尝试在 for 循环中将元素添加到 xml 文件时出现 HIERARCHY_REQUEST_ERR

正如标题所示，我尝试使用 for 循环将元素添加到 xml 文档中。 我有一个ArrayList称为的字符串names我希望迭代，并为每个名称创建一个<user>具有属性的元素name和一个孩子<record>具有以下属性id, time, date, and project.

不幸的是，如果您在下面的代码中向下滚动到createDoc()方法，当我尝试调用doc.appendChild(user)，我收到以下错误：

Exception in thread "main" org.w3c.dom.DOMException: HIERARCHY_REQUEST_ERR: An attempt was made to insert a node where it is not permitted. 
at org.apache.xerces.dom.CoreDocumentImpl.insertBefore(Unknown Source)
at org.apache.xerces.dom.NodeImpl.appendChild(Unknown Source)
at test.XMLwriter.createDoc(XMLwriter.java:131)
at test.XMLwriter.<init>(XMLwriter.java:116)
at test.TestRunner.main(TestRunner.java:33)

我在 stackoverflow 上查看了一些具有相同错误的问题，但它们似乎都是在与我完全不同的情况下发生的。我最好的猜测是，此错误与我试图在同一层次结构级别创建太多父元素有关。

这是代码：

public class XMLwriter {
private ArrayList<String> names;
private Document doc;
private Random rand;
private ArrayList<Element> users;

public XMLwriter() throws ParserConfigurationException, TransformerException{

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

    rand = new Random();
    users = new ArrayList<Element>();
    names = new ArrayList<String>();

    names.add("Ralph Wiggum");names.add("Mr. Hanky");names.add("Bulbasaur");
    names.add("Tyroil Smoochie Wallace");names.add("Scooby Doo");names.add("Neville Longbottom");
    names.add("Jabba the Hutt");names.add("Silky Johnson");names.add("Master Chief");
    names.add("Frodo Baggins");names.add("Clayton Bigsby");names.add("John Snow");
    names.add("Eric Cartman");names.add("Leoz Maxwell Jilliumz");names.add("Aslan");

    createDoc();
    generateFile();

}

public void createDoc(){
    for(int k = 0; k < names.size(); k++)
    {
        users.add(doc.createElement("user"));
    }
    for (int x = 0; x < names.size(); x++){

        //create the elements
        Element record = doc.createElement("record");
        users.get(x).appendChild(record);
        doc.appendChild(users.get(x));//The line that is throwing the error

        //create the attributes
        Attr name = doc.createAttribute("name");
        Attr date = doc.createAttribute("date");
        Attr project = doc.createAttribute("project");
        Attr time = doc.createAttribute("time");
        Attr id = doc.createAttribute("id");

        //give all of the attributes values
        name.setValue(names.get(x));
        date.setValue(new Date().toString());
        project.setValue("Project" + (rand.nextDouble() * 1000));
        time.setValue("" + rand.nextInt(10));
        id.setValue("" + (rand.nextDouble() * 10000));

        //assign the attributes to the elements
        users.get(x).setAttributeNode(name);
        record.setAttributeNode(date);
        record.setAttributeNode(project);
        record.setAttributeNode(time);
        record.setAttributeNode(id);


    }
}

public void generateFile() throws TransformerException{
    TransformerFactory transformerFactory = TransformerFactory.newInstance();
    Transformer transformer = transformerFactory.newTransformer();
    DOMSource source = new DOMSource(doc);
    StreamResult result = new StreamResult(new File("C:\\Users\\sweidenkopf\\workspace\\test\\testxml.xml"));

    // Output to console for testing
    // StreamResult result = new StreamResult(System.out);
    transformer.setOutputProperty(OutputKeys.INDENT, "yes");
    transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");
    transformer.transform(source, result);
}

}

我发现了这个问题的答案。具体方法如下：

我创建了另一个名为<userList>每次 for 循环迭代时，我都会创建新创建的<user>的孩子<userList>.

最后，超出了 for 循环的范围，我做了<userList>整个 xml 文档的子级。

这是感兴趣的人的新代码。您可以阅读评论中的评论createDoc()方法来帮助澄清我上面解释的内容：

public class XMLwriter {
private ArrayList<String> names;
private Document doc;
private Random rand;
private ArrayList<Element> users;

public XMLwriter() throws ParserConfigurationException, TransformerException{

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

    rand = new Random();
    users = new ArrayList<Element>();
    names = new ArrayList<String>();

    names.add("Ralph Wiggum");names.add("Mr. Hanky");names.add("Bulbasaur");
    names.add("Tyroil Smoochie Wallace");names.add("Scooby Doo");names.add("Neville Longbottom");
    names.add("Jabba the Hutt");names.add("Silky Johnson");names.add("Master Chief");
    names.add("Frodo Baggins");names.add("Clayton Bigsby");names.add("John Snow");
    names.add("Eric Cartman");names.add("Leoz Maxwell Jilliumz");names.add("Aslan");

    createDoc();
    generateFile();

}

public void createDoc(){
    Element userList = doc.createElement("userList");//here, I create a new, over-arching element.
    for(int k = 0; k < names.size(); k++)
    {
        users.add(doc.createElement("user"));
    }
    for (int x = 0; x < 2; x++){

        //create the elements
        Element record = doc.createElement("record");
        users.get(x).appendChild(record);
        userList.appendChild(users.get(x));//I make each of the <user> elements a child of the over-arching element
        //The line that was throwing the error

        //create the attributes
        Attr name = doc.createAttribute("name");
        Attr date = doc.createAttribute("date");
        Attr project = doc.createAttribute("project");
        Attr time = doc.createAttribute("time");
        Attr id = doc.createAttribute("id");

        //give all of the attributes values
        name.setValue(names.get(x));
        date.setValue(new Date().toString());
        project.setValue("Project" + (rand.nextDouble() * 1000));
        time.setValue("" + rand.nextInt(10));
        id.setValue("" + (rand.nextDouble() * 10000));

        //assign the attributes to the elements
        users.get(x).setAttributeNode(name);
        record.setAttributeNode(date);
        record.setAttributeNode(project);
        record.setAttributeNode(time);
        record.setAttributeNode(id);


    }
    doc.appendChild(userList);//note how I append this child outside of the for loop
}

public void generateFile() throws TransformerException{
    TransformerFactory transformerFactory = TransformerFactory.newInstance();
    Transformer transformer = transformerFactory.newTransformer();
    DOMSource source = new DOMSource(doc);
    StreamResult result = new StreamResult(new File("C:\\Users\\sweidenkopf\\workspace\\test\\testxml.xml"));

    // Output to console for testing
    // StreamResult result = new StreamResult(System.out);
    transformer.setOutputProperty(OutputKeys.INDENT, "yes");
    transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");
    transformer.transform(source, result);
}

}