What is Cloud Computing?

Someone from the non-technical business side asked me what is this Cloud computing all about. If you search for the term you find a bunch of definitions and descriptions.

Someone from the non-technical business side asked me what is this Cloud computing all about. If you search for the term you find a bunch of definitions and descriptions. For example, on Wikipedia:

“Cloud computing refers to the delivery of computing and storage capacity as a service to a heterogeneous community of end-recipients.”

That doesn’t sound like anything new. We had similar things even in the sixties. You have to read more of the above article to see the differences. But, to see what it really means a blog post, “Startups are Creating a New System of the World for IT“, puts it in context.

Groovy script to bootstrap a Gradle Project

A Groovy script to bootstrap a Gradle Groovy Project. Based on Ted Naleid’s shell script.

I took Ted Naleid’s “Quick Shell Function to Bootstrap a Gradle Groovy Project” example code and converted it to a Groovy script.

1. Fixed. This was not running. I was using triple quoted string, when I should have used the triple single-quoted string for the HEREDOC like usage below.
2. Gradle now includes (since 1.6) a Build Init Plugin that will create a project. This should be used and not the code in this blog post.
In Gradle 1.9 this works:

    gradle init --type java-library

3. Gradle IDE plugins have the ability to create Gradle based project.
4. Would be nice to be able to reuse Maven style “archetypes”.

But, may serve as a Groovy code example.
Listing 1.

// NewGradle.groovy
// Author: Josef Betancourt
// Based on T. Naleid's shell script 

println "Creating files for new Gradle project ..."

new File(".gitignore").withPrintWriter{ w ->

new File("build.gradle") << '''
apply plugin: 'groovy'
apply plugin: 'idea'
apply plugin: 'eclipse'
repositories {
dependencies {
    groovy 'org.codehaus.groovy:groovy:1.8.6'
    compile 'org.apache.ivy:ivy:2.2.0'
task createSourceDirs(description : 
   'Create empty source directories for all defined sourceSets') 
   << {
        sourceSets*.allSource.srcDirs.flatten().each { 
            File sourceDirectory ->        
            if (!sourceDirectory.exists()) {
                println "Making $sourceDirectory"
idea {
    project {
        jdkName = '1.6'

''' // end content

"cmd /c gradle createSourceDirs".execute()

"cmd /c git init".execute()

	sleep 5000 // allow time for all files to be created
	new File(".").eachFile{
		println it

Not expert Groovy, but was easy to do. The bulk of it is the creation of a “here” doc using Groovy’s triple quote string. I didn’t duplicate the last line of Naleid’s script: “ls -a1 && find src # list all created assets”.

This script is not fully cross-platform. The invocation of shell commands at the end are in the Windows format. Left as an exercise to reader is the use of inline AntBuilder to reuse Ant’s exec task. 🙂

2012-03-09: Tweaked the source. Removed use of two temp variables.
2012-03-09: Added the Eclipse plugin. Now after creating the Gradle project executing eclipse will create the eclipse project: gradle eclipse
Or instead generate the Idea project: gradle idea.

Further Reading

  1. Groovy (Programming language)
  2. Groovy
  3. Gradle
  4. Quick Shell Function to Bootstrap a Gradle Groovy Project
  5. Strings and GString
  6. Groovy JDK extensions
  7. Executing External Processes
  8. Using Gradle to Bootstrap your Legacy Ant Builds

Off Topic

Access virtual storage with UNC and mklink on Windows

many ways to do this and of course corresponding security concerns. My quick approach was to just use file directory symbolic links.

I set up a Tomcat app server on a ‘virtual’ hard drive. The virtual drive is assigned a local hard drive letter. But when a Groovlet attempts to access a local file, the file path used is on the default local drive, C:. How to allow access to the non-local file?

Symbolic links
There are probably many ways to do this and of course corresponding security concerns. One of these is to use Universal Naming Convention (UNC) paths. My quick approach is to just use file directory symbolic links. These are supported in most windows versions. On Windows 7 the MKLINK command is available.

You want to access the folder w:\a\b\c on the virtual drive. On the “real” drive you create a link:

mkdir a\b
mklink /D c w:\a\b\c

Now when the app server accesses the “c” folder via a UNC, \\mymachine\a\b\c, it will find it.

Virtual Machine Applicance for development environment

Configuration of a development environment can be very time consuming, error prone, or difficult.

Configuration of a development environment can be very time consuming, error prone, or difficult. This is especially true when investigating or getting up to speed on a new technology or framework. In a corporate environment this is a also a drain on resources and existing developer staff who must take the time to prep a new developer.

One approach to mitigate this is to use a Virtual Appliance.

Virtual appliances are a subset of the broader class of software appliances. Installation of a software appliance on a virtual machine creates a virtual appliance. Like software appliances, virtual appliances are intended to eliminate the installation, configuration and maintenance costs associated with running complex stacks of software.

