fix reactor#896 Reactivate AsciidoctorJ PDF build under JDK9

build.gradle

@@ -22,11 +22,13 @@ buildscript {
 	maven { url "http://repo.spring.io/plugins-release" }
   }
   dependencies {
-	classpath 'org.springframework.build.gradle:propdeps-plugin:0.0.7',
-			'io.spring.gradle:spring-io-plugin:0.0.4.RELEASE',
-			'com.github.jengelman.gradle.plugins:shadow:1.2.0',
-			'org.asciidoctor:asciidoctorj-pdf:1.5.0-alpha.11',
-			"org.jetbrains.kotlin:kotlin-gradle-plugin:${kotlinVersion}"
+	classpath 'org.springframework.build.gradle:propdeps-plugin:0.0.7'
+	classpath 'io.spring.gradle:spring-io-plugin:0.0.4.RELEASE'
+	classpath 'com.github.jengelman.gradle.plugins:shadow:1.2.0'
+	classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:${kotlinVersion}"
+	classpath 'org.jruby:jruby-complete:9.1.17.0'
+	classpath 'org.asciidoctor:asciidoctor-gradle-plugin:1.5.7'
+	classpath 'org.asciidoctor:asciidoctorj-pdf:1.5.0-alpha.16'
   }
 }
 

gradle/doc.gradle

@@ -21,13 +21,7 @@ configure(rootProject) {
 			include "index.asciidoc"
 		}
 		outputDir file("$buildDir/reactor-code/build/asciidoc")
-		//TODO remove once a working combination of asciidoctorj, asciidoctorj-pdf and asciidoctor-gradle-plugin is found
-		if (JavaVersion.current().isJava9Compatible()) {
-		  backends = ['html5']
-		}
-		else {
-		  backends = ['html5', 'pdf']
-		}
+	  backends = ['html5', 'pdf']
 		logDocuments = true
 		options = [
 				doctype: 'book'