Add example with custom task in one and separate files

.gitignore

@@ -1,2 +1,3 @@
 .gradle
+.idea
 build/

21-custom-task-in-one-file/build.gradle

@@ -0,0 +1,18 @@
+// Based on example: https://gradle.org/docs/current/userguide/custom_tasks.html
+
+// Use the default greeting
+task hello(type: GreetingTask)
+
+// Customize the greeting
+task greeting(type: GreetingTask) {
+    greeting = 'greetings from Brno'
+}
+
+class GreetingTask extends DefaultTask {
+    String greeting = 'hello from Y Soft'
+
+    @TaskAction
+    def greet() {
+        println greeting
+    }
+}

22-custom-task-in-buildSrc/build.gradle

@@ -0,0 +1,10 @@
+apply plugin: 'groovy'
+
+import com.ysoft.greeting.GreetingTask
+
+task hello(type: GreetingTask)
+
+// Customize the greeting
+task greeting(type: GreetingTask) {
+    greeting = 'greetings from Brno'
+}

22-custom-task-in-buildSrc/buildSrc/src/main/groovy/com/ysoft/greeting/GreetingTask.groovy

@@ -0,0 +1,13 @@
+package com.ysoft.greeting
+
+import org.gradle.api.DefaultTask
+import org.gradle.api.tasks.TaskAction
+
+class GreetingTask extends DefaultTask {
+    String greeting = 'hello from Y Soft'
+
+    @TaskAction
+    def greet() {
+        println greeting
+    }
+}

README.md

@@ -227,3 +227,29 @@ Result is available at: http://localhost:8080/20-grails
 
 More information: https://github.com/grails/grails-gradle-plugin
 Video recording from Building Grails App With Gradle: http://youtu.be/FwZvDU2Jeh8
+
+
+## 21-custom-task-in-one-file
+
+Gradle has support for defining custom task classes.
+Task class could be extended e.g. from DefaultTask.
+
+You can verify this sample by:
+
+    gradle hello
+    gradle greeting
+
+## 22-custom-task-in-buildSrc
+
+In previous example we discussed how to add custom task. Storing many
+custom tasks in one file makes it unreadable. It's possible to split logic into
+Groovy classes.
+
+Create buildSrc directory with src/main/groovy.
+Store here the class. It's necessary to add package name declaration and imports
+from GradleAPI.
+
+Functionality is the same:
+
+    gradle hello
+    gradle greeting