A virtual appliance is not a complete virtual machine platform, but rather a software image containing a software stack designed to run on a virtual machine platform which may be a Type 1 or Type 2 hypervisor. Like a physical computer, a hypervisor is merely a platform for running an operating system environment and does not provide application software itself. — Virtual Appliance

Creating a Virtual Machine Applicance
The available VM software such as Oracle VirtualBox and the VMware VM have facilities to generate appliances. Thus, when a functioning development environment is created by a lead tech or group, an appliance can be generated for the rest of the team. This appliance can even be provided using a Virtual Desktop Infrastructure (VDI).

Open Virtualization Format
While a VM system can be used to create individual VM instances that can be reused, a more recent technology (supported by some vendors) is the use of OVF:

… is an open standard for packaging and distributing virtual appliances or more generally software to be run in virtual machines.

The standard describes an “open, secure, portable, efficient and extensible format for the packaging and distribution of software to be run in virtual machines”. The OVF standard is not tied to any particular hypervisor or processor architecture. The unit of packaging and distribution is a so called OVF Package which may contain one or more virtual systems each of which can be deployed to a virtual machine.

An OVF package consists of several files, placed in one directory. A one-file alternative is the OVA package, which is a TAR file with the OVF directory inside. — http://en.wikipedia.org/wiki/Open_Virtualization_Format

Using ready made appliances
Each VM vendor can/does make available an appliance marketplace. Thus, one can find ready-made LAMP based environments with a development software stack, for example.

Alternative 1, an installable virtual disk
Where resources are constrained, such as places where developers are still on 3GB of ram and ancient PCs, a Virtual Machine is just not going to cut it.

One easy alternative is to create a dev environment on an installable soft hard drive. TrueCrypt can be used for this purpose. One simply create a true crypt volume, which is just a single file. Then creates the desired dev env in that volume, and that file can now be copied to load into other dev’s workstations as a new hard drive.

TrueCrypt is really for security and privacy concerns, it encrypts data, so may not be ideal for this application. Since TrueCrypt is so useful as a virtual disk, it would be great if it had the option of not encrypting content. But, that would perhaps be outside of its feature space. For that the next alternative is available.

Alternative 2, use VHD files
An alternative is using something directly targeted at virtual disks such as the VHD file format. However, this does not seem to have easily useful public gui or command support (for the end user: developer).

On Windows following the instructions here and using these Send To scripts will allow one to seamlessly use vhd files as mountable hard disk volumes.

Note that Windows 8 will support native mounting of ISO and VHD files.

Further Reading


Exception verification using fault injection via AOP

A simple example is used to show how to use Aspect Oriented Programming to provide fault injection.

A simple example is used to show how to use Aspect Oriented Programming to provide fault injection.


A few months ago I was looking at Java code and thinking there must be a better way to see if this will really work, if there are any issues in how the program would react to exceptional conditions.  I could write some unit tests or force some problems to see if the exception handling is correct and the log file output is really useful.  But is there another way?

I got a solution after a while of thinking: Insert faults.  Now how to do that in an easy and  maintainable way? Not a new idea of course. After doing a web search I found some interesting references.

Funny, today at work I was extending an application and one of the support objects was failing. Turned out to be an index out of bounds problem. The method had adequate exception handling but, of course, an index out of bounds scenario was not tested. In this case the problem would not occur in production (hmmm), but it definitely occurred during development, and was not handled correctly.

Exception Handling

There are many references of correct exception handling strategies and best practices.  However, when creating applications, the developer must still make critical creative decisions about how to handle an exception.    That decision may not be a wise one.  And even if it is, may later prove to have been very unwise since the system requirements and implementation may have changed due to maintenance or requirement evolution.

Testing Approaches

Using various testing methodologies a subsystem can be exhaustively tested for exception handling.  Yet, most testing methods require that the subsystems be isolated in some manner.   This, though very valuable, can give fatal false confidence that the system will behave in a predictable manner in responding to exceptional conditions.

The prime example of this is within the Unit Testing methodologies.  Since Unit Tests are tests of isolated components, they do not test actual exception handling in the live system.  A perfect component can still contribute to system failure when it is used incorrectly or uses other components incorrectly.    For example, a unit test can show that class X’s methods correctly handle and when necessary throw the perfect exception.   That means nothing if components that interact with X don’t correctly use those exceptions:  they swallow, mask, or mistakenly catch them when there is nothing they can do.

Thus, one needs to use Integration Testing to test assemblages of components.  But, we are still back with the same shortcoming as with Unit Testing. Thus we would next need various forms of system testing.  And, that system testing must be a White Box test.  A Black Box test wherein an interface is exercised with various inputs (such as in web test systems or by QA personnel), will not necessarily invoke the full internal API/SPI between components that could be part of a complicated call chain.  Why?  Because, the interface, such as a browser client, will have (we hope) the validation, security, and logging layers implemented so that by the time a system test workflow enters the deep system components within the client or middleware, there is no way to influence the target component state into programmatic intentional failure mode.

