我正在尝试创建一个xml文件。当我创建该文件时，出现此错误。我真的不知道它是什么。这是一个非常奇怪的错误。文件创建正确，但是里面没有任何内容。

Exception in thread "AWT-EventQueue-0" java.lang.AbstractMethodError: gnu.xml.dom.DomDocument.getXmlStandalone()Z
    at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.setDocumentInfo(DOM2TO.java:377)
    at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:131)
    at com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(DOM2TO.java:98)
    at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transformIdentity(TransformerImpl.java:683)
    at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:727)
    at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:340)
    at org.w3c.jigmonitor.controller.Controller.writePerformancesXmlFile(Controller.java:191)
    at org.w3c.jigmonitor.controller.Controller.actionPerformed(Controller.java:68)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2341)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6505)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3321)
    at java.awt.Component.processEvent(Component.java:6270)
    at java.awt.Container.processEvent(Container.java:2229)
    at java.awt.Component.dispatchEventImpl(Component.java:4861)
    at java.awt.Container.dispatchEventImpl(Container.java:2287)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4832)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4492)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4422)
    at java.awt.Container.dispatchEventImpl(Container.java:2273)
    at java.awt.Window.dispatchEventImpl(Window.java:2719)
    at java.awt.Component.dispatchEvent(Component.java:4687)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:703)
    at java.awt.EventQueue.access$000(EventQueue.java:102)
    at java.awt.EventQueue$3.run(EventQueue.java:662)
    at java.awt.EventQueue$3.run(EventQueue.java:660)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:87)
    at java.awt.EventQueue$4.run(EventQueue.java:676)
    at java.awt.EventQueue$4.run(EventQueue.java:674)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:673)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:244)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:163)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:151)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:147)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:139)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:97)

这是我用来创建xml文件的代码：

DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
                    DocumentBuilder docBuilder = docFactory.newDocumentBuilder();

                    Document doc = docBuilder.newDocument();
                    Element rootElement = doc.createElement("performances");
                    doc.appendChild(rootElement);

                    Attr attr = doc.createAttribute("date");
                    attr.setValue(dateFormat.format(cal.getTime()).toString());
                    rootElement.setAttributeNode(attr);

                    //Uptime
                    Element uptime = doc.createElement("uptime");
                    rootElement.appendChild(uptime);

                    Element days = doc.createElement("days");
                    days.appendChild(doc.createTextNode(new Long(duptime).toString()));
                    uptime.appendChild(days);

                    Element hours = doc.createElement("hours");
                    hours.appendChild(doc.createTextNode(new Long(huptime).toString()));
                    uptime.appendChild(hours);

                    Element minutes = doc.createElement("minutes");
                    minutes.appendChild(doc.createTextNode(new Long(muptime).toString()));
                    uptime.appendChild(minutes);

                    Element seconds = doc.createElement("seconds");
                    seconds.appendChild(doc.createTextNode(new Long(suptime).toString()));
                    uptime.appendChild(seconds);

                    //TotalHitCount
                    Element totalhitcount = doc.createElement("totalhitcount");
                    totalhitcount.appendChild(doc.createTextNode(new Long(stats.gettotal_hit_count()).toString()));
                    rootElement.appendChild(totalhitcount);

                    //EmittedBytes
                    Element emittedbytes = doc.createElement("emittedbytes");
                    emittedbytes.appendChild(doc.createTextNode(new Long(stats.getemitted_bytes()).toString()));
                    rootElement.appendChild(emittedbytes);

                    //Avghitsec
                    Element avghitsec = doc.createElement("avghitsec");
                    avghitsec.appendChild(doc.createTextNode(new Float(stats.getavg_hit_sec()).toString()));
                    rootElement.appendChild(avghitsec);

                    //Avgbyteshit
                    Element avgbyteshit = doc.createElement("avgbyteshit");
                    avgbyteshit.appendChild(doc.createTextNode(new Long(stats.getavgbytes_hit()).toString()));
                    rootElement.appendChild(avgbyteshit);

                    //Avgbps
                    Element avgbps = doc.createElement("avgbps");
                    avgbps.appendChild(doc.createTextNode(new Long(stats.getavgbps()).toString()));
                    rootElement.appendChild(avgbps);

                    //Total Threads
                    Element totalthreads = doc.createElement("totalthreads");
                    totalthreads.appendChild(doc.createTextNode(new Long(stats.gettotal_threads()).toString()));
                    rootElement.appendChild(totalthreads);

                    //Idle Threads
                    Element idlethreads = doc.createElement("idlethreads");
                    idlethreads.appendChild(doc.createTextNode(new Long(stats.getidle_threads()).toString()));
                    rootElement.appendChild(idlethreads);

                    TransformerFactory transformerFactory = TransformerFactory.newInstance();
                    Transformer transfomer = transformerFactory.newTransformer();
                    DOMSource source = new DOMSource(doc);
                    StreamResult result = new StreamResult(new File("/home/mazzy/Scrivania/perfor_"+dateFormat.format(cal.getTime()).toString()+".xml"));

                    transfomer.transform(source, result);

我在transfomer method中遇到了异常。知道我得到了什么错误吗？