Q:

How Eclipse Plugin can programmatically pass Java VM Arguments

I'm programming an Eclipse Plugin which is actually a profiler that instruments the code using a Java Agent jar file.
I have programmed a custom Launch Configuration and also defined the Launch Configuration Tab Group for that. They are working fine and running local Java Projects. I want my plugin to automatically pass Java Agent jar file in vm arguments of JavaArgumentsTab so that code can be instrumented.
My Launch Configuration Code
public class MyJavaDelegate extends JavaLaunchDelegate
{
    @Override
    public void launch(ILaunchConfiguration configuration, String mode, ILaunch launch, IProgressMonitor monitor)
            throws CoreException
    {
        super.launch(configuration, mode, launch, monitor);
        System.out.println("Custom Lanucher Launched");
    }
}

My Launch Configuration Tab Group Code
public class MyJavaTabGroup extends AbstractLaunchConfigurationTabGroup
{

    JavaMainTab jmTab;
    JavaArgumentsTab jaTab;
    JavaJRETab jjTab;
    CommonTab cTab;

    @Override
    public void createTabs(ILaunchConfigurationDialog dialog, String mode)
    {
        jmTab = new JavaMainTab();
        jaTab = new JavaArgumentsTab();
        jjTab = new JavaJRETab();
        cTab = new CommonTab();

        setTabs(new ILaunchConfigurationTab[] { jmTab , jaTab, jjTab, cTab });      
    }

}

As JavaArgumentsTab takes the vm arguments, I'm trying to set vm arguments by code but I don't find any method of JavaArgumentsTab class that allow me.

A:

One way to do it is create your own subclass of JavaArgumentsTab and override setDefaults.
setDefaults javadoc is:

Initializes the given launch configuration with default values for
  this tab. This method is called when a new launch configuration is
  created such that the configuration can be initialized with meaningful
  values. This method may be called before this tab's control is
  created.

For e.g.:
import org.eclipse.debug.core.ILaunchConfigurationWorkingCopy;
import org.eclipse.jdt.debug.ui.launchConfigurations.JavaArgumentsTab;
import org.eclipse.jdt.launching.IJavaLaunchConfigurationConstants;

public class CustomJavaArgumentsTab extends JavaArgumentsTab {

    @Override
    public void setDefaults(ILaunchConfigurationWorkingCopy config) {
        // start with the normal defaults for this tab...
        super.setDefaults(config);
        // ... then set/override them with what I want
        // ATTR_VM_ARGUMENTS is defaulted to null, provide my desired default
        config.setAttribute(IJavaLaunchConfigurationConstants.ATTR_VM_ARGUMENTS, "my desired default");
    }
}

As you can see from this screenshot, "my desired default" appears in my launch configuration by default:

