Thursday, February 26, 2015

Awesome Asciidoctor: Change Start Number for Numbered List

With Asciidoctor we can create numbered lists easily. When we want to change the number the list starts with we use the start attribute when we define the list.

== Numbered List

. Makes writing easy
.. Keep focus
.. Syntax
. Different output formats

// Start this list from 10.
.Start from 10
. Makes writing easy
// We can use it on all levels.
.. Keep focus
.. Syntax
. Different output formats

We get the following HTML output when we transform the document:

Written with Asciidoctor 1.5.2.

Wednesday, February 25, 2015

Awesome Asciidoctor: Customize How Missing Attributes Are Handled

Document attributes are like variables for your Asciidoctor document. Normally when we reference an attribute that is not set in our Asciidoctor markup the reference is still in the output. This is very handy, because we immediately see that a document attribute is not set. But we can customize this behavior with the document attribute attribute-missing. We can use the default value skip, which leaves the reference in the output. Another option is drop, which means the reference is dropped from the output. Finally we can set the value to drop-line, where the complete line with the attribute reference is dropped from the output.

In the following sample Asciidoctor markup we set the three values for the attribute attribute-missing:

== Handle Missing Attributes

:attribute-missing: skip

.`:attribute-missing: skip`
Line with attribute {sample-attr}, should show attribute reference.

:attribute-missing: drop

.`:attribute-missing: drop`
Line with attribute {sample-attr}, drops attribute reference.

:attribute-missing: drop-line

.`:attribute-missing: drop-line`
Line with attribute {sample-attr}, is completely dropped.

When we transform this to HTML5 we get the following output:

Written with Asciidoctor 1.5.2.

Thursday, February 19, 2015

Groovy Goodness: Access XML-RPC API

Recently I had to access the XML-RPC WordPress API for a small project. Luckily with Groovy we can access a XML-RPC server in a Groovy way. We need to use the Groovy XML-RPC module, which is a separate dependency. The module provides code to write a XML-RPC server, but also code to access a XML-RPC server as client. We use the class XMLRPCServerProxy in the package groovy.net.xmlrpc to act as a client to a XML-RPC API. The XMLRPCServerProxy class only needs to know the URL to access the API. All API methods are dynamically dispatched to the server, so it is very flexible.

In the following Groovy script we use the WordPress XML-RPC API to access posts:

import groovy.net.xmlrpc.*

// Use correct blog identifier.
def blogId = 0 

// Use correct URL for XML-RPC API.
def blogUrl = 'http://blog/xmlrpc' 

def blogUsername = 'mrhaki'
def blogPassword = 'secret'

// Create client access for XML-RPC API.
// The second parameter is set to true
// to autodetect encoding. Default encoding
// is ISO-8859-1.
def wordPress = new XMLRPCServerProxy(blogUrl, true)

// Now we can access the API methods from WordPress.
// Notice the API method wp.getPosts is dynamically
// available from the XMLRPCServerProxy instance.
def latestFivePost = 
             [number: 5, post_type: 'post'],
             ['post_id', 'post_title'])

latestFivePosts.each { post ->
    println "Blog post (#${post.post_id}): ${post.post_title}"

Written with Groovy 2.4.

Friday, February 6, 2015

Spocklight: Capture and Assert System Output

Spock supports JUnit rules out of the box. We simply add a rule with the @Rule annotation to our Spock specification and the rule can be used just like in a JUnit test. The Spring Boot project contains a JUnit rule OutputCapture to capture the output of System.out and System.err.

In the following example specification we apply the OutputCapture rule and use it in two feature methods:

package com.mrhaki.spock

import spock.lang.*

import org.springframework.boot.test.OutputCapture

class CaptureOutputSpec extends Specification {

    OutputCapture capture = new OutputCapture()

    def "capture output print method"() {
        print 'Groovy rocks'

        capture.toString() == 'Groovy rocks'

    def "banner text must contain given messagen and fixed header"() {
        final Banner banner = new Banner(message: 'Spock is gr8!')


        final List lines = capture.toString().tokenize(System.properties['line.separator'])
        lines.first() == '*** Message ***'
        lines.last()  == ' Spock is gr8! '


 * Class under test. The print method
 * uses println statements to display
 * some message on the console.
class Banner {

    String message 

    void print() {
        println ' Message '.center(15, '*')
        println message.center(15)


Written with Spock-0.7-groovy-2.0.

Wednesday, January 28, 2015

Groovy Goodness: Getting the Indices of a Collection

Since Groovy 2.4 we can use the indices property on a Collection to get the indices of the elements in the collection. We get an IntRange object as a result.

def list = [3, 20, 10, 2, 1]
assert list.indices == 0..4

// Combine letters in alphabet
// with position (zero-based).
def alphabet = 'a'..'z'
def alphabetIndices = [alphabet, alphabet.indices].transpose()
// alphabetIndices = [['a', 0], ['b', 1], ...]

// Find position of each letter
// from 'groovy' in alphabet.
def positionInAlphabet = 'groovy'.inject([]) { result, value ->
    result << alphabetIndices.find { it[0] == value }[1] + 1

assert positionInAlphabet == [7, 18, 15, 15, 22, 25]

Code written with Groovy 2.4.

