Update to the build file to modernize the docs

This commit throws out Docbook and gives us the modern
look and feel for the docs.
It uses Asciidoctor to generate the PDF.

* Polishing for `build.gradle` in regards to asciidoc
* Upgrade to the latest Asciidoc and its plugins
* Combine Asciidoc backends into a single Gradle task
* Fix issues with section levels, duplicated ids and project version in
the docs
* Remove obsolete files: not used by Asciidoc

Author: Jay Bryant

build.gradle

@@ -4,8 +4,7 @@ buildscript {
 		maven { url 'https://repo.spring.io/plugins-release' }
 	}
 	dependencies {
-		classpath 'io.spring.gradle:docbook-reference-plugin:0.3.1'
-		classpath 'org.asciidoctor:asciidoctor-gradle-plugin:1.5.8'
+		classpath 'org.asciidoctor:asciidoctorj-pdf:1.5.0-alpha.16'
 		classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion"
 		classpath "org.jetbrains.kotlin:kotlin-allopen:$kotlinVersion"
 	}
@@ -16,6 +15,7 @@ plugins {
 	id 'base'
 	id 'project-report'
 	id 'idea'
+	id 'org.asciidoctor.convert' version '1.5.9.2'
 }
 
 description = 'Spring Kafka'
@@ -29,7 +29,7 @@ ext {
 	linkScmUrl = 'https://github.com/spring-projects/spring-kafka'
 	linkScmConnection = 'https://github.com/spring-projects/spring-kafka.git'
 	linkScmDevConnection = '[email protected]:spring-projects/spring-kafka.git'
-
+	docResourcesVersion = '0.1.0.RELEASE'
 }
 
 allprojects {
@@ -234,45 +234,58 @@ project ('spring-kafka-test') {
 	}
 }
 
-apply plugin: 'org.asciidoctor.convert'
+configurations {
+	docs
+}
+
+dependencies {
+	docs "io.spring.docresources:spring-doc-resources:${docResourcesVersion}@zip"
+}
+
+task prepareAsciidocBuild(type: Sync) {
+	dependsOn configurations.docs
+	from {
+		configurations.docs.collect { zipTree(it) }
+	}
+	from 'src/reference/asciidoc/'
+	into "$buildDir/asciidoc"
+}
 
 asciidoctor {
-	sourceDir = file("$docsDir")
+	dependsOn 'prepareAsciidocBuild'
+	sourceDir "$buildDir/asciidoc"
 	sources {
 		include 'index.adoc'
 	}
-	backends = ['html5', 'docbook']
-	logDocuments = true
-	options = [
-		doctype: 'book',
-	]
-	attributes = [
-		docinfo: '',
-		toc2: '',
-		'compat-mode': '',
-		imagesdir: '',
-		stylesdir: "stylesheets/",
-		stylesheet: 'golo.css',
-		'spring-kafka-version': "$version",
-		'source-highlighter': 'highlightjs'
-	]
+	resources {
+		from(sourceDir) {
+			include 'images/*', 'css/*', 'js/**'
+		}
+	}
+	backends = ['html5', 'pdf']
+	options doctype: 'book', eruby: 'erubis'
+	attributes  'icons': 'font',
+			'idprefix': '',
+			'idseparator': '-',
+			docinfo: 'shared',
+			sectanchors: '',
+			sectnums: '',
+			stylesdir: 'css/',
+			stylesheet: 'spring.css',
+			'linkcss': true,
+			'source-highlighter=highlight.js',
+			'highlightjsdir=js/highlight',
+			'highlightjs-theme=atom-one-dark-reasonable',
+			'project-version': project.version,
+			'allow-uri-read': ''
 }
 
-
-apply plugin: DocbookReferencePlugin
-
-reference {
-	sourceFileName = 'index.xml'
-	sourceDir = file("$buildDir/asciidoc/docbook")
-	pdfFilename = 'spring-kafka-reference.pdf'
-	expandPlaceholders = ''
+task reference(dependsOn: asciidoctor) {
+	group = 'Documentation'
+	description = 'Generate the reference documentation'
 }
 
-reference.dependsOn asciidoctor
-
-[asciidoctor, reference, referenceEpub, referenceHtmlMulti, referenceHtmlSingle, referencePdf].each {
-	it.onlyIf { "$System.env.NO_REFERENCE_TASK" != 'true' || project.hasProperty('ignoreEnvToStopReference') }
-}
+reference.onlyIf { "$System.env.NO_REFERENCE_TASK" != 'true' || project.hasProperty('ignoreEnvToStopReference') }
 
 sonarqube {
 	properties {
@@ -305,7 +318,7 @@ task api(type: Javadoc) {
 	destinationDir = new File(buildDir, "api")
 }
 
