Bug 198917 set __parameterpage to false for required parameter will cause wrong Exception[0705]
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/impl/EngineTask.java
doValidateParameters( );
			return true;
		}
		catch(ParameterValidationException ex)
		{
			log.log( Level.SEVERE, ex.getMessage( ), ex );
		}
		return false;
	}
	
	protected boolean doValidateParameters() throws ParameterValidationException
	{
		
		usingParameterValues( );
		if ( log.isLoggable( Level.FINE ) )
		{
			loggerParamters( );
		}
		
		ParameterValidationVisitor pv = new ParameterValidationVisitor( );
		boolean result = pv.visit( (ReportDesignHandle) runnable
				.getDesignHandle( ), null );
		if ( pv.engineException != null )
		{
			throw pv.engineException;
		}
		return result;
	}
	
	private class ParameterValidationVisitor extends ParameterVisitor