diff --git a/convention/src/main/kotlin/io/gitlab/jfronny/scripts/JavadocExt.kt b/convention/src/main/kotlin/io/gitlab/jfronny/scripts/JavadocExt.kt
new file mode 100644
index 0000000..8428b15
--- /dev/null
+++ b/convention/src/main/kotlin/io/gitlab/jfronny/scripts/JavadocExt.kt
@@ -0,0 +1,16 @@
+package io.gitlab.jfronny.scripts
+
+import org.gradle.api.Project
+import org.gradle.api.tasks.javadoc.Javadoc
+import org.gradle.external.javadoc.StandardJavadocDocletOptions
+import org.gradle.kotlin.dsl.named
+
+val Javadoc.opts: StandardJavadocDocletOptions
+    get() = options as? StandardJavadocDocletOptions
+    ?: throw TypeCastException("Unexpected javadoc options type")
+
+fun Javadoc.linksOffline(url: String, project: Project) {
+    val task = project.tasks.named<Javadoc>("javadoc").get()
+    opts.linksOffline(url, task.destinationDir.toString())
+    dependsOn(task)
+}
\ No newline at end of file
diff --git a/convention/src/main/kotlin/jf.umldoc.gradle.kts b/convention/src/main/kotlin/jf.umldoc.gradle.kts
new file mode 100644
index 0000000..0afa91d
--- /dev/null
+++ b/convention/src/main/kotlin/jf.umldoc.gradle.kts
@@ -0,0 +1,24 @@
+import io.gitlab.jfronny.scripts.*;
+
+plugins {
+    `java-library`
+}
+
+val umldoc by configurations.creating
+
+dependencies {
+    umldoc("nl.talsmasoftware:umldoclet:2.1.0")
+    umldoc("org.jdrupes.taglets:plantuml-taglet:2.0.1")
+}
+
+tasks.javadoc {
+    source = sourceSets.main.get().allJava
+    opts.docletpath = umldoc.files.toList()
+    opts.doclet = "nl.talsmasoftware.umldoclet.UMLDoclet"
+    opts.tagletPath = umldoc.files.toList()
+    opts.taglets("org.jdrupes.taglets.plantUml.PlantUml", "org.jdrupes.taglets.plantUml.StartUml", "org.jdrupes.taglets.plantUml.EndUml")
+}
+
+java {
+    withJavadocJar()
+}
\ No newline at end of file