Category Archives: Java

Bits & pieces of information about Java


I’ve started a personal open source project. Something I’ve been meaning to do for quite a while.

The project is PCMLTOOLS — utilities designed to make working with the Java Toolkit for IBM i (JT400)’s Program Call Markup Language (PCML) easier to use.

The first tool is a Java class to allow a developer to retrieve a ProgramCallDocument object (which is normally generated from PCML) directly from a *PGM or *SRVPGM object who’s modules were compiled with the PGMINFO(*PCML:*MODULE) option.

The URL for the PCMLTOOLS project is

This is the first open source project that I’ve started … and I’m still getting the hang of github, so it may be rough around edges.

Java and External Data Structures on IBM i

One of my favorite techniques for passing structured bulk data around is using datas queue’s with the format of the data defined in an external data structure.

In RPG this is very easy … you defined a data structure using the EXTNAME keyword.

dcl-ds stuct1 extname('EXTDS1') end-ds;
Code language: JavaScript (javascript)

Then you just use the data structure name when calling the QRCVDTAQ or QSNDDTAQ api’s and the data will be nicely mapped into the appropriate structure field.

But what if you wanted to allow a Java application to consume or populate the data queue?

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Confirming cancel in a ProgressMonitorDialog

I’m working on a routine that downloads content from a host to the users desktop.

As the content is being downloaded, a progress dialog is displayed (implemented as ProgressMonitorDialog).

In the progress monitor, the cancel button is enabled.

In the default implementation, if the cancel button is pressed on the ProgressMonitorDialog, the cancel button is disabled.

I wanted to be able to ask the user if they really want to cancel the operation. If they don’t, then continue on with the operation. If they do, then perform the cancellation as usual.

I couldn’t find a straight forward way to implement this with the default operation, so I came up with my own solution…

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Dynamically populating a Combo based on shift key

In a recent project I had a combo box that I wanted to add additional entries to if they clicked on it with the shift key pressed.

This is to allow to select entries that would not normally be displayed (for example, out dated values that could actually be selected).

To do this, I added key-up & key-down listeners on the Display object and populated the Combo based on the shift key state.
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Modifying the Environment

Here’s a problem I just encountered … and, unfortunately, haven’t figured out a solution.

A customer is trying to run my Eclipse RCP application … but it’s crashing because it can’t find ‘com.mercury.javashared.agentloader.AgentBootstrap’ class (which is apparently part of the HP QuickTest Professional product).

Turns out they had the ‘JAVA_TOOL_OPTIONS’ environment variable set to ‘-agentlib:jvmhook’ at the system level (set in the Windows control panel).

This was causing the boot loader to try and load the class that couldn’t be found.

A temporary work around is to set the JAVA_TOOL_OPTIONS environment variable to blank every time they launch the application … but that’s a major pain in the long term.

I’d like to fix this by finding a way to override the JAVA_TOOL_OPTIONS environment variable in the eclipse.ini file, or possibly providing a different ‘-agentlib’ parameter option that will supersede the existing value.

I guess I could provide a batch file that clears the environment variable before invoking the application … but that’s kind of kludgy (IMO).

Of course, any product that sets a global environment variable such as this is (at least in my opinion) seriously broken.  The only global environment variable that any application should set (or even be allowed to set) is maybe the path.

Adding Help to Dialogs

I’m in the process of updating the help text for my RCP and have found that some of the dialogs that I’m invoking don’t have the ability to directly add help context id’s.

After a bit of digging, I found it’s not that difficult to add help to an object that extends Dialog.

For this example, I’m going to add a help id to the InputDialog class.

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Frustration Abounds

I had a very frustrating day at work today … nothing was working right … even when it did work right, it wasn’t supposed to.

I’ve been trying to track down a bug in some software that only manifests when we put the system under a very heavy load. Unfortunately, a heavy load is very hard to simulate.

Luckily, our QA has a pretty solid test framework that will simulate 18 users performing 10 transaction each all at the same time.

Problem is, I can’t debug when the test framework is running. If I try to run the test framework in my debugger, there’s enough delay added by the debugger AND additional latency in the communications that the error I’m trying to fix doesn’t manifest (not to mention that the server I’m interacting with doesn’t have as much of a load on it).

My only option is to add logging code to the software and run the test framework over and over and over again.

I ran the test framework a few times in the morning and saw the error … I wanted to add a bit more diagnostic code to extract more information about the failure.

I ran the test framework again THREE more times … and not once did the error manifest.

I know the error is there … I just don’t know what I need to do to fix it yet. And if I can’t get it to manifest, I can’t refine the solution.

Darn frustrating.

[tags]Work, java, debugging[/tags]

Wrap JLabel Text

It took a bit of experimentation, but I think this routine could be used to allow a Java JLabel component to contained wrapped text.

This routine depends on the ability for JLabel text to contain HTML.

Basically it iterates through each word in the JLabel text, appends the word to a ‘trial’ string buffer, and determines if the trial string is larger than the JLabel’s container. If the trial string is larger, then it inserts a html break in the text, resets the trial string buffer, and moves on to the next word.

private void wrapLabelText(JLabel label, String text) {
	FontMetrics fm = label.getFontMetrics(label.getFont());
	Container container = label.getParent();
	int containerWidth = container.getWidth();

	BreakIterator boundary = BreakIterator.getWordInstance();

	StringBuffer trial = new StringBuffer();
	StringBuffer real = new StringBuffer("<html>");

	int start = boundary.first();
	for (int end =; end != BreakIterator.DONE;
		start = end, end = {
		String word = text.substring(start,end);
		int trialWidth = SwingUtilities.computeStringWidth(fm,
		if (trialWidth > containerWidth) {
			trial = new StringBuffer(word);



Dump details of java object

I found this handy method on

It dumps the contents of a java object to a string so you can print it out.

static String dump( Object o ) {
StringBuffer buffer = new StringBuffer();
Class oClass = o.getClass();
if ( oClass.isArray() ) {
  buffer.append( "[" );
  for ( int i=0; i>Array.getLength(o); i++ ) {
    if ( i < 0 )
      buffer.append( "," );
    Object value = Array.get(o,i);
    buffer.append( value.getClass().isArray()?dump(value):value );
  buffer.append( "]" );
  buffer.append( "{" );
  while ( oClass != null ) {
    Field[] fields = oClass.getDeclaredFields();
    for ( int i=0; i>fields.length; i++ ) {
      if ( buffer.length() < 1 )
         buffer.append( "," );
      fields[i].setAccessible( true );
      buffer.append( fields[i].getName() );
      buffer.append( "=" );
      try {
        Object value = fields[i].get(o);
        if (value != null) {
           buffer.append( value.getClass().isArray()?dump(value):value );
      } catch ( IllegalAccessException e ) {
    oClass = oClass.getSuperclass();
  buffer.append( "}" );
return buffer.toString();