Java 在把孩子附在孩子身上时有问题

我试图用Java和org.w3c.dom生成一些简单的XML，但当我尝试将一个子对象附加到一个子对象时，我陷入了困境，类似这样：

<root>
     <child>
          <childOfTheChild>Some text</childOfTheChild>
     </child>
</root>

我总是得到同样的结果，那就是：

<root>
     <child>null</child>
</root>

无效的

这段代码中是否有问题，或者可能是其他问题

编辑：

打印功能在某些测试XML中正常工作，否则。。。 因此，该功能无需进行一些美容校正：

//Call System.out.println( print(dokument.getFirstChild()) );
private String print(Node node) {

    String txt = "";  //xml string presentation

    //Get the primary node name and any existing attributes, like <myNode att1='some val'>
    if (node.getNodeType() == node.ELEMENT_NODE) 
    {
        //The name
        txt += "<" + node.getNodeName();

        //Insert the attributes
        if (node.hasAttributes()) 
        {
            NamedNodeMap atts = node.getAttributes();
            for (int i = 0; i < atts.getLength(); i++) {
                Node atts = atts.item(i);
                txt += " " + atts.getNodeName() + " = '" + atts.getNodeValue() + "'";
            }
        }
        txt +=  ">\n";
    }

    int nChilds = -1;

    //Get any existing child nodes, so the <root><child1></child1></root>
    if (node.hasChildNodes()) 
    {
        NodeList childs = node.getChildNodes();
        nChilds  = childs.getLength();


        if (nChilds == 1) 
        {
            txt += childs.item(0).getNodeValue();
        } 
        else 
        {
            for (int j = 0; j < nChilds; j++) {
                txt += print(childs.item(j));
            }
        }
    }

    //And the ending of the primary node, like </root>
    if (node.getNodeType() == node.ELEMENT_NODE) 
    {
        txt += "</" + node.getNodeName();
        txt +=  ">\n";
    }
    return txt;
}

//调用System.out.println（print（dokument.getFirstChild（））；
私有字符串打印（节点）{
String txt=“”；//xml字符串表示法
//获取主节点名称和任何现有属性，如
if（node.getNodeType（）==node.ELEMENT\u node）
{
//名字
txt+=“\n”；
}
int-nChilds=-1；
//获取任何现有子节点，以便
if（node.hasChildNodes（））
{
NodeList childs=node.getChildNodes（）；
nChilds=childs.getLength（）；
如果（nChilds==1）
{
txt+=childs.item（0.getNodeValue（）；
} 
其他的
{
对于（int j=0；j

对我来说很好吗

import static org.junit.Assert.assertTrue;

import java.io.StringWriter;

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.TransformerFactoryConfigurationError;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.junit.Test;
import org.w3c.dom.DOMImplementation;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Text;

public class DomTest {

    @Test
    public void testDom() throws Exception {
        Document document = createEmptyDocument();

        Element root = document.getDocumentElement();
        Element child = document.createElement("child");
        Element childOfTheChild = document.createElement("childOfTheChild");
        Text st = document.createTextNode("Some text");
        childOfTheChild.appendChild(st);
        child.appendChild(childOfTheChild);
        root.appendChild(child);

        assertTrue(serialise(document).contains("Some text"));
    }

    private Document createEmptyDocument() throws ParserConfigurationException {
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        DOMImplementation domImpl = dbf.newDocumentBuilder()
                .getDOMImplementation();
        Document document = domImpl.createDocument(null, "root", null);
        return document;
    }

    private String serialise(Document document)
            throws TransformerFactoryConfigurationError,
            TransformerConfigurationException, TransformerException {
        TransformerFactory xff = TransformerFactory.newInstance();
        Transformer xf = xff.newTransformer();
        StringWriter sw = new StringWriter();
        xf.transform(new DOMSource(document), new StreamResult(sw));
        return sw.toString();
    }
}

---

您是如何将您的文档打印到控制台的？打印功能，在回答：）下添加注释。好的，谢谢！似乎我的打印功能有一些错误，将调试：）。它的意思更像dom，这就是为什么它不像序列化。再次感谢！注：使用DOM-LS替代Transformer方法进行序列化。看见

import static org.junit.Assert.assertTrue;

import java.io.StringWriter;

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.TransformerFactoryConfigurationError;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.junit.Test;
import org.w3c.dom.DOMImplementation;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Text;

public class DomTest {

    @Test
    public void testDom() throws Exception {
        Document document = createEmptyDocument();

        Element root = document.getDocumentElement();
        Element child = document.createElement("child");
        Element childOfTheChild = document.createElement("childOfTheChild");
        Text st = document.createTextNode("Some text");
        childOfTheChild.appendChild(st);
        child.appendChild(childOfTheChild);
        root.appendChild(child);

        assertTrue(serialise(document).contains("Some text"));
    }

    private Document createEmptyDocument() throws ParserConfigurationException {
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        DOMImplementation domImpl = dbf.newDocumentBuilder()
                .getDOMImplementation();
        Document document = domImpl.createDocument(null, "root", null);
        return document;
    }

    private String serialise(Document document)
            throws TransformerFactoryConfigurationError,
            TransformerConfigurationException, TransformerException {
        TransformerFactory xff = TransformerFactory.newInstance();
        Transformer xf = xff.newTransformer();
        StringWriter sw = new StringWriter();
        xf.transform(new DOMSource(document), new StreamResult(sw));
        return sw.toString();
    }
}