-task docsZip(type: Zip) {
+task docsZip(type: Zip, dependsOn: [reference]) {
 	group = 'Distribution'
 	classifier = 'docs'
 	description = "Builds -${classifier} archive containing api and reference " +
@@ -319,7 +332,12 @@ task docsZip(type: Zip) {
 		into 'api'
 	}
 
-	from (reference) {
+	from ('build/asciidoc/html5') {
+		into 'reference'
+	}
+
+	from ('build/asciidoc/pdf') {
+		include 'index.pdf'
 		into 'reference'
 	}
 }

src/reference/asciidoc/index-docinfo.xml

@@ -1,6 +1,17 @@
 [[spring-kafka-reference]]
 = Spring for Apache Kafka
-:toc:
+:toc: left
+:toclevels: 4
+:numbered:
+:icons: font
+:hide-uri-scheme:
+Gary Russell; Artem Bilan; Biju Kunjummen; Jay Bryant
+
+*{project-version}*
+
+(C) 2016 - 2019 by Pivotal Software, Inc.
+
+Copies of this document may be made for your own use and for distribution to others, provided that you do not charge any fee for such copies and further provided that each copy contains this Copyright Notice, whether distributed in print or electronically.
 
 == Preface
 
@@ -15,8 +26,7 @@ include::./whats-new.adoc[]
 
 == Introduction
 
-This first part of the reference documentation is a high-level overview of Spring for Apache Kafka and the underlying
-concepts and some code snippets that can help you get up and running as quickly as possible.
+This first part of the reference documentation is a high-level overview of Spring for Apache Kafka and the underlying concepts and some code snippets that can help you get up and running as quickly as possible.
 
 include::quick-tour.adoc[]
 
@@ -41,8 +51,7 @@ include::si-kafka.adoc[]
 
 == Other Resources
 
-In addition to this reference documentation, we recommend a number of other resources that may help you learn about
-Spring and Apache Kafka.
+In addition to this reference documentation, we recommend a number of other resources that may help you learn about Spring and Apache Kafka.
 
 - https://kafka.apache.org/[Apache Kafka Project Home Page]
 - http://projects.spring.io/spring-kafka/[Spring for Apache Kafka Home Page]

src/reference/asciidoc/index.adoc

@@ -1,4 +1,3 @@
-[[preface]]
 The Spring for Apache Kafka project applies core Spring concepts to the development of Kafka-based messaging solutions.
 We provide a "`template`" as a high-level abstraction for sending messages.
 We also provide support for Message-driven POJOs.

src/reference/asciidoc/preface.adoc

@@ -14,7 +14,7 @@ The following example shows how to do so with Maven:
 <dependency>
   <groupId>org.springframework.kafka</groupId>
   <artifactId>spring-kafka</artifactId>
-  <version>{spring-kafka-version}</version>
+  <version>{project-version}</version>
 </dependency>
 ----
 ====
@@ -24,20 +24,20 @@ The following example shows how to do so with Gradle:
 ====
 [source,groovy,subs="+attributes"]
 ----
-compile 'org.springframework.kafka:spring-kafka:{spring-kafka-version}'
+compile 'org.springframework.kafka:spring-kafka:{project-version}'
 ----
 ====
 
 [[compatibility]]
-===== Compatibility
+==== Compatibility
 
 This quick tour works with the following versions:
 
 * Apache Kafka Clients 2.0.0
 * Spring Framework 5.1.x
 * Minimum Java version: 8
 
-===== A Very, Very Quick Example
+==== A Very, Very Quick Example
 
 As the following example shows, you can use plain Java to send and receive a message:
 
@@ -122,7 +122,7 @@ private Map<String, Object> senderProps() {
 ----
 ====
 
-===== With Java Configuration
+==== With Java Configuration
 
 You can do the same work as appears in the previous example with Spring configuration in Java.
 The following example shows how to do so:
@@ -210,7 +210,7 @@ public class Listener {
 ----
 ====
 
-===== Even Quicker, with Spring Boot
+==== Even Quicker, with Spring Boot
 
 Spring Boot can make things even simpler.
 The following Spring Boot application sends three messages to a topic, receives them, and stops: