Set Java11 as minimal version

* Remove use of 'task.options.release' for Java version configuration in
in favour of Gradle's preferrs 'toolchain'.
* Removed Java 8 from pipelines.
* Bump Gradle to latest v8.0.2
* Remove use of 'io.spring.dependency-management' Gradle plugin in
'spring-boot' app in favor of Gradle's BOM support. This reduces
maintenance since only Boot version needs to be updated.

Fixes #1150

.github/workflows/continuous-integration.yaml

@@ -18,16 +18,13 @@ jobs:
       max-parallel: 4
       matrix:
         java:
-          - '8'
           - '11'
           - '17'
           - '19'
         os:
           - ubuntu-latest
           - macos-latest
         exclude:
-        - os: macos-latest
-          java: '8'
         - os: macos-latest
           java: '19'
     runs-on: ${{ matrix.os }}

asciidoctorj-springboot-integration-test/build.gradle

@@ -11,8 +11,3 @@ dependencies {
 }
 
 test.dependsOn(':asciidoctorj-springboot-integration-test:springboot-app:assemble')
-
-tasks.withType(JavaCompile).configureEach { task ->
-    task.options.release = 17
-}
-

asciidoctorj-springboot-integration-test/springboot-app/build.gradle

@@ -1,6 +1,7 @@
+import org.springframework.boot.gradle.plugin.SpringBootPlugin
+
 plugins {
-	id 'org.springframework.boot' version '3.0.0'
-	id 'io.spring.dependency-management' version '1.1.0'
+	id 'org.springframework.boot' version '3.0.4'
 	id 'java'
 }
 
@@ -13,14 +14,18 @@ repositories {
 
 dependencies {
 	implementation project(':asciidoctorj')
+
+	implementation platform(SpringBootPlugin.BOM_COORDINATES)
 	implementation 'org.springframework.boot:spring-boot-starter-web'
 	implementation 'org.springframework.boot:spring-boot-starter-actuator'
 
 	testImplementation 'org.springframework.boot:spring-boot-starter-test'
 }
 
-tasks.withType(JavaCompile).configureEach { task ->
-	task.options.release = 17
+java {
+	toolchain {
+		languageVersion = JavaLanguageVersion.of(17)
+	}
 }
 
 bootJar {

build.gradle

@@ -113,21 +113,13 @@ subprojects {
 
   plugins.withType(JavaPlugin) {
     project.tasks.withType(JavaCompile) { task ->
-      if (JavaVersion.current().isJava11Compatible()) {
-        task.options.release = 8
-      }
       if (project.hasProperty("showDeprecation")) {
         options.compilerArgs << "-Xlint:deprecation"
       }
       if (project.hasProperty("showUnchecked")) {
         options.compilerArgs << "-Xlint:unchecked"
       }
     }
-    project.tasks.withType(GroovyCompile) { task ->
-      if (JavaVersion.current().isJava11Compatible()) {
-        task.options.release = 8
-      }
-    }
   }
 
   repositories {
@@ -201,7 +193,6 @@ configure(subprojects.findAll { !it.isDistribution() }) {
   javadoc {
     // Oracle JDK8 likes to fail the build over spoiled HTML
     options.addStringOption('Xdoclint:none', '-quiet')
-    options.source('8')
   }
 }
 
@@ -210,6 +201,9 @@ configure(subprojects.findAll { !it.name.endsWith('-distribution') && ! it.name.
   java {
     withJavadocJar()
     withSourcesJar()
+    toolchain {
+      languageVersion.set(JavaLanguageVersion.of(11))
+    }
   }
 
 }

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.0.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.0.2-bin.zip
 networkTimeout=10000
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists