WIP: AVRO-4223 Gradle plugin for generating Java code #3614

frevib · 2026-01-05T07:52:26Z

What is the purpose of the change

Gradle plugin to generate Java code from Avro files

Verifying this change

This change added tests and can be verified as follows:

cd to avro/lang/java/gradle-plugin

./gradlew test

Documentation

Does this pull request introduce a new feature? (yes)
If yes, how is the feature documented? (docs): https://github.com/apache/avro/blob/ae791a0794323440f795cf7265ff542272ed3085/lang/java/gradle-plugin/README.md

Release

BETA 0.0.2 is released and fully works with AVSC files: https://central.sonatype.com/artifact/eu.eventloopsoftware.avro-gradle-plugin/eu.eventloopsoftware.avro-gradle-plugin.gradle.plugin/versions - read docs (above) how to use

BETA 0.0.5 https://plugins.gradle.org/plugin/eu.eventloopsoftware.avro-gradle-plugin

An official release will be done in the coming month

Fix Intellij not finding generated sources Add generating BigDecimal property

Add dynamic output directory

Cleanup readme Change POM artifactId name

…ugin # Conflicts: # doc/package-lock.json

Cleanup

Sineaggi · 2026-01-05T16:30:12Z

...lugin/src/main/kotlin/eu/eventloopsoftware/avro/gradle/plugin/tasks/CompileAvroSchemaTask.kt

+    fun compileSchema() {
+        project.logger.info("Generating Java files from Avro schemas...")
+
+        if (!source.isEmpty) {


If something like DirectoryProperty is used in conjunction with @SkipWhenEmpty , a task state of NO_SOURCE should be used when no sources are available.

How can we log some useful message when we use @SkipWhenEmpty and no sources are available? Now we have the else branch where we log.

Do we need to? Other Gradle tasks (compileJava, compileTestJava etc) don't warn when no sources are available.

From a code point of view, if @SkipWhenEmpty is more idiomatic Gradle, I understand. But we should care about user experience. It will improve UX If the user directly sees why no code was generated because e.g. a wrong directory was provided.

lang/java/gradle-plugin/src/main/kotlin/eu/eventloopsoftware/avro/gradle/plugin/GradlePlugin.kt

Sineaggi · 2026-01-05T16:41:49Z

lang/java/gradle-plugin/README.md

+For Intellij to recognize the newly generated Java files add this to `build.gradle.kts`:
+
+```kotlin
+tasks.named("compileKotlin") { dependsOn(tasks.named("avroGenerateJavaClasses")) }


This is the jank that can be avoided by setting the srcDir using the task to avoid requiring dependsOn fixes https://github.com/apache/avro/pull/3614/changes#r2662114325

Compilation fails if we don't use that line. Unresolved reference 'SomeGeneratedClass.

I've used your method of adding sources: https://github.com/apache/avro/pull/3614/files#diff-02e299025197282b1f1fec4a0fe89c1fb47606fcd9a2b0fc55206ca1ae8f511dR75

This works: 3853d9a#diff-6f6c17b901d3a280371d65a7c7907afd0275f06f4dd28682c65343c4a92a97ebR40

No need to add tasks.named("compileKotlin") { dependsOn(tasks.named("avroGenerateJavaClasses")) } any more. Thanks for pointing it out 🙏

Sineaggi · 2026-01-05T16:43:12Z

lang/java/gradle-plugin/README.md

+
+#### How can I benefit from Kotlin's null safety?
+Use `createNullSafeAnnotations = true` and Java getters will be annotated with 
+`@org.jetbrains.annotations.NotNull`/ `@org.jetbrains.annotations.Nullable`. This way


Gradle has finished migrating to jspecify, Kotlin 2.+ also supports jspecify annotations. Perhaps those should be used by default instead of jetbrains'?

Although JSpecify seems to become the new standard, I'd be hesitant to make this change yet for the Maven plugin.

Here though, as both Gradle and Kotlin are moving in this direction and this plugin is new, I think the JSpecify annotations are a good default to use.

