前台：
     var url = "filter.do?action=filter";
     var xmlDocument = XmlDocument.create();
     var filterInfo = xmlDocument.createElement("filterInfo");
     xmlDocument.appendChild(filterInfo);
     appendSimpleChildNode(xmlDocument, filterInfo, "type", type);
     appendSimpleChildNode(xmlDocument, filterInfo, "condition", condition);  
     xmlHttp = XmlHttp.create();
     xmlHttp.open("POST", url, false);
     xmlHttp.send(xmlDocument.xml);
     var xmlString = xmlHttp.responseText;
     return xmlString;

后台：

        SAXBuilder saxb = new SAXBuilder();
        Document doc = saxb.build(request.getInputStream());
        Element root = doc.getRootElement();
        String type = root.getChildText("type");
        String inputCondition = root.getChildText("condition");