If there is no way to exercise a run time trajectory, then why bother? The reason is that exceptional conditions are exceptional. Resources can be exhausted, systems not available, and so forth. The rule of Fail Fast may not be enough if collaborating components are not exceptionally responsive.

Fault Injection

To see if a system is responding to exceptional conditions, one must wait for those conditions or create them.    Analogously to Fuzz Testing we can dynamically and randomly insert faults.  In Fuzz Testing, inputs are manipulated to a system under test.  In Fault Injection we have to manipulate inputs inside the real system, within the components themselves.  And as in Fuzz Testing, we can employ various strategies to do so, such as randomized faults, etc.   Of course, this system is not the deployed production system, it is the real system in a test environment, an internal full deployment.

Some approaches are: source modification, source macros, annotations, dependency injection (IOC), and Aspect Oriented Programming (AOP). Of course, there are many other techniques as found in open/closed projects, commercial products, and the research community.

Fault Injection using AOP

Since using the real system is required, a viable approach is to use the Instrumentation already available in the Java system. We could dynamically insert code that forces exceptions. AOP as implemented by the AspectJ language can already do this.

The major advantage of using AOP is that the source is not changed in any way. AspectJ is the state of the art in the Java ecosystem for using AOP.

Other approaches


BTrace (a Java oriented approach comparable to DTrace) is very interesting. However, since, like DTrace, it is meant to be safe, defect injection may not be doable. But, see this post on an unsafe mode for BTrace.

Source modification

One way of injecting failure is just to edit the source code and add strategic code that will cause the instigating failure.  An advanced form of this is Mutation Testing.   Code changes could be:  arguments with wrong values, nulls, deliberately thrown exceptions, etc.  For example, one can simply create a method that throws a runtime exception:

     *** DON'T DO THIS ***

    public static void REMOVE_XXX_FROM_XXX_SOURCE(){
          throw new NullPointerException(
             "nt****** DELIBERATE RUNTIME EXCEPTION*****n");

Then insert invocations to this method at strategic points in the code, deploy to a test environment, and see if the expected results are obtained, such as logging output that can identify the cause, or that no side effects are recorded, such as incorrect data storage.

This is a low tech and error prone approach.  Most importantly, this is dangerous.  In the mad development rush to meet deadlines and also eat lunch, this code could make it into production!  Even with that horrific method name, it will wind up in production!  One would have to create deployment filters that stop the process if any “fault” inducing code is included.  Another reason why this is not a good approach is that it doesn’t scale very well.   Forcing exceptions is just one type of verification.  Another is setting values outside of expected ranges or states.  Thus, one would need many different kinds of source code insertions. 

Of course, Unit and Behavior based testing tools sets can supply these required verifications if included into the system as Built-In Self-Tests (BIST).

Built-In Self-Test

In the hardware realm, BIST as found in, for example, IEEE 1149.1 JTAG, has been very successful. On the software side, there is ongoing research on how to implement BIST-like capability. This would make Brad Cox’s concept of the “Software IC” even more powerful.


A somewhat viable approach to source code fault insertion is instead of inserting the faulting code,  insert “include” macros in the original source code that indicates what fault insertion should be done at a location.  A fault injection preprocessor can scan and insert the fault framework’s invocations to accomplish the requirement.  The source code build process can then simply enable or disable the use of the preprocessor.  This would however still require source code modification and an extra maintenance nightmare.  When the code changes the macros may also require change.


Instead of macros, we could also use Annotations.  Annotations could explicitly state the runtime exceptional behavior “service level agreements” at the component level. These SLA could then be systematically manipulated to test if they really hold at the system level.

Dependency Injection

One can also inject exceptional behavior by dependency injection, using programmatic, declarative, or annotations, faulted components could be inserted (or created via Aspect Oriented Programming) into the target system.

AOP Demonstration

In listing one below, an ATM class uses a service to do some banking.

 * Driver class for example. 
 * For a real system see:  https://bitbucket.org/aragost/javahg/
 * @author jbetancourt
public class ATM {
	private BankService service = new BankService(1000);

	 * Perform a banking action.
	public void transaction(){	
	/** Application entry point	 */
	public static void main(String[] args) {
		new ATM().transaction();

Listing two is the BankService being used. Of course, a real service would be more complex.

 * Example service.
public class BankService {
	// Use Long to allow example's null for failure
	// injection.

	private BigDecimal balance;
	public BankService(long savings){
		this.balance = new BigDecimal(savings);
	/** */
	public void deposit(Long amount){
		balance = balance.add(new BigDecimal(amount));
		System.out.println("Deposit:  " + amount);
	/** */
	public void withdraw(Long amount){
		balance = balance.subtract(new BigDecimal(amount));
		System.out.println("Withdraw: " + amount);
	/** */
	public void statement() {
		System.out.println("Balance:  " + balance);		
} // end BankService

A example Non-faulted execution result is:

Report: pointcut usage
  withdrawCut:   true ->  false
  depositCut:  false ->  false
       Deposit: 100
      Withdraw: 200
       Savings: 900

When we run the demo program we get:

Exception at the withdraw method.