Groovy Goodness: Pop And Push Items In a List

Groovy adds the pop and push methods to the List class. With the pop method we remove the last element of the list. And with the push method we add an element to the end of the list.

def list = ['Groovy', 'is', 'great!']

// Remove last item from list
// with pop().
assert list.pop() == 'great!'
assert list == ['Groovy', 'is']

// Remove last item
// which is now 'is'.

// Add new item to end of
// the list (equivalent for add()).

assert list == ['Groovy', 'rocks!']

Code written with Groovy 2.4.

Groovy Goodness: Getting All But the Last Element in a Collection with Init Method

In Groovy we can use the head and tail methods for a long time on Collection objects. With head we get the first element and with tail the remaining elements of a collection. Since Groovy 2.4 we have a new method init which returns all elements but the last in a collection.

In the following example we have a simple list and apply the different methods:

def gr8Tech = ['Groovy', 'Grails', 'Spock', 'Gradle', 'Griffon']

// Since Groovy 2.4 we can use the init method.
assert gr8Tech.init() == ['Groovy', 'Grails', 'Spock', 'Gradle']
assert gr8Tech.last() == 'Griffon'

assert gr8Tech.head() == 'Groovy'
assert gr8Tech.tail() == ['Grails', 'Spock', 'Gradle', 'Griffon']

Code written with Groovy 2.4.

Monday, January 26, 2015

Groovy Goodness: Take Or Drop Last Items From a Collection

We know Groovy has a lot of nice methods for working with collections. For example in previous blog posts we have seen how to take or drop elements from a list and even with a condition. Since Groovy 2.4 we can now also use the dropRight and takeRight methods to take or drop elements from the end of the list.

In the following example we have a simple list and we use the dropRight and takeRight methods to get elements from the list:

def list = ['Simple', 'list', 'with', 5, 'items']

assert list.takeRight(1) == ['items']
assert list.takeRight(2) == [5, 'items']
assert list.takeRight(0) == []
// Whole list, because we take more items then the size of list
assert list.takeRight(6) == ['Simple', 'list', 'with', 5, 'items']

assert list.dropRight(1) == ['Simple', 'list', 'with', 5]
assert list.dropRight(3) == ['Simple', 'list']
assert list.dropRight(5) == []
assert list.dropRight(0) == ['Simple', 'list', 'with', 5, 'items']
assert list == ['Simple', 'list', 'with', 5, 'items']

def array = ['Rock on!', 'Groovy baby!'] as String[]
assert array.takeRight(1) == ['Groovy baby!'] as String[]
assert array.dropRight(1) == ['Rock on!'] as String[]

def range = 0..10
assert range.takeRight(2) == [9,10]
assert range.takeRight(4) == 7..10
assert range.dropRight(5) == 0..5

Written with Groovy 2.4.

Wednesday, January 7, 2015

Gradle Goodness Notebook is Published

Today Gradle Goodness Notebook is published. This book is an electronic publication with all blog posts about Gradle Goodness bundled. The posts are slightly edited and categorized into sections.

The book is published at Leanpub and is available in three formats: PDF, MOBI (for Kindle) and EPUB (for iPad). Updates for the book are free. So new Gradle Goodness blog posts will be added to the book and you will get those free.

It is also possible to buy a Goodness Notebooks bundle. This bundle contains the Groovy and Gradle Goodness Notebook books.

I hope you will enjoy the book and I will keep it up-to-date with new content when I publish new Gradle Goodness blog posts.

Wednesday, December 24, 2014

Gradle Goodness: Rename Ant Task Names When Importing Ant Build File

Migrating from Ant to Gradle is very easy with the importBuild method from AntBuilder. We only have to add this single line and reference our existing Ant build XML file and all Ant tasks can now be executed as Gradle tasks. We can automatically rename the Ant tasks if we want to avoid task name collisions with Gradle task names. We use a closure argument with the importBuild method and return the new task names. The existing Ant task name is the first argument of the closure.

Let's first create a simple Ant build.xml file:


    <target name="showMessage"
        description="Show simple message">

        <echo message="Running Ant task 'showMessage'"/>


    <target name="showAnotherMessage"
        description="Show another simple message">

        <echo message="Running Ant task 'showAnotherMessage'"/>



The build file contains two targets: showMessage and showAnotherMessage with a task dependency. We have the next example Gradle build file to use these Ant tasks and prefix the original Ant task names with ant-:

// Import Ant build and 
// prefix all task names with
// 'ant-'.
ant.importBuild('build.xml') { antTaskName ->

// Set group property for all 
// Ant tasks.
tasks.matching { task ->
}*.group = 'Ant'

We can run the tasks task to see if the Ant tasks are imported and renamed:

$ gradle tasks --all
Ant tasks
ant-showAnotherMessage - Show another simple message [ant-showMessage]
ant-showMessage - Show simple message

We can execute the ant-showAnotherMessage task and we get the following output:

$ gradle ant-showAnotherMessage
[ant:echo] Running Ant task 'showMessage'
[ant:echo] Running Ant task 'showAnotherMessage'


Total time: 3.953 secs

Written with Gradle 2.2.1