java - NO_MODIFICATION_ALLOWED_ERR : An attempt is made to modify an object where modifications are not allowed

Question

您好，我在尝试添加时不允许修改 xml 文件的新节点，我不确定为什么，因为我对另一个文件使用相同的代码并且它工作正常，代码如下:

 public void addStockItem(String itemStr, int qty){
    String path = System.getProperty("user.dir") + "/src/stock.xml";
      try {
    DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
        docFactory.setIgnoringElementContentWhitespace(true);

        DocumentBuilder docBuilder;      

        docBuilder = docFactory.newDocumentBuilder();

        Document doc = docBuilder.parse(path);

        Node root = doc.getFirstChild();

        Node item = doc.createElement("item");
        item.setTextContent(itemStr);
        NamedNodeMap itemAttr = item.getAttributes();
        Attr qtyAttr = doc.createAttribute("quantity");
        qtyAttr.setTextContent(qty+"");
        itemAttr.setNamedItem(qtyAttr);
        root.appendChild(item);

        Transformer transformer = TransformerFactory.newInstance().newTransformer();
        transformer.setOutputProperty(OutputKeys.INDENT, "yes");

        //initialize StreamResult with File object to save to file
        StreamResult result = new StreamResult(new StringWriter());
        DOMSource source = new DOMSource(doc);
        transformer.transform(source, result);
        String xmlString = result.getWriter().toString();

        BufferedWriter out = new BufferedWriter(new FileWriter(path));
        out.write(xmlString);
        out.close();

    } catch (Exception ex) {
        System.out.print(ex);

    }

}

我的 xml 如下:

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE stock SYSTEM "barstock.dtd">

<stock>
   <item quantity="23">dark rum</item>
   <item quantity="5">light rum</item>
   <item quantity="4">vodka</item>
   <item quantity="2">brandy</item>
   <item quantity="3">orange juice</item>
   <item quantity="2">cream</item>
   <item quantity="2">dry vermouth</item>
  <item quantity="7">amaretto</item>
</stock>

使用此 DTD:

<!-- DTD for bar stock (drink ingredients -->
 <!-- One day we should add a way to allow quantities and units to be included -->

     <!ELEMENT stock (item)*>

     <!ELEMENT item  (#PCDATA)>
     <!ATTLIST item quantity CDATA #IMPLIED>

感谢您的帮助。

---

编辑:我(Amir Rachum)将我自己的堆栈跟踪添加到问题中，因为我也遇到了这个问题:

org.w3c.dom.DOMException: NO_MODIFICATION_ALLOWED_ERR: An attempt is made to modify an object where modifications are not allowed.
    at com.sun.org.apache.xerces.internal.dom.ParentNode.internalInsertBefore(Unknown Source)
    at com.sun.org.apache.xerces.internal.dom.ParentNode.insertBefore(Unknown Source)
    at com.sun.org.apache.xerces.internal.dom.NodeImpl.appendChild(Unknown Source)
    at cs236369.hw5.servlets.xml.UploadTheme.addThemeToList(UploadTheme.java:115)
    at cs236369.hw5.servlets.xml.UploadTheme.doPost(UploadTheme.java:91)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
    at java.lang.Thread.run(Unknown Source)

Answer 1

@Amir Rachum，@JustMe:

异常的含义:NO_MODIFICATION_ALLOWED_ERR:如果此节点是只读的，则引发

在上面的代码中，您依靠 doc.getFirstChild(); 为您提供根元素。永远不要这样做，因为根据 DOM 模型，文档的子元素是注释、处理指令、根元素。所以你永远不知道你的 DOM 解析器实现可能会给你处理指令或注释。而是使用以下内容:-

 Element rootelment=document.getDocumentElement();
 //code to create a new node
rootlement.appendChild(newnode);

如果你仍然不确定你的代码，只需在调用appendChild()方法之前打印getNodeType()，然后查看DOM specification是否为只读节点。