Report: pointcut usage
withdrawCut:   true ->   true
depositCut:  false ->  false
Deposit: 100
Exception in thread "main" java.lang.NullPointerException
   at BankService.withdraw_aroundBody2(BankService.java:15
   at BankService.withdraw_aroundBody3$advice(BankService.java:81)
   at BankService.withdraw(BankService.java:1)
   at Main.main(Main.java:16)

Exception at the deposit method.

pointcut usage
withdrawCut:   true ->  false
depositCut:  false ->   true
Exception in thread "main" java.lang.NullPointerException
   at BankService.deposit_aroundBody0(BankService.java:9)
   at BankService.deposit_aroundBody1$advice(BankService.java:81)
   at BankService.deposit(BankService.java:1)
   at Main.main(Main.java:15)

All pointcuts enabled.

pointcut usage
withdrawCut:   true ->  false
depositCut:  false ->   true
Exception in thread "main" java.lang.NullPointerException
   at BankService.deposit_aroundBody0(BankService.java:9)
   at BankService.deposit_aroundBody1$advice(BankService.java:81)
   at BankService.deposit(BankService.java:1)
   at Main.main(Main.java:15)


Now to test the exceptional behavior we want to fault the deposit and withdraw methods.
First we have a way of specifying what we want to fault by using a JSON configuration file:

		"File: properties.json"

The “cuts” settings indicate which AspectJ “pointcut” to turn on. The “random” setting indicates if we want the exceptions to be randomly inserted into the code base at the enabled pointcuts.

The Abstract failure injection aspect. Subclasses (aspects) will supply the actual pointcuts to specify where to ‘do’ the injection.

 * FailureInjectionAspect.aj 
 * @author jbetancourt

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

 * Abstract Aspect that determines if failure should occur.
 * @author jbetancourt
public abstract aspect FailureInjectionAspect {
	private Map<String, Boolean> pointcutFlags = new HashMap<String, Boolean>();
	private volatile boolean initialized =false;
	 * Initialize Failure injection aspect.
	 * @throws Exception 
	protected void init() throws Exception {
		Config config = new Config();
		pointcutFlags = config.getPointcutFlags();		
		initialized = true;

	 * Get boolean value for pointcut name.
	 * @param name pointcut name.
	 * @return true if pointcut enabled.
	 * @throws IOException 
	protected boolean isPointcutEnabled(String name) {
			try {
			} catch (Exception e) {
				throw new IllegalStateException(
						"Could not initialize object",e);
		boolean f = false;	
		Object val = pointcutFlags.get(name);
		if (null != val) {
			f = ((Boolean) val).booleanValue();

		return f;
} // end FailureInjectionAspect.aj

Here is a aspect that uses a nulling type of injection.

 * Example of an aspect for nulling an argument to a method.
 * @author jbetancourt
public aspect AmountFailureAspect extends FailureInjectionAspect {

	/** fault the deposit */
	private pointcut depositCut(Long amount) :
		execution(public void BankService.deposit(Long)) 
		&& if(AmountFailureAspect.aspectOf().isPointcutEnabled("depositCut"))
		&& args(amount) 
		&& !within(FailureInjectionAspect)

	/** fault the withdrawal */
	private pointcut withdrawCut(Long amount) :
		execution(public void BankService.withdraw(Long)) 
		&& if(AmountFailureAspect.aspectOf().isPointcutEnabled("withdrawCut"))
		&& args(amount) 
		&& !within(FailureInjectionAspect)

	/** Null the amount arg */
	void around(Long amount) : depositCut(amount)|| withdrawCut(amount) {
		amount = null;

Here is how to read the configuation JSON file. I use the JSON-Simple library.

import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;
import java.util.HashMap;
import java.util.Map;
import java.util.logging.Level;
import java.util.logging.Logger;

import org.json.simple.JSONObject;
import org.json.simple.JSONValue;

 * @author jbetancourt
public class Config {
	private static final Logger logger = 
	private String configFile = "srcproperties.json";
	private Map<String, Boolean> pointcutFlags = new HashMap<String, Boolean>();
	private volatile boolean initialized = false;
	private String basePath;

	 * @param configFile2 
	 * @throws Exception
	public void configure() throws Exception {
		basePath = new File(".").getAbsolutePath();

		String path = basePath + configFile;

