Add a section on AOT to the Gradle plugin's docs

Closes gh-32750

Author: wilkinsona

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/build.gradle

@@ -97,6 +97,10 @@ task asciidoctorPdf(type: org.asciidoctor.gradle.jvm.AsciidoctorTask) {
 	}
 }
 
+tasks.withType(org.asciidoctor.gradle.jvm.AbstractAsciidoctorTask) {
+	attributes "native-build-tools-version": nativeBuildToolsVersion
+}
+
 javadoc {
 	options {
 		author = true

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/asciidoc/aot.adoc

@@ -0,0 +1,43 @@
+[[aot]]
+= Ahead-of-Time Processing
+Spring AOT is a process that analyzes your code at build-time in order to generate an optimized version of it.
+It is most often used to help generate GraalVM native images.
+
+The Spring Boot Gradle plugin provides tasks that can be used to perform AOT processing on both application and test code.
+The tasks are configured automatically when the {nbt-gradle-plugin}[GraalVM Native Image plugin] is applied:
+
+[source,groovy,indent=0,subs="verbatim,attributes",role="primary"]
+.Groovy
+----
+include::../gradle/aot/apply-native-image-plugin.gradle[]
+----
+
+[source,kotlin,indent=0,subs="verbatim,attributes",role="secondary"]
+.Kotlin
+----
+include::../gradle/aot/apply-native-image-plugin.gradle.kts[]
+----
+
+
+[[aot.processing-applications]]
+== Processing Applications
+Based on your `@SpringBootApplication`-annotated main class, the `processAot` task generates a persistent view of the beans that are going to be contributed at runtime in a way that bean instantiation is as straightforward as possible.
+Additional post-processing of the factory is possible using callbacks.
+For instance, these are used to generate the necessary reflection configuration that GraalVM needs to initialize the context in a native image.
+
+As the `BeanFactory` is fully prepared at build-time, conditions are also evaluated.
+This has an important difference compared to what a regular Spring Boot application does at runtime.
+For instance, if you want to opt-in or opt-out for certain features, you need to configure the environment used at build time to do so.
+To this end, the `processAot` task is a {gradle-dsl}/org.gradle.api.tasks.JavaExec.html[`JavaExec`] task and can be configured with environment variables, system properties, and arguments as needed.
+
+The `nativeCompile` task of the GraalVM Native Image plugin is automatically configured to use the output of the `processAot` task.
+
+
+[[aot.processing-tests]]
+== Processing Tests
+The AOT engine can be applied to JUnit 5 tests that use Spring's Test Context Framework.
+Suitable tests are processed by the `processTestAot` task to generate `ApplicationContextInitialzer` code.
+As with application AOT processing, the `BeanFactory` is fully prepared at build-time.
+As with `processAot`, the `processTestAot` task is `JavaExec` sub-class and can be configured as needed to influence this processing.
+
+The `nativeTest` task of the GraalVM Native Image plugin is automatically configured to use the output of the `processAot` and `processTestAot` tasks.

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/asciidoc/index.adoc

@@ -39,7 +39,7 @@ v{gradle-project-version}
 :buildpacks-reference: https://buildpacks.io/docs
 :paketo-reference: https://paketo.io/docs
 :paketo-java-reference: {paketo-reference}/buildpacks/language-family-buildpacks/java
-:nbt-gradle-plugin: https://graalvm.github.io/native-build-tools/latest/gradle-plugin.html
+:nbt-gradle-plugin: https://graalvm.github.io/native-build-tools/{native-build-tools-version}/gradle-plugin.html
 
 
 
@@ -57,6 +57,8 @@ include::publishing.adoc[leveloffset=+1]
 
 include::running.adoc[leveloffset=+1]
 
+include::aot.adoc[leveloffset=+1]
+
 include::integrating-with-actuator.adoc[leveloffset=+1]
 
 include::reacting.adoc[leveloffset=+1]

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/asciidoc/reacting.adoc

@@ -70,9 +70,13 @@ When Gradle's {application-plugin}[`application` plugin] is applied to a project
 When the {nbt-gradle-plugin}[GraalVM Native Image plugin] is applied to a project, the Spring Boot plugin:
 
 . Applies the `org.springframework.boot.aot` plugin that:
-.. Registers a `ProcessAot` task named `processAot` that will generate AOT-optimized source code for the application.
+.. Registers `aot` and `aotTest` source sets.
+.. Registers a `ProcessAot` task named `processAot` that will generate AOT-optimized source for the application in the `aot` source set.
 .. Configures the Java compilation and process resources tasks for the `aot` source set to depend upon `processAot`.
-. Adds the output of the `aot` source set to the classpath of the `nativeCompile` task.
+.. Registers a `ProcessTestAot` task named `processTestAot` that will generated AOT-optimized source for the application's tests in the `aotTest` source set.
+.. Configures the Java compilation and process resources tasks for the `aotTest` source set to depend upon `processTestAot`.
+. Adds the output of the `aot` source set to the classpath of the `main` GraalVM native binary.
+. Adds the output of the `aotTest` source set to the classpath of the `test` GraalVM native binary.
 . Configures the GraalVM extension to disable Toolchain detection.
 
 

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/gradle/aot/apply-native-image-plugin.gradle

@@ -0,0 +1,5 @@
+plugins {
+	id 'org.springframework.boot' version '{gradle-project-version}'
+	id 'org.graalvm.buildtools.native' version '{native-build-tools-version}'
+	id 'java'
+}

spring-boot-project/spring-boot-tools/spring-boot-gradle-plugin/src/docs/gradle/aot/apply-native-image-plugin.gradle.kts

@@ -0,0 +1,5 @@
+plugins {
+	id("org.springframework.boot") version "{gradle-project-version}"
+	id("org.graalvm.buildtools.native") version "{native-build-tools-version}"
+	java
+}