Sunday, November 09, 2014

Gradle : How to modify tasks post task graph creation

Gradle allows you to script your build file and add hooks in to the build lifecycle so you can maximize flexibility without complicating build setup and tasks.
One of the useful ways to manipulate all tasks once they are loaded by gradle into task execution graph is to use the whenReady lifecycle hook which only gets called when gradle  the complete tasks execution graph.This allows you to dynamically modify task properties, add new properties,etc. This comes helpful when you need to manipulate some tasks based on the user arguments passed in the project or some other project properties.

Below is the snippet that you need to add to make this work:
1:  gradle.taskGraph.whenReady {  
2:   tasks.each {  
3:    it.doFirst {   
4:     println "Calling ${}"  
5:    }  
6:   }  
7:  }  

 sgokak ~Todo $ gradle build  
 Calling compileJava  
 :processResources UP-TO-DATE  
 Calling classes  
 Calling war  
 Calling assemble  
 :compileTestJava UP-TO-DATE  
 :processTestResources UP-TO-DATE  
 Calling testClasses  
 :test UP-TO-DATE  
 Calling check  
 Calling build  

As you can see from the above output, the doFirst Closure  is only executed when the task is actually executed and not for any UP-TO-DATE tasks.


Sunday, June 28, 2009

No If No else Only OOP ;)

While going through the Dzone links , i was happy and amazed to found Anti-IF Campaign . The overall aim of the campaign is to promote OOP usage in place of procedural If's and other conditional programming constructs.This would make you agile and keep complexity under control.

In my current and many of past project , i have seen lots and lots of this happening as this is an easy way for a developer at any level to rationalize behavior using this constructs.But the maintenance hell you get with such crap is huge, even when you are still in System Integration or UAT stage of your project.

To start with applying OOP in your cases ,try to get the abstractions right.This may take some time as this will involve understanding a bit about the domain ,if you already have not.
Another of the best way to get into this mode is refactoring your current code with strong tests under your belt. As i am currently reading Refactoring by Martin Fowler,there is one complete chapter dedicated to removing such rote ,repeating and tangled constructs with delegation and polymorphism .There are other refactorings that talk about putting behaviors in proper classes which again makes this If-else clutter go away and distributes responsibility uniformly across classes.

Hurry!!! Join the Campaign and involve your team.Feel free to share your experiences and thoughts of aligning with Anti-IF Campaign.


Tuesday, May 19, 2009

More Groovier collections

Ranges are a beautiful ways of mangaing feinite sequence with a defined start and end.

println a // prints [1,2,3,4,5]
println a.size() // prints 5
println a.from // prints 1
println //prints 5

println x // prints [a,b,c,d,e,f]

You can also use ranges in subscript way to get part of a list.

x = 2
println a[0..2] // printrs [1,2,3]

You can also loop over each element of a range simple as follows

println it

this prints all elements on new line.

Ranges can work with any objects whose class implments the Commprable interface having next and previous methods.

Another interesting thing that happens with all collections in any programming langugae is looping over it.Groovy has various options to this in many elegant ways.

Classical for .
This is usual for loop found in C,C++,JAVA,etc.this makes you feel home

for(int i=0;i<5;i++)
println i // you know what it prints

Iterable for.
This for works with any class that implments iterable like ranges,lists,maps,etc.
For on ranges

for(i in 0..5)
println i

For on lists

for(i in [1,2,3,4,5])
println i

For on maps

for(e in m)
println e.key + "=" + e.value

For on strings

for(i in "Groovy")
println i // prints ewach character on newline

Another flexible and intuitive nature added to collections in groovy is that all Empty collections are evaluated to false in all boolean checks.
Following all prints true .(trick question : try removing ! :)

println ![]
println !''
println ![:]

Feel free to share your Groovy tips and tricks in the comments section


Sunday, April 19, 2009

Groovier collections

I have been groovying almost over a year now.There are many remarkable things that groovy do in a very simple and intuitive manner .If you haven't start using it, you are already late.Today , i am going to discuss how groovy takes using collection to another level.Currently, i use it for routine scripts and code generation.
Java Collections framework is one of the most used SDK API (esp. in enterprise applications).This Api allows you do handle ,manipulate and represent the Collection of any Java objects.This greatly reduces programming effort where as boosting programming performance and fostering reuse.
Groovy adds to this many useful operators and tweaks to make working with collection api more entertaining experience.
Following is the ways you create a List in groovy:

println L.class //prints class java.util.ArrayList

This showing that ArrayList is used by groovy behind the scenes to create a List representation.

To work with LinkedList do this

L = new LinkedList([0,1,2,3]);
println L.class

To access, any element from the List , you can use array-like notation familiar to most of Java developers.Other ways to retrieve the elements are get and getAt methods expecting the index (-ve index allowed).

println L[2] //prints 2
println L[-3] //prints 1
println L.get(0) //prints 0
println L.getAt(1) //prints 1

The most frequent operation done on a list is to add elements to it.This can be acheived using +=,<< or using add method.To merge 2 lists use, addAll or + operator.

L = [0,1,2,3]
L += 4
L << 5
println L //prints [0,1,2,3,4,5,6]
println L // prints [0,1,2,3,4,5,6,a,b]
K = L + [99,100]
println K // prints [0,1,2,3,4,5,6,a,b.99.100]

Removing an element is equally easy.Use -,-= or call minus.remove() method of list is too supported.