		Object obj = (JSONObject) JSONValue
				.parse(new FileReader(new File(path)));
		Map<String, Map<String, ?>> map = (Map<String, Map<String, ?>>) obj;
		pointcutFlags = (Map<String, Boolean>) map.get("cuts");
		Map<String, Object> settings = (Map<String, Object>) map
		Object r = settings.get("random");
		boolean randomize = (r != null &amp;&amp; ((Boolean)r)) ;
			    "Pointcut usagen%16s %6s    %6s","Name        ",
			for(Map.Entry<String, Boolean>entry : pointcutFlags.entrySet()){
				Boolean prior = entry.getValue();
				Boolean f = Math.random() > 0.65;
					"%15s: %6s -> %6s", entry.getKey(),prior,f));
		initialized = true;		
		logger.log(Level.INFO,"Initialized: " + initialized);
	 * Write the config settings to external JSON file.
	 * Format is: { cutname : boolean , ... }
	 *   Example: {"withdrawCut":true,"depositCut":true}
	 * Will be used to set up behavior analysis service to 
	 * monitor response.
	 * @throws IOException
	protected void saveConfig() throws IOException{
		String json = JSONValue.toJSONString(pointcutFlags);
		File file = new File(basePath + "runtimeProperties.json");
		FileWriter writer = new FileWriter(file);		

	/** getter */
	public Map<String, Boolean> getPointcutFlags() {
		return pointcutFlags;

	/** setter */
	public void setPointcutFlags(Map<String, Boolean> cutFlags) {
		this.pointcutFlags = cutFlags;

	 * Just a shortcut to System.out.println(String).
	 * @param s
	private void println(String s){

Running at the command line

Using AspectJ is much easier in a supporting IDE like Eclipse. Below is the “mess”, unless you love the CLI, of compiling and running in a command shell. Could be made clean by creating aliases, scripts, etc.

cd src
src>javac -d ..bin -cp ..jarsjson-simple-1.1.jar  *.java
src>java -cp ..bin Main
Jun 9, 2011 3:18:24 PM Main main
INFO: Starting Main.....
   Deposit:  100
   Withdraw: 200
   Balance:  900

Now we change the flag from false to true in the runtimeInjection.json file:

src>type runtimeInjection.json | sed "s/false/true/" > temp
src>copy /Y temp runtimeInjection.json
src>del temp

Compile the aspects using the Aspectj “ajc” compiler.  Here we use 1.6 compliance level; destination of output to ..bin folder; and give the classpath.

c:\Users\jbetancourt\Documents\projects\dev\AspectsForNullTesting\src>java\aspectj1.6\bin\ajc -1.6 -d ..\bin -cp "c:\java\aspectj1.6\lib\aspectjrt.
jar;c:\javaaspectj1.6\lib\aspectjtools.jar;c:\javaaspectj1.6\lib\aspectjweaver.jar;..\jars\json-simple-1.1.jar" -sourceroots .

Now we run the same Main program.  Since the pointcut flag is true, the advise is invoked and the list argument to the service(List) is set to null.

c:UsersjbetancourtDocumentsprojectsdevAspectsForNullTesting>java -cp "c:javaaspectj1.6libaspectjrt.jar;c:javaaspectj1.6libaspectjtools
.jar;c:javaaspectj1.6libaspectjweaver.jar;jarsjson-simple-1.1.jar;bin;." Main
Jun 9, 2011 3:25:04 PM Main main
INFO: Starting Main.....
Pointcut usage
Name          Prior    Current
withdrawCut:   true ->  false
depositCut:  false ->  false
c:UsersjbetancourtDocumentsprojectsdevAspectsForNullTesting>java -cp "c:javaaspectj1.6libaspectjrt.jar;c:javaaspectj1.6libaspectjtools
.jar;c:javaaspectj1.6libaspectjweaver.jar;jarsjson-simple-1.1.jar;bin;."   Main
Jun 9, 2011 3:25:10 PM Main main
INFO: Starting Main.....
Pointcut usage
Name          Prior    Current
withdrawCut:   true ->   true
depositCut:  false ->   true
Jun 9, 2011 3:25:10 PM Config exec
INFO: Initialized: true
Exception in thread "main" java.lang.NullPointerException
at BankService.deposit_aroundBody0(BankService.java:19)
at BankService.deposit_aroundBody1$advice(BankService.java:26)
at BankService.deposit(BankService.java:1)
at Main.main(Main.java:16)

c:UsersjbetancourtDocumentsprojectsdevAspectsForNullTesting>java -cp "c:javaaspectj1.6libaspectjrt.jar;c:javaaspectj1.6libaspectjtools
.jar;c:javaaspectj1.6libaspectjweaver.jar;jarsjson-simple-1.1.jar;bin;."   Main
Jun 9, 2011 3:25:13 PM Main main
INFO: Starting Main.....
Pointcut usage
Name          Prior    Current
withdrawCut:   true ->   true
depositCut:  false ->  false
Jun 9, 2011 3:25:13 PM Config exec
INFO: Initialized: true
Deposit:  100
Exception in thread "main" java.lang.NullPointerException
at BankService.withdraw_aroundBody2(BankService.java:25)
at BankService.withdraw_aroundBody3$advice(BankService.java:26)
at BankService.withdraw(BankService.java:1)
at Main.main(Main.java:17)


  • Feb 1, 2012: Just learned about Byteman.
  • April 25, 2013: A new article on using Byteman: http://aredko.blogspot.com/2013/04/fault-injection-with-byteman-and-junit.html

Further Reading

Nicolas Lens – Sumus Vicinae (Flamma Flamma)

Ant InputHandler GUI Using Groovy

Use Groovy to enable Swing based Ant InputHandler GUI interface.


