Bug 155178 [Deploy] Preview report failed on war deployed weblogic server
viewer/org.eclipse.birt.report.viewer/birt/WEB-INF/classes/org/eclipse/birt/report/service/ReportEngineService.java
Object parameterValue = parameters.get( parameterName );
			if ( parameterObj.isHidden( ) )
			{
				continue;
			}
			if ( parameterValue == null && !parameterObj.allowNull( ) )
			{
				missingParameter = true;
				break;
			}
			if ( IScalarParameterDefn.TYPE_STRING == parameterObj.getDataType( ) )
			{
				String parameterStringValue = (String) parameterValue;
				if ( parameterStringValue != null
						&& parameterStringValue.length( ) <= 0
						&& !parameterObj.allowBlank( ) )
				{
					missingParameter = true;
					break;
				}
			}
		}
		return missingParameter;
	}
	/**
	 * uses to clear the data cach.
	 * 
	 * @param dataSet
	 *            the dataset handle
	 * @throws BirtException