doc(crd-generator): add usage description for Gradle users (6722)

Signed-off-by: Bernhard Strähle <[email protected]>

crd-generator/README.md

@@ -0,0 +1,39 @@
+# CRD Generator
+
+## Modules
+
+### CRD Generator v1 (deprecated since 7.0.0)
+
+- **CRD Generator API v1** - `io.fabric8:crd-generator-api`  
+  _Core implementation of the old generator, based on [sundrio](https://github.com/sundrio/sundrio)._ 
+- **CRD Generator annotation processing tool (APT)** - `io.fabric8:crd-generator-apt`  
+  _Annotation processor which hooks into the build process to generate CRDs._
+
+### CRD Generator v2
+- **CRD Generator API v2** - `io.fabric8:crd-generator-api-v2`  
+  _Core implementation of the new generator, based on [Jackson/jsonSchema](https://github.com/FasterXML/jackson-module-jsonSchema)._
+- **CRD Generator Collector** - `io.fabric8:crd-generator-collector`  
+  _Shared component to find and load compiled Custom Resource classes in directories and Jar files._
+- **CRD Generator Maven Plugin** - `io.fabric8:crd-generator-maven-plugin`   
+  _Maven plugin that generates CRDs during the build process._
+- **CRD Generator CLI** - `io.fabric8:crd-generator-cli`    
+  _CLI tool that generates CRDs when executed._
+
+### Utility Modules
+_(not published)_
+
+- **test-apt** - `io.fabric8:crd-generator-test-apt`  
+  _Integration tests for CRD Generator API v1 and the annotation processor tool_
+- **test** - `io.fabric8:crd-generator-test`  
+  _Approval tests for CRD Generator API v1 and v2_
+
+## Usage
+
+- [Introduction and Annotation usage](../doc/CRD-generator.md)
+- [CRD Generator Maven Plugin](maven-plugin/README.md)
+- [CRD Generator CLI tool](cli/README.md)
+- [CRD Generator usage with Gradle in build script](gradle/README.md)
+
+### Deprecated Tools
+
+- [CRD Generator annotation processing tool (APT)](apt/README.md)

crd-generator/gradle/README.md

@@ -0,0 +1,77 @@
+# CRD Generator - Usage with Gradle in build script
+
+The CRD Generator v2 can be used in a [build script](https://docs.gradle.org/current/userguide/writing_build_scripts.html) without an additional plugin:
+
+## Kotlin DSL (`build.gradle.kts`)
+
+```kotlin
+import io.fabric8.crdv2.generator.CRDGenerationInfo
+import io.fabric8.crdv2.generator.CRDGenerator
+import io.fabric8.crd.generator.collector.CustomResourceCollector
+import java.nio.file.Files
+
+plugins {
+    id("java")
+}
+
+group = "io.fabric8.crd-generator.gradle"
+version = "0.0.1-SNAPSHOT"
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    compileOnly("io.fabric8:kubernetes-client-api:7.0.0")
+}
+
+buildscript {
+    repositories {
+        mavenCentral()
+    }
+    dependencies {
+        classpath("io.fabric8:crd-generator-api-v2:7.0.0")
+        classpath("io.fabric8:crd-generator-collector:7.0.0")
+    }
+}
+
+tasks.register("generateCrds") {
+  description = "Generate CRDs from compiled custom resource classes"
+  group = "crd"
+
+  val sourceSet = project.sourceSets["main"]
+
+  val compileClasspathElements = sourceSet.compileClasspath.map { e -> e.absolutePath }
+
+  val outputClassesDirs = sourceSet.output.classesDirs
+  val outputClasspathElements = outputClassesDirs.map { d -> d.absolutePath }
+
+  val classpathElements = listOf(outputClasspathElements, compileClasspathElements).flatten()
+  val filesToScan = listOf(outputClassesDirs).flatten()
+  val outputDir = sourceSet.output.resourcesDir
+
+  doLast {
+    Files.createDirectories(outputDir!!.toPath())
+
+    val collector = CustomResourceCollector()
+      .withParentClassLoader(Thread.currentThread().contextClassLoader)
+      .withClasspathElements(classpathElements)
+      .withFilesToScan(filesToScan)
+
+    val crdGenerator = CRDGenerator()
+      .customResourceClasses(collector.findCustomResourceClasses())
+      .inOutputDir(outputDir)
+
+    val crdGenerationInfo: CRDGenerationInfo = crdGenerator.detailedGenerate()
+
+    crdGenerationInfo.crdDetailsPerNameAndVersion.forEach { (crdName, versionToInfo) ->
+      println("Generated CRD $crdName:")
+      versionToInfo.forEach { (version, info) -> println(" $version -> ${info.filePath}") }
+    }
+  }
+}
+
+tasks.named(JvmConstants.CLASSES_TASK_NAME) {
+  finalizedBy("generateCrds")
+}
+```

doc/CRD-generator.md

@@ -1,4 +1,4 @@
-# CRD generation
+# CRD Generator
 
 The [CRD Generator annotation processing tool (APT)](../crd-generator/apt/README.md) (`io.fabric8:crd-generator-apt`) and its API (`io.fabric8:crd-generator-api`) are being deprecated and will eventually be removed once we offer a complete replacement for all users.
 
@@ -38,7 +38,8 @@ with Maven:
 with Gradle:
 
 > [!NOTE]
-> The Gradle plugin is not available yet. Please use the Maven plugin or the CLI tool.
+> The Gradle plugin is not available yet.  
+> Meanwhile, Gradle users can use the [CRD Generator in a build script](../crd-generator/gradle/README.md).
 
 Now you can define a `class` that extends `io.fabric8.kubernetes.client.CustomResource`
 and the corresponding CRD is generated in the folder: `target/classes/META-INF/fabric8`