With Apache Ant you can get input from the user using the “input” task. When you run Ant in a console window, the DefaultInputHandler is used. This handler just uses the console’s error and input streams.

When you run Ant in a graphical IDE, a Graphical User Interface based input handler may be used. This handler will use the graphics toolkit (on Eclipse that would be SWT) to pop up dialog boxes.

GUI in console?

Can you use GUI input dialogs when running in a command shell? Yes, and it is very easy. (Of, this is true if a gui environment is available to Java runtime, etc.).

First you create an InputHandler subclass that will be used with the Ant command option “-inputhandler class name”. If you use Ant 1.8* you can use a nested “inputputhandler” task in the “input” task within the build script.

Probably a much better approach is to just create a new custom Ant task, “ginput” for this, or even use a macrodef or scriptdef that uses Groovy inline or from a script file.

Another alternative is to use a browser interface for the Ant input. See “Java’s HTTP Server for browser-based Groovy app” for an example of using an embedded server to invoke browser UI.

Why Groovy for this? Just to be able to use the SwingBuilder that potentially could make the Gui creation much simpler. One can envision a full blown form being used for cases where Ant is used outside its traditional use-case.

GUI InputHandler subclass

Below in listing 1, there is an example Groovy source: AntGuiInputHandler.groovy

Much harder is actually getting Ant to use this handler.

Build file

First lets create an Ant build file that will get some input:

<project name="AntGui" default="all" basedir=".">
<target name="all">

    <input message="What is your name?"


Now, compile the Groovy source as follows:

groovyc AntGuiInputHandler.groovy

There are many ways to actually run the Ant build. The simplest but not the best way is to set up your CLASSPATH and then run Ant as usual, for example:

C:\temp\AntGui&amp;gt;set classpath=.;\java\groovyembeddablegroovy-all-1.8.1.jar

C:\temp\AntGui&amp;gt;ant -inputhandler AntGuiInputHandler
Buildfile: C:tempAntGuibuild.xml

[input] prompt=What is your name?
[input] Josef
[echo] Josef from Groovy InputHandler

Total time: 11 seconds

The resulting input dialog is:

Ant GUI InputHandler prompt

Listing 1
Note: I currently have no Swing mojo, so this is just reuse of code snippets. BTW, SwingBuilder could use more docs or examples.

import java.awt.event.WindowEvent
import javax.swing.ActionPropertyChangeListener;

import groovy.swing.SwingBuilder;

import org.apache.tools.ant.BuildException;
import org.apache.tools.ant.input.InputHandler;
import org.apache.tools.ant.input.InputRequest;
import org.apache.tools.ant.input.MultipleChoiceInputRequest;

import javax.swing.*

 * @author jbetancourt
class AntGuiInputHandler implements InputHandler {

	/* (non-Javadoc)
	 * @see org.apache.tools.ant.input.InputHandler#handleInput(org.apache.tools.ant.input.InputRequest)
	public void handleInput(InputRequest request) throws BuildException {
		def response = ''
		println "prompt=${request.getPrompt()}"
		if(request instanceof org.apache.tools.ant.input.MultipleChoiceInputRequest){
			response = 	getMultipleChoiceInput(request)
			response = getTextInput(request)
		println response
		request.setInput("${response} from Groovy InputHandler");
	String getTextInput(InputRequest request){
		//def swingBuilder = new SwingBuilder()
		def response = ''
                // how to do this with the builder?
		response = JOptionPane.showInputDialog(
                   null, 'Project Name','Enter name', JOptionPane.OK_OPTION)

		return response	
	String getMultipleChoiceInput(InputRequest request){
		def swingBuilder = new SwingBuilder()
		def req = (MultipleChoiceInputRequest)request;
		def choices = req.getChoices()
		def defaultValue = req.getDefaultValue()		
		def prompt = request.getPrompt()
	    def pane = swingBuilder.optionPane(
                  selectionValues:choices as Object[], 
		def dialog = pane.createDialog(null, 'dialog')
		def response = pane.getInputValue()
		println "input: ${response}"		
		return response

Pretty groovy use of Groovy!

Previously posted at: “Ant InputHandler GUI Using Groovy

2011-08-16T2159: Just stumbled upon the AntForm project. If I knew about it, I wouldn’t even have tried doing the above. Oh well.

Contextual State Transfer

A lot of software is like this. Sometimes it is just a language or cultural thing. Most of the time it is the software not tracking the user’s contextual state. What is the users goal, and how does the user think they are currently related to that goal.

My TV just connected to the internet, now it wants me to “close”. This is a good example of a user interface not tracking user context.