Sineaggi · 2026-01-05T16:44:09Z

lang/java/gradle-plugin/README.md

+Kotlin will recognize which value is nullable.
+
+#### When I update my schemas and generate code, the Java classes stay the same
+Yes, for now you have to `./gradlew clean` every time you update your Avro schemas.


We should clear controlled output directories (outputDir/testOutputDir) instead of requiring the user to do so.

lang/java/gradle-plugin/src/main/resources/META-INF/eu.eventloopsoftware.properties

Sineaggi · 2026-01-05T17:19:06Z

...-plugin/src/main/kotlin/eu/eventloopsoftware/avro/gradle/plugin/tasks/AbstractCompileTask.kt

+import org.gradle.api.tasks.Input
+import org.gradle.api.tasks.SourceTask
+
+abstract class AbstractCompileTask : SourceTask() {


Gradle's SourceTask is probably not the preferred superclass for this task, that's usually used for things like compilation, analysis. I'd recommend DefaultTask.

DefaultTask is being deprecated. Why is SourceTask not preferred? From the docs: A {@code SourceTask} performs some operation on source files, which is kind of what we're doing.

I've not seen anything that would indicate DefaultTask being deprecated, and I can't imagine they could considering how many tasks already inherit directly from DefaultTask.

That's an error on my side, DefaultTask is indeed not being deprecated.

Anyway, with DefaultTask we don't have source, setIncludes(..) and setExcludes(..)which are very useful in filtering for specific Avro file extension like "**/*.avsc". Then we have to manually filter the FileTree for Avro file extensions. Do you still recommend it?

I think I'm starting to understand why SourceTask is maybe not the right fit. We now use source and sourceDirectory, which are used for the same things. If we use DefaultTask we don't have the issue of this ambiguity, and only use sourceDirectory

...n/src/main/kotlin/eu/eventloopsoftware/avro/gradle/plugin/extension/GradlePluginExtension.kt

Sineaggi · 2026-01-05T17:57:29Z

...lugin/src/main/kotlin/eu/eventloopsoftware/avro/gradle/plugin/tasks/CompileAvroSchemaTask.kt

+
+    @TaskAction
+    fun compileSchema() {
+        project.logger.info("Generating Java files from Avro schemas...")


We should be using the task's logger, not the project's logger. I also don't think these logs provide any useful information.

Sineaggi · 2026-01-05T17:59:19Z

...le-plugin/src/main/kotlin/eu/eventloopsoftware/avro/gradle/plugin/tasks/CompileSchemaTask.kt

+
+
+    private fun getSourceDirectoryFullPath(directoryProperty: Property<String>): File =
+        project.layout.projectDirectory.dir(directoryProperty.get()).asFile


Calling project at runtime is soft-deprecated in Gradle 8, deprecated in Gradle 9 and will be unsupported in Gradle 10. https://docs.gradle.org/8.12.1/userguide/configuration_cache.html#config_cache:requirements:use_project_during_execution

This would be avoided by using DirectoryPropertys, which would already be project-relative.

lang/java/gradle-plugin/src/main/kotlin/eu/eventloopsoftware/avro/gradle/plugin/GradlePlugin.kt

Use directory property instead of Property<String>

Rename classes

Remove unneeded file which is generated by the java-gradle-plugin

Use Task logger instead of project logger

Fix comment

Refactor adding sources

Add custom logical type factories

opwvhk · 2026-01-07T10:11:23Z

lang/java/gradle-plugin/build.gradle.kts

+        name = "Avro Gradle Plugin"
+        description = "Generate Java code from Avro files"
+        inceptionYear = "2025"
+        url = "https://github.com/frevib/avro/"


Suggested change

url = "https://github.com/frevib/avro/"

url = "https://github.com/apache/avro/"

For the non-beta release (and below)

opwvhk · 2026-01-07T10:15:26Z

...c/main/kotlin/eu/eventloopsoftware/avro/gradle/plugin/extension/AvroGradlePluginExtension.kt

+     * at schema compiling time. All files can therefore be referenced as classpath
+     * resources following the directory structure under the source directory.
+     *
+     * @parameter property="sourceDirectory"


Can we use the Maven annotations instead? IMHO they're easier to read (less likely to be missed when reading the code).

opwvhk

Looking good so far!

