Java将XML文档附加到现有文档

这有点棘手，但可以运行以下示例：

public static void main(String[] args) {    documentImpl doc1 = new documentImpl();    Element root1 = doc1.createElement("root1");    Element node1 = doc1.createElement("node1");    doc1.appendChild(root1);    root1.appendChild(node1);    documentImpl doc2 = new documentImpl();    Element root2 = doc2.createElement("root2");    Element node2 = doc2.createElement("node2");    doc2.appendChild(root2);    root2.appendChild(node2);    documentImpl doc3 = new documentImpl();    Element root3 = doc3.createElement("root3");    doc3.appendChild(root3);    // root3.appendChild(root1); // Doesn't work -> DOMException    root3.appendChild(doc3.importNode(root1, true));    // root3.appendChild(root2); // Doesn't work -> DOMException    root3.appendChild(doc3.importNode(root2, true));   }