I am trying to generate a jasper report using jasper server. I have uploaded the created report to server and created a parameter and an input control named roomId When I am calling report with a value, it works. But when the roomId is null, report is empty. Means it does not even have table headers. <parameter name="roomId" class="java.lang.Integer"> <defaultValueExpression><![CDATA[]]></defaultValueExpression></parameter><parameter name="roomIdTemp" class="java.lang.String" isForPrompting="false"> <defaultValueExpression><![CDATA[$P{roomId} == null ? "" : " AND T.ROOM_ID_01 = "+ $P{roomId} + " "]]></defaultValueExpression></parameter> Calling url http://localhost:8081/jasperserver/flow.html?...... to generate report. I am new to jasper reports. Can you please tell me whether this is illegal or not. Or am I missing anything.