When I use the TV to connect to the web the final screen is:

Internet Content Connection Status
The internet content is ready

| Close |

It took me a few nanoseconds to understand and know what to do: it is just a continue box. Other people, I won’t say who, were stumped. “Close” what, the internet connection I was just trying to establish, case to the DVD cabinet? The fix in this case is to use the word ‘continue’ instead of ‘close’.

A lot of software is like this. Sometimes it is just a language or cultural thing. Most of the time it is the software not tracking the user’s contextual state. What is the users goal, and how does the user think they are currently related to that goal.

Here is another example, I just committed some files into a version control system. What my intent is now is just to exit the graphical app, I did the commit, or did I? Now I am faced with three buttons, ‘commit’, ‘undo’, ‘cancel’. What if I hit commit again? What does ‘cancel’ do? Isn’t that just like undo? It turns out that I really did commit, and ‘cancel’ is the exit button.

There are multiple flows in an application. The internal software control and data flows, and the external flows. The most important flow is the user flow, what the user embodies in their experience, culture, dexterity, and intelligence. Perhaps what is needed is a CxST (Contextual State Transfer) approach.

The user is using a Contextual Prediction Engine, the human brain. Apps, are glorified Finite State Machines. Perhaps modern “AI” can bridge that gap automatically?

Great systems track the contextual state of the user.


JSON configuration file format

JSON is a data interchange format. Should it also be used as a configuration file format?

JSON is a data interchange format. Should it also be used as a configuration file format, a JSON-CF?

Had to write yet another properties file for configuration info. Started to think that maybe there are better alternatives. Wondered about JSON for this.

What are requirements of a configuration file format?

  • Simple
  • Human readable
  • Cross platform
  • Multi-language support
  • Unicode support

Looks like JSON has all the right qualities.

If all you want to pass around are atomic values or lists or hashes of atomic values, JSON has many of the advantages of XML: it’s straightforwardly usable over the Internet, supports a wide variety of applications, it’s easy to write programs to process JSON, it has few optional features, it’s human-legible and reasonably clear, its design is formal and concise, JSON documents are easy to create, and it uses Unicode.
— Norman Walsh, Deprecating XML

JSON-CF Limitations

  • Instead of angle brackets as in XML, we have quotation marks everywhere.

What does it need?

  • Inline comments, see for example, json-comments
  • Interpolation (property expansion)
  • Namespaces
  • Inheritance
  • Includes
  • Date value
  • Schema
  • Cascading


            "modified":"1 April 2001",
            "dc:author": "John Doe"
             "name":"John Doe",
             "organization":"Acme Widgets Inc."
             "_comment_server":"use IP address in case network name resolution is not working",

Programmatic Access using Groovy

Now we can easily read this file in Java. Using Groovy is much easier, of course. Groovy version 1.8 has built-in JSON support, great blog post on this here.

import groovy.json.*;

def result = new JsonSlurper().
                          parseText(new File("config.json").text)

result.each{ section ->
	println "$sectionn"

>groovy readConfig.groovy
Resulting in Groovy style data structure, GRON, (look ma, no quotation marks):

logger_parser={qualname=compiler.parser, level=DEBUG, propagate=1, handlers=hand01}

owner={organization=Acme Widgets Inc., name=John Doe}

_HEADER={dc:author=John Doe, modified=1 April 2001}

database={port=143, file=payroll.dat, server=, _comment_server=use IP address in case network name resolution is not working}

logger_root={level=NOTSET, handlers=hand01}

In Groovy you can access the data with GPath expressions:
println “server: ” + result.database.server

You can also pretty print JSON, for example:
println JsonOutput.prettyPrint(new File(“config.json”).text)


Raised the question of the use of JSON as a configuration file format.

What I don’t like is the excess quotation marks. YAML is more attractive in this sense. But, the indentation as structure in YAML, similar to Python, may not be wise in configuration files.

Well, what is the answer, should there be a JSON-CF? I don’t know. A very perceptive caution is given by Dare Obasanjo commenting on use of new techniques in general:

So next time you’re evaluating a technology that is being much hyped by the web development blogosphere, take a look to see whether the fundamental assumptions that led to the creation of the technology actually generalize to your use case.