L = [0,1,2,3]
L -= [3]
println L //prints [0,1,2]
L = L.minus(2)
println L //prints [0,1]
println L //prints [1]

Reversing the content of the list can be done as

L = [0,1,2,3]
println L.reverse() //prints [3,2,1,0]

Using map is easier than ever, the content left to the : is the key and to the right is the value.

M= ['a':'A','b':'B','c':'C']
println M // prints [a:A,b:B,c:C]
println M.getClass() //prints java.util.LinkedHashMap.We cannot use .class as . is reserved to access the key-values
println new HashMap(['a':'A','b':'B','c':'C']) // prints [a:A,b:B,c:C]

Retreiving value can be done numerous ways.

M= ['a':'A','b':'B','c':'C']
println M.a // prints A
println M['a'] // prints A
println M.get('c') // prints C
println M.getAt('b') // prints B
println M.getAt('x') // prints null as no key is matched.

Adding new key-value pairs too has various alternative.

M= ['a':'A','b':'B','c':'C']
M['d'] = 'D'
println M // prints ['a':'A','b':'B','c':'C','d':'D']
println M // prints ['a':'A','b':'B','c':'C','d':'D','e':'E']
println M // prints ['a':'A','b':'B','c':'C','d':'D','e':'E','f':'F']

Remove a pair with remove method paasing the Key.

M= ['a':'A','b':'B','c':'C']
M.remove('b') = 'D'
println M // prints ['a':'A','c':'C']

i'll cover more groovy stuff in upcoming posts.
till then...happy Groovying ;)

P.S : Syntax high lighting help from here.


Saturday, April 04, 2009

Freemind on Ubuntu

Today i installed JDK6u13 and wanted to try out Freemind , one of the best free mind mapping tools.As i am still very new to mind mapping but a seasoned Java developer , i thought that i will start rolling soon with this tool.But , it turned otherwise.

After unzipping the freemind (binaries for any operating system - max - all inclusive) version to /opt,i chmodED it as executable.Now ,i tried to start it with the shell script file provided and what i got was

Exception in thread "main" java.awt.AWTError: Cannot load AWT toolkit:
at java.awt.Toolkit.getDefaultToolkit(
at java.awt.GraphicsEnvironment.getLocalGraphicsEnvironment(
at java.awt.Window.(
at java.awt.Frame.(
at javax.swing.JFrame.(
at freemind.main.FreeMind.(
at freemind.main.FreeMind.main(
Caused by: java.lang.UnsatisfiedLinkError: libgtkpeer: cannot open shared object file: No such file or directory
at java.lang.Runtime._load(
at java.lang.Runtime.loadLibrary(
at java.lang.System.loadLibrary(
at java.lang.Class.initializeClass(
at java.lang.Class.forName(
at java.awt.Toolkit.getDefaultToolkit(
...6 more

Even though , i installed JDK6u13 and had it as my default java executable after updating the .profile file, then to some how this script was picking up the java from gcj package.

so i started to dig and find out is this happening.Sooner using sudo update-java-alternatives -l i was able to find out that i only had gcj installed and registerd in ubuntu.

X@X-desktop:/opt/Freemind$ sudo update-java-alternatives -l
java-gcj 1041 /usr/lib/jvm/java-gcj

Now, i was in search of a resource which will show me how to get java from JDK6u13 to be my default.After a quick google , i found this.So next set i ran

X@X-desktop:/opt/Freemind$ sudo update-alternatives --install "/usr/bin/java" "java" "/opt/jdk1.6.0_13/bin/java" 1
X@X-desktop:/opt/Freemind$ sudo update-alternatives --set java /opt/jdk1.6.0_13/bin/java

And then started the shell started

Drop me a cooment if this helps you , or you have good mind mapping sites/online book urls.


Sunday, February 01, 2009

Want to begin TDD?

i have joined the Test-driven development yahoo mailing group.Its a great place to see all levels of TDD practitioners out there and their innovative ideas.
One of the thread there mentioned a resource which may help you kickstart the TDD.

TDD Problems
This present programmer with problems that will help them learn and improve their TDD skills.The problem categorization is huge and divided into games,Web related,and many more.
This is worth a check for any TDD practitioners .This will help beginners improvise their skills whereas advanced user to guide their colleagues to follow TDD.


Tuesday, October 21, 2008

Loading Jars Dynamically

Post after really long time..from now on ..i ''ll be frequently updating this with random but interesting java posts.
Earlier this week i had a requirement to dynamically load some classes in the current JVM's classpath from some external Jar files.
The way to load classes dynamically from any particular location is to use a
Lets see some code.

//Here u specify the URL for a jar on the file system
String filePath = "jar:file:///" + sysfilePath + "!/";
//Make a URL out of It.
URL url = new URL(filePath);
//Use the ClassLoder to Load that Jar
//You can pass in as many URL you want to the classloader
URLClassLoader clazzLoader = new URLClassLoader(new URL[]{url});

I am thinking to build a fluent interface on this classloader which will allow me to dynamically load more jars as the application goes along.

While researching and googling for this, i upon this JCL.Worth a try.

Do you have any recommendations or alternative approaches?Do comment below.