Generate reference docs with docbook-gradle-plugin

The docbook-gradle-plugin has been custom-developed specifically to
handle Spring projects. It is highly opinionated, and not terribly
configurable in its current form. Sources and documentation are
available via the 'gradle-plugins' github repository at

    https://github.com/cbeams/gradle-plugins

Note that this repository may soon move locations to the SpringSource
GitHub organization, in which case the url will be

    https://github.com/SpringSource/gradle-plugins

In any case, the build plans for these plugins can be found at

    https://build.springsource.org/browse/GRADLEPLUGINS

build.gradle

+buildscript {
+    repositories {
+        maven { url 'https://repo.springsource.org/plugins-snapshot' }
+    }
+    dependencies {
+        classpath 'org.springframework.build.gradle:docbook-reference-plugin:0.1.2-SNAPSHOT'
+    }
+}
+
 configure(allprojects) {
     apply plugin: 'java'
     apply plugin: 'eclipse'
@@ -35,6 +44,12 @@ configure(allprojects) {
 configure(rootProject) {
     description = 'Spring Framework'
 
+    apply plugin: 'docbook-reference'
+
+    reference {
+        sourceDir = file('src/reference/docbook')
+    }
+
     // don't publish the default jar for the root project
     configurations.archives.artifacts.clear()