java - 在java中写入XML文件时出错

Question

我正在尝试使用 Java 编写一个 xml 文件，并且想将变量字符串发送到方法 document.createElement(var) ，但它给了我这个错误:

"Exception in thread "main" org.w3c.dom.DOMException: INVALID_CHARACTER_ERR: An invalid or illegal XML character is specified. 
    at com.sun.org.apache.xerces.internal.dom.CoreDocumentImpl.createElement(Unknown Source)
    at eg.edu.alexu.csd.oop.draw.WriteXML.<init>(WriteXML.java:47)
    at eg.edu.alexu.csd.oop.draw.Test.main(Test.java:25)"

这个错误是因为 var 是一个变量

public class WriteXML {

public WriteXML() throws FileNotFoundException, ParserConfigurationException, IOException{
    DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
    DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
    Document xmlDoc = docBuilder.newDocument();
    for(int i=0 ; i<shapes.length ; i++){
        //class
        s = shapes[i].getClass().getName().toString();
        Element rootElement =  xmlDoc.createElement(s);
}

Answer 1

数字不能用作标签名称。这是一个简化的测试:

// Generates the error
DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
Document xmlDoc = docBuilder.newDocument();
xmlDoc.createElement("0");

您可以使用属性或文本内容来设置数字。

DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = docFactory.newDocumentBuilder();
Document xmlDoc = docBuilder.newDocument();
xmlDoc.createElement("Red").setTextContent("0");

XML Specification

我不确定，但我认为相关行是:

[Definition: A Name is an Nmtoken with a restricted set of initial characters.] Disallowed initial characters for Names include digits, diacritics, the full stop and the hyphen.