  • After writing and posting this I searched the topic and, of course, this is not a new question. Search. I updated the reading list below with some useful links.
  • JSON Activity Streams are an example of how JSON is used in new ways.
  • schema.org types and properties as RDFS in the JSON format: schema.rdfs.org/all.json
  • Just learned that node.js uses the NPM package manager which uses a JSON config file format.
  • Jan 7, 2012: Java JSR 353: Java API for JSON Processing

Further Reading
Apache Avro 1.7.7 Specification Schemas
Analysis of JSON use cases compared to XML
JSON Validation Roundup
A very simple data file metaformat
HAL – Hypertext Application Language
NPM configuration file format
XML or YAML for configuration files
Using JSON for Language-independent Configuration Files
INI file
Comparison of data serialization formats
Data File Formats, in Art of Unix Programming, Eric Steven Raymond.
ConfigParser – Work with configuration files
Cascading Configuration Pattern
RFC 4627
XML-SW,a skunkworks project by Tim Bray. Brings a bunch of XML complex together into one spec.
ISO 8601
Learning from our Mistakes: The Failure of OpenID, AtomPub and XML on the Web
Groovy Object Notation (GrON) for Data Interchange
Groovy 1.8 Introduces Groovy to JSON
JSON-LD ‘JSON for Linking Data
JSON Schema


” Sacred Place ” , R.Towner / P. Fresu, live in Innsbruck , Part 4

The incredible suckiness of text editors

This should be simple, find every instance of “txtXXXX”, where XXXX can be any string, and you want the search to be non-greedy. Hah.

This should be simple, find every instance of “txtXXXX”, where XXXX can be any string, and you want the search to be non-greedy. Hah.

I needed to find these strings so I can insert them into a new file, then apply a regexp to create a bunch of source code. This is just a very elementary regular expression use: “txt.*?”

  • Notepad++: doesn’t support “?”.
  • GVim: /”txt.{-}” ugly! and how do I reuse the results (doable but hard)
  • windows notepad: lol!
  • Eclipse IDE: “txt.*?” but, you can’t find them all and reuse the results.

Long story short, I opened a command shell and did:

type page.html | egrep -o "txt.*?"

Not perfect, I still get too much of the line containing the match, but it is at least reusable. egrep is that installed with cygwin.

I, of course, am not complaining about text editors based on this one little issue. There is a long list of pain points, as with any software type.

I remember using a great editor that really knew how to optimize a developers work, SlickEdit. This task would have been a yawn.

In SlickEdit, real standard regexps are used, the output goes to a search output panel, etc., did I mention it does real columns? Alas, it is expensive, and companies probably won’t spend on it; we’re lucky we even have jobs in this age.


Tomcat 7 change ROOT application

How to change Tomcat 7 default ‘/’ web application.

The default application of a fresh install of Tomcat 7 is ROOT. You want to remove it and use your own?

I’m running a supported Tomcat instance and it’s trial period ended. I’ll just stick with plain old Tomcat. Perhaps for a business, the enhanced Tomcat (only change is a better management console?) would make more sense. For personal use I just installed version 7. Maybe they improved the setup experience. I gave up trying to change the default web app from ROOT to my own “home”.

Nope, still makes no sense. You’d think there would be a FAQ or something on this. The kludge way is to just put your app into ROOT. Yuck. Well, its possible and easy. I found the hint here, in one of the comments.. Thanks Joe!

The trick is that you have to add a context configuration for the default web app AND you CAN’T do this with an external context file, ROOT.xml. It won’t work. Instead, add this context to the Host node in the server.xml file.

Example snippet from my conf/server.xml:

      <Host name="localhost"  appBase="webapps"
            unpackWARs="true" autoDeploy="true">

        <!-- SingleSignOn valve, share authentication between web applications
             Documentation at: /docs/config/valve.html -->
        <Valve className="org.apache.catalina.authenticator.SingleSignOn" />

        <!-- Access log processes all example.
             Documentation at: /docs/config/valve.html
             Note: The pattern used is equivalent to using pattern="common" -->
        <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs"  
               prefix="localhost_access_log." suffix=".txt"
             pattern="%h %l %u %t &amp;quot;%r&amp;quot; %s %b" resolveHosts="false"/>
		<Context path="" docBase="home">

			<!-- Default set of monitored resources -->

			<!-- Uncomment this to disable session persistence across Tomcat restarts -->
			<Manager pathname="" />

			<!-- Uncomment this to enable Comet connection tacking (provides events
				 on session expiration as well as webapp lifecycle) -->
			<Valve className="org.apache.catalina.valves.CometConnectionManagerValve" />



The diff is:

>               <Context path="" docBase="home">
>                       <!-- Default set of monitored resources -->
>                       <WatchedResource>WEB-INF/web.xml</WatchedResource>
>                       <!-- Uncomment this to disable session persistence across Tomcat restarts -->
>                       <!--
>                       <Manager pathname="" />
>                       -->
>                       <!-- Uncomment this to enable Comet connection tacking (provides events
>                                on session expiration as well as webapp lifecycle) -->
>                       <!--
>                       <Valve className="org.apache.catalina.valves.CometConnectionManagerValve" />
>                       -->
>               </Context>

I hope this helps.

Note, before doing the above, please verify that this information is correct. Perhaps everyone is reading the Tomcat docs incorrectly or there really is a configuration discrepancy.

12Feb2011: Funny, if you make the above change and still leave the ROOT application folder in the webapps folder, you can not open the original ROOT at http://host:port/ROOT, even if you add another context node in host. I guess I still don’t grok Tomcat config.


Ralph Towner — Green and Golden