Update readme with versioning New release: 0.0.5

frevib · 2026-01-07T15:39:51Z

New BETA 0.0.5release is now on Gradle plugin portal: https://plugins.gradle.org/plugin/eu.eventloopsoftware.avro-gradle-plugin.

Remove Maven publishing, only publish in Gradle plugin registry

Add generated code before compilation, so no dependsOn(..) is needed any more

Release 0.0.7

frevib added 30 commits November 19, 2025 21:24

Add Gradle plugin bootstrap

3f04a2c

Add test for generating Java code

7a18d79

Rename task

e6082e6

Add Maven publish

8947e41

Rever change to Java file

d0b8794

Rever changes to Java files

ea3e5b6

Cleanup

2589fdd

Add schemaType

28934e0

Cleanup test

737e585

Use Path instead of File for tests

543c66b

Remove null checks because it's Kotlin

5f1ac64

Improve test

3a9ae61

Add test source and output dir

93d7194

Refactor

afd90c8

Add field visibility property

b765eb7

Add excludes property

1b0d7f5

Add stringType and templateDirectory

fafd298

Add properties

634cd63

Add properties

f71ba50

Check if source directories exist

7c67834

Cleanup

453c7a0

Cleanup

1b449b4

Cleanup

4fdab98

Add readme

c4a06ae

Move to SourceTask

1b6efe7

Fix Intellij not finding generated sources Add generating BigDecimal property

Update readme

6c0b29e

Add dependency for generated sources

444d91c

Update reamde

6daa02e

Add dynamic output directory

Remove unneeded adding of dependency

626e90c

Update readme

21c8340

frevib added 2 commits January 5, 2026 16:30

AVRO-4223

2a5b93c

Cleanup readme Change POM artifactId name

Merge remote-tracking branch 'upstream/main' into AVRO-4223-gradle-pl…

8cb27ef

…ugin # Conflicts: # doc/package-lock.json

github-actions bot removed the website label Jan 5, 2026

AVRO-4223

8b1acc5

Cleanup

Sineaggi reviewed Jan 5, 2026

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Sineaggi reviewed Jan 5, 2026

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Sineaggi reviewed Jan 5, 2026

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...n/src/main/kotlin/eu/eventloopsoftware/avro/gradle/plugin/extension/GradlePluginExtension.kt Outdated Show resolved Hide resolved

Sineaggi reviewed Jan 5, 2026

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frevib added 7 commits January 6, 2026 09:16

AVRO-4223

89378cf

Use directory property instead of Property<String>

AVRO-4223

e247865

Rename classes

AVRO-4223

01f1ae7

Remove unneeded file which is generated by the java-gradle-plugin

AVRO-4223

47b34d4

Use Task logger instead of project logger

AVRO-4223

8094451

Fix comment

AVRO-4223

61ed721

Refactor adding sources

AVRO-4223

6a6f3c9

Add custom logical type factories

opwvhk reviewed Jan 7, 2026

View reviewed changes

AVRO-4223

cb6fbf4

Update readme with versioning New release: 0.0.5

frevib added 3 commits January 7, 2026 16:47

AVRO-4223

f041b10

Remove Maven publishing, only publish in Gradle plugin registry

AVRO-4223

3853d9a

Add generated code before compilation, so no dependsOn(..) is needed any more

AVRO-4223

3ac3f41

Release 0.0.7



		private fun getSourceDirectoryFullPath(directoryProperty: Property<String>): File =
		project.layout.projectDirectory.dir(directoryProperty.get()).asFile

	url = "https://github.com/frevib/avro/"
	url = "https://github.com/apache/avro/"

WIP: AVRO-4223 Gradle plugin for generating Java code #3614

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WIP: AVRO-4223 Gradle plugin for generating Java code #3614

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frevib commented Jan 5, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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opwvhk Jan 7, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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frevib commented Jan 7, 2026

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frevib commented Jan 5, 2026 •

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