code: public String getPropValue (String propName){
  		String propValue = null;
  		propValue = System.getProperty(propName);
  		IServiceReference[] refs = null;
  		if (propValue == null) {
  			try {
  				refs = getPlatformServices().getServiceReferences(IVariableResolver.class.getName(), "(name=" + getName() + ")");  //$NON-NLS-1$ //$NON-NLS-2$
  			} catch (PlatformServicesException e) {
  				if (log.isLoggable(Level.SEVERE)) {
  					log.log(Level.SEVERE, e.getMessage(), e);
  				}
  			}
  			if (refs != null) {
  				for (IServiceReference sr : refs) {
  					IVariableResolver resolver = (IVariableResolver)getPlatformServices().getService(sr);
  					try {
  						propValue = resolver.resolve(propName);
  						if (propValue != null) {
  							break;
  						}
  					} finally {
  						getPlatformServices().ungetService(sr);
  					}
  				}
  			}
  		}
  		return propValue;
  	}
docs: Returns the value for the property name used by the aggregator. By default,
  it returns the system property indicated by the specified key. This method may be overriden by the platform
  dependent implementation of the aggregator.
  @param propName
  @return Value of the property