtension.java	83.33% <83.33%> (ø)	2.00 <2.00> (?)
...spathmainclass/JibClasspathMainClassExtension.java	83.33% <83.33%> (ø)	2.00 <2.00> (?)

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[thomasmey]

please have a look again, look good to me now.
and thanks for your patience with me 😄

[chanseokoh]

Sorry for the delay. There are a few things to fix, but given the delay, I'll take care of it after merging this.

Thank you very much for this great contribution! It'll be very useful to many people.